Background
A sound knowledge of pathophysiology of a disease and clinical pharmacology and therapeutics (CPT) of a drug is required for safe and rational prescribing. The aim of this study was therefore to assess how adequately the undergraduate CPT teaching had prepared interns in Nigeria for safe and rational prescribing and retrospectively, to know how they wanted the undergraduate curriculum to be modified so as to improve appropriate prescribing. The effect of internship training on the prescribing ability of the interns was also sought.

Methods
A total of 100 interns were randomly selected from the Lagos State University Teaching Hospital (LASUTH), Ikeja; Lagos University Teaching Hospital (LUTH), Idiaraba; General Hospital Lagos (GHL); the EKO Hospital, Ikeja; and Havana Specialist Hospital, Surulere. A structured questionnaire was the instrument of study. The questionnaire sought information about the demographics of the interns, their undergraduate CPT teaching, experience of adverse drug reactions (ADRs) and drug interactions since starting work, confidence in drug usage and, in retrospect; any perceived deficiencies in their undergraduate CPT teaching.

Results
The response rate was 81%. All the respondents graduated from universities in Nigeria. The ability of the interns to prescribe rationally (66, 81.4%) and safely (47, 58%) was provided by undergraduate CPT teaching. Forty two (51.8%) respondents had problems with prescription writing. The interns would likely prescribe antibiotics (71, 87.6%), nonsteroidal analgesics (66, 81.4%), diuretics (55, 67.9%), sedatives (52, 62.9%), and insulin and oral hypoglycaemics (43, 53%) with confidence and unsupervised. The higher the numbers of clinical rotations done, the more confident were the respondents to prescribe unsupervised (?2 = 19.98, P < 0.001). Similarly, respondents who had rotated through the four major clinical rotations and at least a special posting (?2 = 11.57, P < 0.001) or four major clinical rotations only (?2 = 11.25, P < 0.001) were significantly more confident to prescribe drugs unsupervised.

Conclusion
Undergraduate CPT teaching in Nigeria appears to be deficient. Principles of rational prescribing, drug dose calculation in children and pharmacovigilance should be the focus of undergraduate CPT teaching and should be taught both theoretically and practically. Medical students and interns should be periodically assessed on prescribing knowledge and skills during their training as a means of minimizing prescribing errors.