Effect of recommended dosage range on the prescribing of antidepressants.

The aim of the study was to explore the role that suggested dosage range may play in suboptimal prescribing practice of tricyclic antidepressants. Clinicians practising in adult psychiatry were shown a clinical vignette of melancholia (as per DSM-III-R). One of two questionnaires on treatment practices, specifying either 75-200 mg or 75-425 mg of an unnamed tricyclic antidepressant, were randomly distributed to subjects. A highly significant (p = 0.001) difference was found: those who were given a narrow dosage range prescribed an average of 82.5 mg/day less antidepressant than those for whom the dosage range had been widened, indicating that the range within which dosages are recommended affects prescribing practices. When erroneously constrained, the range may contribute toward sub-optimal prescribing practices and as a consequence toward treatment-resistant depression.