Psychotropic drug-drug interactions are of importance to the practising psychiatrist. These interactions if kept unaware, may lead to complications which at times may even be fatal. Drug interactions may be pharmacodynamic and pharmacokinetic. Pharmacodynamic, e.g. Amitriptyline and Benztropine resulting in enhanced anticholinergic adverse effects or MAOI and selective serotonin reuptake inhibitor (SSRI) resulting in hypertensive crisis. Pharmacokinetic, e.g. CYP450 enzymes induction or inhibition, p glycoprotein, an ATP dependant extruding transporter induction or inhibition, or absorption, distribution or excretion of drug altered due to coadministration of another drug, e.g. Carbamazepine a microsomal enzyme inducer may decrease the efficacy of Haloperidol; absorption of Ziprasonidone may be enhanced by presence of food.