Letter: Fenfluramine and dreaming

Drug-induced nightmares

OBJECTIVE

To compile and assess the English-language literature on drug-induced nightmares, excluding nightmares secondary to drug withdrawal or drug-associated night terrors.

DATA SOURCES

Published articles, letters, case reports, and abstracts in English were identified by MEDLINE (1966-May 1998) searches using the search term nightmares, chemically induced. Additional articles were obtained from bibliographies of retrieved articles.

DATA EXTRACTION

All case reports of drug-induced nightmares were evaluated using the Naranjo algorithm for causality. Clinical studies of drugs that reported nightmares as an adverse effect were assessed for frequency of occurrence.

DATA SYNTHESIS

Nightmares, defined as nocturnal episodes of intense anxiety and fear associated with a vivid, emotionally charged dream experience, are generally classified as a parasomnia. Possible pharmacologic mechanisms for drug-induced nightmares, such as REM suppression and dopamine receptor stimulation, are reviewed. However, the vast majority of therapeutic agents implicated in causing nightmares have no obvious pharmacologic mechanism.

CONCLUSIONS

Assessing causality with an event such as a nightmare is difficult because of the high incidence of nightmares in the healthy population. Using qualitative, quantitative, and possible pharmacologic mechanism criteria, it appears that sedative/hypnotics, beta-blockers, and amphetamines are the therapeutic modalities most frequently associated with nightmares. These drug classes have a plausible pharmacologic mechanism to explain this effect. Dopamine agonists also have evidence of causality, with dopamine receptor stimulation as a possible pharmacologic mechanism.

Effect of dexfenfluramine on sleep in healthy subjects

The acute effects of dexfenfluramine on nocturnal sleep were studied in ten healthy male subjects by means of sleep EEG recordings and ratings of subjective sleep quality. Four different dosages (3 mg, 7 mg, 15 mg, and 30 mg) were tested, administered over a period of 3 days each. Under 15 mg and 30 mg dexfenfluramine, only slight effects on sleep were observed: 15 mg led to decreased sleep efficiency in the first night of medication, and to reduced percentage of slow wave sleep in the first and third night. A significant lengthening of REM latency was present in the third night under 30 mg dexfenfluramine, without changes in other REM sleep parameters. Daily doses of 3 mg and 7 mg dexfenfluramine did not influence sleep, except for a significant REM latency reduction observed in the first night under 3 mg. Apart from a transient slight impairment under 30 mg, ratings of subjective sleep quality did not mirror any impact of dexfenfluramine. The data suggest that therapeutic dosages of dexfenfluramine only slightly influence nocturnal sleep, which contrasts with the known impact of other anti-obesity agents like the amphetamines. Unlike classical antidepressants, dexfenfluramine does not reduce REM sleep; in light of a hypothetical link between REM sleep reduction and antidepressant action of a drug, dexfenfluramine is not expected to have a pronounced antidepressant effect.