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Cariprazine (Vraylar) — Complete Pharmacology Teaching

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1. Identity & Classification

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2. Mechanism of Action — The Star Feature: D3 >> D2

Receptor Profile

Critical concept: Dopamine's own Ki for D3 is ~60 nM. Cariprazine's Ki is 0.09 nM — ~667× more potent than dopamine at D3. In contrast, aripiprazole (Ki ~17.7 nM) and risperidone (Ki ~8 nM) cannot successfully compete with dopamine for the D3 receptor at clinical doses. Cariprazine and blonanserin are the only clinically available agents that reliably block D3 in vivo.

PET Evidence

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3. Why Does D3 Partial Agonism Matter?

Presynaptic D3 in the VTA → More Dopamine in PFC

• D3 receptors sit as somatodendritic autoreceptors on mesocortical dopamine cell bodies in the VTA
• Normally: dopamine activates these D3 autoreceptors → inhibits further dopamine release → reduced cortical dopamine → depression, negative symptoms, cognitive deficits
• Cariprazine blocks these VTA D3 autoreceptors → disinhibits the mesocortical neurons → increased dopamine release onto D1 receptors in the prefrontal cortex
• Downstream effect: improved motivation, energy, cognition, negative symptoms — the "brightening" effect

Postsynaptic D3 in Limbic Regions → Antipsychotic

• Blockade of postsynaptic D3 in limbic emotional striatum reduces dopamine overactivity → antipsychotic and mood-stabilizing effects

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4. Pharmacokinetics

Absorption

• Oral, well absorbed; Tmax: 3–6 hours
• Food does not significantly affect absorption

Metabolism — The "Three Active Moieties" Concept

• All three moieties are equipotent at therapeutic receptors
• Metabolized by CYP3A4 (primary) and CYP2D6
• Steady state: cariprazine + DCAR reach it in 1–2 weeks; DDCAR takes 4–8 weeks
• Elimination: ~21% excreted in urine

Clinical Implications of the Long Half-Life

1. Slow accumulation — patients starting cariprazine see a gradual rise in active drug over weeks (set expectations)
2. Long washout — when stopped, the active moiety persists in plasma for weeks (important for drug interactions and switching)
3. Potential "oral depot" — Stahl's notes cariprazine's metabolite kinetics make it theoretically suitable for development as a weekly/biweekly oral depot formulation
4. CYP3A4 interactions — if co-prescribed with a strong CYP3A4 inhibitor (e.g., ketoconazole, clarithromycin), reduce the cariprazine dose; strong inducers would reduce efficacy

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5. FDA-Approved Indications & Dosing

• Lower doses (1.5–3 mg) favor D3 selectivity and antidepressant effects
• Higher doses (3–6 mg) engage more D2 and are needed for schizophrenia/mania
• Slow titration reduces akathisia
• No dose adjustment needed for mild-moderate hepatic or renal impairment

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6. Clinical Trial Evidence

Schizophrenia (3 positive trials)

• Phase II: cariprazine 1.5–4.5 mg vs risperidone 4 mg vs placebo → cariprazine significantly improved total PANSS
• Trial 2: 3 mg and 6 mg superior to placebo (aripiprazole 10 mg as active reference)
• Trial 3: 3–6 mg and 6–9 mg both superior to placebo

Bipolar Mania (3 positive trials)

• Two flexible-dose studies (3–12 mg/day) → cariprazine > placebo on YMRS
• Third trial: 3–6 mg and 6–12 mg both beat placebo; no efficacy advantage for higher dose range

Bipolar I Depression (key trial)

• Cariprazine 0.75, 1.5, or 3.0 mg/day vs placebo
• 1.5 mg and 3 mg significantly improved MADRS; 0.75 mg did not separate from placebo
• Low metabolic burden compared to quetiapine makes this a preferred option

Adjunctive MDD

• 8-week trial: adjunctive cariprazine 1–2 mg/day, 2–4.5 mg/day, or placebo added to antidepressant
• 2–4.5 mg/day group showed significantly greater improvement on MADRS
• FDA approved in 2022 for this indication

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7. Adverse Effects

Most Common

Metabolic Profile — A Major Advantage

• Very low propensity for weight gain
• Minimal metabolic disturbance (minimal glucose and lipid effects)
• Comparable to lurasidone in this regard — both are preferred when metabolic side effects are a concern

Black Box Warnings

1. Increased mortality in elderly patients with dementia-related psychosis (class warning for all antipsychotics — not specifically proven worse for cariprazine)
2. Neonatal EPS/withdrawal — neonates exposed in the third trimester are at risk for EPS and withdrawal symptoms after delivery

Pregnancy Considerations

• Dopamine-modulating drugs as a class: neonatal EPS/withdrawal risk in 3rd trimester exposure

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8. Comparison with Aripiprazole (its closest "cousin")

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9. Place in Therapy — Where to Use Cariprazine

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10. Drug Interactions

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11. Summary: The "CARIP" Mnemonic

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12. Key Exam Points

1. Cariprazine has higher affinity for D3 than dopamine itself (Ki 0.09 nM vs dopamine's 60 nM) — this is unique
2. It is the only antipsychotic with head-to-head data showing superiority over risperidone for negative symptoms
3. Two major active metabolites — DDCAR has a half-life of 1–3 weeks, making washout prolonged
4. Bipolar depression dose (1.5–3 mg) is lower than schizophrenia/mania dose (1.5–6 mg)
5. The antidepressant mechanism works via VTA D3 autoreceptor blockade → disinhibition of mesocortical dopamine → ↑ PFC D1 stimulation
6. Very low metabolic burden — good choice in patients with obesity/diabetes risk
7. Adjunctive MDD approval came in 2022 — the most recent FDA indication
8. Akathisia > parkinsonism in its EPS profile (because 5-HT1A partial agonism reduces parkinsonism)

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