ACTIONS

IONAMIN is a sympathomimetic amine with pharmacologic activity similar to the prototype drug of this class used in obesity, amphetamine (d- and d/amphetamine). Actions include central nervous system stimulation and elevation of blood pressure. Tachyphylaxis and tolerance have been demonstrated with all drugs of this class in which these phenomena have been looked for.

Drugs of this class used in obesity are commonly known as "anorectics" or "anorexigenics." It has not been established, however, that the action of such drugs in treating obesity is primarily one of appetite suppression. Other central nervous system actions, or metabolic effects may be involved.

Adult obese subjects instructed in dietary management and treated with "anorectic" drugs, lose more weight on the average than those treated with placebo and diet, as determined in relatively short- term clinical trials.

The magnitude of increased weight loss of drug-treated patients over placebo-treated patients is only a fraction of a pound a week. The rate of weight loss is greatest in the first weeks of therapy for both drug and placebo subjects and tends to decrease in succeeding weeks. The possible origins of the increased weight loss due to the various drug effects are not established. The amount of weight loss associated with the use of an "anorectic" drug varies from trial to trial, and the increased weight loss appears to be related in proof to variables other than the drugs prescribed, such as the physician-investigator, the population treated, and the diet prescribed. Studies do not .permit conclusions as to the relative importance of the drug and non-drug factors on weight loss.

The natural history of obesity is measured in years, whereas the studies cited are restricted to a few weeks´ or months´ duration; thus, the total impact of drug-induced weight loss over that of diet alone must be considered clinically limited.

The bioavailability of IONAMIN has been studied in humans in which blood levels of phentermine were measured by a gas chromatography method. Blood levels obtained with the 15 mg and 30 mg resin complex formulations indicated slower absorption with a reduced but prolonged peak concentration and without a significant difference in prolongation of blood levels when compared with the same doses of phentermine hydrochloride. The clinical significance of these differences is not known. In clinical trials establishing the efficacy of IONAMIN, a single daily dose produced an effect comparable to that produced by other regimens of "anorectic" drug therapy.

Bookmark this page: