Lurasidone (Latuda)

Mechanism of Action

FDA-Approved Indications

1. Schizophrenia - adults and adolescents (age 13-17)
2. Bipolar I Depression - as monotherapy in adults and pediatric patients (age 10-17)
3. Bipolar I Depression - as adjunctive therapy with lithium or valproate in adults

Pharmacokinetics

• Bioavailability: Low (9-19%); must be taken with at least 350 calories of food to significantly improve absorption
• Tmax: 1-3 hours after dose
• Volume of distribution: 6,173 L (highly distributed)
• Protein binding: High
• Metabolism: Almost entirely via CYP3A4 (oxidative N-dealkylation, norbornane ring hydroxylation, S-oxidation); has two active and two inactive metabolites
• Elimination half-life: ~18 hours (once-daily dosing)
• Excretion: Primarily fecal (80%), ~9% renal

Dosing

Adverse Effects

• Minimal weight gain
• Low risk of dyslipidemia - the Maudsley Prescribing Guidelines (15th ed.) lists lurasidone among the lowest-risk antipsychotics for dyslipidemia (alongside amisulpride, aripiprazole, ziprasidone)
• Low sedation (low H1 affinity)
• Low anticholinergic burden (low M1 affinity)

• Orthostatic hypotension (~1.1%)
• Hyperprolactinemia (as with most D2 antagonists)
• Hyperglycemia / metabolic syndrome (monitor blood glucose)
• Tardive dyskinesia risk (class effect)
• Neuroleptic Malignant Syndrome (NMS) (rare but serious)
• QTc prolongation: Generally low risk; one case report of QTc >500 ms has been documented

Black Box Warnings

1. Increased mortality in elderly patients with dementia-related psychosis (class warning for all antipsychotics)
2. Suicidal thoughts and behaviors in children, adolescents, and young adults (applies due to antidepressant indications)

Contraindications

• Hypersensitivity to lurasidone or tablet components
• Concomitant use with strong CYP3A4 inhibitors (ketoconazole, clarithromycin, ritonavir, voriconazole, mibefradil) - contraindicated
• Concomitant use with strong CYP3A4 inducers (rifampin, St. John's wort, phenytoin, carbamazepine) - contraindicated

Drug Interactions (CYP3A4-based)

• Strong CYP3A4 inhibitors: CONTRAINDICATED (massively increases lurasidone exposure)
• Moderate CYP3A4 inhibitors (diltiazem, atazanavir, erythromycin, fluconazole, verapamil): Reduce lurasidone dose by half; maximum 80 mg/day (or 40 mg/day per some references)
• Grapefruit / grapefruit juice: Avoid (CYP3A4 inhibition)
• Strong CYP3A4 inducers: CONTRAINDICATED (may reduce efficacy to sub-therapeutic levels)

Comparison in Bipolar Depression

Off-Label Uses

• Bipolar II depression
• Mixed depressive episodes
• Irritability associated with autism spectrum disorder

Key Clinical Pearls

1. Must take with food (≥350 calories) - without food, bioavailability drops dramatically
2. Once-daily dosing (18h half-life) - improves adherence
3. No dose titration required at initiation (can start at therapeutic dose of 40 mg)
4. Favorable metabolic profile - a good choice when weight gain or dyslipidemia is a concern
5. Unique among atypicals in having strong 5-HT7 antagonism - may explain both antidepressant effects and cognitive benefits

Pimavanserin (Nuplazid)

Mechanism of Action

FDA-Approved Indication

Pharmacokinetics

• Absorption: Oral only; median Tmax ~6 hours (range 4-24h); unaffected by food (unlike lurasidone)
• Protein binding: ~95% (dose-independent)
• Metabolism: Predominantly CYP3A4/CYP3A5, with minor contribution from CYP2J2, CYP2D6, and other enzymes; forms active metabolite AC-279 (does not cross blood-brain barrier, doesn't contribute to clinical effect)
• Half-life: Very long - 57 hours for parent drug, 200 hours for AC-279 metabolite
• Excretion: Less than 1% recovered in urine (mostly fecal/hepatic)
• Pimavanserin/AC-279 do not cause clinically significant CYP inhibition or induction (fewer interaction concerns than many antipsychotics)

Dosing

• 34 mg once daily, orally, without titration
• Can be taken with or without food
• No dose adjustment needed for mild-moderate hepatic/renal impairment

Adverse Effects (vs. placebo, from pivotal trials)

