| Indication | For the management of exogenous obesity as a short-term (a few weeks) adjunct in a regimen of weight reduction based on caloric restriction. |
| Pharmacodynamics | Used to treat obesity, Fenfluramine decreases caloric intake by increasing serotonin levels in the brain's synapses. Fenfluramine acts as a serotonin reuptake inhibitor. It also causes release of serotonin from the synaptosomes. This in turn increases serotonin transmission in the feeding centre of the brain which suppresses appetite. |
| Mechanism of action | Fenfluramine binds to the serotonin reuptake pump. This causes inhbition of serotonin uptake and release of serotonin. The increased levels of serotonin lead to greater serotonin receptor activation which in turn lead to enhancement of serotoninergic transmission in the centres of feeding behavior located in the hypothalamus. This suppresses the appetite for carbohydrates. |
| Absorption | Fenfluramine is well-absorbed from the gastrointestinal tract, and a maximal anorectic effect is generally seen after 2 to 4 hours. |
| Volume of distribution | Not Available |
| Protein binding | Not Available |
| Metabolism | Hepatic. |
| Route of elimination | Not Available |
| Half life | 20 hours |
| Clearance | Not Available |
| Toxicity | Agitation and drowsiness, confusion, flushing, tremor (or shivering), fever, sweating, abdominal pain, hyperventilation, and dilated non-reactive pupils seem frequent in fenfluramine overdosage. Reflexes may be either exaggerated or depressed and some patients may have rotary nystagmus. Tachycardia may be present, but blood pressure may be normal or only slightly elevated. Convulsions, coma, and ventricular extrasystoles, culminating in ventricular fibrillation, and cardiac arrest, may occur at higher dosages. Less than 5 mg/kg are toxic to humans. Five-ten mg/kg may produce coma and convulsions. Reported single overdoses have ranged from 300 to 2000 mg; the lowest reported fatal dose was a few hundred mg in a small child, and the highest reported nonfatal dose was 1800 mg in an adult. Most deaths were apparently due to respiratory failure and cardiac arrest. Toxic effects will appear within 30 to 60 minutes and may progress rapidly to potentially fatal complications in 90 to 240 minutes. Symptoms may persist for extended periods depending upon the dose ingested. |