Current Role of Herbal Preparations

Abstract

For many herbal remedies, precise information concerning composition, dose standardisation, clinical activity, interactions with other drugs and side effects is lacking. One of the best-researched herbal agents is St John's wort (hypericum). It has been shown to be an effective and safe antidepressant in more than 50 double-blind trials that involved comparisons with both placebo and standard antidepressants including selective serotonin reuptake inhibitors (SSRIs). Its mode of action, which involves reuptake inhibition of serotonin, noradrenaline and dopamine, is comparable to those of chemical antidepressants. Like the chemical antidepressants, it suffers from a "lag-period" of 34 weeks before it becomes fully effective and must be taken for at least 6 months to effect a lasting remission. It has been used in seasonal affective disorder (SAD) with good effect. Rarely, photosensitivity may occur, but only in cases of pathological sun allergy. Like chemical antidepressants, hypericum interacts in the metabolism of a number of other drugs, notably anticoagulants, theophylline preparations, oral contraceptives, antimigraine drugs, and HIV drugs. This may result in reduced effectiveness of both drugs and such combinations are therefore best avoided. A number of clinical trials have shown kava kava to be an effective anxiolytic and sleep-inducer, particularly in patients under stress. However, following reports of liver toxicity, it has been withdrawn from sale pending further investigation of these reports. On the other hand, valerian would appear to be a safe hypnotic for long-term use, although not for an immediate effect. Valerian increases deep (delta) sleep strikingly and beneficially and, by so doing, may augment the immune system. Ginkgo biloba enhances memory and the peripheral circulation. In double-blind trials, its efficacy has been demonstrated even in Alzheimer's disease, and it does not appear to have any appreciable side effects. Herbal remedies have much to offer in the treatment of psychiatric disorders and merit further scientific investigation.