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Antihypertensive Drugs in Pregnancy
Tiina Podymow, MD, FRCPC,* Phyllis August, MD, MPH†
Summary: Blood pressure targets and medications that are safe differ in pregnant women
compared with nonpregnant individuals. The principles of treatment for mild, moderate, and
severe hypertension in pregnancy, chronic versus gestational versus preeclampsia, and
women hypertensive at term versus remote from term are reviewed. The choice of antihypertensive drugs also is discussed; methyldopa, labetalol, and nifedipine, among others,
appear safe for use in pregnancy, whereas angiotensin converting enzyme inhibitors and
angiotensin receptor blockers should be avoided. The management of increased blood
pressure in the postpartum period, and agents to use in lactation, are also discussed.
Semin Nephrol 31:70-85 © 2011 Elsevier Inc. All rights reserved.
Keywords: Hypertension, pregnancy, antihypertensive drugs, postpartum, lactation
ypertension, the most common medical
disorder of pregnancy, is reported to
complicate 1 in 10 gestations,1,2 and affects an estimated 240,000 women in the
United States each year.3 The principles of antihypertensive treatment in pregnancy represents
a departure from the nonpregnant adult (7th Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of
High Blood Pressure [JNC-7]) guidelines.4 First,
during pregnancy the priority is to distinguish
pre-existing (chronic) from hypertension specific
to pregnancy (gestational hypertension and preeclampsia). Second, much of the obstetric literature categorizes blood pressure levels as either
mild (140-159/90-109 mm Hg) or severe (ⱖ160/
110 mm Hg), rather than by stages (as in JNC-7)
(Table 1). Third, in contrast to hypertension
guidelines in adults, which emphasize the importance of systolic blood pressure, much of the
obstetric literature focuses on diastolic blood
pressure, in part because of a lack of clinical trials
to support one approach versus another. Finally,
the focus of treatment is primarily limited to the 9
H
*Division of Nephrology, McGill University Health Center, Royal Victoria
Hospital, Montreal Quebec Canada.
†Division of Nephrology and Hypertension, Weill Medical College of Cornell
University, New York, NY.
Address reprint requests to Tiina Podymow, MD, FRCPC, Division of Nephrology, McGill University Health Center, Royal Victoria Hospital, 687
Pine Ave W, Ross 2.38, Montreal, Quebec, Canada H3A 1A1. E-mail:
[email protected]
0270-9295/ - see front matter
© 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.semnephrol.2010.10.007
70
months of pregnancy, a time frame that permits
the trade-off of slightly higher blood pressures
than targeted in nonpregnant individuals to minimize fetal exposure to antihypertensive medications. In this setting, antihypertensive medications are mainly used to prevent or treat severe
hypertension, to prolong pregnancy for as long as
safely possible thereby maximizing the gestational
age of the infant, and to minimize fetal exposure
to medications that may have adverse effects. During pregnancy, the challenge is in deciding when
to use antihypertensive medications, and what
level of blood pressure to target. The choice of
antihypertensive agents is less complex because
only a small proportion of currently available
drugs have been evaluated adequately in pregnant
women and many are contraindicated; some
carry Food and Drug Administration (FDA) classifications that suggest or demand their avoidance
in pregnancy (classes D and X). Appropriate use
of antihypertensive drugs in specific pregnancyassociated hypertensive disorders, including therapeutic blood pressure goals and criteria for selecting specific antihypertensive drugs, are
discussed in this review.
TREATMENT OF
SPECIFIC HYPERTENSIVE DISORDERS
There are four major hypertensive disorders in
pregnancy, each with unique pathophysiologic
features that have implications for antihypertensive therapy:
Seminars in Nephrology, Vol 31, No 1, January 2011, pp 70-85
Antihypertensive drugs in pregnancy
71
Table 1. Blood Pressure Classification: JNC-7 Compared With NHBPEP
JNC-7 Blood Pressure Classification
(Nonpregnant), mm Hg
Normal: SBP ⱕ120 DBP ⱕ80
Prehypertension: SBP 120-139 or DBP 80-89
Stage 1 hypertension: SBP 140–159 or DBP 90–99
Stage 2 hypertension: SBP 160-179 or DBP 100-110
Stage 3 hypertension: SBP 180-209 or DBP 110-119
NHBPEP Blood Pressure
Classification (Pregnant), mm Hg
Normal/acceptable in pregnancy: SBP
ⱕ140 and DBP ⱕ90
—
Mild hypertension: SBP 140-150 or DBP
90-109
Severe hypertension: ⱖ160 systolic or
ⱖ110 diastolic
—
JNC-7, The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood
Pressure.4
NHBPEP, National High Blood Pressure Education Program Working Group Report on High Blood Pressure in Pregnancy.1
Chronic Hypertension
Chronic hypertension, defined as blood pressure (BP) of 140/90 mm Hg or greater either
predating pregnancy or developing earlier than
20 weeks’ gestation, complicates approximately 3% of pregnancies. The cause is largely
essential hypertension, which is more frequent
in African American patients and women who
are of advanced maternal age, or who are
obese. Women of childbearing age with stage 1
(mild) essential hypertension (Table 1) who are
free of target organ damage and are in good
health have an excellent prognosis for pregnancy. Although at increased risk for superimposed preeclampsia (see later), many will naturally experience a physiologic lowering of
blood pressure during pregnancy, and a reduction in the requirement for any previously prescribed antihypertensive medication. The goal
of treatment is to maintain blood pressure at a
level that minimizes maternal cardiovascular
and cerebrovascular risk. Prevention of preeclampsia is desirable, however, current evidence has not shown that either specific blood
pressure targets in pregnancy or specific antihypertensive agents modify the risk of superimposed preeclampsia in women with pre-existing hypertension.5
term), with associated proteinuria: 1⫹ on dipstick
and by definition at least 300 mg/24-hour urine.
