Can propranolol (beta blocker) lower body temperature?

Propranolol's Effect on Body Temperature

Yes, propranolol can lower body temperature, particularly in cases of centrally-mediated fever following traumatic brain injury and in certain thermoregulatory conditions.

Mechanisms of Action

• Propranolol is a non-selective beta-blocker that crosses the blood-brain barrier due to its lipophilic properties, which contributes to its central nervous system effects 1
• It blocks both peripheral and central effects of adrenaline, which can affect thermoregulatory processes 1
• Propranolol has been shown to reduce centrally-mediated fevers in patients with traumatic brain injury 2

Clinical Evidence for Temperature Reduction

• Case studies have demonstrated that propranolol (20-30 mg every 6 hours) can reduce centrally-mediated fevers by at least 1.5°C within 48 hours in patients with traumatic brain injury 2
• When propranolol was discontinued in these patients, temperatures increased to greater than 38.0°C within 3 days, suggesting a direct temperature-lowering effect 2
• Propranolol has been successfully used to treat central fevers in children with decerebrate posturing following traumatic brain injury 2

Effects on Thermoregulation During Exercise

• During exercise in heat, propranolol can alter thermoregulatory responses:
  • It increases total sweat production compared to placebo, particularly during the initial hour of exercise 3
  • It reduces forearm blood flow at any given core temperature, suggesting altered peripheral vasodilation 4
  • Despite these changes, propranolol doesn't significantly alter core temperature during prolonged exercise 4

Hypothermia and Propranolol Metabolism

• Interestingly, hypothermia affects propranolol metabolism - hepatic metabolic elimination of propranolol is decreased during hypothermic conditions 5
• This creates a potential feedback loop where propranolol-induced temperature reduction could further affect its own metabolism 5

Potential Side Effects and Precautions

• Common side effects of propranolol include bradycardia, hypotension, fatigue, cold extremities, and sleep disturbances 1, 6
• Propranolol is contraindicated in patients with asthma, COPD, bradycardia, heart block, or heart failure 1
• Patients with diabetes should use propranolol with caution as it may mask symptoms of hypoglycemia 1, 7
• In pediatric patients treated for infantile hemangiomas, propranolol-induced temperature changes may be related to hypoglycemia 6

Clinical Applications

• Propranolol's temperature-lowering effect has been specifically documented in treating central fevers following traumatic brain injury 2
• This effect appears most pronounced in patients with symptoms of autonomic dysfunction, including tachycardia and profuse sweating 2
• The temperature-lowering effect may persist until signs of autonomic dysfunction abate 2

In conclusion, propranolol can lower body temperature, particularly in cases of centrally-mediated fever, though the effect varies depending on the clinical context and may be related to its action on autonomic regulation.