The Therapeutic Products Directorate (TPD) has been informed that serious cardiac adverse reactions have been reported to the FDA by US health professionals following the use of Fen-Phen (a combination of fenfluramine and phentermine).

While the drugs have been approved individually in Canada for use as add-on medication in the short-term (meaning a few weeks to no longer than three months) management of obesity, the use of these two approved products in combination has not been approved. It is, however, known that physicians may prescribe the two drugs in combination for the treatment of obesity.

The Therapeutic Products Directorate advises physicians against prescribing fenfluramine and phentermine in combination, or any other combination of anti-obesity drugs, until further information becomes available.

The US FDA have, in their data base of adverse reactions, a total of 33 reported cases of cardiac valvulopathy in young obese women who were taking Fen-Phen. In Canada, there are one possibly two cases of adverse cardiac events which have been reported to the Bureau of Drug Surveillance.

The cardiac lesions reported to the US FDA were serious, with some patients requiring surgery and heart valve replacements, although no deaths have been reported to-date. The duration of treatment in these patients ranged from one month to 16 months, with an average treatment duration of 10 months. In the majority of cases, the doses of each drug were in the range of dosage recommendations for the use of the individual drugs.

There is no definitive causal relationship that has yet been confirmed between valvular heart disease and the combined use of these products, however the trend is considered to be serious enough to warrant early intervention and information sharing with physicians.

In addition, there have been 6 reported cases in Belgium of similar adverse reactions occurring following the use of another combination of anti-obesity drugs: diethylpropion and fenfluramine.

In Canada, the trade names for Fenfluramine are: PONDERAL and PONDIMIN: for Phentermine: FASTIN and IONAMIN, and for Diethylpropion: TENUATE.

Health Canada will continue to monitor reports of adverse reactions from all sources.

Questions about specific drugs should be addressed to the manufacturers of that drug. Health care professionals are encouraged to report any cases of cardiac valvular disease or any other serious adverse reactions associated with the use of antiobesity drugs, including any combination of anti-obesity drugs to the manufacturer and directly to the Canadian Adverse Drug Reaction Monitoring Program (613)957-0335, Therapeutic Products Directorate, Health Canada, Ottawa, Ontario.

Health Canada Fen Phen Advisory Note