This syndrome occurs in 5% to 8% of all pregnancies, and is thought to be a consequence of abnormalities in the maternal vessels supplying the
placenta, leading to poor placental perfusion and
release of factors.6,7 This leads to widespread endothelial dysfunction with multi-organ system
clinical features, such as hypertension, proteinuria, and cerebral (edema, occipital headaches,
seizures) and hepatic dysfunction (extension to
hemolysis elevation of liver enzymes, low platelets).6 As currently understood, the hypertension
of preeclampsia is a consequence of placental
underperfusion, thus lowering systemic blood
pressure is not believed to reverse the primary
pathogenic process, and antihypertensive medication has never been shown to cure or reverse
preeclampsia. Nevertheless, control of hypertension may allow for expectant management of preeclampsia, prolonging pregnancy remote from
term. As well, in women with preeclampsia-eclampsia, intracerebral hemorrhage remains the
most common cause of death,8 so control of severe and rapid increases of blood pressure is the
main goal of clinical management, often requiring
the use of antihypertensive medication.
Superimposed Preeclampsia
Preeclampsia-Eclampsia
Preeclampsia-eclampsia is a syndrome characterized by new-onset hypertension in later pregnancy (usually after 20 weeks, but often closer to
Superimposed preeclampsia complicates approximately 25% of pregnancies in women
with chronic hypertension, five times the rate
observed in the general population.9 At times it
72
may be difficult to distinguish exacerbation of
chronic hypertension from superimposed preeclampsia, but it is usually prudent to err toward treating the latter. Principles of management are similar to those outlined earlier for
preeclampsia, although women with pre-existing hypertension and superimposed preeclampsia may be more likely to develop severe hypertension, requiring multiple antihypertensive
medications.
Gestational Hypertension
Gestational hypertension, formerly called transient hypertension in previous texts and guidelines, occurs in approximately 6% of pregnancies and is defined as de novo hypertension
developing in the latter half of pregnancy not
associated with the systemic features of preeclampsia (eg, proteinuria). The precise diagnosis frequently is made in hindsight; if laboratory
tests remain normal, and blood pressure decreases postpartum, then the diagnosis was gestational hypertension rather than preeclampsia
or chronic hypertension. Women with gestational hypertension should be considered to be
at risk for preeclampsia because approximately
15% to 45% of women initially in the gestational
hypertension category develop preeclampsia.
Progression to preeclampsia is more likely if
gestational hypertension appears early, there is
a history of prior miscarriage or hypertension
during a previous pregnancy, as well as in those
with higher blood pressure.10,11 As in women
with chronic hypertension, antihypertensive
medications should be prescribed with the goal
of preventing maternal consequences of severe
hypertension because there is no evidence that
targeted blood pressure control prevents preeclampsia.
Occasionally, women with apparent gestational hypertension remain hypertensive after
delivery. These women most likely have preexisting chronic hypertension that was masked
in early pregnancy by physiologic vasodilation.
The natural history of hypertension in the postpartum period, and the maximum time to normalization (beyond which chronic hypertension should be diagnosed), appears to be
hypertension of 140/90 mm Hg or greater per-
T. Podymow and P. August
sisting beyond 3 months postpartum. This is
discussed further in a later section.
Although all four types of hypertension in
pregnancy may lead to maternal and perinatal
complications, preeclampsia (regardless of
blood pressure level) and severe hypertension (regardless of type) are those associated
with the highest maternal and perinatal risks.
The mothers usually do well, but the main
risks are placental abruption, accelerated hypertension leading to hospitalization, and target organ damage, such as cerebral vascular
catastrophe.1 The fetus is far more vulnerable; risks include growth restriction and prematurity owing to worsening of maternal disease necessitating early delivery.12
MILD TO MODERATE
HYPERTENSION IN PREGNANCY
The benefits of antihypertensive therapy for
mild to moderately increased blood pressure
in pregnancy (ⱕ160/110 mm Hg), either
chronic or de novo, have not been shown in
clinical trials. Recent reviews, including a Cochrane meta-analysis, concluded that there
are insufficient data to determine the benefits
and risks of antihypertensive therapy for mild
to moderate hypertension (defined as blood
pressure 140-160 mm Hg systolic or diastolic
blood pressure 90 –109 mm Hg).5,13-16 Of
note, with antihypertensive treatment, there
seems to be less risk of developing severe
hypertension (relative risk, 0.50; with a number needed to treat of 10) but no difference in
outcomes of preeclampsia, neonatal death,
preterm birth, and small for gestational age
babies with treatment.5
International guidelines for the treatment of
hypertension in pregnancy vary with respect to
thresholds for starting treatment and targeted BP
goals, but all are higher than the Joint National
Committee guidelines for treatment of (nonobstetric) hypertension. Therapy is recommended
in the United States for a BP of 160/105 mm Hg or
greater,1 with no set treatment target; in Canada
for women with no comorbid conditions therapy
is recommended for blood pressure of 140 to
150/90 mm Hg or greater, targeting diastolic pressure to 80 to 90 mm Hg17,18 and in those with
comorbid conditions targeting 130 to 139/80 to
Antihypertensive drugs in pregnancy
89 mm Hg; and in Australia increases of 160/90
mm Hg or greater are treated to a target of no less
than 110 systolic.19 A retrospective review of 28
patients who suffered stroke in the setting of
preeclampsia (54% died) showed that the cause
of stroke was usually arterial hemorrhage, and the
average blood pressure prestroke was 159 to
198/81 to 133 mm Hg.20 In this case series,
systolic hypertension (155-160 mm Hg) was
more prevalent than diastolic hypertension (ie,
most women did not reach a diastolic BP of 110
mm Hg). This report underscores the need for
clinical trials and evidence-based guidelines for
antihypertensive treatment in pregnant
women. Our practice is to initiate treatment
when blood pressure is 150 systolic or greater
or 90 to 100 mm Hg diastolic. Other clinicians
may wait until diastolic BPs reach 100 mm Hg
before treating. One should note that in the
presence of any signs of end-organ damage
(electrocardiogram or imaging changes suggesting cardiac hypertrophy, alterations in the optic
fundi, borderline high or frankly abnormal creatinine levels) the patient’s hypertension is
treated as if she were not pregnant.
