Health Library


  • Coenzyme Q 10 (CoQ 10 ) —Supplementation Possibly Helpful
  • Milk Thistle —Possible Helpful Interaction
  • Fish Oil —Possible Helpful Interaction
  • Ginkgo —Possible Helpful Interaction
  • Vitamin E —Possible Helpful Interaction
  • Vitamin B6 —Possible Helpful Interaction
  • DHEA —Possible Helpful Interaction
  • Glycine —Possible Helpful Interaction
  • Phenylalanine —Possible Increased Risk of Tardive Dyskinesia
  • Kava —Possible Increased Risk of Dystonic Reactions
  • St. John's Wort, Other Herbs —Potential Increased Risk of Photosensitivity
  • Yohimbe —Possible Dangerous Interaction

Phenothiazine drugs are primarily used for the treatment of schizophrenia and other forms of psychosis.

Medications in this family include

  • Chlorpromazine hydrochloride (Thorazine)
  • Fluphenazine (Permitil, Prolixin)
  • Mesoridazine besylate (Serentil)
  • Perphenazine (Trilafon)
  • Prochlorperazine (Compazine)
  • Promazine hydrochloride (Sparine)
  • Promethazine hydrochloride (Anergan [injectable], Phenergan)
  • Thioridazine hydrochloride (Mellaril)
  • Trifluoperazine hydrochloride (Stelazine)
  • Triflupromazine hydrochloride (Vesprin [injectable])
  • and others
Coenzyme Q 10 (CoQ 10 ) Supplementation Possibly Helpful

Preliminary studies suggest that phenothiazine drugs might deplete the body of coenzyme Q 10 (CoQ 10 ). 1,2 While there is as yet no evidence that taking CoQ 10 supplements provides any specific benefit, supplementing with CoQ 10 on general principle might be a good idea if you are taking phenothiazine drugs.

Fish OilPossible Helpful Interaction

Fish oil contains essential fatty acids in the omega-3 family. Fish oil, its constituents, and a slightly modified fish oil constituent called ethyl-EPA have all been tested for treatment of depression. Incomplete and inconsistent evidence hints that these substances might augment the effectiveness of standard medications used for schizophrenia. 15-20

Milk ThistlePossible Helpful Interaction

Milk thistle might protect against the liver toxicity sometimes caused by phenothiazine drugs. 3

GinkgoPossible Helpful Interaction

Preliminary evidence suggests that ginkgo might reduce the side effects and increase the efficacy of various antipsychotic medications. 4,12

Vitamin EPossible 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, 5,6 but the largest and best-designed study failed to find benefit. 21 For more information, see the full Tardive Dyskinesia article.

Vitamin B 6Possible Helpful Interaction

A pilot study suggests that vitamin B 6 may be helpful for the treatment of tardive dyskinesia (TD). In this 4-week, double-blind crossover trial of 15 individuals, treatment with vitamin B 6 significantly improved TD symptoms as compared to placebo. 11 Benefits were seen after 1 week of treatment. However, the dosage of vitamin B 6 used in this study was quite high (400 mg daily). Toxicity has been reported with daily intake of vitamin B 6 at half this dose.

Vitamin B 6 might also reduce symptoms of akathesia, a type of restlessness associated with phenothiazine antipsychotics. 13

Dehydroepiandrosterone (DHEA)Possible Helpful Interaction

One small, double-blind study found that use of DHEA reduced the Parkinson-like movement disorders that may occur in people taking phenothiazine drugs. 14

GlycinePossible 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 regarding this latter class of symptoms. 22-24

PhenylalaninePossible Increased Risk of Tardive Dyskinesia

There are some indications that using the supplement phenylalanine while taking antipsychotic drugs might increase your risk of developing tardive dyskinesia. 7,8

KavaPossible Increased Risk of Dystonic Reactions

Besides the late-developing complication of tardive dyskinesia, antipsychotic drugs can cause more immediately 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. 9

St. John's Wort , Other Herbs 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 herb and drug might increase the risk further.

YohimbePossible Dangerous Interaction

The herb yohimbe is relatively toxic, and can cause problems if used incorrectly. Phenothiazine medications may increase the risk of toxicity. 10


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