Download APPOPRIATE PRESCRIBING MEDICINE

APPOPRIATE PRESCRIBING MEDICINE
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Evaluate and clearly define the patient's problem
Specify the therapeutic objective.
Select the appropriate drug therapy.
Initiate therapy with appropriate details and consider
nonpharmacologic therapies.
Give information, instructions, and warnings.
Evaluate therapy regularly (e.g., monitor treatment
results, consider discontinuation of the drug) .
Consider drug cost when prescribing.
Use computers and other tools to reduce prescribing
errors.
Primum non nocere
• Hippocrates' advice still holds today.
• Prescribe only where necessary, and consider benefits versus
risks.
• Involve the patient in decisions about their care and respect
patient autonomy.
• Note the patient's age, medical history (especially of any
hepatic or renal dysfunction) and any concurrent medication.
• Think about dosage carefully; manufacturers' recommended
doses are based on population studies and assume 'one dose
fits all'. However, there are genetic differences.
• New drugs are often marketed at the highest therapeutic level
to demonstrate effectiveness in large numbers of patients but
companies are not required to provide data on lowest
effective dose.
Safe prescribing
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Evidence-based prescribing
Interaction with other drugs
Concordance, tolerability and formulation
Adverse effects
Checking dosages
Using prescribing formularies
Key recommendations for practice
• Scenario 1: A five-year-old boy who had pink eye and a clear ocular
discharge was started on antibiotic drops four days ago and initially
improved, but today the redness and irritation has returned.
• Scenario 2: A patient seen yesterday for a sleep-depriving cough was
started on antibiotics, but the cough still kept her awake last night.
• Scenario 3: A generally healthy 70-year-old woman who takes
nonsteroidal anti-inflammatory drugs (NSAIDs) for her osteoarthritis now
reports ankle edema. In your absence, a colleague had started her on a
calcium channel blocker for newly diagnosed hypertension.
• Scenario 4: A 20-year-old woman with sinus pain who was prescribed a
fluoroquinolone by the overnight call physician called this morning to
request a cheaper alternative medication.
• Scenario 5: A 29-year-old woman has presented to the office. She is
obese, has type 2 diabetes, and is reporting elevated blood pressures
measured at home and at work. You are considering starting her on an
angiotensin-converting enzyme inhibitor.
Evaluate and Clearly Define the
Patient's Problem
• In scenario 1, the child treated with antibiotic drops likely
had a viral conjunctivitis that did not need specific
treatment. If the child has become sensitive to the
prescribed medication, his recurrent symptoms represent
morbidity related to an unnecessary prescription.
• In scenario 4, it is assumed that the woman with sinus pain
was diagnosed with a bacterial infection over the
telephone on the basis of a symptom, rather than as part of
an examination. Prescribing a quinolone to a woman of
childbearing age exposes her child to serious teratogenic
side effects if she turns out to be pregnant. Defining the
problem clearly as “sinus pain in a woman of childbearing
age” might have led to a more appropriate management
course
Specify the Therapeutic Objective
• Specifying the therapeutic objective allows physicians to
direct prescribing to a clear goal with expected outcomes.
This can be illustrated using several of the clinical scenarios.
In scenario 5, which involves the woman with diabetes and
the added diagnosis of hypertension, one clear therapeutic
objective would be to obtain sustained blood pressure
readings of less than 130/80 mm Hg.
• In scenario 2, which involves the patient with nocturnal
cough, the objective of restoring sleep was not met with
the antibiotic prescription; the antibiotic was most likely
unnecessary. For the woman with sinus pain (scenario 4),
even if an antibiotic was necessary, prescribing a
medication that the patient could not afford clearly missed
the therapeutic objective.
Select the Appropriate Drug Therapy
• The WHO guide suggests that physicians develop
a formulary of personal drugs (P-drugs). P-drugs
are effective, inexpensive, well-tolerated drugs
that physicians regularly prescribe to treat
common problems. Detailed guidance on
developing a personal formulary can be found in
the WHO manual, which is available at
http://whqlibdoc.who.int/hq/1994/WHO_DAP_9
4.11.pdf.2 The STEPS (Safety, Tolerability,
Effectiveness, Price, Simplicity) framework also
can help with building a P-drug formulary.
Select the Appropriate Drug Therapy
• In scenario 3, which involves the patient with
osteoarthritis, inappropriate prescribing may have
been harmful. Her hypertension may be a side effect of
the NSAID she was receiving, and her ankle edema
could be a side effect of the antihypertensive she was
receiving. Perhaps the NSAID should have been
discontinued and an adequate dose of acetaminophen,
taken three or four times daily, should have been
prescribed for her pain rather than adding another
medication and inducing a second side effect. This
example illustrates that it is important to consider a
patient's age, chronic disease status, and other
medications currently being taken before choosing a
treatment.
