Which drugs cause hypothermia and how do they do it?

October 5, 2025 •

4 min read

In a study of geriatric inpatients, those taking antipsychotic drugs (APDs) had a hypothermia incidence of 2.6%, compared to 1.3% in those not taking APDs [1.9.1]. Understanding which drugs cause hypothermia is critical for patient safety, especially in vulnerable populations.

Quick Summary

Many common medications can dangerously lower body temperature by interfering with the brain's thermoregulation, causing vasodilation, or reducing heat production. Antipsychotics, sedatives, opioids, and ethanol are primary culprits.

Key Points

Core Mechanism: Many drugs cause hypothermia by disrupting the brain's thermostat (the hypothalamus), increasing heat loss through vasodilation, or reducing heat production by inhibiting shivering [1.5.2].
Major Culprits: Antipsychotics, sedatives, opioids, anesthetics, and ethanol (alcohol) are the most frequently implicated drug classes in causing hypothermia [1.2.1, 1.2.4].
Antipsychotic Risk: Both first and second-generation antipsychotics, like risperidone and olanzapine, are a significant cause of drug-induced hypothermia by altering hypothalamic function [1.2.2, 1.4.1].
Vulnerable Populations: The elderly, individuals with comorbidities like hypothyroidism, and those taking multiple CNS-acting drugs (polypharmacy) are at a significantly higher risk [1.8.4, 1.9.1].
Alcohol's Deception: Alcohol creates a false feeling of warmth by causing vasodilation, which actually accelerates body heat loss and increases hypothermia risk [1.8.5].
Environmental Amplification: The hypothermic effect of any medication is greatly exacerbated by exposure to cold environments [1.8.4].
A Medical Emergency: Drug-induced hypothermia is a serious condition that can lead to cardiovascular events and even death; it requires prompt medical attention for management and rewarming [1.4.5, 1.10.5].

What is Drug-Induced Hypothermia?

Hypothermia is a potentially life-threatening condition defined by a core body temperature below 35°C (95°F) [1.4.5, 1.8.1]. While often associated with exposure to cold environments, it can also be a side effect of various medications, a phenomenon known as drug-induced hypothermia. This occurs when a drug interferes with the body's complex system of thermoregulation [1.4.3]. The risk is not limited to prescription medications; substances like alcohol can also significantly impair the body's ability to stay warm [1.8.5]. In a 2021 study on psychogeriatric inpatients, those treated with antipsychotic drugs (APDs) were found to have a 2.6% incidence of hypothermia, double the rate of non-APD-treated patients [1.9.1]. This underscores the importance of awareness among both clinicians and patients.

How Medications Disrupt Body Temperature Regulation

The human body maintains a stable core temperature through a thermoregulatory center in the hypothalamus, a region of the brain [1.5.2]. Medications can trigger hypothermia by disrupting this system through several primary mechanisms:

Central Nervous System (CNS) Impairment

Many drugs depress the central nervous system, which includes the hypothalamus. This impairment dulls the brain's ability to accurately sense the body's temperature and initiate appropriate responses like shivering to generate heat or vasoconstriction to conserve it [1.5.2, 1.7.3]. General anesthetics, sedatives, and ethanol all act on the CNS, widening the temperature range the body tolerates before triggering a response [1.5.2].

Peripheral Vasodilation

Certain drugs cause peripheral vasodilation, which is the widening of blood vessels near the skin's surface [1.4.3, 1.7.1]. This increases blood flow to the skin, causing a rapid loss of heat to the environment [1.5.2]. Alcohol is well-known for this effect, creating a deceptive feeling of warmth while actually accelerating heat loss [1.8.5].

Reduced Heat Production

Some medications can decrease the body's metabolic rate or directly inhibit shivering, which is the body's primary mechanism for rapidly generating heat through muscle contractions [1.5.1, 1.7.1]. By preventing or reducing these thermogenic responses, drugs leave the body more susceptible to cooling. Opioids and anesthetics are known to reduce shivering thresholds [1.3.2, 1.6.5].

Key Drug Classes That Cause Hypothermia

A wide range of medications has been associated with hypothermia. Some of the most frequently implicated classes include:

Antipsychotics

Both typical (first-generation) and atypical (second-generation) antipsychotics are strongly linked to hypothermia [1.2.2]. Drugs like olanzapine, risperidone, haloperidol, and chlorpromazine can alter thermoregulation by blocking dopamine (D2) and serotonin (5-HT2A) receptors in the hypothalamus [1.4.1, 1.4.4, 1.4.5]. Antipsychotics with strong 5-HT2 antagonism and low D2-receptor affinity may be most likely to induce this effect [1.3.3, 1.9.1].

Sedatives and Hypnotics

This class includes benzodiazepines (e.g., diazepam, lorazepam) and barbiturates (e.g., phenobarbital) [1.2.4]. These drugs cause general CNS depression, which impairs hypothalamic function and reduces muscle tone, thereby decreasing heat production from shivering [1.2.1, 1.5.3].

Opioids

Opioids such as morphine, fentanyl, and oxycodone can cause hypothermia by acting on the hypothalamus and promoting vasodilation [1.5.2, 1.6.5]. They reduce the core temperature thresholds for both shivering and vasoconstriction, making the body less responsive to cold [1.6.5].

