Monoamine oxidase inhibitors fenfluramine

The amphetamines should not be used together with or within 14 days of any monoamine oxidase inhibitors severe hypertensive reactions and on occasion confu-sional states (for example with fenfluramine) can occur (SED-9, 9). 

Anorectic drugs, which are structurally related to the amphetamines, act mainly on the satiety centre in the hypothalamus and also increase general physical activity (1). All of them, except fenfluramine, stimulate the central nervous system and can cause restlessness, nervousness, irritabihty, and insomnia. Adverse effects also occur through sympathetic stimulation and gastrointestinal irritation. Drug interactions can occur with monoamine oxidase inhibitors. Dexamfetamine, phenmetrazine, and benzfetamine can cause dependence. Some of them have been associated with cardiac valvulopathy and primary pulmonary hypertension (2). 

Anorectic drugs act mainly on the satiety centre in the hypothalamus (1). They also have metabohc effects involving fat and carbohydrate metaboUsm. Most of them are structurally related to amfetamine and increase physical activity. Their therapeutic effect tends to abate after some months, and part of this reduction in effect may be due to chemical alterations in the brain. Fenfluramine commonly produces drowsiness in normal doses, but has stimulaut effects in overdosage. Dexamfetamine, phenmetrazine, and benzfetamine all tend to cause euphoria, with a risk of addiction. Euphoria occasionally occurs with amfepramone (diethylpropion), phentermine, and chlorphentermine, but to a much lesser extent. Some adverse effects are due to sympathetic stimulation and gastrointestinal irritation these may necessitate withdrawal but are never serious. There are interactions with monoamine oxidase inhibitors and antihypertensive drugs. 

Fenfluramine can cause acute confusion if it is given together with monoamine oxidase inhibitors (SED-9, 9). 

Maher TJ, Ulus IH, Wurtman RJ. Phentermine and other monoamine-oxidase inhibitors may increase plasma serotonin when given with fenfluramines. Lancet 1999 353(9146) 38. 

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