Medication Summary
Antipsychotic medications diminish the positive symptoms of schizophrenia and prevent relapses.
Antipsychotics, 1st Generation
Class Summary
First-generation (conventional or typical) antipsychotics, are strong dopamine D2 antagonists. However, each drug in this class has various effects on other receptors, such as serotonin type 2 (5-HT2), alpha1, histaminic, and muscarinic receptors.
First-generation antipsychotics have a high rate of extrapyramidal side effects, including rigidity, bradykinesia, dystonias, tremor, and akathisia. Tardive dyskinesia (TD)—that is, involuntary movements in the face and extremities—is another adverse effect that can occur with first-generation antipsychotics. Neuroleptic malignant syndrome (NMS) can occur with these agents.
Chlorpromazine
Chlorpromazine is a phenothiazine antipsychotic that is a dopamine D2 receptor antagonist. It was the first conventional antipsychotic developed and is still in wide use for treatment of schizophrenia. Chlorpromazine is available in oral tablets, syrup, and concentrate; as an injectable solution for intramuscular (IM) administration; and in suppository form.
Chlorpromazine is a low-potency medication and is associated with sedation and weight gain.
Fluphenazine (Modecate, Modecate Concentrate, Moditen)
Fluphenazine is a high-potency typical antipsychotic that blocks postsynaptic dopaminergic D1 and D2 receptors. It has some alpha-adrenergic and anticholinergic effects. It is available orally and in a depot formulation (fluphenazine decanoate). A short-acting IM injection is also available for acute agitation. Fluphenazine is clinically comparable to haloperidol, a first-generation antipsychotic with similar potency, route of administration, side effects, and efficacy.
Haloperidol (Haldol, Haldol Decanoate)
Haloperidol is a dopamine D2 antagonist noted for high potency and low potential for causing orthostasis. The drawback is the high potential for extrapyramidal symptoms or dystonia. Haloperidol can interact with CYP3A4 and CYP2D6 inhibitors and inducers. It also can interact with drugs that prolong QTc intervals. Haloperidol is available in tablets, as a liquid concentrate, in IM and intravenous (IV) forms, and in long-acting IM form for depot injection.
Perphenazine
Perphenazine is a phenothiazine antipsychotic that blocks postsynaptic dopaminergic receptors and has alpha-adrenergic blocking effects. It has slightly lower potency than haloperidol and it sometimes classified as a midpotency drug. It is available in an oral formulation.
Thiothixene
Thiothixene is a dopamine D2 antagonist with anticholinergic and alpha-blocking effects. It is rarely used in the United States now.
Trifluoperazine
Trifluoperazine is a piperazine phenothiazine agent that is an antagonist at the postsynaptic mesolimbic dopaminergic D2 receptors.
Loxapine inhaled (Loxitane)
Loxapine's mechanism of action is unknown but probably involves antagonism of central dopamine D2 and serotonin 5-HT2A receptors. The inhaled dosage form is indicated for acute treatment of agitation associated with schizophrenia or bipolar I disorder in adults.
Inhaled loxapine is a first-generation agent that may be similar to second-generation agents. In a new formulation, it can be inhaled, which may make it attractive for some patients.
Loxapine inhaled is the first noninjectable therapy to treat acute agitation associated with schizophrenia and bipolar I disorder. Approval by the US Food and Drug Administration (FDA) was based on 2 phase III studies of 658 individuals.
Antipsychotics, 2nd Generation
Class Summary
Second-generation (novel or atypical) antipsychotics, with the exception of aripiprazole, are dopamine D2 antagonists, but are associated with lower rates of extrapyramidal adverse effects and TD than the first-generation antipsychotics. However, they have higher rates of metabolic adverse effects and weight gain.
Asenapine (Saphris)
Asenapine is indicated for acute and maintenance treatment of schizophrenia. It is absorbed poorly in the gastrointestinal (GI) tract and thus is available in a sublingual form. The most common side effects include sedation, weight gain, dizziness, extrapyramidal symptoms, and oral hypoesthesia.
Asenapine's mechanism of action is unknown. Its efficacy is thought to be mediated through a combination of antagonist activity at dopamine D2 and serotonin 5-HT2 receptors. Asenapine exhibits high affinity for serotonin 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT5, 5-HT6, and 5-HT7 receptors; dopamine D2, D3, D4, and D1 receptors; alpha1- and alpha2-adrenergic receptors; and histamine H1 receptors, with moderate affinity for H2 receptors. The addition of serotonin antagonism to dopamine antagonism may improve the negative symptoms of psychoses and may reduce the incidence of extrapyramidal adverse effects when compared with typical antipsychotics.
