Brexpiprazole in Breastfeeding
The same prolactin-suppression story as aripiprazole — but with the thinnest evidence base of any commonly used antipsychotic: a single polypharmacy case report. The reassurance is "probably low infant exposure"; the warning is a class effect plus a real-world pharmacovigilance signal the FDA label doesn't mention.
⏱ The 30-Second Review — for busy clinicians
- The thinnest evidence base of any common SGA. One published milk study (Konishi 2024, a polypharmacy case) found RID <1.1% — reassuring for direct infant exposure, but n=1. Compare olanzapine (~170 infants), even aripiprazole (~4).
- Same class, same prolactin risk. Brexpiprazole is a D₂ partial agonist like aripiprazole — a weaker one, but still capable of suppressing prolactin. The 2025 Koukopoulos review concluded all D₂ partial agonists "should be better avoided" while breastfeeding.
- A real-world signal the label omits. A FAERS analysis found a strong "lactation disorder" signal (n=6, ROR 48) and "breast discharge" (n=10, ROR 23), plus a second case report of low milk production — yet the FDA label carries no lactation-specific warning. Clinicians relying on the label alone will miss this.
- It shares aripiprazole's trade-off — favorable metabolism and lactation risk. Like aripiprazole, brexpiprazole sits in the lower-risk metabolic tier (better than olanzapine). So the metabolic benefit doesn't single it out from aripiprazole; what makes it harder to recommend in lactation is the near-empty evidence base, not a metabolic penalty.
- If breastfeeding is a priority, switch class — to quetiapine (prolactin-neutral) or olanzapine (prolactin-raising), ideally before delivery. Switching to brexpiprazole from aripiprazole won't help. Monitor supply by day 3–4 if continuing.
The Bottom Line
Brexpiprazole is a data-deficient, high-caution agent for breastfeeding. The FDA label states plainly that no lactation studies have been conducted to assess its presence in human milk, its effects on the infant, or its effects on milk production.1 A single published case report (Konishi 2024) measured it in milk at an RID below 1.1% — reassuring for direct infant exposure, but a sample of one, in a woman on three antipsychotics simultaneously.2 The dominant concern is the same as aripiprazole's: as a D₂ partial agonist, brexpiprazole can suppress prolactin and threaten supply. That risk is not merely theoretical — a FAERS pharmacovigilance analysis found a strong "lactation disorder" signal (and "breast discharge"), and a second case report described reduced milk production, none of which appears in the label.35 The 2025 Koukopoulos systematic review concluded D₂ partial agonists "should be better avoided" during breastfeeding.4 Bottom line: infant exposure looks low on extremely thin data; the milk-supply risk is the real issue; and because brexpiprazole lacks aripiprazole's metabolic advantage, there is little to offset it — if breastfeeding is a priority, prefer quetiapine or olanzapine.
The entire human milk evidence base for brexpiprazole is one case report — and that patient was on brexpiprazole, risperidone, and quetiapine at once, so brexpiprazole-specific effects on the infant or on supply cannot be isolated. The low RID is genuinely reassuring for direct exposure, but "reassuring" and "established" are different words. This is the thinnest lactation evidence base of any commonly prescribed SGA — against olanzapine's ~170 infants and aripiprazole's ~4 — and the chapter's caution flows directly from that emptiness.9
Pharmacology & the Single Case
A 30-year-old woman with schizophrenia took brexpiprazole 2 mg daily plus risperidone and low-dose quetiapine through pregnancy and postpartum. Milk brexpiprazole concentrations rose over the first days postpartum (≈1 → 6 µg/L, days 4–6), the estimated RID was below 1.1%, and brexpiprazole detectable in neonatal plasma at birth (placental transfer) declined postpartum despite continued breastfeeding — suggesting minimal accumulation from milk.2 The authors judged breastfeeding "still possible" given an RID far under 10%. The unavoidable caveat: one patient, polypharmacy, sparse sampling.
The FDA Label — Silence & an Animal Signal
The Rexulti label's lactation section is notable for what it doesn't contain.
What it says
No lactation studies have been conducted to assess brexpiprazole in human milk, its effects on the infant, or its effects on milk production; brexpiprazole is present in rat milk; and the standard benefit/risk balancing statement applies.1
What it does not say (unlike aripiprazole)
- No warning about prolactin suppression or decreased milk supply (aripiprazole's label warns of "clinically relevant decreases in milk supply").
- No infant-monitoring recommendation (aripiprazole's label advises monitoring for dehydration and inadequate weight gain).
- No mention of lactation-failure reports.
