Portal de Periódicos da CAPES

The meaning and importance of drug potency in medicine

1966; Wiley; Volume: 7; Issue: 5 Linguagem: Inglês

10.1002/cpt196675577

1532-6535

Mark Weatherall,

Epilepsy research and treatment

The term “potency” is ambiguous, because it may refer to the quantity of drug necessary to produce a given effect, or it may refer to the maximum response which can be achieved with the drug. In the first sense, cyclopenthiazide is more potent than frusemide, and in the second sense the reverse is true. Potency cannot be measured in precise and absolute terms without detailed specification of the method of measurement, and then it becomes an excessively arbitrary measurement. Relative potency is more easily determined, but it also is variable according to the circumstances in which it is assessed. An approximate estimate of potency is afforded by the dose ordinarily used therapeutically. For some groups of drugs, variation in effective dose is enormous and for others, quite small. The causes of such variations are not well known, but probably involve the cumulation of several separate factors. Differences in maximal effect generally indicate a different mode of action and raise doubts about the strict comparability of the drugs concerned. Such differences have definite therapeutic utility. Otherwise high potency (in the sense of small effective dosage) has some advantages and some disadvantages to a therapist and is, at best, a minor merit in most circumstances.