Haloperidol

Summary of Interactions with Vitamins, Herbs, and Foods
(for details about the summarized interactions, read the full article)

May be Beneficial: Depletion or interference—The medication may deplete or interfere with the absorption or function of the nutrient. Taking these nutrients may help replenish them.	Iron* Sodium*
May be Beneficial: Side effect reduction/prevention—Taking these supplements may help reduce the likelihood and/or severity of a potential side effect caused by the medication.	Ginkgo biloba Milk thistle* Vitamin E
May be Beneficial: Supportive interaction—Taking these supplements may support or otherwise help your medication work better.	Glycine
Avoid: Reduced drug absorption/bioavailability—Avoid these supplements when taking this medication since the supplement may decrease the absorption and/or activity of the medication in the body.	Coffee and tea*
Check: Other—Before taking any of these supplements or eating any of these foods with your medication, read this article in full for details.	Potassium
Adverse interaction	None known

Interactions with Dietary Supplements

Glycine
Two double-blind studies have found that 0.4–0.8 mg/kg body weight per day of glycine can reduce the so-called negative symptoms of schizophrenia when combined with haloperidol and related drugs.¹ ² Negative symptoms include reduced emotional expression or general activity. The action of glycine in combination with the drugs was greater than the drugs alone, suggesting a synergistic action. Another double-blind study using approximately half the amount in the positive studies could not find any benefit from adding glycine to antipsychotic drug therapy.³ Patients with low blood levels of glycine appeared to improve the most when given glycine in addition to their antipsychotic drugs.⁴ No side effects were noticed in these studies, even when more than 30 grams of glycine were given daily.

Iron
Haloperidol may cause decreased blood levels of iron.⁵ The importance of this interaction remains unclear. Iron should not be supplemented unless a deficiency is diagnosed.

Potassium
Haloperidol may cause hyperkalemia (high blood levels of potassium) or hypokalemia (low blood levels of potassium).⁶ The incidence and severity of these changes remains unclear. Serum potassium can be measured by any doctor.

Vitamin E
Haloperidol and related antipsychotic drugs can cause a movement disorder called tardive dyskinesia. Several double-blind studies suggest that vitamin E may be beneficial for treatment of tardive dyskinesia.⁷ Taking the large amount of 1,600 IU per day of vitamin E simultaneously with antipsychotic drugs has also been shown to lessen symptoms of tardive dyskinesia.⁸ It is unknown if combining vitamin E with haloperidol could prevent tardive dyskinesia.

Sodium
Haloperidol may cause hyponatremia (low blood levels of sodium).⁹ The incidence and severity of these changes remains unclear.

Interactions with Herbs

Milk thistle (Silybum marianum)
Haloperidol may cause liver damage. A double-blind study in 60 women treated with drugs such as haloperidol were given 800 mg per day silymarin extract made from milk thistle.¹⁰ Test subjects who were given silymarin experienced a significant decrease in free radical levels, unlike those given placebo.

Ginkgo biloba
In a double-blind trial, supplementation of schizophrenic patients with Ginkgo biloba extract, in the amount of 250 mg per 2.2 pounds of body weight per day for 12 weeks, enhanced the effectiveness of haloperidol and also reduced the side effects of the drug.¹¹

Interactions with Foods and Other Compounds

Coffee and Tea
Cofee and tea are reported to cause precipitation of haloperidol in the test tube.¹² If this interaction happens in people, it would reduce the amount of haloperidol absorbed and the effectiveness of therapy. People taking haloperidol may avoid this possible interaction by taking haloperidol one hour before or two hours after drinking coffee or tea.

Alcohol
Haloperidol may cause drowsiness.¹³ Alcohol may compound this drowsiness and increase the risk of accidents during activities requiring alertness. People should avoid alcohol-containing products during haloperidol therapy.

References

1. Heresco-Levy U, Javitt DC, Ermilov M, et al. Double-blind, placebo-controlled, crossover trial of glycine adjuvant therapy for treatment-resistant schizophrenia. Br J Psychiatry 1996;169:610–7.

2. Javitt DC, Zylberman I, Zukin SR, et al. Amelioration of negative symptoms in schizophrenia by glycine. Am J Psychiatry 1994;151:1234–6.

3. Potkin SG, Costa J, Roy S, et al. Glycine in treatment of schizophrenia—theory and preliminary results. In: Meltzer HY (ed). Novel Antipsychotic Drugs. New York: Raven Press, 1990:179–88.

4. Heresco-Levy U, Javitt DC, Ermilov M, et al. Double-blind, placebo-controlled, crossover trial of glycine adjuvant therapy for treatment-resistant schizophrenia. Br J Psychiatry 1996;169:610–7.

5. Threlkeld DS, ed. Central Nervous System Drugs, Antipsychotic Agents. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, May 1998, 266k–6m.

6. Threlkeld DS, ed. Central Nervous System Drugs, Antipsychotic Agents. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, May 1998, 266k–6m.

7. Adler LA, Peselow E, Rotrosen J, et al. Vitamin E treatment of tardive dyskinesia. Am J Psychiatry 1993;150:1405–7.

8. Adler LA, Edson R, Lavori P, et al. Long-term treatment effects of vitamin E for tardive dyskinesia. Biol Psychiatry 1998;43:868–72.

9. Threlkeld DS, ed. Central Nervous System Drugs, Antipsychotic Agents. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, May 1998, 266k–6m.

10. Palasciano G, Portincasa P, Palmieri V, et al. The effect of silymarin on plasma levels of malon-dialdehyde in patients receiving long-term treatment with psychotropic drugs. Curr Ther Res 1994;55:537–45.

11. Zhang XY, Zhou DF, Zhang PY, et al. A double-blind, placebo-controlled trial of extract of Ginkgo biloba added to haloperidol in treatment-resistant patients with schizophrenia. J Clin Psychiatry 2001;62:878–83.

12. Lasswell WL Jr, Weber SS, Wilkins JM. In vitro interaction of neuroleptics and tricyclic antidepressants with coffee, tea, and gallotannic acid. J Pharm Sci 1984;73:1056–8.

13. Threlkeld DS, ed. Central Nervous System Drugs, Antipsychotic Agents. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, May 1998, 266k–6m.

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The information presented in Healthnotes 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 March 2005.