When the diagnosis is preeclampsia, the gestational age, as well as the level of BP, influence
the use of antihypertensive therapy. At or near
term, women with preeclampsia are likely to be
delivered. Severe hypertension should always
be treated, but the treatment of moderate hypertension can be reassessed postpartum. If
preeclampsia develops remote from term, and
expectant management is undertaken, treatment of severe hypertension should be initiated, and blood pressure lowered to 140/90
mm Hg with oral medications, as described
later. It should be emphasized that there are no
studies addressing safe blood pressure treatment targets for pregnant women, and guidelines and reviews generally recommend treating to blood pressure levels that are likely to be
protective against acute adverse cerebrovascular or cardiovascular events, which is usually in
the range of 135 to 155/85 to 90 mm Hg.18,21
When antihypertensive therapy is used in
women with preeclampsia, fetal monitoring is
advisable to recognize fetal distress, which
might be attributable to reduced placental perfusion. Management of early onset preeclamp-
73
sia (⬍34 wk) includes judicious use of antihypertensive medications, avoiding both high
(⬎160/110 mm Hg) as well as low (⬍120/80
mm Hg) blood pressures. Although not found
to be effective by Cochrane and other analyses,
bed rest, and close in-hospital maternal and
fetal monitoring, frequently are prescribed.
Control of hypertension and careful monitoring
have been shown to permit postponement of
delivery in selected cases for an average of 2
weeks, which has been associated with improved outcomes later in childhood.22 It must
be emphasized that daily assessment of both
maternal (review of symptoms, BP, and blood
work) and fetal well-being are necessary in such
cases, and delivery may be necessary if either
deteriorate.
For women with chronic hypertension and
mild to moderately increased BP before pregnancy, it is reasonable to expect that pressures
may decrease early in pregnancy, owing to
physiologic vasodilation, and if there is no
known target organ damage, clinicians can consider discontinuing antihypertensive treatment
and monitoring, provided patients are followed
up closely. Therapy then can be initiated if the
BP again increases to 140 to 150/90 to 100 mm
Hg.23 In women with underlying renal dysfunction, it is reasonable to choose a slightly lower
threshold for treatment.9 There are a wide variety of agents available for use, and orally administered antihypertensives can be used in
standard doses in pregnancy (Table 2). First-line
recommended agents for nonsevere hypertension are methyldopa and labetalol, with nifedipine as second-line, although the latter is now
used quite commonly.
SEVERE HYPERTENSION
There is consensus that treatment is indicated
for severe hypertension in pregnancy, defined as 160/110 mm Hg or greater, to prevent intracerebral hemorrhage and maternal
death.1,24 Those with hypertensive encephalopathy, hemorrhage, or eclampsia require
treatment with parenteral agents to lower
mean arterial pressure (two-thirds diastolic ⫹
one-third systolic blood pressure) by 25%
over minutes to hours, and then to further
lower blood pressure to 160/100 mm Hg over
74
T. Podymow and P. August
Table 2. Drugs for Gestational or Chronic Hypertension in Pregnancy
Drug (FDA Risk
Classification)
Dose (oral)
Concerns or Comments
Preferred agent
methyldopa (B)
0.5-3.0 g/d in 2-4 divided doses
Second-line agents*
Labetalol (C)
Nifedipine (C)
200-1,200 mg/d in 2-3 divided
doses
30-120 mg/d of a slow-release
preparation
50-300 mg/d in 2-4 divided
doses
Drug of choice according to NHBPEP
working group; safety after first
trimester well documented,
including 7-year follow-up
evaluation of offspring
May be associated with fetal growth
restriction
May inhibit labor; little experience
with other calcium entry blockers
Few controlled trials, long
experience with few adverse events
documented; useful in
combination with sympatholytic
agent; may cause neonatal
thrombocytopenia
May decrease uteroplacental blood
flow; may impair fetal response to
hypoxic stress; risk of growth
restriction when started in first or
second trimester (Atenolol); may
be associated with neonatal
hypoglycemia at higher doses
Majority of controlled studies in
normotensive pregnant women
rather than hypertensive patients;
can cause volume contraction and
electrolyte disorders; may be useful
in combination with methyldopa
and vasodilator to mitigate
compensatory fluid retention
Leads to fetal loss in animals; human
use associated with cardiac defects,
fetopathy, oligohydramnios,
growth restriction, and neonatal
anuric renal failure, which may be
fatal; direct renin inhibitors—no
reports in pregnancy: avoid
Hydralazine (C)
␤-receptor
blockers (C)
Hydrochlorothiazide
(C)†
Contraindicated
ACE-Is and AT1receptor
antagonists,
direct renin
inhibitors (D)†
Depends on specific agent
12.5-25 mg/d
—
No antihypertensive agent has been proven safe for use during the first trimester. Drug therapy indicated for uncomplicated
chronic hypertension when diastolic BP was 100 mm Hg or greater (Korotkoff V). Treatment at lower levels may be indicated
for patients with diabetes mellitus, renal disease, or target organ damage.
