Digoxin prescribing in general practice 1967--77.

Data from a survey of general-practitioner prescribing from 1967 to 1977 were examined to see how news of the changed potency of "Lanoxin" tablets in 1972 and of unbranded digoxin in 1975 had affected prescribing patterns. A stong downward trend in average daily dose was found, equivalent to a halving in lanoxin, almost as much in digoxin, and a one-fifth fall in prepared digitalis. This trend, however, preceded the publicity on potency and bioavailability, and in the case of lanoxin was apparent during the time that bioavailability fell. It had two components--reduced frequency of tablets per day, and increased popularity of low-dose tablets. From 1972 the proprietary 250 microgram tablet of lanoxin was prescribed increasingly at the expense of unbranded digoxin, but at a lower daily frequency until 1975. The number of people treated with digoxin and lanoxin has risen overall and constitutes perhaps 6% of those over 65. The determinants of prescribing behaviour are complex.