Download VASODILATORS

- If other drug therapies do not achieve the
desired reduction in blood pressure, it is
sometimes necessary to use a direct
vasodilator.
- Most of the vasodilators are reserved for
use in severe hypertension or hypertensive
emergencies.
hydralazine ,minoxidil and nitroprusside.
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- Act directly on vascular smooth muscle to
cause muscle relaxation, leading to
vasodilation and drop in blood pressure.
- They do not block the reflex .
- They are indicated for the treatment of
severe hypertension .
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Nitroprusside is used intravenously; hydralazine is
available for oral, intravenous, and intramuscular;
and minoxidil is available as an oral agent only.
These drugs are rapidly absorbed and widely
distributed. They are metabolized in the liver and
primarily excreted in urine.
They cross the placenta and enter breast milk .
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- The vasodilators are contraindicated in the
presence of known allergy to the drug.
- with any condition that could be
exacerbated by a sudden fall in blood
pressure, such as cerebral insufficiency.
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- These drugs are also contraindicated with
pregnancy unless the benefit to the mother
clearly outweighs the potential risk because
of the potential for adverse effects on the
fetus or neonate.
- If they are needed by a nursing
mother,another method of feeding the baby
should be selected,because of the potential
for adverse effects on the baby.
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The adverse effects most frequently seen with
these drugs are related to the changes in
blood pressure.
These include dizziness, anxiety, and
headache; reflex tachycardia,heart failure,
chest pain, and edema; skin rash and lesions
(abnormal hair growth with minoxidil); and GI
upset, nausea, and vomiting.
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- Cyanide toxicity (dyspnea,headache,
vomiting, dizziness, ataxia, loss of
consciousness, absent reflexes, dilated
pupils,pink color, distant heart sounds, and
shallow breathing) may occur with
nitroprusside, which is metabolized to
cyanide and also suppresses iodine uptake
and can cause hypothyroidism.
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Thiazide and thiazide-like diuretics: bendrofl
umethiazide
(Naturetin), chlorothiazide (Diuril),
hydrochlorothiazide
(HydroDIURIL), hydrofl umethiazide
(Saluron), methyclothiazide (Enduron),
trichlormethiazide
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Potassium-sparing diuretics: amiloride
(Midamor),
spironolactone (Aldactone), and triamterene
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Beta-blockers block vasoconstriction,
decrease heart
rate, decrease cardiac muscle contraction,
and tend
to increase blood fl ow to the kidneys,
leading to a
decrease in the release of renin.
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Beta-blockers used to treat
hypertension include the following agents:
acebutolol
(Sectral), atenolol (Tenormin), betaxolol
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bisoprolol (Zebeta), carteolol (Cartrol),
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(Kerlone),
metoprolol
(Lopressor), nadolol (Corgard), nebivolol
(Bystolic),
penbutolol (Levator), pindolol (Visken),
propranolol
(Inderal), and timolol (Blocadren).
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Alpha-adrenergic blockers inhibit the
postsynaptic
alpha1-adrenergic receptors, decreasing
sympathetic
tone in the vasculature and causing vasodilation,
which leads to a lowering of blood pressure.
However,
these drugs also block presynaptic alpha2receptors,
preventing the feedback control of
norepinephrine
release.
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Alpha-adrenergic blockers include the
following agents: phenoxybenzamine
(Dibenzyline)
and phentolamine (Regitine).
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Alpha1-blockers used to treat hypertension
include the following agents: doxazosin
(Cardura),
prazosin (Minipress), and terazosin (Hytrin).
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Alpha2-blockers used to treat hypertension
include
the following agents: clonidine (Catapres),
guanfacine
(Tenex), and methyldopa (generic).
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