Current and Future Developments in Hypertension

Antihypertensive Drug Interactions

Author(s): Cigdem Usul Afsar and Sibel Ozyazgan

Pp: 115-123 (9)

DOI: 10.2174/9789811422720119010006

* (Excluding Mailing and Handling)


Systemic hypertension is a chronic disease which results in complications such as heart failure, renal failure or stroke. Polypharmacy is getting more important in this population. There are many mechanisms by which drugs may interact, mostly pharmacokinetic (absorption, distribution, metabolism, and elimination) or pharmacodynamic, or additive toxicity. Absorption of drugs can be affected by foods, antacids and antidiarrhoeals.

Distribution of the drugs can be changed by the volumetric status of the body and binding of drugs to proteins such as p-glycoproteins.

The most important class of drug interactions involves the cytochrome P450 (CYP) microsomal enzyme system, which metabolizes a variety of drugs and herbal products. Cytochrome P450 enzymes metabolize approximately 60% of prescribed drugs, with CYP3A4 responsible for about half of this metabolism.

Diuretics are renally eliminated and more vulnerable to drug interactions which take place in the kidney. Probenecid, nonselective nonsteroidal antiinflammatory drugs (NSAIDs), beta-lactam antibiotics, valproic acid, methotrexate, cimetidine and antivirals decrease the tubular secretion of loop diuretics from the proximal tubulus.

Pharmacodynamic interactions between similarly acting drugs may lead to additive or even over-additive effects (potentiation). A good example for antihypertensive drugs is the combination of intravenous verapamil and a β-blocker, which may cause additive impairment and increase the risk of A-V (atrio-ventricular) block.

The interaction of antihypertensives and NSAIDs is another important type of interaction. In this chapter, we mentioned all the interactions of antihypertensive agents through kinetic and dynamic ways.

Keywords: Systemic hypertension, Polypharmacy, Pharmacokinetic, Absorption, Distribution, Elimination, Pharmacodynamic, Additive toxicity, Antidiarrhoeals, Pharmacokinetic interactions, Cytochrome P450, Losartan, Kinins, Eplerenone, Propranolol, Bioavailability, Antihypertensives, Diuretics, Digoxin, Renin inhibitors.

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