[Smoking and drug interactions].

Smoking causes certain clinically significant drug interactions. Polycyclic aromatic hydrocarbons induce CYP1A2 enzyme, which is important in metabolism of several drugs. This enzyme induction can lead todecreased efficacy of certain psychoactive drugs, teophylline, warfarin, certain antiarythmicsand anticancer drugs. In addition, nicotine may interfere with the action of beta-blockers and benzodiatsepines through pharmacodynamic mechanisms. After smoking cessation the induced metabolism begins to normalize increasing the risks related to elevated drug concentrations. The risk is highestwhen using drugs with narrow therapeutic ratio, such as clozapine and theophylline. Compared to enzyme inhibition, enzyme-induction takes significantly longer to develop and longer to normalize after abolition of the enzyme inductor. When planning smoking cessation or when a smoker is acutely hospitalized, the medication has to be screened and need for changes in dosages and measurements of drug concentrations to be evaluated.