Olanzapine is an atypical antipsychotic drug of the thienobenzodiazepine group and has become a prominent part of psychiatric clinical practice over the past two decades. Still, adverse reactions to this drug and its potential side effects can be very costly and cause suffering for the patient, resulting in potential disability or sometimes even death.
The introduction of olanzapine and other second-generation antipsychotics is generally considered a breakthrough in the treatment of people with schizophrenia due to the lower incidence of “typical” extrapyramidal side effects such as parkinsonism, dyskinesia, dystonia, and akathisia when compared to high-potency first-generation antipsychotics.
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Common side effects
Albeit structurally and functionally related to clozapine, which is a drug that became famous as the first “atypical” antipsychotics, olanzapine possesses a more favorable side effect profile. The most common adverse effects of olanzapine include mild to moderate sedation, dizziness, constipation, akathisia or restlessness, and increased levels of liver transaminases, particularly alanine transaminase (ALT).
Some of the most notable metabolic side effects of olanzapine include weight gain, type II diabetes mellitus, dyslipidemia, hyperglycemia, insulin resistance, hyperprolactinemia, hypertension and cardiovascular disease. Furthermore, the prevalence of diabetes in schizophrenic patients is approximately 1.5 to 2 times greater as compared to the prevalence reported in the general population.
Olanzapine can impair hypothalamic thermoregulatory mechanisms, resulting in hyperthermia. In addition, the use of anticholinergic medications combined with dehydration can raise body temperature even more. Arthralgia, joint disorders, neck rigidity, back pain, increased creatine kinase, and tardive dyskinesia represent some of the prominent neuromuscular side effects of this drug.
Hypersensitive reactions with fever and hepatitis are the most common dermatological side effects linked to olanzapine usage. Other dermatological adverse reactions can include various hyperpigmentations of the skin, vesiculobullous rash eruptive xanthomas, and purpura associated with thrombocytopenia.
As compared to first-generation antipsychotics, olanzapine has not been associated with causing a significant increase in prolactin levels. Different research groups have proven that elevations of prolactin during olanzapine treatment were not found to be significantly greater in comparison to placebo. Furthermore, these levels were found to be significantly less in individuals taking olanzapine as compared to those taking haloperidol.
Contraindications and precautions
Postural hypotension with subsequent reflex tachycardia, dizziness, and sometimes even syncope can be observed during the initial dose-titration period of olanzapine. These reactions stem from α-1 adrenergic blocking effects; therefore, olanzapine should be used cautiously in patients with cardiovascular or cerebrovascular disease, dehydrated patients, patients taking antihypertensive medications, as well as the elderly.
Patients with a history of clinically significant low white blood cell counts or drug-induced neutropenia should have their complete blood counts frequently monitored during the first few months of taking olanzapine. This initial monitoring period is crucial, as leukopenia, neutropenia, and agranulocytosis have all been reported as potential side effects of the drug.
There may also be the occurrence of a withdrawal syndrome, with symptoms that can include myoclonic jerking, headache, nightmares, restlessness, piloerection, depression, and blurred vision. The possibility of a suicide attempt is inherent in schizophrenia and bipolar disorders; therefore, close supervision of high-risk patients should always accompany therapy with olanzapine.