Abbreviation: NHBPEP, National High Blood Pressure Education Program.
Modified from reference 113.
*We omitted some agents (eg, clonidine, ␣-blockers) because of limited data on use for chronic hypertension in pregnancy.
†We would classify in category X.
subsequent hours.1 In treating severe hypertension, it is important to avoid hypotension
because the degree to which placental blood
flow is autoregulated likely is limited, and
aggressive lowering may cause fetal distress.
In women with preeclampsia, treatment of
acute severe hypertension should be initiated
at lower than usual doses because these pa-
Antihypertensive drugs in pregnancy
75
Table 3. Drugs for Urgent Control of Severe Hypertension in Pregnancy
Drug (FDA Risk)*
Dose and Route
Concerns or Comments†
Labetalol (C)
10-20 mg IV, then 20-80 mg
every 20-30 min, maximum,
300 mg; for infusion, 1-2
mg/min IV
Hydralazine (C)
5 mg, IV or IM, then 5-10 mg
every 20-40 min; once BP
controlled repeat every 3 h;
for infusion, 0.5-10 mg/h; if
no success with 20 mg IV or
30 mg IM, consider another
drug
Tablets recommended only:
10-30 mg oral dose, repeat
in 45 min if needed
Because of a lower incidence of
maternal hypotension and
other side effects, its IV use
now supplants that of
hydralazine; avoid in women
with asthma or congestive
heart failure
A drug of choice according to
NHBPEP working group; long
experience of safety and
efficacy
Nifedipine (C)
Diazoxide (C)
30-50 mg IV every 5-15 min
Relatively contraindicated
nitroprusside (C)‡
Constant infusion of 0.25-5
␮g/kg/min IV
We prefer long-acting
preparations; although
obstetric experience with
short-acting preparations has
been favorable it is not
approved by US FDA for
management of hypertension
Use is waning; may arrest
labor; causes hyperglycemia
Possible cyanide toxicity if used
for ⬎4 h; agent of last resort
Indicated for acute increase of diastolic BP of 105 mm Hg or greater; goal is gradual reduction to 90 to 100 mm Hg.
Abbreviation: IM, intramuscular; IV, intravenous; NHBPEP, National High Blood Pressure Education Program.
Modified from reference 113.
*US Food and Drug Administration classification, C indicates that studies in animals have revealed adverse effects on the fetus
(teratogenic, embryocidal, or other) and/or there are no controlled studies in women, or studies in women and animals are
not available. Drugs should be given only if the potential benefits justify the potential risk to the fetus.
†Adverse effects for all agents, except as noted, may include headache flushing, nausea, and tachycardia (primarily owing to
precipitous hypotension and reflex sympathetic activation).
‡We would classify in category D: there is positive evidence of human fetal risk, but the benefits of use in pregnant women may
be acceptable despite the risk (eg, if the drug is needed in a life-threatening situation or for a serious disease for which safer
drugs cannot be used or are ineffective).
tients may be intravascularly volume depleted
and at increased risk for hypotension. Principles of treatment are outlined in Table 3; of
note, a meta-analysis of 24 trials (2,949
women) in which different antihypertensive
drugs were compared for the treatment of
severe hypertension in pregnancy concluded
that there are insufficient data to favor one
agent over another,25 although other studies
have concluded that agents other than parenteral hydralazine (eg, parenteral labetalol or
oral nifedipine) are preferable owing to reduced maternal and fetal adverse effects.26
CHOICE OF ANTIHYPERTENSIVE DRUGS
The FDA reviews human and animal data to
assign letter grades corresponding to risk of
fetal exposure in pregnancy. Most antihypertensive agents used in pregnancy are designated as category C, which states that human
studies are lacking and animal studies are either
positive for fetal risk or are lacking, and that the
drug should be given only if potential benefits
justify potential risks to the fetus.27 This category cannot be interpreted as no evidence of
risk, and is so broad to preclude usefulness in
76
practice, leading some groups to suggest that
the FDA classification be abandoned, or at least
modified so as to be more useful to the clinician.28,29 The following information is thus
based on clinical case series, small studies, and
meta-analyses.
