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Patient Counseling about Herbal-Drug Interactions
Hussain, Md. Sarfaraj
Abstract
Many people have the mistaken notion that, being natural, all herbs and foods are safe; this is not so. Very often, herbs
and food may interact with medications you normally take, result in serious reactions. During the latter part of this century the
practice of herbalism has become mainstream throughout the world. This is due remove to the recognition of the value of
traditional medical systems in the world. Herbal medicines are mixtures of more than one active ingredient. The multitude of
pharmacologically active compounds obviously increases the likelihood of interactions taking place. Hence, the likelihood of
herb-drug interactions is theoretically higher than drug-drug interactions because synthetic drugs usually contain single chemical
entity. Case reports and clinical studies have highlighted the existence of a number of clinically important interactions, although
cause-and-effect relationships have not always been established. Herbs and drugs may interact either pharmacokinetically or
pharmacodynamically. The predominant mechanism for this interaction is the inhibition of cytochrome P-450 3A4 in the small
intestine; result in a significant reduction of drug presystemic metabolism. An additional mechanism is the inhibition of Pglycoprotein,
a transporter that carries drug from the enterocyte back to the gut lumen, result in a further increase in the fraction of
drug absorbed. Some herbal products (e.g. St. John’s wort) have been shown to lower the plasma concentration (and/or the
pharmacological effect) of a number of conventional drugs including cyclosporine, indinavir, irinotecan, nevirapine, oral
contraceptives and digoxin. The data available so far, concerning this interaction and its clinical implications are reviewed in this
article. It is likely that more information regarding such interaction would crop up in the future, awareness of which is necessary
for achieving optimal drug therapy.
Keywords
Herbal drug; Herbal Preparation; herbal–drug interaction; drug–drug interaction; Cytochrome P-450
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