Initiate Therapy with Appropriate Details and
Consider Nonpharmacologic Therapies
• Prescriptions should be clear, legible, and written in
plain language. The National Coordinating Council on
Medication Error Reporting and Prevention
recommends eliminating most abbreviations for
medication instructions, such as qd (daily), qid (four
times daily), and qod (every other day). They also
recommend eliminating abbreviations for drug names,
such as MSO4 (morphine sulfate). To be effective,
prescribers should eliminate nonstandard
abbreviations that are easily misread, such as nonnative language characters (e.g., μ). Using plain native
language for all prescription writing allows the patient
to read and draw attention to any errors.
Initiate Therapy with Appropriate Details and
Consider Nonpharmacologic Therapies
• Prescriptions should include specific indications for
anticipated duration of therapy. For example, write out
“as needed for severe back pain” instead of using the
abbreviation prn (as needed). Adding the statement,
“instructions in Spanish please,” to the prescription
(perhaps implemented as a check box on the
prescription form) offers a safety net for physicians and
pharmacists to reduce prescribing errors for Spanishspeaking patients. Patients taking complex
prescriptions like prednisone tapers may need
additional written instructions, as may visually
impaired patients who have difficulty reading medicine
bottle labels. Physicians should consider reducing
transcription errors by prescribing electronically
Consider Nonpharmacologic
Therapies
• Nonpharmacologic therapy remains an important
treatment option. In scenario 5, the woman with
diabetes and the added diagnosis of hypertension may
not need medication if she loses weight and exercises.
A patient with chronic headaches may respond to
relaxation training, and a patient with insomnia may
improve with better sleep hygiene. Studies have
shown that physicians often write prescriptions of
doubtful benefit because of perceived pressure to
prescribe medications. However, these perceptions
may be inaccurate. Asking a patient directly about
therapeutic goals may shed light on his or her
willingness to use nonpharmacologic options when
available.
Give Information, Instructions, and
Warnings
• Physicians should educate patients about the
intended use, expected outcomes, and potential
side effects for each prescribed medication
• it is important to address the common and the
rare but serious ones
• Physicians must describe how the medication
should (and should not) be administered,
including any important relationships to food,
time of day, and other medications being taken
by the patient
Give Information, Instructions, and
Warnings
• Physicians also may want to highlight special drugrelated information such as avoiding alcohol when
taking metronidazole (Flagyl), staying out of the sun
when taking tetracycline, and the possibility of sexual
side effects with selective serotonin reuptake
inhibitors. Explaining that certain side effects are timelimited can help prevent a patient from discontinuing a
needed therapy. Patients can demonstrate their
understanding of the medication by repeating back
pertinent information. At the end of the visit, the
prescriber should ensure that the patient knows when
to return for monitoring and whether therapy
continues after this single prescription
Evaluate Therapy Regularly
• Systematically reviewing medications at every visit allows the
prescriber to monitor treatment effectiveness and reduce
problems, particularly in older patients who are most
susceptible to polypharmacy.
• A medication review may include revisiting a diagnosis,
evaluating possible side effects, searching for drug
interactions, and ceasing unnecessary medications.
• A review also helps avoid the prescribing cascade, which
involves a physician adding additional drugs to a patient's
regimen to treat side effects of other medications.
Consider Drug Cost When Prescribing
• Physicians often fail to consider cost as an important
prescribing factor
• In one study, two thirds of older patients planned to
underuse their medications because of cost. Even for
patients not requiring chronic medications, filling a
prescription that costs the equivalent of several days'
pay can be an unpleasant shock.
• Asking about a patient's access to a medical
prescription card can help to avoid formulary conflicts
and delays in starting therapy.
• A local pharmacist also can suggest alternatives that
decrease cost.
Writing prescriptions
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if you are hand-writing one,
write legibly in indelible inkdate the prescription and state the full name and
address of the patient.
All prescriptions should be signed by the prescriber.
It is a legal requirement in the case of prescription-only medicines to state the age
for children under 12 years, but it's good practice to do so in all cases.
Other things to take care of include:
Write generics unless there are bioavailability issues, as this will enable the
pharmacist to dispense any suitable preparation, avoiding expense and delay.
Avoid unnecessary use of decimal points (eg 3 mg, not 3.0 mg).
For quantities less than 1 gram, write in milligrams (eg 500 mg, not 0.5 g).
For quantities less than 1 milligram, write in micrograms (eg 100 micrograms, not
0.1 mg).
Don’t abbreviate micrograms, nanograms or units. Use millilitres (ml or mL) not
cubic centimeters or c.c.
Writing prescriptions
• Schedules should preferably be written in native language, without
abbreviation
• For prn dosage, state minimum dose interval and maximum total amount.
• Specify the strength and quantity. In the absence of this information the
pharmacist will attempt to contact you. If unable to do so, they can use
their discretion and professional judgement to dispense up to five days'
worth of treatment or appropriate amounts of combination packs or oral
contraceptives. If they have insufficient information to make a judgement,
they will return the prescription to you.
• If you want anything other than the name, strength, and dosage of the
tablets to appear on the label, write it on the prescription in inverted
commas - eg 'Sedative Tablets'.
• Avoid abbreviations of drug names and preparations as these can be
misinterpreted.
