Amphetamine toxicity masked by concomitant γ-hydroxybutyrate (GHB) ingestion

We report a case of a young male with amphetamine toxicity initially obscured by concomitant use of gamma-hydroxybutyrate (GHB), and the sympathomimetic symptoms emerged after GHB's effects receded. A 24-year-old unconscious man presented to emergency department showed the following vital signs upon admission: blood pressure 136/58 mmHg; heart rate 79 bpm; SpO2 87% under ambient air; body temperature 36.1 °C; Glasgow Coma Scale score 3. The pupils were not dilated. Arterial blood gas test revealed respiratory acidosis (pH = 7.229, pCO2 = 64.4 mmHg, pO2 = 42.3 mmHg, HCO3 = 26.3 mmol/L). Intubation was performed and the patient was transferred to intensive care unit. The patient regained consciousness and became agitated in association with sinus tachycardia (heartrate 143 bpm; blood pressure 173/61 mmHg). A few hours later, he experienced abrupt desaturation (SpO2 65%) and profuse, pinkish, frothy sputum. Chest radiography revealed a bat-wing perihilar shadowing, and computed tomography showed bilateral ground-glass opacity and an alveolar pattern from acute pulmonary edema. A high dose of benzodiazepine with a midazolam pump at 50 mg/h was administered to relieve symptoms. The patient's friends confessed to concomitant use of amphetamine and GHB. The urine toxicology result was positive for amphetamine (≧500 ng/mL). The patient improved later and was extubated at 4 days after the mitigation of pneumonia and discharged uneventfully 8 days later. In our patient, amphetamine intoxication was initially masked by concomitant use of GHB but appeared as GHB's effect attenuated. We wish to remind clinicians of variable clinical presentations of polydrug abuse.