Introduction
Olanzapine is a thienobenzodiazepine classified as an atypical or second-generation antipsychotic agent. The second-generation antipsychotics were introduced in the 90s and quickly gained traction due to their impressive efficacy, reduced risk for extrapyramidal side effects and reduced susceptibility to drug-drug interactions. Olanzapine very closely resembles clozapine and only differs by two additional methyl groups and the absence of a chloride moiety.
Uses
Olanzapine is an antipsychotic drug used in the management of schizophrenia, bipolar 1 disorder, and agitation associated with these disorders.
Olanzapine was initially used orally and intramuscularly for the chronic treatment of schizophrenia in patients over 13 years old and other psychiatric disorders such as bipolar I disorder including mixed or manic episodes.
Olanzapine is also indicated, in combination with lithium or valproate for the short-term treatment of acute manic or mixed episodes associated with bipolar I disorder in adults.
As well, olanzapine is indicated, in combination with fluoxetine for the treatment of episodes of depression associated with bipolar disorder type 1 and treatment-resistant depression in patients over 10 years old.
Olanzapine is also approved for the management of psychomotor agitation associated with schizophrenia and bipolar I mania.
Schizophrenia is a complex biochemical brain disorder that affects the person's ability to differentiate reality. It is usually observed as the presence of delusions, hallucinations, social withdrawal and disturbed thinking.
Bipolar disorder is a mental health condition defined by periods of extreme mood disturbances. It is categorized in different types from which type 1 is known to involve episodes of severe mania and often depression while type 2 presents less severe forms of mania.
Olanzapine is also indicated in combination with samidorphan for the treatment of bipolar I disorder, either as an adjunct to lithium or valproate or as monotherapy for the acute treatment of manic or mixed episodes or as maintenance therapy, and for the treatment of schizophrenia in adults.
Associated Conditions
Pharmacodynamics
The effect of olanzapine in the D2 receptor is reported to produce the positive effects of this drug such as a decrease in hallucinations, delusions, disorganized speech, disorganized thought, and disorganized behavior. On the other hand, its effect on the serotonin 5HT2A receptor prevents the onset of anhedonia, flat affect, alogia, avolition and poor attention. Based on the specific mechanism of action, olanzapine presents a higher affinity for the dopamine D2 receptor when compared to the rest of the dopamine receptor isotypes. This characteristic significantly reduces the presence of side effects.
Clinical trials for the original use of olanzapine demonstrated significant effectiveness in the treatment of schizophrenia and bipolar disorder in adults and acute manic or mixed episodes associated with bipolar disorder in adolescents.
The effect of olanzapine on dopamine and serotonin receptors has been suggested to reduce chemotherapy-induced nausea and vomiting as those receptors are suggested to be involved in this process. For this effect, several clinical trials have been conducted and it has been shown that olanzapine can produce a significant increase in total control of nausea and vomiting. In a high-level study of the effect of olanzapine for this condition, a complete response on the delay phase was observed in 84% of the individual and control of emesis of over 80% despite the phase.
Mechanism of Action
The activity of olanzapine is achieved by the antagonism of multiple neuronal receptors including the dopamine receptor D1, D2, D3 and D4 in the brain, the serotonin receptors 5HT2A, 5HT2C, 5HT3 and 5HT6, the alpha-1 adrenergic receptor, the histamine receptor H1 and multiple muscarinic receptors.
As abovementioned, olanzapine presents a wide profile of targets, however, its antagonistic effect towards the dopamine D2 receptor in the mesolimbic pathway is key as it blocks dopamine from having a potential action at the post-synaptic receptor. The binding of olanzapine to the dopamine D2 receptors is easily dissociable and hence, it allows for a certain degree of dopamine neurotransmission.
On the other hand, olanzapine acts in the serotonin 5HT2A receptors in the frontal cortex in a similar manner than the reported on dopamine D2 receptors. This determined effect allows for a decrease in adverse effects.
Absorption
Olanzapine presents a linear pharmacokinetic profile and, after daily administration, it reaches steady-state in about a week. Under the administration of a normal dosage of olanzapine, the steady-state plasma concentration does not seem to exceed 150 ng/ml with an AUC of 333 ng/h/ml.
The absorption of olanzapine is not affected by the concomitant administration of food. The pharmacokinetic profile of olanzapine is characterized by reaching peak plasma concentration of 156.9 ng/ml approximately 6 hours after oral administration.
Volume of Distribution
The volume of distribution of olanzapine is reported to be of 1000 liters which indicate a large distribution throughout the body.
Protein Binding
Olanzapine is largely bound to plasma proteins and hence, about 93% of the administered dose is bound. The main proteins for binding are albumin and alpha-1 acid glycoprotein.
Route of Elimination
Olanzapine is mainly eliminated through metabolism and hence, only 7% of the eliminated drug can be found as the unchanged form. It is mainly excreted in the urine which represents around 53% of the excreted dose followed by the feces that represent about 30%.
Half Life
Olanzapine presents a half-life ranging between 21 to 54 hours with an average half-life of 30 hours.
Clearance
The mean clearance rate of olanzapine is of 29.4 L/hour however, some studies have reported an apparent clearance of 25 L/h.
Toxicity
The toxicity symptoms of olanzapine are known to include somnolence, mydriasis, blurred vision, respiratory depression, hypotension, extrapyramidal symptoms and anticholinergic effects. The overdosage effects in children are generally associated with more significant side effects.
The maximum registered dosage of olanzapine in clinical trials was of 300 mg and it was reported to present drowsiness and slurred speech. However, on post-marketing surveillance, a wide range of symptoms have been presented including agitation, dysarthria, tachycardia, extrapyramidal symptoms, and reduced consciousness. One case of overdosage-driven death was reported after ingestion of 450 mg of olanzapine. In the cases of acute overdosage, the establishment of adequate oxygenation and ventilation, gastric lavage and administration of activated charcoal with a laxative is recommended.
In carcinogenesis studies, olanzapine was showed to present an increase in the incidence of liver hemangiomas and hemangiosarcomas as well as mammary gland adenomas, and adenocarcinomas. On fertility studies, there was solely found impairment in male mating performance and delays in ovulation. There is no evidence of mutagenic, genotoxic potential not adverse events on fertility.
Food Interactions
- Avoid alcohol. Alcohol may potentiate CNS adverse effects and orthostatic hypotension.
- Take with or without food. The absorption of olanzapine is unaffected by food.
Dosage
Monotherapy for Mania: Initially 15 mg once daily. Daily dosage may subsequently be adjusted on the basis of individual clinical status within the range of 5-20 mg daily. Dosage greater than 15 mg only after reassessment. Maximum dose is 20 mg daily.
