Thioridazine

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Also indexed as:

Mellaril

Thioridazine is used to treat symptoms associated with psychosis; depression with worry and restlessness in adults; irritability, worry, and fear in elderly; and severe behavioral problems in children, including fighting and hyperactivity. It is classified as a phenothiazine neuroleptic.

Herbs

Summary of Interactions for Thioridazine

Depletion or interference	Vitamin A
Adverse interaction	Bacopa Lithium*
Side effect reduction/prevention	Coenzyme Q10 Potassium*
Supportive interaction	Niacin*
Reduced drug absorption/bioavailability	None known
Other (see text)	Vitamin C*

An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.

Interactions with Supplements

Vitamin A

A review of people taking thioridazine showed that they had higher blood levels of vitamin A than did individuals not using the drug.¹ More research is necessary to determine whether taking vitamin A supplements with thioridazine might cause dangerously high vitamin A levels. Until more is known, people taking thioridazine should exercise caution with vitamin A supplementation and be alert for side effects such as bone pain, headaches, dry scaly skin, and hair loss.

Potassium

Some people taking thioridazine experience changes in the electrical activity of the heart, which sometimes improve with potassium supplementation.² More research is needed to determine if people taking thioridazine might prevent heart problems by supplementing with potassium.

Niacin (nicotinic acid)

In a controlled study, individuals taking thioridazine for psychosis cooperated better and withdrew less from other people when niacin, 300-1,500 mg each day, was added.³ Whether people who are taking thioridazine for other mental health problems might benefit from niacin supplementation is unknown.

Coenzyme Q10

Phenothiazine drugs like thioridazine can cause changes in heart activity in some people, which might be prevented with coenzyme Q10 supplementation.⁴ Therefore, some doctors and pharmacists may recommend coenzyme Q10 supplements to individuals taking thioridazine.

Lithium

Lithium is a mineral that may be present in some supplements and is also used in large amounts to treat mood disorders such as bipolar disorder (manic depression). One study reviewed four cases in which individuals stabilized on lithium medication developed side effects such as delirium, seizures, and abnormal electrical activity in the brain when thioridazine was added.⁵ Further research is needed to determine whether similar side effects might occur in individuals taking thioridazine and supplemental lithium.

Vitamin C

Taking phenothiazine drugs can stop menstruation in some women. A 45-year-old woman taking thioridazine started menstruating once she began supplementing with 6 grams of vitamin C daily.⁶ Controlled studies are needed to determine whether women taking thioridazine, who are experiencing menstrual changes, might benefit from supplemental vitamin C. Vitamin C might also enhance the effectiveness of neuroleptic drugs, such as thioridazine, in the treatment of schizophrenia. One uncontrolled study showed that 10 of 13 individuals experienced a reduction in disorganized thoughts, hallucinations, and suspicious thoughts when 8 grams of vitamin C was added to their daily drug therapy.⁷ Controlled studies are needed to determine whether people taking thioridazine for schizophrenia might benefit from vitamin C supplementation.

Interactions with Herbs

Bacopa

An animal study found that the effects of chlorpromazine, a drug similar to (perphenazine, prochlorperazine, thioridazine), were enhanced when a bacopa extract was given along with it.⁸ Until more is known, people taking medications from this family of drugs (called phenothiazines) should not take bacopa.

Other Interactions

Alcohol

Drinking alcoholic beverages while taking thioridazine may enhance the actions of alcohol, such as drowsiness, dizziness, and lack of concentration,⁹ and should be avoided. Two individuals withdrawing from chronic alcohol consumption experienced serious changes in heart function when they were given thioridazine;¹⁰ therefore, the drug should be used with caution in people who are attempting to quit drinking.

References

1. Curtis JL. Effects of medication on plasma vitamin A concentrations. Clin Chem 1976;22:695.
2. Sydney MA. Ventricular arrhythmias associated with use of thioridazine hydrochloride in alcohol withdrawal. Br Med J 1973;4:467.
3. Lehmann HE, Ban TA, Saxena BM. Nicotinic acid, thioridazine, fluoxymesterone and their combinations in hospitalized geriatric patients. Can Psychiatr Assoc J 1972;17:315-20.
4. Kishi T, Makino K, Okamoto T, et al. In Yamamura Y, Folkers K, Ito Y, eds. Biochemical and Clinical Aspects of Coenzyme Q, Volume 2. Amsterdam: Elsevier/North Holland Biomedical Press, 1980, 139-57.
5. Spring GK. Neurotoxicity with combined use of lithium and thioridazine. J Clin Psychiatry 1979;40:135-8.
6. Kanofsky JD, Kay SR, Lindenmayer JP, Seifter E. Ascorbic acid action in neuroleptic-associated amenorrhea. J Clin Psychopharmacol 1989;9:388-9 [letter].
7. Beauclair L, Vinogradov S, Riney SJ, et al. An adjunctive role for ascorbic acid in the treatment of schizophrenia? J Clin Psychopharmacol 1987;7:282-3.
8. Ganguly DK, Malhotra CL. Some behavioral effects of an active fraction from Herpestis monniera Linn. (Brahmi). Indian J Med Res 1967;55:473-82.
9. Sifton DW, ed. Physicians Desk Reference. Montvale, NJ: Medical Economics Company, Inc., 2000, 1973-4.
10. Sydney MA. Ventricular arrhythmias associated with use of thioridazine hydrochloride in alcohol withdrawal. Br Med J 1973;4:467.

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Last Review: 01-21-2009

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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires February 2010.

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