**5. Heroine**

Morphine and its semisynthetic analogue heroin are the most commonly used recreational narcotic drugs. Narcotic agents act centrally on the vasomotor center to increase parasympathetic and reduce sympathetic activity [48, 53]. These autonomic changes, combined with histamine release from mast cell degranulation, can result in bradycardia and hypotension [53]. Sinus bradycardia, benign atrioventricular block, and resulting atrial or ventricular automatic ectopy and tachycardia were all reported. ECGs of 511 opioid addicts were analyzed. The main anomalies detected were sinus bradycardia, type-1 atrioventricular block, wandering atrial pacemaker, supraventricular and ventricular ectopic beats, and QT prolongation [58].

Methadone is another synthetic opioid used for the treatment of opioid addiction and for its analgesic effect. Methadone is responsible for QT prolongation and occurrence of torsade de pointes (TdP) especially when QT interval exceeds 500 ms. TdP should always be suspected in patients receiving methadone and presenting with syncope [59, 60]. Correction of predisposing factors as hypokalemia and hypomagnesemia is recommended, in case of prolonged QT and TdP. Magnesium perfusion is proposed, even in case of normal serum magnesium concentration. Alternative drugs can be used when corrected QT exceeds 500 ms [59].