SYMPATHETIC
NERVOUS SYSTEM INHIBITORS
Methyldopa is still widely used for treatment of
hypertension in pregnancy and remains one of
the only drugs for which a 7.5-year follow-up
evaluation of the newborn of treated mothers is
available. It is a centrally acting ␣2-adrenergic
agonist prodrug, which is metabolized to
␣-methyl norepinephrine and then replaces
norepinephrine in the neurosecretory vesicles
of adrenergic nerve terminals. Blood pressure
control is gradual, over 6 to 8 hours, owing to
the indirect mechanism of action. It is not
thought to be teratogenic based on limited data
and a more than 40-year history of use in pregnancy. It has been assessed in a number of
prospective trials in pregnant women, compared with placebo30-32 or with alternative antihypertensive agents.32-35 Treatment with
methyldopa has been reported to prevent subsequent progression to severe hypertension in
pregnancy36 and does not appear to have adverse effects on uteroplacental or fetal hemodynamics37 or on fetal well being.31 One placebo-controlled trial (⬎200 women with diastolic
BP ⱖ90 mm Hg at entry) noted fewer midpregnancy losses in patients randomized to methyldopa30 but this observation was not confirmed
in a more recent trial of similar size.31 Importantly, birth weight, neonatal complications,
and development during the first year were
similar in children exposed to methyldopa as in
the placebo group.38,39 Also in the earlier-noted
follow-up study of offspring who were exposed
to methyldopa in utero, at 7.5 years of age,
intelligence and neurocognitive development
were similar to controls.40 It is unfortunate that
this landmark 1993 study did not result in a
standard method of evaluation applied to all
antihypertensive drugs prescribed to pregnant
women.
Adverse effects are consequences of central ␣2-agonism or decreased peripheral sym-
T. Podymow and P. August
pathetic tone. These drugs act at sites in the
brainstem to decrease mental alertness and
impair sleep, leading to a sense of fatigue or
to depression in some patients. Frequently,
decreased salivation leading to xerostomia is
experienced. Methyldopa also can cause liver
enzyme increases in 5% of patients; both hepatitis and hepatic necrosis have been reported.41 Some patients will develop a positive antinuclear antigen, or antiglobulin
(Coombs) test with chronic use, and this occasionally is associated with clinical hemolytic anemia. In these cases, medications from
other classes are substituted.
Clonidine (Catapres; Boehringer Ingelheim
Pharmaceuticals, Inc, Ridgefield, CT), a selective ␣2-agonist, acts similarly and is comparable
with methyldopa with respect to safety and
efficacy,42 but of some concern is a small controlled follow-up study of 22 neonates that reported an excess of sleep disturbance in clonidine-exposed infants.43 In pregnancy, it is
mainly used as a third-line agent for multidrug
control of refractory hypertension.
PERIPHERALLY ACTING
ADRENERGIC-RECEPTOR ANTAGONISTS
␤-blockers have been used extensively in pregnancy. Although several randomized trials comparing ␤-blockers with either placebo or other
agents have been conducted,33,34,44,45 there are
still unresolved issues regarding their use in pregnancy because of a few small studies that suggested an association with lower birth weight
infants. None of the ␤-blockers have been associated with teratogenicity. In a meta-analysis and
Cochrane review,46 individual agents were not
distinguishable in their perinatal effects with the
exception of atenolol (Tenormin; AstraZeneca
Pharmaceuticals), which in one small study was
started at 12 to 24 weeks’ gestation and resulted
in clinically significant fetal growth restriction
and decreased placental weight compared with
placebo.47 This observation was supported by a
subsequent retrospective review comparing
atenolol with alternative therapies.48 Given differences in ␤-blockers with respect to lipid solubility and receptor specificity, the potential
for clinically relevant differences between
agents exists, but has not been investigated in
Antihypertensive drugs in pregnancy
pregnancy. Oral ␤-blockade had been associated with non– clinically significant neonatal
bradycardia15,49; though in a systematic review
of trials, labetalol did not (along with oral methyldopa, nifedipine, or hydralazine) appear to
cause neonatal heart rate effects.50 Parenteral
therapy has been found to increase the risk of
neonatal bradycardia, requiring intervention in
one of six newborns.15 Further reassurance is
derived from a 1-year postpartum follow-up
study that showed normal development of infants exposed to atenolol in utero.51
Maternal outcomes are improved with the
use of ␤-blockers, with effective control of maternal blood pressure, decreased incidence of
severe hypertension, and decreased rate of preterm admission to the hospital15; they have
been found in a recent Cochrane analysis to be
more effective in lowering blood pressure compared with methyldopa in 10 trials.5
Labetalol (Trandate; Prometheus Laboratories, Inc, San Diego, CA), a nonselective
␤-blocker with vascular ␣1-receptor blocking
capabilities has gained wide acceptance in
pregnancy. When administered orally to
women with chronic hypertension, it appears
as safe31,35,52,53 and effective as methyldopa,
although neonatal hypoglycemia with higher
doses has been reported.54 Of some concern,
one placebo-controlled study reported an association with fetal growth restriction in the
management of preeclampsia remote from
term.53 Parenterally it is used to treat severe
hypertension, and because of a lower incidence of maternal hypotension and other side
effects, many find this drug preferable to hydralazine.26
Adverse effects may be predicted as consequences of ␤-receptor blockade. Fatigue, lethargy, exercise intolerance (owing to ␤2-blocking
effects in skeletal muscle vasculature), peripheral
vasoconstriction, sleep disturbance (with use of
more lipid-soluble drugs), and bronchoconstriction may be seen, however, discontinuation owing to side effects is uncommon.5
Peripherally acting ␣1-adrenergic antagonists
are second-line antihypertensive drugs in nonpregnant adults. These are indicated during
pregnancy in the management of hypertension
owing to suspected pheochromocytoma; both
77
prazosin (Minipres; Pfizer Inc, New York, NY)
and phenoxybenzamine (Dibenzyline; WellSpring Pharmaceutical Corp) have been used,
with ␤-blockers as adjunctive agents after
␣-blockade is accomplished.55,56 Because there
is limited experience with these agents in pregnancy, their routine use cannot be advocated.
