DRUG INTERACTIONS SECTION

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 Diazepam: May potentiate orthostatic hypotension. (7.1, 7.2)

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 Alcohol: May potentiate orthostatic hypotension. (7.1) 

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 Carbamazepine: Increased clearance of olanzapine. (7.1) 

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 Fluvoxamine: May increase olanzapine levels. (7.1) 

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 CNS Acting Drugs: Caution should be used when taken in combination with other centrally acting drugs and alcohol. (7.2) 

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 Antihypertensive Agents: Enhanced antihypertensive effect. (7.2) 

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 Levodopa and Dopamine Agonists: May antagonize levodopa/dopamine agonists. (7.2) 

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 Lorazepam (IM): Increased somnolence with IM olanzapine. (7.2) 

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 Other Concomitant Drug Therapy: When using olanzapine in combination with lithium or valproate, refer to the Drug Interactions sections of the package insert for those products. (7.2)

7 DRUG INTERACTIONS

The risks of using olanzapine in combination with other drugs have not been extensively evaluated in systematic studies.

7.1 Potential for Other Drugs to Affect Olanzapine

Diazepam

The co-administration of diazepam with olanzapine potentiated the orthostatic hypotension observed with olanzapine [see Drug Interactions (7.2)].

Cimetidine and Antacids

Single doses of cimetidine (800 mg) or aluminum- and magnesium-containing antacids did not affect the oral bioavailability of olanzapine.

Inducers of CYP1A2

Carbamazepine therapy (200 mg bid) causes an approximately 50% increase in the clearance of olanzapine. This increase is likely due to the fact that carbamazepine is a potent inducer of CYP1A2 activity. Higher daily doses of carbamazepine may cause an even greater increase in olanzapine clearance.

Alcohol

Ethanol (45 mg/70 kg single dose) did not have an effect on olanzapine pharmacokinetics. The co-administration of alcohol (i.e., ethanol) with olanzapine potentiated the orthostatic hypotension observed with olanzapine [see Drug Interactions (7.2)].

Inhibitors of CYP1A2

Fluvoxamine: Fluvoxamine, a CYP1A2 inhibitor, decreases the clearance of olanzapine. This results in a mean increase in olanzapine Cmax following fluvoxamine of 54% in female nonsmokers and 77% in male smokers. The mean increase in olanzapine AUC is 52% and 108%, respectively. Lower doses of olanzapine should be considered in patients receiving concomitant treatment with fluvoxamine.

Inhibitors of CYP2D6

Fluoxetine

Fluoxetine (60 mg single dose or 60 mg daily dose for 8 days) causes a small (mean 16%) increase in the maximum concentration of olanzapine and a small (mean 16%) decrease in olanzapine clearance. The magnitude of the impact of this factor is small in comparison to the overall variability between individuals, and therefore dose modification is not routinely recommended.

Warfarin

Warfarin (20 mg single dose) did not affect olanzapine pharmacokinetics [see Drug Interactions (7.2)].

Inducers of CYP1A2 or Glucuronyl Transferase

Omeprazole and rifampin may cause an increase in olanzapine clearance.

Charcoal

The administration of activated charcoal (1 g) reduced the Cmax and AUC of oral olanzapine by about 60%. As peak olanzapine levels are not typically obtained until about 6 hours after dosing, charcoal may be a useful treatment for olanzapine overdose.

Anticholinergic Drugs

Concomitant treatment with olanzapine and other drugs with anticholinergic activity can increase the risk for severe gastrointestinal adverse reactions related to hypomotility. Olanzapine should be used with caution in patients receiving medications having anticholinergic (antimuscarinic) effects [see Warnings and Precautions (5.14)].

7.2 Potential for Olanzapine to Affect Other Drugs

CNS Acting Drugs

Given the primary CNS effects of olanzapine, caution should be used when olanzapine is taken in combination with other centrally acting drugs and alcohol.

Antihypertensive Agents

Olanzapine, because of its potential for inducing hypotension, may enhance the effects of certain antihypertensive agents.

Levodopa and Dopamine Agonists

Olanzapine may antagonize the effects of levodopa and dopamine agonists.

Lorazepam (IM)

Administration of intramuscular lorazepam (2 mg) 1 hour after intramuscular olanzapine for injection (5 mg) did not significantly affect the pharmacokinetics of olanzapine, unconjugated lorazepam, or total lorazepam. However, this co-administration of intramuscular lorazepam and intramuscular olanzapine for injection added to the somnolence observed with either drug alone [see Warnings and Precautions (5.7)].

Lithium

Multiple doses of olanzapine (10 mg for 8 days) did not influence the kinetics of lithium. Therefore, concomitant olanzapine administration does not require dosage adjustment of lithium [see Warnings and Precautions (5.16)].

Valproate

Olanzapine (10 mg daily for 2 weeks) did not affect the steady state plasma concentrations of valproate. Therefore, concomitant olanzapine administration does not require dosage adjustment of valproate [see Warnings and Precautions (5.16)].

Effect of Olanzapine on Drug Metabolizing Enzymes

In vitro studies utilizing human liver microsomes suggest that olanzapine has little potential to inhibit CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A. Thus, olanzapine is unlikely to cause clinically important drug interactions mediated by these enzymes.

Imipramine

Single doses of olanzapine did not affect the pharmacokinetics of imipramine or its active metabolite desipramine.

Warfarin

Single doses of olanzapine did not affect the pharmacokinetics of warfarin [see Drug Interactions (7.1)].

Diazepam

Olanzapine did not influence the pharmacokinetics of diazepam or its active metabolite N-desmethyldiazepam. However, diazepam co-administered with olanzapine increased the orthostatic hypotension observed with either drug given alone [see Drug Interactions (7.1)].

Alcohol

Multiple doses of olanzapine did not influence the kinetics of ethanol [see Drug Interactions (7.1)].

Biperiden

Multiple doses of olanzapine did not influence the kinetics of biperiden.

Theophylline

Multiple doses of olanzapine did not affect the pharmacokinetics of theophylline or its metabolites.

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