Phenothiazines (drug interactions)
Phenothiazines are a class of medications primarily used to treat schizophrenia and other forms of psychosis. Their efficacy can be influenced by various drug interactions, making it essential for patients to discuss all medications and supplements they are taking with their healthcare provider. Certain supplements, such as coenzyme Q10, fish oil, and milk thistle, may offer potential benefits for individuals on phenothiazines, possibly enhancing treatment effectiveness or mitigating side effects. Conversely, some substances, like phenylalanine and kava, could increase the risk of serious side effects, including tardive dyskinesia and dystonic reactions.
Moreover, herbs like St. John's wort can heighten photosensitivity, while alcohol and caffeine can interfere with the drugs' effectiveness and safety. Patients with specific health conditions should also be cautious, as phenothiazines can interact negatively with various prescription medications. Overall, a comprehensive understanding of these interactions is crucial for safe and effective treatment with phenothiazines, emphasizing the importance of open communication with healthcare professionals.
Phenothiazines (drug interactions)
- DEFINITION: Drugs used to treat schizophrenia and other forms of psychosis.
- INTERACTIONS: Belladonna, coenzyme Q10, milk thistle, fish oil, ginkgo, vitamin E, vitamin B6, DHEA, glycine, jimsonweed, phenylalanine, kava, St. John’s wort, valerian root, yohimbe, prescription medications, alcohol, caffeine
- DRUGS IN THIS FAMILY: Chlorpromazine hydrochloride (Thorazine), fluphenazine (Permitil, Prolixin), perphenazine (Trilafon), prochlorperazine (Compazine), promazine hydrochloride (Sparine), promethazine hydrochloride (injectable, Phenergan)
Coenzyme Q10 (CoQ10)
Effect: Supplementation Possibly Helpful
Preliminary studies suggest that phenothiazine drugs might deplete the body of CoQ10. While there is no evidence that taking CoQ10 supplements provides any specific benefit, supplementing with CoQ10 might be a good idea if one is also taking phenothiazine drugs.
Fish Oil
Effect: Possible Helpful Interaction
Fish oil contains essential fatty acids in the omega-3 family. Its constituents, including a slightly modified fish oil constituent called ethyl eicosapentaenoic acid (ethyl-EPA), have all been tested for depression treatment. Incomplete and inconsistent evidence suggests that these substances might augment the effectiveness of standard medications used for schizophrenia.
Milk Thistle
Effect: Possible Helpful Interaction
Milk thistle might protect against the liver toxicity sometimes caused by phenothiazine drugs.
Ginkgo
Effect: Possible Helpful Interaction
Preliminary evidence suggests that ginkgo might reduce the side effects and increase the efficacy of various antipsychotic medications.
Vitamin E
Effect: Possible Helpful Interaction
One of the most feared side effects of phenothiazines is the development of a permanent side effect called tardive dyskinesia (TD). This late-developing (tardy, or tardive) complication consists of annoying uncontrollable movements (dyskinesias), particularly in the face.
In early studies, vitamin E had shown some promise for treating tardive dyskinesia, but the largest and best-designed study failed to find benefit.
Vitamin B6
Effect: Possible Helpful Interaction
A pilot study suggests that vitamin B6 may be helpful for the treatment of tardive dyskinesia (TD). In this four-week, double-blind crossover trial of fifteen persons, treatment with vitamin B6 significantly improved TD symptoms compared with placebo. Benefits were seen after one week of treatment. However, the dosage of vitamin B6 used in this study was quite high (400 mg daily). Toxicity has been reported with daily intake of vitamin B6 at one-half this dose. Vitamin B6 might also reduce symptoms of akathisia, a type of restlessness associated with phenothiazine antipsychotics.
Dehydroepiandrosterone (DHEA)
Effect: Possible Helpful Interaction
One small, double-blind study found that the use of DHEA reduced the Parkinson-like movement disorders that may occur in people taking phenothiazine drugs.
Glycine
Effect: Possible Helpful Interaction
Phenothiazine drugs are most effective for the “positive” symptoms of schizophrenia, such as hallucinations and delusions. (Such symptoms are called “positive” because they indicate the presence of abnormal mental functions rather than the absence of normal mental functions.) In general, however, these medications are less helpful for the “negative” symptoms of schizophrenia, such as apathy, depression, and social withdrawal. Some evidence hints that the supplement glycine might enhance the effectiveness of phenothiazines in relation to this latter class of symptoms.
Phenylalanine
Effect: Possible Increased Risk of Tardive Dyskinesia
There are some indications that using the supplement phenylalanine while taking antipsychotic drugs might increase one’s risk of developing tardive dyskinesia.
Kava
Effect: Possible Increased Risk of Dystonic Reactions
Besides the late-developing complication of tardive dyskinesia, antipsychotic drugs can cause another movement disorder: dystonic reactions (sudden intense movements of the neck and eyes). There is some evidence that the herb kava can increase the risk or severity of this side effect.
St. John’s Wort, Other Herbs
Effect: Potential Increased Risk of Photosensitivity
Phenothiazines can cause increased sensitivity to the sun. Various herbs, including St. John’s wort and dong quai, can also cause this problem. Combined treatment with these herbs and phenothiazines might increase the risk further.
Yohimbe
Effect: Possible Dangerous Interaction
The herb yohimbe is relatively toxic and can cause problems if used incorrectly. Phenothiazine medications may increase the risk of toxicity.
Other Interactions
Several additional herbs and supplements may offer positive and negative effects when taken with phenothiazines. For example, valerian root, known for its sedative properties, may cause dangerous levels of sedation when combined with phenothiazines. Herbs with anticholinergic effects, such as belladonna and jimsonweed, should also be avoided when taking phenothiazines. There is a long list of medications that interact with phenothiazine, ranging from minor to major interactions. Patients are encouraged to discuss all prescription medications with their healthcare provider before taking phenothiazine. Prescription medications that should be avoided include anticholinergic medications, antihypertensive medications, and medications for Parkinson's disease. Further, patients suffering from numerous conditions, such as certain cancers, heart disease, and lung, kidney, or brain disorders, should avoid taking phenothiazine due to potential medication interactions. Alcohol should be avoided when taking phenothiazine, as it may cause excess central nervous system depression and increase sedation to dangerous levels. Caffeine may make phenothiazines less effective.
Bibliography
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