Probable pregabalin and amantadine-containing cold medication intoxication in an adolescent with rhabdomyolysis: Case...

Routine urine toxicology screening may be misleading when adolescents present with acute psychotic symptoms and systemic toxicity after exposure to drugs not included in the screening panel. We report a 17-year-old girl with no known psychiatric or neurologic illness who developed agitation, persecutory delusions, fever, diaphoresis, tachycardia, limb rigidity, and a brief generalized tonic-like episode after suspected repeated nonprescribed pregabalin misuse and misuse of an amantadine-containing over-the-counter cold preparation. Collateral history and medication packaging retrospectively suggested 1200 mg pregabalin per episode with six tablets of the cold preparation per episode, corresponding to estimates of 600 mg amantadine and 1500 mg acetaminophen. Serum or urine concentrations of pregabalin and amantadine were not measured, and the serum acetaminophen concentration or international normalized ratio was not obtained. A limited qualitative urine toxicology screen was negative, but the panel did not include pregabalin, amantadine, acetaminophen, caffeine, or chlorpheniramine. Creatine kinase increased from 9590 to 13,840 U/L. Serum myoglobin exceeded the assay upper limit (>2700 ng/mL) and urinalysis supported myoglobinuria. Renal function remained normal. Troponin I remained normal despite creatine kinase-MB elevation, and cardiac assessment did not support primary myocardial necrosis. Neuroimaging and electroencephalography detected no explanatory abnormality. The working diagnosis was probable mixed-medication intoxication with acute delirium, psychotic symptoms, multifactorial rhabdomyolysis, and spontaneous pneumomediastinum with a small pneumothorax. Treatment consisted of drug withdrawal, hydration, cooling, benzodiazepine-based sedation, short-term antipsychotic treatment for dangerous agitation, and conservative pulmonary observation. Creatine kinase decreased to 495 U/L by day 15. This case highlights the need for collateral medication histories and expanded toxicological testing when routine screening is negative.