• Don't invent compound generic names, especially for sustained-release
preparations.
Prescribing in children
• Children, and particularly neonates, differ
from adults in their response to drugs. Special
care is needed in ensuring the drug prescribed
is appropriate and that the correct dosage is
given, especially in the neonatal period.
Factors affecting drug disposition in
children
• Oral absorption:
– Variable gastric and intestinal transit time: in young
infants, gastric emptying time is prolonged and only
approaches adult values at around 6 months of age. In
older infants, intestinal hurry may occur.
– Increased gastric pH: gastric acid output does not
reach adult values until the second year of life.
– Other factors: gastrointestinal contents, posture,
disease states and therapeutic interventions, such as
drug therapy, can also affect the absorption process
Factors affecting drug disposition in
children
• Distribution:
– Increased total body water: as a percentage of total
body weight, the total body water and extracellular
fluid volume decrease with increasing age. Neonates
require higher doses of water-soluble drugs, on an
mg/kg basis, than adults.
– Decreased plasma protein binding: plasma protein
binding in neonates is reduced as a result of low levels
of albumin and globulins and an altered binding
capacity. High circulating bilirubin levels in neonates
may displace drugs from albumin
Factors affecting drug disposition in
children
• Metabolism:
– Enzyme systems mature at different times and may be
absent at birth, or present in considerably reduced
amounts.
– Altered metabolic pathways may exist for some drugs.
– Metabolic rate increases dramatically in children and
is often greater than in adults. Compared with adults,
children may require more frequent dosing or higher
doses on an mg/kg basis.
• Excretion:
– Complete maturation of renal function is not reached
until 6-8 months of age.
Route of administration and drug
regimes
• Compliance in children is influenced by the
formulation, taste, appearance and ease of
administration of a preparation.
• Prescribed regimens should be tailored to the
child's daily routine. Where possible,
treatment goals should be set in collaboration
with the child.
Route of administration and drug
regimes
• Whenever possible, the use of products which avoid
the need for administration during school hours should
be considered (eg modified-release preparations or
drugs with long half-lives). When administration at
school is unavoidable, consideration should be given to
prescribing and supplying the school time dose in a
separate labelled container.
• Most schools will request written permission from
parents to administer the medicine, or may ask parents
to return to school to give the medicine themselves.
• Whenever possible, painful intramuscular (IM)
injections should be avoided in children.
Prescription writing
• Inclusion of age is a legal requirement in the case of prescriptiononly medicines for children under 12 years of age, but it is
preferable to state the age for all prescriptions for children. It is
particularly important to state the strengths of capsules or tablets.
• Although liquid preparations are particularly suitable for children,
they may contain sugar which encourages dental decay. Sugar-free
medicines are preferred for long-term treatment. Many children are
able to swallow tablets or capsules and may prefer a solid dose
form; involving the child and parents in choosing the formulation is
helpful.
• When a prescription for a liquid oral preparation is written and the
dose ordered is smaller than 5 mL, an oral syringe will be supplied.
• Parents should be advised not to add any medicines to the infant's
feed, since the drug may interact with the milk or other liquid in it;
moreover the ingested dosage may be reduced if the child does not
drink all the contents.
Dosages
• Children are not mini-adults. Pediatric doses
should be obtained from a pediatric dosage
reference text and not extrapolated from the
adult dose.
• When considering drug use in children, the
following age groups should be used: neonate
(birth to 1 month), infant (1 month to 2 years),
child (2 to 12 years) and adolescent (12 to 18
years).
Dose calculation
• Children's doses may be calculated from adult doses by
using age, body-weight, or body-surface area, or by a
combination of these factors. The most reliable
methods are those based on body-surface area.
• Body-weight may be used to calculate doses expressed
in mg/kg. Young children may require a higher dose per
kg than adults because of their higher metabolic rates.
• Other problems need to be considered. For example,
calculation by body-weight in the overweight child may
result in much higher doses being administered than
necessary; in such cases, dose should be calculated
from an ideal weight, related to height and age
Dose calculation
• Body-surface area estimates are more
accurate for calculation of pediatric doses
than body-weight since many physiological
phenomena correlate better to body-surface
area.
• Body-surface area may be calculated from
height and weight by means of a nomogram
or using the Body Surface Area (BSA)
calculator
Rx
• ℞ is a symbol meaning "prescription".
• It is sometimes transliterated as "Rx" or just "Rx".
• This symbol originated in medieval manuscripts as an abbreviation of the
Late Latin verb recipe, the imperative form of recipere, "to take" or "take
thus’’
• Today, when a medical practitioner writes a prescription beginning with
"℞", he or she is completing the command.
• Folk theories about the origin of the symbol ℞ note its similarity to the Eye
of Horus or to the ancient symbol for Zeus or Jupiter, (♃), gods whose
protection may have been sought in medical contexts.
• The word "prescription", from "pre-" ("before") and "script" ("writing,
written"), refers to the fact that the prescription is an order that must be
written down before a compound drug can be prepared. Those within the
industry will often call prescriptions simply "scripts".