Olanzapine USP is an atypical antipsychotic that belongs to the thienobenzodiazepine class. The chemical designation is 2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno[2,3-b] [1,5]benzodiazepine. The molecular formula is C 17 H 20 N 4 S, which corresponds to a molecular weight of 312.44. The chemical structure is:
Olanzapine USP is a yellow crystalline solid, which is practically insoluble in water.
Olanzapine tablets, USP is intended for oral administration only.
Each tablet contains olanzapine USP equivalent to 2.5 mg (8 µmol), 5 mg (16 µmol), or 10 mg (32 µmol). Inactive ingredients are crospovidone, hydroxypropyl cellulose, lactose monohydrate, magnesium stearate, microcrystalline cellulose. The coating contains hypromellose, titanium dioxide and polyethylene glycol.
The mechanism of action of olanzapine, in the listed indications is unclear. However, the efficacy of olanzapine in schizophrenia could be mediated through a combination of dopamine and serotonin type 2 (5HT 2 ) antagonism.
Olanzapine binds with high affinity to the following receptors: serotonin 5HT 2A/2C , 5HT 6 (Ki=4 nM, 11 nM, and 5 nM, respectively), dopamine D 1-4 (K i =11 nM to 31 nM), histamine H 1 (Ki=7 nM), and adrenergic α 1 receptors (K i =19 nM). Olanzapine is an antagonist with moderate affinity binding for serotonin 5HT 3 (K i =57 nM) and muscarinic M 1-5 (K i =73 nM, 96 nM, 132 nM, 32 nM, and 48 nM, respectively). Olanzapine binds with low affinity to GABA A , BZD, and β-adrenergic receptors (K i >10 µM).
Oral Administration, Monotherapy — Olanzapine is well absorbed and reaches peak concentrations in approximately 6 hours following an oral dose. It is eliminated extensively by first pass metabolism, with approximately 40% of the dose metabolized before reaching the systemic circulation. Food does not affect the rate or extent of olanzapine absorption. Pharmacokinetic studies showed that olanzapine tablets and olanzapine orally disintegrating tablets dosage forms of olanzapine are bioequivalent.
Olanzapine displays linear kinetics over the clinical dosing range. Its half-life ranges from 21 to 54 hours (5th to 95th percentile; mean of 30 hr), and apparent plasma clearance ranges from 12 L/hr to 47 L/hr (5th to 95th percentile; mean of 25 L/hr). Administration of olanzapine once daily leads to steady-state concentrations in about 1 week that are approximately twice the concentrations after single doses. Plasma concentrations, half-life, and clearance of olanzapine may vary between individuals on the basis of smoking status, gender, and age.
Olanzapine is extensively distributed throughout the body, with a volume of distribution of approximately 1,000 L. It is 93% bound to plasma proteins over the concentration range of 7 ng/mL to 1,100 ng/mL, binding primarily to albumin and α 1 -acid glycoprotein.
Metabolism and Elimination — Following a single oral dose of 14 C labeled olanzapine, 7% of the dose of olanzapine was recovered in the urine as unchanged drug, indicating that olanzapine is highly metabolized. Approximately 57% and 30% of the dose was recovered in the urine and feces, respectively. In the plasma, olanzapine accounted for only 12% of the AUC for total radioactivity, indicating significant exposure to metabolites. After multiple dosing, the major circulating metabolites were the 10-N-glucuronide, present at steady state at 44% of the concentration of olanzapine, and 4´-N-desmethyl olanzapine, present at steady state at 31% of the concentration of olanzapine. Both metabolites lack pharmacological activity at the concentrations observed.
Direct glucuronidation and cytochrome P450 (CYP) mediated oxidation are the primary metabolic pathways for olanzapine. In vitro studies suggest that CYPs 1A2 and 2D6, and the flavin-containing monooxygenase system are involved in olanzapine oxidation. CYP2D6 mediated oxidation appears to be a minor metabolic pathway in vivo , because the clearance of olanzapine is not reduced in subjects who are deficient in this enzyme.
Intramuscular Administration — Olanzapine IntraMuscular results in rapid absorption with peak plasma concentrations occurring within 15 to 45 minutes. Based upon a pharmacokinetic study in healthy volunteers, a 5 mg dose of intramuscular olanzapine for injection produces, on average, a maximum plasma concentration approximately 5 times higher than the maximum plasma concentration produced by a 5 mg dose of oral olanzapine. Area under the curve achieved after an intramuscular dose is similar to that achieved after oral administration of the same dose. The half-life observed after intramuscular administration is similar to that observed after oral dosing. The pharmacokinetics are linear over the clinical dosing range. Metabolic profiles after intramuscular administration are qualitatively similar to metabolic profiles after oral administration.
Renal Impairment — Because olanzapine is highly metabolized before excretion and only 7% of the drug is excreted unchanged, renal dysfunction alone is unlikely to have a major impact on the pharmacokinetics of olanzapine. The pharmacokinetic characteristics of olanzapine were similar in patients with severe renal impairment and normal subjects, indicating that dosage adjustment based upon the degree of renal impairment is not required. In addition, olanzapine is not removed by dialysis. The effect of renal impairment on metabolite elimination has not been studied.
