Excessive sweating + Fenfluramine
Fenfluramine is known to produce excessive sweating, a physical effect. Profuse perspiration exceeding normal thermoregulatory needs, common with stimulants and empathogens, contributing to dehydration risk.
About Excessive sweating
Excessive sweating (diaphoresis) during psychoactive substance use refers to perspiration that significantly exceeds the amount needed for normal temperature regulation. Users may find themselves drenched in sweat despite being in a comfortable temperature environment and without engaging in strenuous physical activity. The sweating can be generalized across the entire body or concentrated in specific areas such as the palms, forehead, back, and underarms.
The mechanism varies by substance class. Sympathomimetic stimulants (amphetamines, cocaine, MDMA) activate the sympathetic nervous system, increasing the output of eccrine sweat glands through both direct adrenergic stimulation and indirect effects via elevated metabolic rate and body temperature. Serotonergic substances can trigger sweating through stimulation of central thermoregulatory pathways in the hypothalamus. During opioid withdrawal, sympathetic rebound after chronic opioid-mediated suppression produces profuse sweating as part of the broader withdrawal syndrome. Some psychedelics produce sweating during the come-up phase as part of a general autonomic activation response.
The clinical significance of excessive sweating lies primarily in its contribution to dehydration and electrolyte depletion. Sustained heavy sweating can deplete the body's water and sodium reserves rapidly, particularly when combined with physical activity (dancing), warm environments, and inadequate fluid intake. Dehydration impairs thermoregulation further, creating a dangerous positive feedback loop. Conversely, awareness of sweating and dehydration risk has led some MDMA users to overcompensate by drinking excessive water, which can cause equally dangerous hyponatremia (water intoxication).
Management involves drinking water or electrolyte-containing beverages at a moderate, steady rate (approximately 500ml per hour during physical activity), wearing breathable clothing, taking breaks in cool environments, and monitoring urine color as an indicator of hydration status. If sweating is accompanied by high fever, confusion, or cessation of sweating despite overheating, immediate medical attention is required. The sweating itself, while uncomfortable and socially conspicuous, is not inherently dangerous -- it is the downstream consequences of fluid and electrolyte loss that pose the real risk.