Black Box Warning

Warnings & Precautions

• QT interval prolongation - avoid in patients with arrhythmias or on other QT-prolonging drugs
• Contraindicated with hypersensitivity to pimavanserin (rash, urticaria, angioedema reported)
• CYP3A4 interactions:
  • Moderate/strong CYP3A4 inducers (modafinil, nafcillin, efavirenz, rifampin, phenytoin, carbamazepine): reduce pimavanserin exposure - not recommended
  • Strong CYP3A4 inhibitors: increase pimavanserin exposure - dose reduction to 10 mg/day recommended (per FDA label)
• Serotonergic interactions: caution with other serotonergic drugs (theoretical serotonin syndrome/NMS risk)
• Pregnancy: insufficient human data; not teratogenic in animal studies at tested doses

Comparative Evidence

Key Clinical Pearls

1. Only drug specifically FDA-approved for Parkinson's disease psychosis
2. No D2 blockade - does not worsen Parkinsonian motor symptoms, unlike most antipsychotics
3. Very long half-life (57h) allows once-daily dosing without titration, but also means slow washout if adverse effects occur
4. Unaffected by food, unlike lurasidone which requires ≥350 calories with dosing
5. Real-world data suggests better mortality safety in PDP compared to concerns extrapolated from the dementia-related psychosis black box warning
6. Not indicated for schizophrenia or dementia-related psychosis outside of PD - trials in these areas have not supported approval

Cariprazine (Vraylar)

Mechanism of Action

History & Development

• September 2015: Schizophrenia and bipolar I disorder (manic/mixed episodes)
• 2022: Adjunctive treatment for major depressive disorder (MDD)
• 2025: FDA expanded to pediatric populations — schizophrenia (age 13+) and bipolar I manic/mixed episodes (age 10+)

FDA-Approved Indications

1. Schizophrenia (adults; adolescents 13+ as of 2025)
2. Bipolar I disorder — acute manic/mixed episodes (adults; pediatric 10+ as of 2025)
3. Bipolar I depression (monotherapy)
4. Major depressive disorder — adjunctive to antidepressant therapy

Pharmacokinetics

• Absorption: Peak concentration in 3-6 hours; not significantly affected by food
• Active metabolites: Desmethyl cariprazine (DCAR) and didesmethyl cariprazine (DDCAR) — both equipotent to parent drug at target receptors
• Steady state: Cariprazine/DCAR reach steady state in 1-2 weeks; DDCAR takes 4-8 weeks due to its very long half-life
• Half-life: Parent drug 2-5 days; DDCAR considerably longer, causing substantial accumulation
• Metabolism: Extensive via CYP3A4 and CYP2D6
• Excretion: ~21% of dose in urine; excretion half-life 2-4 days (parent) and 1-3 weeks (active metabolite)

Adverse Effects (indication-specific)

Warnings & Precautions

• Black box warning: Increased mortality in elderly patients with dementia-related psychosis (class warning for all antipsychotics/dopamine modulators)
• Neuroleptic malignant syndrome (NMS)
• Tardive dyskinesia
• Metabolic changes (hyperglycemia, dyslipidemia, weight gain — though less pronounced than many SGAs)
• Leukopenia/neutropenia
• Orthostatic hypotension and syncope
• Seizures
• Impaired body temperature regulation
• Third-trimester pregnancy exposure: risk of neonatal EPS/withdrawal symptoms
• Dose reduction required with strong CYP3A4 inhibitors

Comparative Evidence (Recent Systematic Reviews/Meta-Analyses)

• A 2024 network meta-analysis in CNS Drugs (PMID 39382790) evaluated cariprazine's efficacy across the psychosis spectrum (schizophrenia and bipolar disorder) via RCTs.
• A 2024 systematic review in Harvard Review of Psychiatry (PMID 39514868) examined cariprazine's effects on cognition in schizophrenia and bipolar disorder — relevant given its D3-preferring mechanism.
• A 2024 meta-analysis in Journal of Affective Disorders (PMID 38942207) assessed cariprazine in acute treatment of unipolar and bipolar depression.
• A 2025 systematic review (PMID 40679420) explored cariprazine plus clozapine combination therapy as a promising strategy for treatment-resistant schizophrenia.

Key Clinical Pearls

1. Unique D3 > D2 selectivity — the only US-marketed dopamine modulator with this profile
2. Broadest indication range among newer atypicals: schizophrenia, bipolar mania, bipolar depression, AND adjunctive MDD
3. Long half-life / slow accumulation — patients may not see full effect (or full side effects) for several weeks; also means slow symptom resolution if effects are unwanted, requiring patience with dosing changes
4. Low metabolic liability — favorable choice for weight/metabolic-conscious prescribing, similar to lurasidone
5. Now approved for pediatric use (schizophrenia 13+, bipolar mania 10+) as of the 2025 label expansion
6. EPS/akathisia are the main practical tolerability concerns, more so than metabolic effects

