PARIS -- French doctors said Friday that experiments in which HIV patients temporarily stopped taking their cocktail of anti-retrovirals to avoid some of their side-effects and then resumed taking the drugs were showing dramatic promise. The technique was tried out on a small group of U.S. patients two years ago and HIV researchers have been trying it on bigger groups of volunteers ever since in order to fine-tune it. Anti-retrovirals are the prime clinical weapon in the fight against the Human Immunodeficiency Virus (HIV). In many people, they have been found to suppress levels of HIV to below detectable levels. But this does not mean that the virus is eliminated. It holes up somewhere -- the main suspected refuge is the lymph glands -- and bounces back if the drugs are stopped. Other than their cost, which is prohibitive for poor countries bearing the brunt of the AIDS epidemic, the anti-retrovirals have significant side-effects, notably a huge buildup in abdominal fat but also resistance to insulin, a bigger risk of heart attacks and rise in cholesterol levels. Doctors speaking at a seminar organized by France's National Agency for AIDS Research (ANRS) reported enthusiastically on experiments under which patients temporarily halted taking the anti-retrovirals. Among newly-infected individuals, "therapy interruption has had no short-term adverse effects and can be conducted safely," AFP quoted Bruno Hoen of Saint-Jacques Hospital in the eastern city of Besancon, who is coordinating a trial called Primstop. The success was even more marked among patients who had suffered repeated failures with anti-retrovirals or were even at an advanced stage of infection, said Christine Katlama of Paris's Piete-Salpetriere Hospital. Two trials are being conducted in France. They began in November 2001 and the results are expected to be published shortly. One cycle calls for stopping the drugs for two months then resuming it for the two months, followed by another two-month interruption, and so on. The other trial calls for a stoppage of one month, followed by a resumption of three weeks. The specialists added that for patients whose viral levels had been successfully stabilized at low levels by the anti-retrovirals, it was probably advisable to wait six months before initiating the start-stop program. And they caution that no patient should take the stop-start program without close medical supervision.