ABSTRACT
Increasing numbers of people are seeking symptomatic relief of psychiatric disorders by using dietary supplements. Since this is generally without medical supervision (Fugh-Berman and Cott, 1999; Wong et al., 1998), it is essential that clinicians avail themselves of the extensive literature available on natural products so that potential problems can be avoided. Herb-drug interactions can be of two primary types: pharmacokinetic and pharmacodynamic. Dynamic interactions are those having to do with the mechanism of action, e.g. where the drug’s pharmacologic actions may be in opposition to or in addition to one another. Pharmacokinetic interactions are the result of alterations in the absorption, distribution, metabolism or excretion of medications when given together with specific drugs, foods or supplements. Interactions between botanical products and prescribed medications could increase or decrease the action of the drug, though the majority of interactions are likely to go unnoticed due to their having only minor effects on drug plasma levels. For a few, this is not the case, and illustrations will be given to provide a basis by which many of the most serious interactions can be prevented. Since kinetic interactions are of much greater relative importance, only they will be considered here. While some pharmacokinetic information on herbal medicines is available (De Smet and Brouwers, 1997), much more is needed in order to put in proper perspective the vagaries of clinical anecdotes and in vitro experiments. Therefore, this chapter will not be a laundry list of putative interactions, but will offer an explanation of the primary types of kinetic interactions as well as a critical summary of reports concerning specific, illustrative herb-drug interactions, especially St John’s wort (Hypericum perforatum; SJW).
