A patient ingested some unknown substance and presented with myoclonic jerks seizures, tachycardia and hypotension.The ECG showed a hea rate of 120/minute with QRS interval of 0.16 seconds. The atrial blood revealed a ph of 7.25, PCO2 of 30 mmHg and HCO3 of 15 mmol/L. the most likely cause of poisoning is ingesion of-

Ans. is 'c' i.e., Imipramine C/F of TCA (Tricyclic Anidepressant) poisoning Tricyclic antidepressant poisoning o TCAs act primarily by inhibiting serotonin and norepinephrine reuptake. It results in elevation of extracellular concentration of these neurotransmitters. o The toxic effects of TCAs are caused by four main pharmacological propeies: (i) Inhibition of norepinephrine reuptake at nerve terminals. (ii) Direct alpha adrenergic block. Anticholinergic action (iv) Membrane stabilizing or quinidine like effect on myocardium Clinical features o Clinical features of TCAs poisoning may be on various systems: (i) CNS: Seizures (convulsions), drowsiness, coma, muscle spasm, rigidity, pyramidal signs, delirium, respiratory depression, ophthalmoplegia (ii) CVS: Tachycardia, hypotension, arrhythmias, ECG changes (Prolongation of PR/QRS/QT interval, right axis detion, R wave greater than S wave, ST/T wave changes), hea block, vasodialatation, cardiogenic shock Anticholinergic: Dry mouth, blurred vision, dilated pupils, urinary retention, absent bowel sound, pyrexia (iv) Metabolic: Acidosis.