Herbal medicinals are being used by an increasing number of patients who typically do not advise their clinicians of concomitant use. Known or potential drug-herb interactions exist and should be screened for. If used beyond 8 weeks, Echinacea could cause hepatotoxicity and therefore should not be used with other known hepatoxic drugs, such as anabolic steroids, amiodarone, methotrexate, and ketoconazole. However, Echinacea lacks the 1,2 saturated necrine ring associated with hepatoxicity of pyrrolizidine alkaloids. Nonsteroidal anti-inflammatory drugs may negate the usefulness of feverfew in the treatment of migraine headaches. Feverfew, garlic, Ginkgo, ginger, and ginseng may alter bleeding time and should not be used concomitantly with warfarin sodium. Additionally, ginseng may cause headache, tremulousness, and manic episodes in patients treated with phenelzine sulfate. Ginseng should also not be used with estrogens or corticosteroids because of possible additive effects. Since the mechanism of action of St John wort is uncertain, concomitant use with monoamine oxidase inhibitors and selective serotonin reuptake inhibitors is ill advised. Valerian should not be used concomitantly with barbiturates because excessive sedation may occur. Kyushin, licorice, plantain, uzara root, hawthorn, and ginseng may interfere with either digoxin pharmacodynamically or with digoxin monitoring. Evening primrose oil and borage should not be used with anticonvulsants because they may lower the seizure threshold. Shankapulshpi, an Ayurvedic preparation, may decrease phenytoin levels as well as diminish drug efficacy. Kava when used with alprazolam has resulted in coma. Immunostimulants (eg, Echinacea and zinc) should not be given with immunosuppressants (eg, corticosteroids and cyclosporine). Tannic acids present in some herbs (eg, St John wort and saw palmetto) may inhibit the absorption of iron. Kelp as a source of iodine may interfere with thyroid replacement therapies. Licorice can offset the pharmacological effect of spironolactone. Numerous herbs (eg, karela and ginseng) may affect blood glucose levels and should not be used in patients with diabetes mellitus.
In recent years, there has been increasing recognition that akathisia occurs not only as an acute, self-limited complication of dopamine (DA) antagonist treatment, but also as a persistent form, called tardive akathisia. We represent a retrospective analysis of clinical features and therapeutic trials in 52 cases of this disorder. Although most patients developed this disorder after years of DA antagonist treatment (mean = 4.5 years), a significant proportion (34%) developed it within 1 year. The characteristic motor features included frequent, complex stereotyped movements. The legs were most frequently involved, showing marching in place and crossing/uncrossing. Trunk rocking, respiratory grunting and moaning, and complex hand movements such as face rubbing or scratching also occurred. In the 26 patients who were able to discontinue DA antagonists, akathisia persisted for years (mean = 2.7 years, range of 0.3-7 years) until abatement of symptoms or last follow-up. Younger patients were more likely to have remission or therapeutic suppression of akathisia at follow-up. In our experience, the catecholamine-depleting drugs reserpine and tetrabenazine were the most effective agents for suppressing symptoms, producing improvement in 87 and 58% of patients treated, respectively. However, improvement was limited in many patients, and at last follow-up only 33% of patients had complete abatement of their symptoms. In conclusion, tardive akathisia is a particularly disabling form of tardive dyskinesia, frequently persistent for years and often resistant to therapy.
With the ever-increasing population of cigarette smokers, the potential for cigarette smoke to affect drug therapy both pharmacokinetically and pharmacodynamically is significant. The overriding pharmacokinetic effect is increased drug metabolism through the induction of liver enzymes. The constituents of tobacco smoke, primarily nicotine, have their own pharmacological effects which may potentiate or antagonise the desired pharmacological effect of a particular drug, thereby affecting its efficacy. Furthermore, end-organ responsiveness may also be altered by tobacco. These latter 2 aspects constitute altered clinical pharmacodynamics. Approximately 30 drugs have been evaluated in terms of cigarette smoking. Induction of liver enzymes has been shown to increase the metabolism of imipramine, meprobamate, oestrogens, pentazocine, phenylbutazone, theophylline and warfarin. Nicotine has been shown to inhibit diuresis, alter ulcer healing, impair subcutaneous absorption, affect protein binding and stimulate catecholamine release; these effects have been evaluated in terms of therapy with frusemide (furosemide), histamine H2-antagonists, insulin, lignocaine (lidocaine) and beta-blockers, respectively. The interactions have not been correlated with clinical significance in all cases. Diminished end-organ responsiveness may account for reduced drowsiness in smokers receiving chlorpromazine and benzodiazepines, compared with non-smokers. Smoking has been associated with diminished pain tolerance, requiring increased dosages of morphine, pethidine (meperidine) and propoxyphene. Enzyme-inducers such as carbamazepine, phenytoin and phenobarbitone appear to be minimally affected by cigarette smoke, perhaps because hepatic enzymes are already maximally stimulated. Codeine, corticosteroids and nortriptyline do not appear to be affected by cigarette smoke. The bioavailability of glutethimide is higher in smokers, but this has not been associated with greater efficacy. The effect of smoking on paracetamol (acetaminophen) has been variable, depending on the extent of smoking, and does not appear to be of clinical significance.
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