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The
WHO Guide to Good Prescribing (Table
2) was demonstrated to be effective in a randomised trial
5,
and other authors have subsequently also recommended the P-drug
approach to improving prescribing. 6–9 This
approach is also the basis of a web based prescribing curriculum
developed by the National Prescribing Service for senior medical
students.10
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Case
history
Lionel is 62 years old and has had three documented blood
pressures over 140/90 as well as 24 hour ambulatory blood pressure
monitoring showing a mean daytime BP of 162/82. He is slightly
overweight (BMI 28), is an ex-smoker, and drinks 2–3 glasses of
wine per night. He has some arthritis in his knees that he takes
Celebrex® (celecoxib) for. He also
has diet controlled diabetes, with no
evidence of diabetic complications. |
Using
the WHO Guide to Good Prescribing
1.
Make the diagnosis
OK, this bit is easy: hypertension.
2.
Set the therapeutic goal for the individual patient
The therapeutic goal is what you want your therapy to achieve put in
terms of a meaningful outcome for the patient. A useful way of thinking
of it is that the therapeutic goal is the answer to the patient’s
question: ‘Why am I taking this medication’?
Hence,
in our example of managing hypertension, the therapeutic goal is to
prevent cardiovascular events rather than just reducing the blood
pressure per se.
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3.
Decide on therapeutic approach
This is a decision about how best to achieve the therapeutic goal. For
Lionel, this would mean using pharmacological as well as non-drug therapy
(weight loss, salt restriction) to reduce his blood pressure.
Consideration should be given to ceasing the Celebrex as this can
aggravate hypertension. 11 This
step also involves assessing and addressing his lipids, dietary
advice, or consideration of aspirin as primary prevention as all of
these are relevant in preventing a cardiovascular event,
independently of blood pressure.
4.
Choose a drug class
The choice is based on their comparative efficacy, safety, cost and
suitability.
Efficacy
In terms of hypertension all drugs have similar efficacy for reducing
blood pressure except for thiazides which are particularly effective for
isolated systolic hypertension.12
Our goal for Lionel is preventing cardiovascular events and some
differences in outcomes are emerging from meta-analysis of hypertension
studies, particularly showing that calcium channel blockers may not be
as effective in preventing cardiac events13.
There is also evidence from the HOPE study14
that diabetic patients may get a mortality benefit from
angiotensin converting enzyme (ACE) inhibitors independent of their
effect on blood pressure. Angiotensin converting enzyme inhibitors would
also be effective in preventing diabetic renal complications, so in
terms of efficacy, ACE inhibitors would be our first choice, followed by
thiazides.
Safety
When considering the safety of a drug it is important to consider the
frequency as well as the severity of adverse reactions. It is also
important to recognise special groups who may be particularly at risk of
adverse reactions. The incidence of withdrawal due to
adverse reactions with different antihypertensives has
been shown to be similar in blinded head-to-head studies.13,15–17
However, some patients may have certain pre-existing
conditions that place them at special risk of adverse effects with
certain agents,
e.g. gout with thiazides. |