When the body’s core temperature rises significantly above the normal range of approximately 98.6°F (37°C), the condition is known as hyperthermia. This is distinct from a fever, which involves a controlled increase in the body’s temperature set point orchestrated by the brain’s hypothalamus, often in response to infection. Drug-induced hyperthermia results from an imbalance where the body generates too much heat or cannot efficiently dissipate the heat it creates. This uncontrolled elevation in temperature can be triggered by a wide variety of substances, including both common prescription medications and recreational drugs.
Physiological Processes That Raise Body Temperature
Drugs cause an increase in body temperature by interfering with the body’s natural thermal regulation processes in three primary ways.
The first involves the direct disruption of the hypothalamus, the central control center for temperature regulation in the brain. This area normally functions like a thermostat, but certain drugs can confuse or override its signals, leading to dysregulation.
The second major mechanism is increased heat generation, often through excessive metabolic activity. Some drugs dramatically accelerate metabolic processes, such as increasing muscle activity or triggering a hypermetabolic state.
The third mechanism involves impairing the body’s ability to lose heat, which is achieved mainly through sweating and peripheral vasodilation. Sweating cools the body through evaporation, while vasodilation—the widening of blood vessels near the skin’s surface—allows warm blood to move closer to the environment for heat exchange. Drugs that block these cooling responses can cause heat to accumulate quickly.
The severity of drug-induced hyperthermia depends on which mechanisms are affected, sometimes leading to core temperatures over 105.8°F (41°C). This uncontrolled heat can cause cellular damage, leading to severe complications like rhabdomyolysis, kidney failure, and multi-organ failure.
Drug Categories That Increase Heat Production
A number of substances raise body temperature by accelerating internal metabolic processes, creating a dangerous heat load. Sympathomimetics, a class of drugs that mimic the effects of adrenaline and noradrenaline, are a major contributor. Substances like cocaine, amphetamines, and MDMA (ecstasy) cause massive releases of these stimulating neurotransmitters, leading to increased motor activity and a sustained increase in metabolism. This intense internal activity leads to a hypermetabolic state where heat is produced faster than the body can dissipate it.
Specific psychiatric medications can also trigger syndromes characterized by severe muscle rigidity, which acts as an intense form of heat production. Serotonin syndrome, often linked to high doses or combinations of serotonergic drugs like SSRIs and MAOIs, is characterized by muscle clonus and hyperreflexia.
Another distinct syndrome is Neuroleptic Malignant Syndrome (NMS), primarily associated with the use of antipsychotic medications. NMS causes a severe form of muscle stiffness often described as “lead pipe” rigidity, along with an altered mental state and autonomic instability.
A separate condition is Malignant Hyperthermia, an inherited disorder triggered by volatile anesthetic agents and the muscle relaxant succinylcholine. This syndrome causes an uncontrolled release of calcium within muscle cells, resulting in sustained, severe muscle contraction and a rapid rise in body temperature.
Drug Categories That Impair Cooling
While some drugs force the body to generate excess heat, others prevent the body from releasing the heat it produces, effectively trapping it inside.
The most prominent class of drugs that impairs cooling is anticholinergics, which work by blocking the neurotransmitter acetylcholine. Since acetylcholine is required to activate the sweat glands, blocking its action severely compromises the ability to sweat—the body’s most effective cooling mechanism. Without the ability to cool through evaporation, a person taking these drugs may quickly overheat. This anticholinergic effect is found in medications including certain antihistamines, tricyclic antidepressants, and some older generation antipsychotics.
Other drug classes impair cooling by constricting blood vessels, which hinders peripheral vasodilation. Beta-blockers, for example, reduce the ability of blood vessels to widen, limiting the shunting of warm blood to the skin surface for heat exchange. Stimulant drugs also cause vasoconstriction, creating a dangerous combination of generating more heat while trapping it within the body.
Diuretics, commonly used for high blood pressure, also indirectly impair the cooling system by causing dehydration. By increasing the excretion of water and salts, diuretics reduce the body fluid volume available for sweat production, limiting heat dissipation.
Recognizing and Responding to Elevated Body Temperature
Recognizing the signs of drug-induced hyperthermia is paramount, as the condition can progress rapidly from discomfort to a life-threatening emergency. Early symptoms often include confusion, agitation, and an unusually rapid heart rate. The skin may initially appear flushed and warm, but the cessation of sweating is a particularly dangerous sign, indicating a complete failure of the body’s cooling mechanisms. In more severe cases, the person may develop rigidity, convulsions, or a decrease in their level of consciousness. Any core body temperature reading exceeding 102.2°F (39°C) following drug exposure warrants immediate intervention.
The immediate first aid response is to move the individual to a cool environment and remove any excess clothing to facilitate heat loss. External cooling should be started immediately, using methods such as spraying the skin with water and fanning them vigorously to promote evaporative cooling. Applying ice packs to areas where large blood vessels are close to the surface, like the neck, armpits, and groin, can help rapidly cool the blood. Emergency services should be called immediately, as drug-induced hyperthermia requires professional attention. Unlike a common fever, this condition does not respond to typical fever-reducing medications like acetaminophen or ibuprofen. Medical professionals focus on supportive care, rapid cooling, and, in severe cases, may administer specific medications like benzodiazepines to reduce agitation or muscle activity that is generating heat.