Ethanol (Alcohol)

Alcohol is a frequent factor in cases of accidental hypothermia [1.8.3]. It causes peripheral vasodilation, leading to significant heat loss, and also impairs judgment and CNS function, which can lead to prolonged exposure to cold environments [1.7.3, 1.8.5]. Its effects are poikilothermic, meaning it impairs adaptation to both cold and heat [1.7.1].

Anesthetics

General anesthetics like propofol and volatile agents, as well as neuraxial (spinal or epidural) anesthesia, profoundly disrupt thermoregulation. They induce vasodilation, lower the metabolic rate, and inhibit central thermoregulatory control [1.3.2, 1.5.1].

Other Medications

Other drug classes have also been linked to hypothermia, including:

Beta-blockers [1.2.1]
Tricyclic antidepressants [1.7.3]
Oral antihyperglycemics [1.8.1]
Acetaminophen (in overdose) [1.2.3]
Valproic Acid [1.4.2, 1.7.3]

Comparison of Common Hypothermia-Inducing Drug Classes


Drug Class	Examples	Primary Mechanism(s)	Notes
Antipsychotics	Risperidone, Olanzapine, Haloperidol	Hypothalamic disruption via dopamine & serotonin receptor blockade [1.4.1]	One of the most common causes of drug-induced hypothermia [1.2.2].
Sedative-Hypnotics	Diazepam, Phenobarbital, Lorazepam	CNS depression, impaired shivering [1.2.4, 1.5.3]	Risk is compounded when combined with other CNS depressants [1.8.4].
Opioids	Morphine, Fentanyl, Oxycodone	Hypothalamic impairment, vasodilation, reduced shivering threshold [1.5.2, 1.6.5]	Can affect thermoregulation even at therapeutic doses.
Ethanol (Alcohol)	Beer, Wine, Spirits	CNS depression, significant peripheral vasodilation, impaired judgment [1.7.3, 1.8.5]	Creates a false sensation of warmth, increasing risk [1.8.5].
Anesthetics	Propofol, Sevoflurane, Spinal Block	Profound hypothalamic depression, vasodilation, reduced metabolism [1.3.2]	A very common and expected effect during surgery.

Who Is Most at Risk?

Certain individuals are more susceptible to developing drug-induced hypothermia. Key risk factors include:

Advanced Age: The elderly often have a reduced ability to sense cold, a decreased metabolic rate, and impaired vasoconstriction [1.8.4, 1.9.1].
Comorbidities: Conditions like hypothyroidism, sepsis, diabetes, and cardiovascular disease can predispose an individual to hypothermia [1.8.1, 1.8.4].
Polypharmacy: The simultaneous use of multiple medications, especially those that act on the CNS (e.g., antipsychotics plus benzodiazepines), increases the risk [1.8.2, 1.8.4].
Alcohol or Illicit Drug Use: These substances impair judgment and thermoregulation [1.8.3, 1.8.5].
Environmental Exposure: The presence of any of these risk factors is significantly amplified by exposure to a cold environment [1.8.4].

Conclusion

Drug-induced hypothermia is a serious and underrecognized adverse effect of many commonly prescribed medications and other substances. Antipsychotics, sedatives, opioids, and alcohol are among the primary agents capable of disrupting the body's natural ability to maintain its core temperature. Awareness of which drugs cause hypothermia, understanding the underlying mechanisms, and recognizing the populations at highest risk are essential for prevention and timely intervention. Patients, especially the elderly and those on multiple medications, should be mindful of the risks and discuss any concerns with their healthcare provider.

For more information from a trusted medical source, consider visiting the Mayo Clinic's page on Hypothermia. [1.8.5]

Frequently Asked Questions

Yes, in certain situations. For example, an overdose of acetaminophen has been associated with hypothermia [1.2.3]. It's crucial to use all medications as directed.

Antipsychotic drugs are one of the most well-documented classes associated with drug-induced hypothermia, with studies showing a significantly increased incidence in patients taking them [1.2.2, 1.9.1].

Yes. Alcohol causes peripheral vasodilation, which makes you lose body heat faster, even though you might feel warm initially. It also impairs shivering and judgment, increasing the overall risk of hypothermia [1.7.1, 1.8.5].

Early symptoms can be subtle and may include shivering (though it may be absent), confusion, pallor (pale skin), slurred speech, and fatigue [1.9.1, 1.10.5]. In severe cases, a person may appear unconscious with a very weak pulse [1.2.4].

Be aware of your medications' side effects, dress warmly in cold weather, avoid combining alcohol with sedating medications, and discuss your risks with a healthcare provider, especially if you are elderly or have multiple health conditions [1.8.5, 1.10.5].

The elderly often have impaired thermoregulatory responses, such as reduced shivering and vasoconstriction. They are also more likely to have comorbidities and be taking multiple medications (polypharmacy), which collectively increase the risk [1.8.4, 1.9.1].

Yes, certain types of antidepressants, particularly tricyclic antidepressants (TCAs), have been reported to cause hypothermia by affecting central thermoregulation [1.7.3, 1.8.5].