CALCIUM-CHANNEL BLOCKERS
Calcium-channel antagonists have been used to
treat chronic hypertension, mild preeclampsia
presenting late in gestation, and urgent hypertension associated with preeclampsia. Orally
administered nifedipine (Adalat [Bayer HealthCare Pharmaceuticals, Calgary, Alberta], Procardia [Pfizer Inc]) and verapamil (Isoptin; Ranbaxy Pharmaceuticals Inc) do not appear to pose
a teratogenic risk to fetuses exposed in the first
trimester.57 Most investigators have focused on
the use of nifedipine, although there are reports
of nicardipine (Cardene; EKR Therapeutics,
Inc),58,59 isradipine,60 felodipine (Plendil [AstraZeneca Pharmaceuticals], Renedil [Sanofi-Aventis]),61 and verapamil (Isoptin).62 Amlodipine
(Norvasc; Pfizer Inc), the dihydropyridine calcium-channel blocker widely used for treatment
of hypertension in nonpregnant hypertensive
patients, has not been studied extensively in
pregnancy. We are only aware of one small case
series in pregnancy, however, it is commonly
used in pregnancy and appears safe.63 Maternal
side effects of the calcium-channel blockers include tachycardia, palpitations, peripheral
edema, headaches, and facial flushing.64 Nifedipine does not appear to cause a detectable
decrease in uterine blood flow.65,66 Short-acting
dihydropyridine calcium antagonists, particularly when administered sublingually, are now
not recommended for the treatment of hypertension in nonpregnant patients because of reports of myocardial infarction and death in hypertensive patients with coronary artery
disease.67 Administration of short-acting nifedipine capsules has been, in case reports, associated with maternal hypotension and fetal distress.68,69 If rapid blood pressure control is
desired, then we recommend using parenteral
labetalol or hydralazine until the desired target is
achieved. One study has shown efficacy and
safety of long-acting oral nifedipine in pregnant
78
patients with severe hypertension in pregnancy,70
and given possible untoward fetal effects of shortacting sublingual nifedipine,68,69 we also advocate
use of the long-acting preparation.
A concern with the use of calcium antagonists for BP control in preeclampsia relates to
the concomitant use of magnesium sulfate to
prevent seizures; additive effects between nifedipine and magnesium sulphate were observed in a few cases, leading to neuromuscular blockade, myocardial depression, or
circulatory collapse.71-73 However, these
agents are commonly used together in practice23,74,75 and a recent evaluation76 provided
evidence that they may be used together
without increased risk.
Diuretics
Diuretics commonly are prescribed in patients
with essential hypertension and, given their apparent safety, the National High Blood Pressure
Education Program Working Group on High
Blood Pressure in Pregnancy concluded that
they may be continued during pregnancy (with
an attempt made to decrease the dose; see
later) or used in combination with other agents,
especially for women deemed likely to have
salt-sensitive hypertension.1 Older anecdotal
studies suggested that diuretics might prevent
preeclampsia, a finding that was supported by a
(now discredited) meta-analysis (published in
1985) of nine randomized trials involving more
than 7,000 subjects.77 Although volume contraction might be expected to limit fetal
growth, outcome data have not supported
these concerns.77 However, mild volume contraction with diuretic therapy may lead to hyperuricemia, and in so doing invalidate serum
uric acid levels as a laboratory marker in the
diagnosis of superimposed preeclampsia.
In women already taking, hydrochlorothiazide may be continued during pregnancy; the
use of low doses (12.5-25 mg/d) may minimize
untoward metabolic effects such as impaired
glucose tolerance and hypokalemia.23 Triamterene and amiloride do not appear to be
teratogenic based on a small number of case
reports.23 Spironolactone is not recommended
because of its antiandrogenic effects noted during fetal development in animal models, al-
T. Podymow and P. August
though this was not borne out in an isolated
clinical case.78
SEROTONIN2-RECEPTOR BLOCKERS
Serotonin-induced vasodilation is mediated by
S1 receptors and subsequent release of prostacyclin and nitric oxide. Endothelial dysfunction
and loss of endothelial S1 receptors allows serotonin, whose levels are greatly increased in
pregnancy, to react only with S2 receptors, resulting in vasoconstriction and platelet aggregation. Ketanserin is a selective S2-receptor–
blocking drug that decreases systolic and
diastolic BP in nonpregnant patients with acute
or chronic hypertension. Ketanserin has not
been found to be teratogenic in animals or
human beings, and has been studied during
pregnancy primarily in Australia and South Africa in small trials, which suggest it may be safe
and useful in the treatment of chronic hypertension in pregnancy, preeclampsia, and hemolysis elevation of liver enzymes, low platelets
syndrome.79,80 Ketanserin has not been FDA
approved in the United States.
DIRECT VASODILATORS
Hydralazine (Apresoline; Novartis Pharmaceuticals Corp) selectively relaxes arteriolar smooth
muscle by an as yet unknown mechanism. Its
greatest utility is in the urgent control of severe
hypertension, or as a third-line agent for multidrug control of refractory hypertension. It is effective orally, intramuscularly, or intravenously;
parenteral administration is useful for rapid control of severe hypertension. Adverse effects are
mostly those caused by excessive vasodilation or
reflex sympathetic activation, and include headache, nausea, flushing, or palpitations. Chronic
use can lead, in rare cases, to a pyridoxine-responsive polyneuropathy or to immunologic reactions
including a drug-induced, lupus-like syndrome.