Hepatic Impairment — Although the presence of hepatic impairment may be expected to reduce the clearance of olanzapine, a study of the effect of impaired liver function in subjects (n=6) with clinically significant (Childs Pugh Classification A and B) cirrhosis revealed little effect on the pharmacokinetics of olanzapine.
Geriatric — In a study involving 24 healthy subjects, the mean elimination half-life of olanzapine was about 1.5 times greater in elderly (≥65 years) than in nonelderly subjects (<65 years). Caution should be used in dosing the elderly, especially if there are other factors that might additively influence drug metabolism and/or pharmacodynamic sensitivity [see Dosage and Administration (2)].
Gender — Clearance of olanzapine is approximately 30% lower in women than in men. There were, however, no apparent differences between men and women in effectiveness or adverse effects. Dosage modifications based on gender should not be needed.
Smoking Status — Olanzapine clearance is about 40% higher in smokers than in nonsmokers, although dosage modifications are not routinely recommended.
Race — In vivo studies have shown that exposures are similar among Japanese, Chinese and Caucasians, especially after normalization for body weight differences. Dosage modifications for race are, therefore, not recommended.
Combined Effects — The combined effects of age, smoking, and gender could lead to substantial pharmacokinetic differences in populations. The clearance in young smoking males, for example, may be 3 times higher than that in elderly nonsmoking females. Dosing modification may be necessary in patients who exhibit a combination of factors that may result in slower metabolism of olanzapine [see Dosage and Administration (2)].
Adolescents (ages 13 to 17 years) —In clinical studies, most adolescents were nonsmokers and this population had a lower average body weight, which resulted in higher average olanzapine exposure compared to adults.
Carcinogenesis — Oral carcinogenicity studies were conducted in mice and rats. Olanzapine was administered to mice in two 78-week studies at doses of 3 mg/kg/day, 10 mg/kg/day, 30 mg/kg/day/20 mg/kg/day (equivalent to 0.8 to 5 times the daily oral MRHD based on mg/m 2 body surface area) and 0.25 mg/kg/day, 2 mg/kg/day, 8 mg/kg/day (equivalent to 0.06 to 2 times the daily oral MRHD based on mg/m 2 body surface area). Rats were dosed for 2 years at doses of 0.25 mg/kg/day, 1 mg/kg/day, 2.5 mg/kg/day, 4 mg/kg/day (males) and 0.25 mg/kg/day, 1 mg/kg/day, 4 mg/kg/day, 8 mg/kg/day (females) (equivalent to 0.13 to 2 times and 0.13 to 4 times the daily oral MRHD based on mg/m 2 body surface area, respectively). The incidence of liver hemangiomas and hemangiosarcomas was significantly increased in 1 mouse study in female mice at 2 times the daily oral MRHD based on mg/m 2 body surface area. These tumors were not increased in another mouse study in females dosed up to 2 to 5 times the daily oral MRHD based on mg/m 2 body surface area; in this study, there was a high incidence of early mortalities in males of the 30 mg/kg/day/20 mg/kg/day group. The incidence of mammary gland adenomas and adenocarcinomas was significantly increased in female mice dosed at ≥2 mg/kg/day and in female rats dosed at ≥4 mg/kg/day (0.5 and 2 times the daily oral MRHD based on mg/m 2 body surface area, respectively). Antipsychotic drugs have been shown to chronically elevate prolactin levels in rodents. Serum prolactin levels were not measured during the olanzapine carcinogenicity studies; however, measurements during subchronic toxicity studies showed that olanzapine elevated serum prolactin levels up to 4-fold in rats at the same doses used in the carcinogenicity study. An increase in mammary gland neoplasms has been found in rodents after chronic administration of other antipsychotic drugs and is considered to be prolactin mediated. The relevance for human risk of the finding of prolactin mediated endocrine tumors in rodents is unknown [see Warnings and Precautions (5.15)].
Mutagenesis — No evidence of genotoxic potential for olanzapine was found in the Ames reverse mutation test, in vivo micronucleus test in mice, the chromosomal aberration test in Chinese hamster ovary cells, unscheduled DNA synthesis test in rat hepatocytes, induction of forward mutation test in mouse lymphoma cells, or in vivo sister chromatid exchange test in bone marrow of Chinese hamsters.
Impairment of Fertility — In an oral fertility and reproductive performance study in rats, male mating performance, but not fertility, was impaired at a dose of 22.4 mg/kg/day and female fertility was decreased at a dose of 3 mg/kg/day (11 and 1.5 times the daily oral MRHD based on mg/m 2 body surface area, respectively). Discontinuance of olanzapine treatment reversed the effects on male mating performance. In female rats, the precoital period was increased and the mating index reduced at 5 mg/kg/day (2.5 times the daily oral MRHD based on mg/m 2 body surface area). Diestrous was prolonged and estrous delayed at 1.1 mg/kg/day (0.6 times the daily oral MRHD based on mg/m 2 body surface area); therefore olanzapine may produce a delay in ovulation.
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