Antihypertensive drug interactions

The administration of more than one drug to a patient always raises the possibility that the efficacy and/or toxicity of one drug might be altered by the simultaneous or prior administration of the other. When such an event occurs, it is termed a ‘drug interaction’. Not unexpectedly, the incidence of drug interactions is directly related to the number of drugs administered; hence, the treatment of the hypertensive patient, which often requires a multiple drug regimen, would be predicted to be associated with a significant number of drug interactions. It should be clearly recognized, however, that not all drug interactions are deleterious; indeed, in the development of therapeutic objectives, advantage can be taken of known drug interactions to provide the patient with the greatest efficacy at the lowest toxicity. In general, when efficacy is improved and toxicity diminished, the drug interaction can be beneficial, whereas, when efficacy is diminished and toxicity enhanced, the interaction is harmful and is referred to as an ‘adverse drug interaction’ [1].