Easy to overlook in the label's nonclinical section: in rats dosed from organogenesis through lactation at 73× the MRHD, there was impaired nursing by dams, low birth weight, decreased pup weight gain, and increased perinatal pup deaths — none of which appeared at 24× MRHD. Animal data don't translate directly, but "impaired nursing" is mechanistically consistent with the D₂-partial-agonist prolactin effect, and together with the human FAERS signal it strengthens the biological plausibility of brexpiprazole-related lactation impairment.1
"Prolactin-Neutral" ≠ "Lactation-Safe"
Brexpiprazole's prolactin profile is more nuanced than aripiprazole's — and that nuance is exactly where clinicians get misled.
The pharmacology
Brexpiprazole has lower D₂ intrinsic activity than aripiprazole — a "weaker" partial agonist — so in schizophrenia and MDD trials it produces little net prolactin change and is often described as "prolactin-sparing" or "prolactin-neutral."67 Pooled trial analyses show only small median prolactin changes, low rates of prolactin-related adverse events, and a tendency for prolactin to fall over time in patients with elevated baselines from prior antipsychotics. A 2025 dose-response meta-analysis grouped brexpiprazole among agents with negligible prolactin-elevation risk.13
Those trial data are used to reassure that brexpiprazole won't cause hyperprolactinemia side effects (galactorrhea, amenorrhea, sexual dysfunction) — true, and useful in general practice. But "neutral on average" is not "inert": the pediatric label notes a substantial fraction of adolescent females shifting from normal to abnormal prolactin on brexpiprazole, a reminder that the prolactin effect varies by population.6 More to the point, lactation needs the opposite of neutrality: prolactin must be dramatically elevated (often 100–300 ng/mL) to establish and sustain milk production. An agent that keeps prolactin "neutral" — preventing the normal postpartum surge — can be enough to impair lactation, even if it never causes hyperprolactinemia. The schizophrenia prolactin data describe the wrong endpoint (avoiding excess) for the wrong population (non-lactating). They cannot be read as lactation safety.
A FAERS pharmacovigilance analysis of 8,559 brexpiprazole adverse-event reports found disproportionate signals for "lactation disorder" (n=6, ROR 48.09) and "breast discharge" (n=10, ROR 23.18) — "reproductive system and breast disorders" flagged as a class of reactions not mentioned in the label.3 A separate conference abstract (Berlin 2020) reported low breast-milk production with brexpiprazole.5 FAERS cannot establish causation (reporting bias, confounding by indication), and the co-occurrence of "breast discharge" likely reflects unmasking of prior prolactin-raising antipsychotics — but the lactation-disorder signal points the same direction as the mechanism, the animal data, and the aripiprazole class experience.
The Class Effect & the Aripiprazole Comparison
Brexpiprazole has to be read as a member of the D₂ partial agonist class (aripiprazole, brexpiprazole, cariprazine), which shares the prolactin-suppressing mechanism. The 2025 Koukopoulos review of all three concluded that pregnancy use looks relatively reassuring but that during breastfeeding they "should be better avoided."4
| Property | Aripiprazole | Brexpiprazole | Cariprazine |
|---|---|---|---|
| D₂ intrinsic activity | Higher | Lower | Intermediate |
| Prolactin suppression | Moderate–high | Low–moderate | Low–moderate |
| Predicted lactation risk | High (74% failure documented)8 | Moderate–high (class + FAERS signal) | Moderate–high (class; no data) |
| Weight-gain risk | Low | Low–moderate | Low |
| Human lactation data | Very limited (~4 infants) | Minimal (1 case) | None |
Pharmacologically, brexpiprazole's weaker D₂ partial agonism should mean less prolactin suppression than aripiprazole and perhaps less lactation impairment. But that hypothesis has never been tested in lactating women, and the FAERS lactation signal suggests the clinical reality may not match the prediction. Until head-to-head lactation data exist, treat brexpiprazole as carrying the same class-level lactation risk as aripiprazole — the theoretical edge is not something to stake an infant's nutrition on.
It would be convenient to say brexpiprazole is easier to set aside than aripiprazole because it lacks a metabolic upside — but that isn't true. Network meta-analyses place brexpiprazole in the same lower-risk metabolic tier as aripiprazole and cariprazine, clearly better than olanzapine (some weight gain occurs, but well short of olanzapine's). So brexpiprazole carries the same trade-off as aripiprazole — favorable metabolism set against a prolactin/supply risk — not a worse one. What actually distinguishes it is the evidence base: aripiprazole at least has the Nanjundaswamy cohort and ~4 infants; brexpiprazole has n=1. The case for caution rests on data-emptiness plus the class signal, not on a metabolic penalty that doesn't exist.
