Objective: To analyse associations between indicators for adoption of new drugs and to test the hypothesis that physicians' early adoption of new drugs is a personal trait independent of drug groups.
Methods: In a population-based cohort study using register data, we analysed the prescribing of new drugs by Danish general practitioners. Angiotensin-II antagonists, triptans, selective cyclo-oxygenase-2 antagonists and esomeprazol were used in the assessment. As indicators of new drug uptake, we used adoption time, cumulative incidence, preference proportion, incidence rate and prescription cost and volume. For each measure, we ranked the general practices. Ranks were pair-wise plotted, and Pearson's correlation coefficient ( r) was calculated. Next, we analysed the correlation between ranks across different drug classes.
Results: For all indicators, the general practitioners' adoption of one group of drugs was poorly associated with adoption of others ( r</=0.49), indicating that early adoption of one type of drugs is not associated with early adoption of another. For all drug groups, adoption time adjusted for practice size was only weakly associated with other indicators ( r: -0.56 to -0.27). Indicators, based on cost and volume of drugs, were highly correlated ( r: 0.96-0.99), and the others correlated reasonably well ( r: 0.51-0.91).
Conclusions: Within drug groups, indicators of drug adoption, except for adoption time, correlate reasonably well. However, the theory that physicians' early adoption of new drugs is a personal trait independent of the type of drug could not be confirmed. The notion of the early-drug-adopting general practitioner may be mistaken.