CLOZAPINE

Interactions with Dietary Supplements

Glycine
The use of glycine may interfere with the efficacy of clozapine as an antipsychotic drug. In a double-blind trial, people with chronic, treatment-resistant schizophrenia were given clozapine (400–1,200 mg per day) and either glycine (30 g per day) or placebo for 12 weeks.¹ The combination of clozapine and glycine was not effective at decreasing symptoms. In contrast, participants who took clozapine without glycine had a 35% reduction in some symptoms. Therefore, the combination should be avoided until more is known.

N-acetyl cysteine and Vitamin C
Clozapine can inhibit the formation of immune cells that protect the body from invading organisms. Test tube studies show that N-acetyl-cysteine and vitamin C block the formation of immune cell–damaging compounds produced when clozapine is broken down.² Controlled studies are necessary to determine whether supplementing N-acetyl-cysteine and vitamin C might prevent harmful side effects in people taking clozapine.

Selenium
One controlled study showed that taking clozapine can decrease blood levels of selenium, a mineral with antioxidant activity.³ While more research is needed to determine whether people taking clozapine might require selenium supplementation, until more information is available, some health practitioners recommend supplementation.

L-tryptophan
Some people who take clozapine become mentally depressed after taking the drug for a few weeks. Studies have shown that clozapine can reduce blood levels of the amino acid L-tryptophan, which is often deficient in people with depression.⁴ More controlled research is needed to determine whether the interaction is significant and whether individuals taking clozapine might benefit from supplemental L-tryptophan or 5-hydroxytryptophan (5-HTP).