Infant Impact & the Postpartum PK Surge
Direct exposure — low (on thin data)
The single case found RID <1.1%, neonatal plasma declined postpartum despite continued nursing, and the metabolite DM-3411 is pharmacologically inactive.2 As with aripiprazole, the dominant infant risk is indirect — inadequate nutrition from low supply, not drug toxicity.
Neonatal adaptation (third-trimester exposure)
Antipsychotic-exposed neonates can show extrapyramidal/withdrawal signs (agitation, hypertonia/hypotonia, tremor, somnolence, respiratory distress, feeding difficulty) in the first hours-to-days — reflecting in-utero exposure, not milk. These shouldn't be blamed on breastfeeding or used to stop it; if supply is adequate, nursing can continue with supportive monitoring.1
What to monitor
- Weight — the critical metric; track closely in the first two weeks if supply is uncertain.
- Hydration — ≥6 wet diapers/day by day 4–5.
- Sedation/irritability — rare at this RID, but monitor as with any SGA.
In the Konishi case, maternal brexpiprazole levels rose ~3.5-fold by postpartum day 5 versus delivery day (the same rise was seen for the co-administered quetiapine and paliperidone), as pregnancy-related increases in clearance reversed.2 The general phenomenon — antepartum antipsychotic levels running well below baseline, then rebounding postpartum — is well documented for other agents too.11 A woman comfortable on her dose during pregnancy may transiently reach much higher levels in the first postpartum week, which could deepen both side effects and prolactin suppression. Consider a trough level around one week postpartum in a patient who was stable antepartum, and adjust accordingly.
Supply Guardrail & Comparative Position
The Supply Guardrail Protocol
- Day 0–1: initiate breastfeeding; formula available at bedside.
- Day 3–4 milk check: assess for lactogenesis II (engorgement, transitional milk). If absent → begin supplementation, consider a prolactin level, consult lactation. Don't wait.
- Day 5–14: if partial supply, hybrid-feed; weigh the infant at least twice weekly.
- Weeks 2–12: if stable and gaining, continue; if supply fails, transition to formula with reassurance, or switch agent if recovery is desired.
- After any dose increase: re-start a 2-week supply watch — the effect is dose-dependent, and a supply adequate at 1 mg may falter at 2 mg. Warn the patient before any dose change.
Comparative Positioning
| Agent | RID | Prolactin | Milk-supply risk | Infant data | Recommendation |
|---|---|---|---|---|---|
| Quetiapine | ~0.1–0.4% | Minimal | Low | Moderate | First-line |
| Olanzapine | 1–2.5% | ↑ (mild) | Low (may support supply) | Most extensive (~170) | First-line |
| Aripiprazole | ~1–8% (varies) | ↓↓ (partial agonist) | High (74% failure) | Very limited (~4) | Infant-safe; high supply risk |
| Brexpiprazole | <1.1% (1 case) | ↓ (partial agonist) | Likely high (class + FAERS) | Minimal (n=1) | Data-deficient; class-level caution |
| Cariprazine | Unknown | ↓ (partial agonist) | Likely high (class effect) | None | Insufficient data; avoid |
| Risperidone / paliperidone | 2.3–4.7% | ↑↑ | Low (may support supply) | Moderate | Compatible w/ monitoring |
A patient on aripiprazole with lactation failure sometimes asks about switching to brexpiprazole because it's "newer" or "better tolerated." It will not fix the supply problem — the prolactin-suppressing mechanism is shared. The correct rescue is a switch out of the class: to quetiapine (prolactin-neutral) or olanzapine (prolactin-raising). Frame it for the patient: "the milk-supply problem comes from the type of medicine, not the brand — we need a different type, not a newer version of the same type."
Clinic-Ready Tools
Decision Algorithm
- Is breastfeeding a high priority? No → brexpiprazole can continue; formula feeding fully supported. Yes → step 2.
- Pregnant (planning) or already postpartum? Pregnant → ideal time to act (step 3). Postpartum → go to the supply protocol (step 4).
- Predelivery planning: preferred path is a switch to quetiapine or olanzapine in the second trimester (≥4 weeks to stabilize) — removes the class risk. Per ACOG, weigh any switch against the risk of psychiatric destabilization, and don't change an agent a patient is stable on for lactation reasons alone without that calculus.10 If the patient declines or is stable only on brexpiprazole, set explicit expectations and arrange the supply guardrail.
- Postpartum: formula at bedside day 0; day 3–4 milk check; hybrid-feed if partial; switch or exclusive formula (no guilt) if supply fails. Re-watch supply for 2 weeks after any dose increase.
