A patient ingested some unknown substance and presented with myoclonic jerks, seizures, tachycardia and hypotension. ECG shows a heart rate of 120/min. The arterial blood revealed a pH of 7.25, pCO2 of 30 mm Hg and bicarbonate ions are 15 mmol/L. The most likely poisonous agent is:

Ans. (C) Imipramine(Ref: KDT 8/e p486, 487)Features are typical of tricyclic antidepressant poisoning. TCAs possess anticholinergic activity that can result in tachycardia. These agents can lead to metabolic acidosis (pH < 7 4, HCO3- < 24 mmol/L). Seizures and myoclonic jerks are other features of TCA poisoning.