When I Use a Word . . .

Good prescribing: benefits, hazards, harms, and risks

    The National Prescribing Centre, now part of the National Institute for Health and Care Excellence, published A Single Competency Framework for all Prescribers in 2012. A draft of the revised version should appear on the website of the Royal Pharmaceutical Society later this year (see www.rpharms.com/what-s-happening-/news_show.asp?id=2666), and all prescribers should read it when it appears and offer comments.

So are you a good prescriber? Well, it helps if you understand what the relevant words mean.

    The framework emphasises the importance of assessing the risks and benefits of therapy, which used to be called the benefit to risk ratio. But benefit is a possible outcome, whereas risk is a probability. Since one should compare like with like, the appropriate comparator for benefit is not risk but harm. Let’s see why, by defining the words: benefits, hazards, harms, and risks.

    Benefits are favourable outcomes in individuals or populations. When you prescribe a medicine it may be for prevention (contraception, immunisation), diagnosis (edrophonium in myasthenia gravis), relief of symptoms (analgesia), or cure (penicillin in pneumonia).

    Diseases and medicines both provide hazards, which are potential sources of harm. Risk, whatever you call it (attributable or excess risk, absolute or relative risk), describes the probability of such harms during exposure to the hazard.

    Drug harms are unwanted outcomes: symptomatic hurt (pain, breathlessness); organ damage, either symptomatic (rash, stroke) or asymptomatic (agranulocytosis, QT prolongation); or combinations of these. However, risks can also describe benefits (a good risk, a desirable risk, a preferred risk), even though we’re not used to thinking of the chance of benefit as a risk.

    On the other hand, failure to benefit also constitutes a risk—of harms due to the disease. Failure to take antimalarial drug prophylaxis increases the risk of malaria. Failure of oral contraception, through poor adherence or increased metabolism of the oestrogen in the pill (from induction, say, by rifampicin or carbamazepine), increases the risk of an unwanted pregnancy.

    Withholding treatment of a hypertensive crisis carries risks: acute end organ damage, causing aortic dissection, heart failure, papilloedema, stroke, renal failure, death. Of course, appropriate drug treatment also carries risks, but in hypertensive emergencies the risks are smaller than those of withholding treatment and are more acceptable.

 So, here’s a simple recipe for improving your prescribing in fulfilling the competency framework. Weigh up three probabilities (or risks):

•  The probability of benefit from the treatment.

•  The probability of harm from the treatment.

• The probability of harm if you don’t use the treatment.

Jeff Aronson, clinical pharmacologist，Centre for Evidence Based Medicine, Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK

[email protected]