Amphetamine and atropine interaction: A reason for concern?

Sir,

Interactions between amphetamines and drugs used by anesthetists may be unpredictable and even lead to cardiovascular collapse.[12] Female, 18-year-old, body mass index of 39, scheduled for videolaparoscopic appendectomy. Laboratory examinations were normal. Anesthesia was inducted with propofol, fentanyl and atracurium, orotracheal intubation was performed. Anesthesia was maintained with isoflurane at 1.5% in nitrous oxide and oxygen (1:1). During the procedure, arterial pressure, oxygen saturation, end-tidal carbon dioxide pressure and endotracheal pressure have remained normal. At the end of the procedure, prostigmine (2 mg) and atropine (1 mg) have been administered. Afterwards, the patient presented supraventricular tachycardia (heart rate = 180 bpm) and arterial hypotension (arterial pressure = 73/28 mmHg). Acute lung edema developed rapidly eliminating a large amount of rosy frothy secretion through the tracheal tube associated to signs of decreased perfusion and SpO2 drop to 56%. Chest X-ray: Bilateral interstitial pulmonary infiltrates and arterial gasometry: Hypoxemia and hypocapnia. Then the patient was transferred to the intensive care unit and a catheter was placed into the pulmonary artery and showed a pattern of cardiogenic shock. Transesophageal echocardiogram: Diffuse hyperkinesia of the left ventricle, whose ejection fraction was equal to 30%. An intravenous infusion of noradrenaline and milrinone were initiated with a partial improvement of the clinical picture. The patient improved on the following days with the cessation of vasopressor support and of sedation. On the 4th post-operative day: Ejection fraction of 65% at the echocardiogram and on the 5th post-operative day tracheal extubation was performed, without sequelae. At hospital discharge, the patient's relatives informed that she made chronic use of fenproporex without medical prescription, in order to lose weight. Amphetamines produce most of their effects by releasing biogenic amines, from their storage places in nerve endings. Its actions include: (1) Stimulating action in the central nervous system and (2) increasing alpha and beta peripheral sympathetic tones. The chronic use leads to central and peripheral depletion of catecholamines, mainly reducing noradrelanine reserves.[34] In this patient's case, the interaction between amphetamine and atropine may have caused tachyarrhythmia, arterial hypotension and acute lung edema. After a complete depletion of endogenous catecholamines, hypotension and ventricular dysfunction refractory occurred. Experiments in rats have shown that administering doses of amphetamine successively followed by a dose of atropine may cause severe hypotension and even a cardiovascular collapse.[5] There is no pharmacological explanation for the interaction between these drugs. In this situation, in case of severe hypotension, it is recommended to use vasopressors with direct action.[6] Anesthesia in patients using amphetamines requires a careful administration of drugs that interfere in the synthesis, release and reuptake of catecholamines, as unpredictable and severe interactions may occur.