Caffeine, Smoking, and Some Herbal Medications Interfere with Olanzapine

Olanzapine, first introduced in 1996 as a treatment for schizophrenia, acts by inhibiting the action of two primary neurotransmitters, dopamine and serotonin, in certain brain centers. It also acts to correct an imbalance of nerve impulse transmissions thought to be responsible for certain mental disorders. Certain substances can interfere with the drug’s effectiveness.

Olanzapine is highly metabolized in the liver. Although food does not affect absorption of the drug, caffeine and smoking can affect blood levels. Both caffeine and smoking interact with liver enzyme P450-CYP1A2, the very enzyme that metabolizes olanzapine. Caffeine markedly increases blood levels of the drug and in turn increases the risk of adverse reactions. Smoking can decrease the blood levels of the drug, making it less likely to be effective. Certain herbal medications can also interfere with the drug. Kola and ma huang (ephedrine) can increase central nervous system stimulation. Gingseng may have MAO inhibitor properties and should not be used with olanzapine. Valerian and kava-kava can interact with olanzapine to increase drowsiness.