Hydralazine has been used in all trimesters of
pregnancy and data have not shown an association with teratogenicity, although neonatal thrombocytopenia and lupus have been reported.81 It
has been widely used for chronic hypertension in
the second and third trimesters, but its use has
been supplanted by agents with more favorable
side-effect profiles.82 For acute severe hyperten-
Antihypertensive drugs in pregnancy
sion later in pregnancy, intravenous hydralazine
has been associated with more maternal and perinatal adverse effects than intravenous labetalol or
oral nifedipine,26 such as maternal hypotension,
cesarean deliveries, placental abruptions, Apgar
scores less than 7, and oliguria.15 Furthermore,
common side effects of hydralazine, such as headache, nausea, and vomiting, mimic the symptoms
of deteriorating preeclampsia. Effects on uteroplacental blood flow are unclear, likely owing to
variation in the degree of reflex sympathetic activation, and fetal distress may result via a precipitous decrease in maternal pressure.83-85
Isosorbide dinitrate (Isordil; Valeant Pharmaceuticals International), a nitric oxide donor
acting primarily on capacitance vessels, has
been investigated in a small study of gestational
hypertensive and preeclamptic pregnant patients. It did not affect cerebral perfusion pressure despite significant changes in maternal
blood pressure, thus decreasing the risk for
ischemia and infarction when blood pressure is
decreased.86
Sodium nitroprusside is a direct nitric oxide donor that nonselectively relaxes both
arteriolar and venular vascular smooth muscle. Administered only by continuous intravenous infusion, it is easily titrated because it
has a near-immediate onset of action and duration of effect of 3 minutes. Nitroprusside
metabolism releases cyanide, which can
reach toxic levels with high infusion rates;
cyanide is metabolized to thiocyanate, whose
own toxicity usually occurs after 24 to 48
hours of infusion unless its excretion is delayed owing to renal insufficiency. Nitroprusside is seldom used in pregnancy, usually only
in cases of life-threatening refractory hypertension in the moments before delivery.87 Adverse effects include excessive vasodilation
and cardioneurogenic (ie, paradoxic bradycardia) syncope in volume-depleted preeclamptic women.88 The risk of fetal cyanide
intoxication remains unknown; in one literature review of 24 exposed fetuses there did
not appear to be an association between sodium nitroprusside use and fetal demise.89
Given the long experience with hydralazine
and alternative utility of parenteral labetalol
79
or oral calcium-channel blockers, this drug is
considered as a last resort.
ANGIOTENSIN CONVERTING
ENZYME INHIBITORS AND
ANGIOTENSIN RECEPTOR ANTAGONISTS
Angiotensin converting enzyme inhibitors (ACE-I)
and angiotensin-receptor blockers (ARBs) are
both class D drugs according to FDA classification, although we approach them as if contraindicated, especially in the second or third trimesters, because of toxicity associated with reduced
perfusion of the fetal kidneys. Use is associated
with a fetopathy similar to that observed in Potter’s syndrome (ie, bilateral renal agenesis) including renal dysgenesis, oligohydramnios as a result
of fetal oliguria, calvarial and pulmonary hypoplasia, intrauterine growth restriction, and
fatal neonatal anuric renal failure.90,91 ARB
use in pregnancy also has caused similar fetal
renal abnormalities, as well as fetal demise,
attributed primarily to renal failure.92-94
First trimester exposure to ACE-I recently
has been associated with a greater incidence
of malformations of the cardiovascular and
central nervous systems. Of 29,096 pregnancies analyzed, 209 were exposed to ACE-I in
the first trimester alone, associated with a
relative risk of congenital malformation of
2.71, when compared with no antihypertensive medication or other types of antihypertensive medication.95 Whether adverse outcomes are owing to a hemodynamic effect in
the fetus or to specific (nonhemodynamic)
requirements for angiotensin II as a fetal
growth factor is unknown. A more recent
study of pregnancies recorded in the Swedish
Birth Registry reported an increase in cardiac
malformations in fetuses exposed to ACE-Is in
the first trimester, however, similar risks also
were observed in women who reported taking other antihypertensive drugs, particularly
␤-blockers.96 As such, first trimester use of
ACE-I and ARB medications should be
avoided. Because exposure to ACE-Is during
the first trimester cannot be considered safe,
it may be best to counsel women to switch to
alternate agents while attempting to conceive. However, in those who inadvertently
become pregnant while taking ACE-I or ARBs,
80
T. Podymow and P. August
Table 4. Maternal Antihypertensive Medications Usually Compatible With Breastfeeding
ACE-I
Calcium-Channel Blocker
␤-Blocker
Diuretics
Other
Captopril
Enalapril
Quinapril
Diltiazem
Nifedipine
Verapamil
Labetalol
Nadolol
Oxprenolol
Propranolol
Timolol
Furosemide
Hydrochlorothiazide
Spironolactone
Hydralazine
Methyldopa
Minoxidil
Diuretics (furosemide, hydrochlorothiazide, spironolactone) may reduce milk production. Metoprolol is classified as compatible
with breastfeeding, although it is concentrated in human milk. Acebutolol and atenolol should not be used in nursing mothers.
Data from the American Academy of Pediatrics.111
the risk of birth defects increases from 3% to
7%95; it has not been our practice to recommend pregnancy termination. Of note, direct
renin inhibitors might be expected to have
similar effects as ACE-Is and ARBs in pregnancy, however, we are unaware of any reports of their use in pregnancy; they should
be avoided in this setting.
