Hypericum perforatum L. Hypericaceae (St. John's wort), has been used since the time of ancient Greece for its many medicinal properties. Modern usage is still quite diverse and includes wound healing, kidney and lung ailments, insomnia and depression. This plant has been known to contain a red pigment, hypericin, and similar compounds, which have been assumed to be the primary active constituent(s) in this plant genus. A crude Hypericum extract was tested in a battery of 39 in vitro receptor assays, and two enzyme assays. A sample of pure hypericin was also tested. Hypericin had affinity only for NMDA receptors while the crude extract had significant receptor affinity for adenosine (nonspecific), GABAA, GABAB, benzodiazepine, inositol triphosphate, and monoamine oxidase (MAO) A and B. With the exception of GABAA and GABAB, the concentrations of Hypericum exact required for these in vitro activities are unlikely to be attained after oral administration in whole animals or humans. These data are consistent with recent pharmacologic evidence suggesting that other constituents of this plant may be of greater importance for the reported psychotherapeutic activity. Alternative pharmacologic mechanisms for Hypericum's antidepressant activity are critically reviewed and the possible importance of GABA receptor binding in the pharmacology of Hypericum is highlighted. Some of these results have been previously reported.
The interactions between ethanol and antidepressant drugs (both tricyclics and newer non-tricyclics) were studied in mice. The ability of these drugs to enhance the sedative effects of ethanol at two different doses (3.2 and 4.0 g/kg) was measured. The percentage of mice losing the righting-reflex was used for the lower dose, and the duration of ethanol-induced sleep was used at the higher dose. The relative order of potency was amitriptyline greater than or equal to imipramine > maprotiline = mianserin > desipramine greater than or equal to chlorimipramine > iprindole greater than or equal to alaproclate > norzimelidine greater than or equal to zimelidine. Amitriptyline (60 mg/kg) caused death in all mice when combined with 4.0 g/kg ethanol. Clinically established antidepressants which enhanced ethanol sedation only at doses considerably above therapeutic levels were zimelidine and iprindole. The relative potency of the antidepressants to enhance ethanol sedation is correlated with their inherent sedative properties which are in turn related to their ability to block central 5-HT, alpha-NA, muscarinic and H1-receptors. Amitriptyline (20 mg/kg) was found to increase ethanol plasma levels to 202, 167 and 132% of control values at 30, 60 and 90 min after ethanol administration, respectively. Desipramine, mianserin and alaproclate also increased ethanol plasma levels initially, but to a lesser extent. These findings suggest that in addition to their sedative effect, several antidepressants, particularly amitriptyline, are likely to interact with ethanol by increasing its concentration in plasma.
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