FDA press release, June 5, 1998. Although physicians may prescribe any drug off-label, many are reluctant to do so. The reason for this is that they put themselves at more risk for a malpractice law suit. Physicians make decisions to prescribe off-label based on clinical experience and clinical studies. However, clinical studies may not reveal medication complications.
Rare complications can arise, and result in law suits.
While pulmonary hypertension was a known side-effect of fenfluramine, heart valve damage was not. For more on the pitfalls of off-label prescribing and other perspectives, see the articles below. Free speech for medicine. Science must be key in off-label drug information. Drug approvals for new indications.