POSTPARTUM HYPERTENSION
In the postpartum period, previously normotensive women have been noted to have an
increase in BP that reaches a maximum on the
fifth postpartum day, and in one study 12% of
patients had a diastolic BP exceeding 100 mm
Hg.97 This is thought to be a consequence of
physiologic volume expansion and fluid mobilization in the postpartum period. Postpartum
there are currently no management guidelines
(as also noted in a recent Cochrane analysis98),
but Tan and de Swiet99 suggested that antihypertensive drugs should be given if the blood
pressure exceeds 150 mm Hg systolic or 100
mm Hg diastolic in the first four days postpartum. Medications may be continued until blood
pressure normalizes and then may be stopped.
This may occur days to several weeks postpartum, and home blood pressure monitoring
by the patient may be helpful in this regard. In
the postpartum period, hypertension as a result
of gestational hypertension and preeclampsia
appears to normalize by 3 months.100 Beyond
this period, if patients continue to require antihypertensive agents to maintain a normal blood
pressure, chronic hypertension may be diagnosed. Choice of antihypertensive agent in the
postpartum period often is influenced by breast
feeding,101 but in general the agents commonly
used in the antepartum period may be continued postpartum (Table 4).
In select cases of women with severe preeclampsia, there appears to be some benefit to
a brief course of furosemide diuresis in the days
postpartum in those patients with hypertension
accompanied by symptomatic pulmonary or peripheral edema.102
A few case reports have reported that nonsteroidal anti-inflammatory agents may contribute to postpartum hypertension,103 and hypertensive effects in nonpregnant individuals are
well documented. Thus, in postpartum patients
who already are hypertensive, nonsteroidal anti-inflammatory agents should be used cautiously, or should perhaps be avoided.
BREASTFEEDING
We could locate no well-designed studies assessing neonatal effects of maternally administered antihypertensive drugs delivered via
breast milk. The pharmacokinetic principles
that govern drug distribution to milk and ensuing exposure to the infant are well established.104,105 Milk, secreted by alveolar cells, is a
suspension of fat globules in a protein-containing aqueous solution with a pH lower than that
of maternal plasma. Factors that favor drug passage into milk are a small maternal volume of
distribution, low plasma protein binding, high
lipid solubility, and lack of charge at physiologic pH. Even when drugs are ingested by
nursing infants, exposure depends on volume
ingested, intervals between drug administration
Antihypertensive drugs in pregnancy
and nursing, oral bioavailability, and the capacity of the infant to clear the drug.106 Neonatal
exposure to methyldopa via nursing is likely
low and it generally is considered safe (Table
4). Atenolol and metoprolol are concentrated in
breast milk, possibly to levels that could affect
the infant; by contrast, exposure to labetalol
and propranolol appears low.107 Although milk
concentrations of diuretics are low and considered safe, these agents, by inducing volume
contraction in the mother, can decrease milk
production significantly.108 There are reports of
calcium-channel blocker transfer into breast
milk,109 but relative infant doses of nifedipine,
verapamil, and diltiazem are low, and all are
safe during breast feeding. Sufficient data exist
for the safety of three ACE-Is: captopril, enalapril, and quinapril; the concentrations are 1%
to 2% of that found in blood, with the infant
receiving approximately 0.03% of the regular
dose.106,110 Based on these findings the American Academy of Pediatrics deems these drugs
compatible with breast feeding.111 There are
currently insufficient data on angiotensin II–
receptor blockers; varied animal data show detectable milk levels and at this time our recommendation is not to use.
CONCLUSIONS
Use of antihypertensive agents in pregnancy for
control of mild to moderate hypertension or for
control of severe hypertension is summarized
in Tables 2 and 3. As of 2011 there appeared to
be little evidence to support the concept that
blood pressure control in pregnant women
with chronic hypertension will prevent the subsequent occurrence of preeclampsia, which is
the cause for most adverse outcomes in these
patients. Because blood pressure decreases in
early pregnancy, decreasing or even discontinuing medication and monitoring often is possible in women with mild or moderate hypertension. Preventing worsening hypertension in the
mother appears to be the greatest benefit in
pregnancy according to available meta-analytic
data, and we recommend a threshold for treatment of most pregnant hypertensive women of
140 to 150 mm Hg systolic, and/or 95 to 100
mm Hg diastolic, to prevent such worsening
hypertension. Acceptable agents include meth-
81
yldopa, labetalol, and nifedipine, in standard
doses. ACE-Is and angiotensin-receptor blockers should be avoided in all trimesters; when
administered in the second and third trimesters
they are associated with a characteristic fetopathy, neonatal renal failure, and death, and thus
are contraindicated. Cohort data lead to recommendations to avoid in the first trimester as
well. Finally, control of severe hypertension in
pregnancy has been studied in a recent metaanalysis, and this suggests that intravenous labetalol or oral nifedipine are as effective as
intravenous hydralazine, with fewer side effects.
Many research questions surrounding hypertension in pregnancy and preeclampsia remain
unanswered. Preconception management of
hypertension, the necessity for antihypertensive agents, specific drug agents, racial differences, and blood pressure levels for initiation of
therapy and treatment targets all remain to be
determined. Current guidelines rely only on evidence from small, largely underpowered trials
and expert opinion. Finally, studies of antihypertensive medication in pregnancy often evaluate the effectiveness of a drug without examining fetal outcomes associated with harm.112
Future studies must include detailed outcomes
of risk and benefit for both the mother and
baby. Better surveillance systems to routinely
monitor adverse events and the number of
women exposed to particular agents are required to guide treatment efficacy, advance our
knowledge of drug safety, and, ultimately, improve treatment options.
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