Olanzapine chemical structure
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Zyprexa

Olanzapine (Zyprexa®, Zydis®, or in a combination with fluoxetine as Symbyax®) was the second atypical antipsychotic to gain FDA approval and has become one of the most commonly used atypical antipsychotics. Olanzapine has been FDA approved for the treatment of schizophrenia, acute mania in bipolar disorder, agitation associated with schizophrenia and bipolar disorder, and as maintenance treatment in bipolar disorder. Olanzapine is manufactured and marketed by the pharmaceutical company Eli Lilly and Company. It is available as a pill that comes in the strengths of 2.5 mg, 5 mg, 7.5 mg, 10 mg, 15 mg, and 20 mg. more...

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It is also available as Zydis orally disintegrating tables in the strengths of 5 mg, 10 mg, 15 mg, and 20 mg.

Olanzapine can also be used to treat anxiety, although it is not commonly recommended for that purpose due to the strong side effects and expense. In particular, unlike benzodiazapenes, antipsychotics are non-addictive. Some psychiatrists have also been known to prescribe it to eating disorder patients, due both to its mood stabilising effects and tendency to increase weight.

Pharmacology

Olanzapine is structurally similar to clozapine, and is classified as a thienobenzodiazepine. Olanzapine has a high affinity for dopamine and serotonin receptors. Like most atypical antipsychotics compared to the older typical ones, Olanzapine has a lower affinity for histamine, cholinergic muscarinic and alpha adrenergic receptors. The mechanism of action of olanzapine is unknown, however it is theorized that olanzapine's antipsychotic activity is mediated primarily by antagonism at dopamine receptors, specifically D2. Serotonin antagonism may also play a role in the effectiveness of olanzapine, but the significance of 5-HT2A antagonism is debated among researchers. Antagonism at muscarinic, histaminic and alpha adrenergic receptors likely explains some of the side effects of olanzapine, such as anticholinergic effects, weight gain, sedation and orthostatic hypotension.

Pharmacokinetics

Olanzapine displays linear kinetics. Its elimination half-life ranges from 21 to 54 hours. Steady state plasma concentrations are achieved in about a week. Olanzapine undergoes extensive first pass metabolism and bioavailability is not affected by food.

Metabolism

Olanzapine is metabolized by the Cytochrome P450 system isoenzymes 1A2 and 2D6 (minor pathway). Drug metabolism may be increased or decreased by agents that induce (e.g. cigarette smoke) or inhibit (e.g. fluvoxamine or ciprofloxacin) CYP1A2 activity respectively.

Adverse events

Adverse events reported in the package insert for olanzapine include dry mouth, dizziness, sedation, insomnia, orthostatic hypotension, akathisia, and weight gain. Olanzapine is reported to cause extrapyramidal symptoms, tardive dyskinesia and neuroleptic malignant syndrome, although at a much reduced rate when compared to the classical antipsychotics.

Recently the FDA required the manufacturers of all atypical antipsychotics to include a warning about the risk of hyperglycemia and diabetes with atypical antipsychotics. Additionally there are some case reports of olanzapine-induced diabetic ketoacidosis. There is data showing that olanzapine can decrease insulin sensitivity. In addition, increased triglyceride levels may also be an issue with olanzapine. Impaired glucose metabolism, high triglycerides, and obesity have been shown to be constituents of the metabolic syndrome and may increase the risk of cardiovascular disease. The data suggests that olanzapine may be more likely to cause adverse metabolic effects than some of the other atypical antipsychotics.

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Kentucky Medicaid puts Zyprexa on prior authorization
From Drug Cost Management Report, 10/1/02

Zyprexa requires prior authorization for coverage by the Kentucky Medicaid program as of Oct. 1, 2002. No other state has placed such a restriction on prescriptions of Zyprexa, says Jim Dailey, advocacy director of the National Alliance for the Mentally Ill-Kentucky.

Physicians must now assert to the state program that Zyprexa is better for a particular patient than any other available choice, based on some experience with the patient, he explains.

Eli Lilly's Zyprexa is the most expensive of the drugs in the class of atypical antipsychotics, which are used to treat schizophrenia and psychotic disorders. Figures from Scott-Levin show Zyprexa retail sales in 2001 were larger than those of the two closest competitors--Risperdal and Seroquel--combined. Dailey asserts that Zyprexa's higher price tag "is the only reason they went on prior authorization. [The action is a] message to the manufacturer that it's got to get its prices in line."

Dailey says that at the Pharmacy and Therapeutics (P&T) Committee hearing on the Zyprexa matter, there was testimony that statistically, there is no difference in efficacy among the atypical antipsychotic drugs. While not necessarily disputing the point, he contends that Zyprexa is likely to be more effective for some patients, as Risperdal and Seroquel may well be for others.

Responding to public pressure, Dailey says the P&T committee of the state Medicaid program decided on Sept. 19 that patients already on Zyprexa are "grandfathered." Their physicians need not obtain prior authorization for coverage.

At the same time, Dailey notes, the P&T panel rejected its own earlier proposal to limit Zyprexa prescriptions to "fail first" cases--ones in which patients already had been on either Risperdal or Seroquel (drugs in the same class) for 30 days, and they and their physicians judged the earlier prescription a failure.

For more information, contact Dailey at (502) 245-5287 or jpd737@aol.com.

COPYRIGHT 2002 Atlantic Information Services, Inc.
COPYRIGHT 2003 Gale Group

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