How should fever caused by trihexyphenidyl be managed?

Management of Fever Caused by Trihexyphenidyl

Fever caused by trihexyphenidyl requires immediate discontinuation of the medication and supportive care, as it can progress to potentially life-threatening hyperthermia.

Mechanism and Recognition

• Trihexyphenidyl, an anticholinergic medication, can cause fever through its parasympatholytic activity that impairs sweating (anhidrosis) and disrupts normal thermoregulation 1
• Drug-induced fever typically appears after 7-10 days of medication administration and resolves after discontinuation of the offending agent 2
• Trihexyphenidyl-induced fever may progress to malignant hyperthermia, a potentially fatal condition, particularly when administered in hot weather or to patients with underlying conditions 1, 3

Management Algorithm

Immediate Actions

1. Discontinue trihexyphenidyl immediately upon suspicion of drug-induced fever 1, 3
2. Implement cooling measures including:
   • Physical cooling methods (cool environment, ice packs, cooling blankets) 1
   • Intravenous fluid administration to maintain hydration 1

Supportive Care

• Monitor vital signs closely, particularly temperature, heart rate, and blood pressure 4
• Perform chest radiography to rule out pneumonia or other infectious causes 4
• Monitor for signs of autonomic instability (irregular pulse, tachycardia, diaphoresis) which may indicate progression to Neuroleptic Malignant Syndrome 1

Pharmacological Management

• Avoid antipyretic medications for the sole purpose of reducing temperature, as they may mask the resolution of the drug-induced fever 4
• Consider small doses of diazepam or short-acting barbiturates if CNS excitation is observed 1
• Do not use phenothiazines as they can intensify anticholinergic toxicity and potentially cause coma 1

Special Considerations

High-Risk Patients

• Elderly patients are more sensitive to anticholinergic effects and at higher risk for complications 1
• Patients with cardiac, liver, or kidney disorders require closer monitoring 1
• Individuals with pre-existing disturbances in sweating are at increased risk for anhidrosis and hyperthermia 1

Complications to Monitor

• Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) with resulting hyponatremia 3
• Progression to heat stroke, particularly in hot weather or when combined with other medications affecting thermoregulation 5
• Neuroleptic Malignant Syndrome, characterized by hyperpyrexia, muscle rigidity, altered mental status, and autonomic instability 1

Prevention of Recurrence

• Avoid rechallenge with trihexyphenidyl, as this can trigger rapid recurrence of fever, potentially with more severe symptoms 2
• Consider alternative medications for the original indication that have lower anticholinergic burden 1
• Educate patients about the importance of avoiding hot environments and maintaining adequate hydration when taking anticholinergic medications 1

Monitoring for Resolution

• Fever typically resolves within days after discontinuation of trihexyphenidyl 2
• In some cases of drug-induced fever, symptoms may persist until the drug is completely eliminated from the body 6
• Follow-up monitoring should continue until temperature has normalized and all signs of anticholinergic toxicity have resolved 3