Formal teaching in clinical pharmacology was never part of the curriculum at the American University of Beirut Faculty of Medicine. Based on feedback from students and on recommendations of academic bodies, we have introduced, since June 2008, twice-monthly "rational prescribing" sessions during the required internal medicine rotation in year 4 of medical school. All sessions were designed according to the innovative Team-based Learning format and concluded by having the students practice prescription writing and personal formulary development based on the World Health Organization criteria. Our 18-month experience showed that students were very satisfied with the course and the teaching approach, and that their performance on prescription writing and formulary development had improved. Although further studies are needed to explore the impact of team-based learning on additional performance measures, we recommend it as an effective alternative for teaching clinical pharmacology in medical schools.