Asenapine transdermal (Secuado)
Asenapine transdermal is indicated for the treatment of schizophrenia. The patch is applied once daily. Adverse reactions were consistent with sublingual asenapine.
The mechanism of action is unknown. The efficacy thought to be mediated via combined antagonist activity at dopamine D2 and serotonin type 2 (5-HT2) receptors.
Clozapine (Clozaril, FazaClo)
Clozapine is the oldest atypical antipsychotic agent and probably the most effective. Because it is associated with about a 1% risk of agranulocytosis, patients must undergo white blood cell (WBC) count monitoring every week for the first 6 months (the period of greatest risk), then every 2 weeks for 6 months, and finally every 4 weeks, as long as the absolute neutrophil count (ANC) is normal. If the ANC drops, a strict protocol of monitoring and possibly medication cessation must then be followed.
Clozapine is an antagonist at adrenergic, cholinergic, histaminergic, and serotonergic receptors. It has some dopamine D2 antagonism and high D4 affinity. It carries a high adverse effect burden, including sedation, drooling, constipation, and possible cardiac effects. Because it can cause agranulocytosis, patients must have regular blood tests. It is indicated for refractory schizophrenia and for reducing the risk of recurrent suicidal behavior in schizophrenia or schizoaffective disorder.
The anticholinergic adverse effects, sedation, and drooling can be burdensome. Constipation and cardiac adverse effects (cardiomyopathy and myocarditis) can be life-threatening. However, approximately one third of patients who have not responded to conventional antipsychotic agents do better on clozapine. Violence, hostility, and suicidality may be diminished with the use of clozapine.
Iloperidone (Fanapt)
Iloperidone is indicated for acute treatment of schizophrenia. Its precise mechanism of action is unknown, but it is known to antagonize dopamine D2 and serotonin 5-HT2 receptors. However, it shows high affinity for 5-HT2A, D2, and D3 receptors and low-to-moderate affinity for D1, D4, H1, 5-HT1A, 5HT6, 5-HT7, and NE alpha1 receptors. Adverse effects include dizziness, orthostatic hypotension, tachycardia, weight gain, dry mouth, and sedation. Iloperidone causes fewer extrapyramidal symptoms than do other antipsychotics.
Lurasidone (Latuda)
Lurasidone is an atypical antipsychotic whose precise mechanism of action is unknown. It is a dopamine D2 and serotonin 5-HT2A receptor antagonist. It is indicated for schizophrenia in adults and is approved by the FDA to treat schizophrenia in adolescents (aged 13-17 y)
A major route of metabolism for lurasidone is via CYP3A4. Dose reduction is recommended in the presence of moderate CYP3A4 inhibitors. Coadministration with strong CYP3A4 inducers is not recommended.
Olanzapine (Zyprexa, Zyprexa Zydis, Zyprexa Relprevv)
Olanzapine is a selective monoaminergic antagonist at serotonin, dopamine D1-4, muscarinic, histamine H1, and alpha1-adrenergic receptors. It is available as a regular tablet, a rapidly disintegrating tablet, a short-acting injectable solution, and a long-acting injectable formulation. The most common side effects of olanzapine include weight gain, sedation, akathisia, hypotension, dry mouth, and constipation. It is also approved by the FDA to treat schizophrenia in adolescents.
Olanzapine/samidorphan (Lybalvi)
Indicated for treatment of schizophrenia in adults. It is also approved for bipolar I disorder as monotherapy or as an adjunct to lithium or valproate. Olanzapine acts through a combination of dopamine and serotonin type 2 antagonism. Samidorphan is an opioid antagonist and mitigates weight gain associated with olanzapine.
Paliperidone (Invega, Invega Sustenna, Invega Trinza)
Paliperidone is the major active metabolite of risperidone and was the first oral agent to allow once-daily dosing. It is indicated for acute and maintenance treatment of schizophrenia adults and is also approved by the FDA to treat schizophrenia in adolescents. Its mechanism of action not completely understood but is thought to involve antagonism of dopamine D2 and serotonin 5HT-2A receptors. Paliperidone also elicits antagonist activity at adrenergic alpha1 and alpha2 receptors and histamine H1 receptors. Paliperidone is available in an osmotic delivery capsule and in long-term injectable IM forms (once monthly, q3mo).
Quetiapine (Seroquel, Seroquel XR)
Quetiapine may act by antagonizing dopamine and serotonin receptors. It is used for treatment of schizophrenia in adults and is also approved by the FDA to treat schizophrenia in adolescents. Quetiapine is available in immediate-release and extended-release tablets. Major adverse effects include sedation, orthostatic hypotension, akathisia, dry mouth, and weight gain.
