Drug Interactions:
Phenothiazines

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 Q10 (CoQ10)

Supplementation Possibly Helpful

Preliminary studies suggest that phenothiazine drugs might deplete the body of coenzyme Q₁₀ (CoQ₁₀).^1,2 While there is as yet no evidence that taking CoQ₁₀ supplements provides any specific benefit, supplementing with CoQ₁₀ on general principle might be a good idea if you are taking phenothiazine drugs.

Milk Thistle

Possible Helpful Interaction

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

Ginkgo

Possible Helpful Interaction

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

Vitamin E

Might Reduce Symptoms of Tardive Dyskinesia

One of the most feared side effects of phenothiazines is the development of a permanent side effect called tardive dyskinesia. This late-developing (tardy, or tardive) complication consists of annoying uncontrollable movements (dyskinesias), particularly in the face.

There is some evidence that high doses of vitamin E might reduce symptoms of tardive dyskinesia.^5,6

Vitamin B6

Supplementation Possibly Helpful

A pilot study suggests that vitamin B₆ may be helpful for the treatment of TD. In this 4-week double-blind crossover trial of 15 individuals, treatment with vitamin B₆ significantly improved TD symptoms as compared to placebo.¹¹ Benefits were seen after 1 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 half this dose.

Phenylalanine

Possible 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

Kava

Possible 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 HerbsPotential 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.

Yohimbe

Possible Dangerous Interaction

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

Last reviewed March 2002 by Medical Review Board

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