Atypical antipsychotics

Atypical antipsychotics

Atypical antipsychotic drugs are agents designed to treat schizophrenia. They include aripiprazole, clozapine, olanzapine, paliperidone, quetiapine, risperidone, and ziprasidone.

Pharmacokinetics

Atypical antipsychotics are absorbed after oral administration.

Metabolism and excretion

Atypical antipsychotics are metabolized by the liver. Metabolites of clozapine, olanzapine, quetiapine, and ziprasidone are inactive, whereas risperidone and paliperidone have active metabolites. They’re highly plasma protein-bound and eliminated in urine, with a small portion eliminated in stool.

Pharmacodynamics

Atypical antipsychotics typically block the dopamine receptors, but to a lesser extent than the typical antipsychotics, resulting in far fewer extrapyramidal adverse effects. Additionally, atypical antipsychotics block serotonin receptor activity.

Putting it together

These combined actions account for their effectiveness against the positive and negative symptoms of schizophrenia with minimal extrapyramidal effects.

Pharmacotherapeutics

Atypical antipsychotics are considered the first line of treatment for patients with schizophrenia because of equal or improved effectiveness combined with improved tolerability.

Lower doses do for dementia

Atypical antipsychotics are commonly used to treat behavioral and psychotic symptoms in patients with dementia. Dosages are significantly lower for these patients than for patients with schizophrenia.

Drug interactions

Drugs that alter the P-450 enzyme system alter the metabolism of some atypical antipsychotics.

The straight “dopa”

Atypical antipsychotics counteract the effects of levodopa and other dopamine agonists. 

Warning!

Adverse reactions to atypical antipsychotics

Atypical antipsychotics have fewer extrapyramidal effects than typical anti-psychotics and carry a minimal risk for seizures (except for clozapine).

Aripiprazole

Aripiprazole is a newer atypical antipsychotic and may produce mild sedation.

Clozapine

Clozapine is associated with agranulo-cytosis (an abnormal decrease in white blood cells). Weight gain is common, and seizures may also occur.

Olanzapine

Olanzapine places the patient at minimal risk for extrapyramidal effects. Weight gain is common.

Quetiapine

Quetiapine is associated with sedation.

Risperidone and paliperidone

Risperidone and paliperidone have a higher risk of extrapyramidal effects than other atypical antipsychotics, especially when prescribed at doses at the higher range of normal.

Ziprasidone

Because ziprasidone may cause electrocardiogram changes, it’s usually recommended as an alternative therapy only after the patient has failed to respond to other atypical antipsychotics.