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