Action and Drug Interactions

Effectiveness of the three available phosphodiesterase inhibitors is essentially comparable, but differences exist in duration of action, and to a small degree, incidence of side effects and drug interactions. 

Ohnhaus EE, Berger W, Duckert F, Oesch F. The influence of dimethylbiguanide on phenprocoumon elimination and its mode of action. A drug interaction study. Klin Wochenschr 1983 61(17) 851-8. 

The monoamine oxidase inhibitors epitomize cyclical fashions in drug use and the impact of adverse effects. They were the first psychotropic drugs for which a clear biochemical action was defined. Early excitement was quickly tempered by reports of liver toxicity with the hydrazine derivatives, leading to synthesis of the cyclopropylamine drug, tranylcypromine, which in turn elicited the food and drug interactions that led to an overall decline in popularity. 

Therapeutic interchange involves the dispensing of chemically different drugs that are considered to be therapeutically equivalent. Therapeutically equivalent drugs are chemically dissimilar but produce essentially the same therapeutic outcome and have similar toxicity profiles. Usually these drugs are within the same pharmacologic class. They frequently differ in chemistiy, mechanism of action, and pharmacokinetic properties, and may possess different adverse reaction, toxicity, and drug interaction profiles. 

The appropriate use of antiepileptic drugs requires a thorough understanding of their clinical pharmacology, e.g., mechanism of action, pharmacokinetics, adverse reaction, dosage forms, and drug interactions. 

Rational polytherapy—The concurrent use of two or more drugs for patients not responding to monotherapy. The combination of drugs is based on a consideration of mechanism of action, clinical pharmacokinetics, adverse reactions, and drug interactions. 

Toxicity and drug interactions Mouth ulcers and gastrointestinal effects occur commonly. Possible antiplatelet action warrants caution in patients taking anticoagulants or conventional antiplatelet drugs. 

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