Risperidone (Risperdal, Risperdal Consta, Risperdal M-Tab)
Risperidone has both dopamine D2 and serotonin 5-HT2 antagonism. It is approved by the FDA to treat schizophrenia in adults and adolescents. It is available in tablets, oral disintegrating tablets, and an oral solution, as well as a long-acting form for IM injection that uses microspheres made of biodegradable polymers. It has few anticholinergic effects. Primary adverse effects of risperidone include mild sedation, hypotension, akathisia, increase in prolactin, and weight gain.
Ziprasidone (Geodon)
Ziprasidone antagonizes dopamine D2, serotonin 5-HT2, histamine H1, and alpha1-adrenergic receptors. It is available in capsule and short-acting IM injection forms. It is indicated for treatment of acute agitation in patients with schizophrenia. Ziprasidone appears to cause less weight gain, hyperglycemia, and hyperlipidemia than other drugs in its category do.
Cariprazine (Vraylar)
The precise mechanism by which cariprazine works for schizophrenia is unknown. Efficacy could be mediated through a combination of partial agonist activity at central dopamine (D2) and serotonin 5-HT1A receptors. Cariprazine forms 2 major metabolites, desmethyl cariprazine (DCAR) and didesmethyl cariprazine (DDCAR), which have in vitro receptor binding profiles similar to the parent drug.
Serotonin-Dopamine Activity Modulators
Class Summary
Serotonin-dopamine activity modulators (SDAMs) act as a partial agonist at 5-HT1A and dopamine D2 receptors at similar potency, and as an antagonist at 5-HT2A and noradrenaline alpha1B/2C receptors.
Brexpiprazole (Rexulti)
Serotonin-dopamine activity modulator (SDAM) indicated for schizophrenia. Dosage modifications are necessary with renal or hepatic impairment. Dosage modifications are also needed for individuals who are poor metabolizers of CYP2D6, or if coadministered drugs alter metabolism by CYP2D6 or CYP3A4.
Aripiprazole (Abilify, Abilify Maintena, Aristada)
Aripiprazole shows high affinity for D2, D3, 5-HT1A, and 5HT2A receptors and moderate affinity for D4, 5HT2C, 5-HT7, alpha1 adrenergic, and H2 receptors and possesses moderate affinity for the serotonin reuptake transporter. It is thought to be a partial agonist at dopamine D2 and serotonin 5-HT1A receptors and an antagonist at serotonin 5-HT2A receptors, alpha1, and histamine H1 receptors. It is available in tablets, orally disintegrating tablets, and short- and long-term (once-monthly, q6wk) IM injections. The most common adverse effects include headache, nausea, vomiting, insomnia, tremor, and constipation.
Oral aripiprazole is indicated for acute and maintenance treatment of schizophrenia. It is also used for acute and maintenance treatment of bipolar I disorder, adjunctive therapy for major depressive disorder, and treatment of irritability associated with autistic disorder. It is also approved by the FDA to treat schizophrenia in adolescents.
The IM injections are indicated for adults and may be used once monthly (Abilify Maintena, Aristada), every 6 weeks (Aristada 882 mg), or every 2 months (Aristada 1064 mg).
Lumateperone (Caplyta)
The mechanism of action of lumateperone in the treatment of schizophrenia is unknown; however, efficacy could be mediated through a combination of antagonist activity at central serotonin 5-HT2A receptors and postsynaptic antagonist activity at central dopamine D2 receptors. It is indicated for treatment of adults with schizophrenia.
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Cortical activation patterns during verbal working memory maintenance. Healthy controls (A), patients with schizophrenia (B), and significantly different activation between groups (subtraction of SZ-CO) (C) are shown. The time series plots in the middle column show activation associated with true memory maintenance (red lines) relative to the baseline activities (blue line). Bright parts in the middle of each plot represent 1-volume (1.5 s) after onset, and offset of the maintenance phase (4.5 secs). All p-values are corrected with false discovery rate of q< 0.005. Image courtesy of Kim J, Matthews NL, and Park S. An event-related fMRI study of phonological verbal working memory in schizophrenia. PLoS One. 2010; 5(8): e12068.
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Cortical activation patterns during false memory trials. (A) False memory, baseline in controls (CO). (B) False memory, baseline in schizophrenia (SZ). (C) SZ – CO. All p-values are corrected with a false discovery rate of q< 0.005. The time course plots show false memory-related activities (yellow) and true memory-related activities (red) relative to the baseline (blue). Image courtesy of Kim J, Matthews NL, and Park S. An event-related fMRI study of phonological verbal working memory in schizophrenia. PLoS One. 2010; 5(8): e12068.
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Magnetic resonance imaging showing differences in brain ventricle size in twins. The twin on the right has schizophrenia, whereas the twin on the left does not. Image courtesy of Dr. Daniel Weinberger, Clinical Brain Disorders Branch, National Institutes of Health.
