IT HAS been hailed as the wonder drug of the 90s - relief in a capsule from the crippling symptoms of clinical depression, eating disorders and even premenstrual tension, without the worrying side effects of other anti-depressants.
But is it being used as a cure-all, a happy drug for people merely suffering from a case of the blues? In the United States and Britain, doctors have been expressing their concern that the drug is not only being handed out to anyone who asks for a little pick-me-up, but that it may be being abused by anorexics as a feel-good weight controller.
Its clinical name is fluoxetine, but 10 million people worldwide know it as Prozac, the trademark for the pill first marketed by the American drug company, Eli Lilly and Company. The same substance has also been marketed as Zeloft, Seroxat and Cipram.
Prozac is prescribed by doctors in more than 60 countries - including Hong Kong. It is the world's top-selling anti-depressant, and is one of the world's most studied medicines.
Prozac works by improving the effect on the brain of a mood-enhancing chemical called serotonin. Neurons in the brain use chemicals to communicate by producing electronic signals which are felt as emotions, thoughts and memories. Prozac stops cells from re-absorbing serotonin.
But its mind-altering ability has led doctors and patients to prescribe and demand the drug for conditions beyond its original target of clinical depression. Today the most popular reason for taking Prozac in the US, though unapproved, is chronic malaise, a feeling of mental uneasiness.
More worrying, say observers, is the growing use by ambitious professionals who use the drug to improve concentration, competitiveness and the ability to stay awake for deadlines.