Cariprazine (Vraylar) — Dosing

Adult Dosing by Indication

Pediatric Dosing (per 2025 label expansion)

Dose Adjustments for CYP3A4 Interactions

• Schizophrenia/bipolar mania: start 0.5 mg, may increase to 0.75 mg if needed
• Bipolar depression/adjunctive MDD: 0.5 mg once daily (no further increase)

• Schizophrenia/bipolar mania: start 0.75 mg, may increase to 1.5 mg if needed
• Bipolar depression/adjunctive MDD: 0.75 mg once daily
• Initiating cariprazine is not recommended in pediatric patients taking a strong or moderate CYP3A4 inhibitor
• If a strong or moderate CYP3A4 inhibitor is later withdrawn, the cariprazine dose may need to be increased back toward standard levels
• Strong CYP3A4 inducers (rifampin, carbamazepine, phenytoin) reduce cariprazine exposure — coadministration is generally avoided/not recommended

Special Populations

• Pediatric: Approved dosing exists now (2025 expansion) for schizophrenia (13+) and bipolar mania (10+); bipolar depression and adjunctive MDD remain unstudied in children per the textbook data
• Renal/hepatic impairment: Use with caution; specific guidance is limited given minimal renal excretion of parent compound
• Elderly: Per Maudsley Prescribing Guidelines, starting dose in older adults remains 1.5 mg once daily for schizophrenia, with further titration guided by tolerability (elderly patients are more susceptible to EPS/orthostatic effects and carry the black box mortality warning for dementia-related psychosis)

Key Practical Points on Titration

1. Titrate slowly to reduce akathisia — Stahl's Essential Psychopharmacology notes that akathisia (the main tolerability issue) "can be much reduced by slow-dose titration," even though the official label allows relatively fast titration (next-day increases in mania).
2. Delayed onset of full effect/side effects — Due to the long half-life of the active metabolite DDCAR (steady state takes 4-8 weeks), patients should be monitored for several weeks after initiation or any dose change, since adverse reactions may be late-appearing and short-term trial data may underestimate real-world incidence.
3. Slow washout — if the drug needs to be stopped (e.g., adverse effect, drug interaction, pregnancy), the active metabolite can persist in plasma for weeks, so effects (both good and bad) don't disappear quickly.
4. EPS and akathisia occur in a dose-dependent fashion — higher doses within each range carry more motor side effect risk.

Brexanolone (Zulresso)

What It Was

Mechanism of Action

• Positive allosteric modulator of GABA-A receptors (both synaptic and extrasynaptic), enhancing chloride (Cl⁻) current
• Mimics the naturally occurring drop in allopregnanolone that happens after delivery — allopregnanolone levels rise progressively through pregnancy, peak in the third trimester, then fall abruptly postpartum
• The hypothesized mechanism in PPD: brexanolone restores allopregnanolone levels and normalizes GABA-A receptor function that becomes dysregulated by this abrupt postpartum drop (Goodman & Gilman's Pharmacological Basis of Therapeutics)

Pharmacokinetics

• Route: IV infusion only (never had an oral formulation)
• Terminal half-life: ~9 hours
• Metabolism: Non-CYP450 pathways — aldo-keto reduction, glucuronidation, and sulfation; only ~1% excreted unchanged
• Excretion: ~47% of metabolites in urine, ~42% in feces
• Renal impairment: Parent drug disposition unaffected by renal function, but the IV solubilizing excipient (betadex sulfobutyl ether sodium) can accumulate in severe renal impairment (GFR <5 mL/min)
• Drug interactions: No clinically significant pharmacokinetic interactions reported; weak in vitro CYP2C9 inhibitor but no demonstrated clinical effect on other drugs
• Linear pharmacokinetics across the 30-270 mcg/kg/h infusion range with low intersubject variability (<21%)

Dosing & Administration (Historical)

REMS Program (Risk Evaluation and Mitigation Strategy)

• Risk of excessive sedation and sudden loss of consciousness
• Requirement for continuous pulse oximetry monitoring
• Mandatory administration at a certified healthcare facility with a healthcare provider present who could intervene
• Patients could not drive, operate machinery, or care for themselves/dependents during the infusion until fully alert

Adverse Effects

• Sedation: ~27% of patients vs. 14% placebo (most significant safety concern)
• Headache
• Dizziness
• Somnolence
• Risk of sudden loss of consciousness (boxed warning)

Efficacy Data

Why It Was Discontinued / Replaced

1. Mandatory 60-hour hospitalization
2. Cost of inpatient stay plus REMS-certified facility requirement
3. Continuous monitoring burden
4. Separation of mother from newborn during a 2.5-day inpatient stay — clinically counterproductive for bonding/breastfeeding in PPD