Prescribing by numbers: pharmacoeconomic consideration

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Editor, – Referring to comments made by P. Neeskens (Aust Prescr 2000;23:115) on the usefulness of the number needed to treat (NNT), it is worth mentioning that the figures were misquoted. The original article by Eve Hurley (Aust Prescr 2000;23:38) stated that X = event rate control was 4.1% and that Y = event rate active (with gemfibrozil) was 2.7%. In Dr Neeskens' comments these two figures were transposed.

While it may be true that the NNT does not always give a feel of the relevance of an intervention, it certainly does provide a useful measure for comparing interventions when pharmacoeconomic evaluations are performed. From the Helsinki Heart study, it can be calculated that to treat the 71 men for 5 years with gemfibrozil just to prevent one event would cost: 220 (ZAR) x 12 (months) x 71 (men) x 5 (years) = 937 200 ZAR (South African Rands) in drug costs alone. This is equivalent to $220 000. If there is a cost-effective non-pharmacological intervention or an alternative drug that provides the same or similar relative risk reduction (of 34% as quoted) then the use of NNT will help in decision-making for policy-makers as well as clinicians.

N. Malangu
Medunsa School of Pharmacy
South Africa