Patient Script — "Say It Like This"
"Brexpiprazole is a newer medicine, and the good news is that very little of it — under 1% — seems to reach the baby through milk, so direct safety for the baby looks reassuring. But there's an important catch: we have almost no breastfeeding data on it specifically, and it belongs to the same family as an older medicine, aripiprazole, that often lowers the hormone needed to make milk. We expect a similar risk, and there are early real-world reports of milk-supply problems with brexpiprazole.
Your options: one, if breastfeeding really matters to you, switch before the baby comes to a medicine like quetiapine or olanzapine that doesn't lower your milk hormone. Two, stay on brexpiprazole and try, knowing you may need to add formula and that we'll watch your supply closely. Three, formula-feed, which is a healthy choice and lets you stay on a medicine that works for you.
Whatever we choose, we'll track the baby's weight closely in the first weeks — and there's no wrong answer here. A stable, well mother is what matters most."
EMR Documentation Template
Quick Reference
Evidence
n=1 human milk case (RID <1.1%, polypharmacy); FDA label has NO lactation data. Thinnest base of any common SGA.
The Risk
D₂-partial-agonist class → prolactin suppression. FAERS "lactation disorder" ROR 48 + a low-supply abstract + animal "impaired nursing" — all point the same way. The distinction from aripiprazole is data (n=1), not metabolism.
The Move
If breastfeeding matters → switch class (quetiapine/olanzapine), ideally pre-delivery. Not to another partial agonist. Monitor supply day 3–4; re-watch after any dose increase.
If supply fails despite real effort, normalize formula feeding as valid and healthy and document that reassurance — a well, stable mother matters more to the infant than the feeding route. With brexpiprazole the guilt can be sharper because the data are so thin that failure feels unexplained; naming the class mechanism ("this is the medication type, not something you did") is part of the care.
References
- Rexulti (brexpiprazole) — US prescribing information (lactation, clinical pharmacology, nonclinical toxicology sections). DailyMed.
- Konishi T, Kitahiro Y, Fujiwara N, et al. Pharmacokinetics of brexpiprazole, quetiapine, risperidone, and the active metabolite paliperidone in a postpartum woman and her baby. Ther Drug Monit. 2024;46(5):687–691. doi:10.1097/FTD.0000000000001197. PMID 38648649
- Jiang Y, Zhou L, Shen Y, Zhou Q, Ji Y, Zhu H. Safety assessment of brexpiprazole: real-world adverse event analysis from the FAERS database. J Affect Disord. 2024;346:223–229. doi:10.1016/j.jad.2023.11.025. PMID 37956832
- Koukopoulos A, Janiri D, Milintenda M, et al. Dopamine partial agonists in pregnancy and lactation: a systematic review. Pharmaceuticals (Basel). 2025;18(7):1010. doi:10.3390/ph18071010
- Berlin S, Bodnar K. Low breast milk production associated with brexpiprazole (Rexulti). Breastfeed Med. 2020;15(S1):A-3 (abstract). doi:10.1089/bfm.2020.29162.abstracts
- Ivkovic J, Lindsten A, George V, et al. Effect of brexpiprazole on prolactin: an analysis of short- and long-term studies in schizophrenia. J Clin Psychopharmacol. 2019;39(1):13–19. doi:10.1097/JCP.0000000000000979
- Clayton AH, Ivkovic J, Chen D, George V, Hobart M. Effect of brexpiprazole on prolactin in adjunctive MDD: short- and long-term analyses. J Clin Psychopharmacol. 2020;40(6):560–567. doi:10.1097/JCP.0000000000001294
- Nanjundaswamy MH, Shah A, Lotlikar S, et al. Lactation-related side effects of aripiprazole: a study from perinatal psychiatry services in India. J Clin Psychopharmacol. 2025;45(3):258–266. doi:10.1097/JCP.0000000000001997
- Uguz F. Second-generation antipsychotics during the lactation period: a comparative systematic review on infant safety. J Clin Psychopharmacol. 2016;36(3):244–252. doi:10.1097/JCP.0000000000000491
- American College of Obstetricians and Gynecologists. Treatment and management of mental health conditions during pregnancy and postpartum: ACOG Clinical Practice Guideline No. 5. Obstet Gynecol. 2023;141(6):1262–1288. doi:10.1097/AOG.0000000000005202
- Westin AA, Brekke M, Molden E, et al. Treatment with antipsychotics in pregnancy: changes in drug disposition. Clin Pharmacol Ther. 2018;103(3):477–484. doi:10.1002/cpt.770
- National Library of Medicine. Drugs and Lactation Database (LactMed): Brexpiprazole. Bethesda, MD; updated 2025.
- Lin TC, Huang HC, Chen YS, et al. Dose-response of antipsychotic-related prolactin changes: a meta-analysis. Psychoneuroendocrinology. 2025;162:106950. doi:10.1016/j.psyneuen.2024.106950
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