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Treatment Mechanisms
Cariprazine acts as an antipsychotic that is effective against the positive and negative symptoms of schizophrenia. Unlike many antipsychotics that are D2 and 5-HT2A receptor agonists, cariprazine is a D2 and D3 partial agonist. It also has a higher affinity for D3 receptors. The D2 and D3 receptors are important targets for the treatment of schizophrenia, because the overstimulation of dopamine receptors has been implicated as a possible cause of schizophrenia. Cariprazine acts to inhibit overstimulated dopamine receptors (acting as an antagonist) and stimulate the same receptors when the endogenous dopamine levels are low. Cariprazine’s high selectivity towards D3 receptors could prove to reduce side effects associated with the other antipsychotic drugs, because D3 receptors are mainly located in the ventral striatum and would not incur the same motor side effects (extrapyramidal syndrome) as drugs that act on dorsal striatum dopamine receptors. Cariprazine also acts on 5-HT1A receptors, though the affinity is considerably lower than the affinity to dopamine receptors (seen in monkey and rat brain studies). In the same studies, cariprazine has been noted to increase procognitive effects, the mechanisms of which are currently under investigation.

Pharmacodynamics and Pharmacokinetics
Cariprazine has partial agonist as well as antagonist properties depending on the endogenous dopamine levels. It is highly potent at D3/D2 sites, and has a low potency at 5-HT2C sites. Cariprazine has a high oral bioavailability and can cross the blood brain barrier easily in humans In rats, the oral bioavailability was 52 % (with a dose of 1 mg/kg).

Side Effects
The most prevalent side effects for cariprazine include akathisia, insomnia, and weight gain. In Phase III trial for schizophrenia, 66.7 % of patients experienced these side effects, as well as other issues such as metabolic problems, extrapyramidal syndrome (EPS) side effects, and sedation. This suggests that cariprazine might not make it past Phase III testing for schizophrenia because its tolerability is lower those of its competitors.

These side effects are considerably lower in the phase III trials for bipolar disorder 1, so cariprazine might have more of a future as an antimanic drug.