Brexanolone (Zulresso)

What it treats

Brexanolone is approved by the U.S. Food and Drug Administration to treat postpartum depression in adults.

Off-label use is limited given the logistics of administration. Off-label means a purpose the label doesn't formally list even though evidence and practice support it.

How it works

Brexanolone is a lab-made version of allopregnanolone, a chemical the body normally makes from progesterone. Allopregnanolone acts on GABA-A receptors, one of the brain's main calming systems.

Allopregnanolone levels rise during pregnancy and drop rapidly after delivery. That drop is thought to be part of what triggers postpartum depression in some people. Delivering brexanolone as a continuous infusion for 60 hours briefly restores those signaling patterns, and for many patients this produces a rapid, sustained shift in mood.

Receptor mechanism (detail)

Brexanolone is a synthetic allopregnanolone, a positive allosteric modulator of both synaptic and extrasynaptic GABA-A receptors. It's structurally distinct from benzodiazepines and boosts tonic (extrasynaptic) inhibition that benzodiazepines don't reach. The 60-hour infusion provides sustained receptor engagement thought to reset the pathophysiology of postpartum depression.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual.

60-hour continuous IV infusion with a titration schedule:

• Hours 0 to 4: 30 μg/kg/hour.
• Hours 4 to 24: 60 μg/kg/hour.
• Hours 24 to 52: 90 μg/kg/hour (or 60 μg/kg/hour if 90 isn't tolerated).
• Hours 52 to 56: 60 μg/kg/hour.
• Hours 56 to 60: 30 μg/kg/hour.

The full course is a single infusion, not a repeated one.

Safety monitoring

• REMS program. Only certified sites can administer brexanolone.
• Continuous pulse oximetry for the full 60 hours.
• Assessment for excessive sedation and sudden loss of consciousness every 2 hours (with an alertness check).
• A caregiver to help care for the infant while the mother is receiving treatment.
• Blood pressure and heart rate.
• Suicidality in patients under 25 (FDA boxed warning applies to all antidepressants; postpartum context modifies but doesn't remove this consideration).

What to expect

Common side effects

Common side effects include:

• Sedation.
• Dizziness.
• Dry mouth.
• Flushing.
• Loss of consciousness (uncommon but the reason for the REMS).

Most effects are during the infusion window. Sedation typically resolves as the infusion tapers and stops.

Serious side effects and warnings

Boxed warning: Excessive sedation and sudden loss of consciousness. Because of these risks, brexanolone is available only through a REMS program with continuous monitoring throughout the infusion.

• Sudden loss of consciousness. Can happen without warning. Continuous monitoring is designed to catch and manage this.
• Sedation. Can be marked; a caregiver is needed for the infant during treatment.
• Blood pressure changes.
• Suicidality. As with any antidepressant, monitoring for worsening mood or suicidality is part of the picture.

Sexual side effects

Sexual side effects aren't a prominent feature of the acute infusion.

Weight, appetite, and sleep

Brexanolone doesn't have the weight and appetite profile of chronic antidepressants because it's a single course. Sleep during the infusion is often deeper than usual because of the sedative effect.

Starting and dosing basics

This section is general background, not a dosing instruction for any individual. The plan is made by the prescriber and infusion team.

Brexanolone is delivered as a single continuous IV infusion at a certified site under REMS. A caregiver is arranged for the infant. Breastfeeding is possible with brief interruption around the infusion at some centers. Vital signs, oxygen saturation, and alertness are checked continuously.

Missed doses and interactions

There are no missed doses to worry about because the treatment is a single course.

Interactions matter mostly with other CNS depressants: benzodiazepines, opioids, alcohol, and sedating antihistamines will add to sedation. The infusion team screens for these ahead of time.

Stopping and tapering

The infusion tapers itself at the end (down to 30 μg/kg/hour over the last 4 hours). No further taper is needed. Ongoing depression treatment planning (antidepressant, psychotherapy) usually starts before the infusion ends.

Pregnancy and breastfeeding

Brexanolone is used specifically in the postpartum period, so this is central. Transfer into breast milk is limited but not zero. Some centers pause breastfeeding for the 60-hour infusion and resume after; others don't. The prescriber and pediatrician plan the specifics.

Cost and generic availability

Brexanolone is brand-only (Zulresso). List price for the infusion course is high (in the tens of thousands of dollars, not counting hospital costs). Insurance coverage varies widely; some manufacturer assistance is available. The cost and logistics are among the reasons oral zuranolone has taken over much of this space.

Common questions

Why is postpartum depression treated differently from other depression? The rapid drop in allopregnanolone (and other reproductive hormones) after delivery seems to play a specific role in postpartum depression. Brexanolone directly addresses that biology. It's not the only treatment for postpartum depression, but it's the first designed for this specific timing and mechanism.

Why 60 hours? The 60-hour infusion length was chosen based on trials showing that sustained exposure produces a durable response.

Can I breastfeed during the infusion? It's possible. Transfer into breast milk is limited. Practice varies by center; the team plans this ahead of time.

Why the REMS program? Sedation and sudden loss of consciousness during the infusion are why continuous monitoring is required. The REMS structure enforces that.

Should I get brexanolone or zuranolone? Zuranolone (oral) is often the more practical choice today because it's taken at home over 14 days rather than as a 60-hour inpatient infusion. Brexanolone remains an option when oral treatment isn't a good fit for a specific situation.

Questions to ask your prescriber

• Am I a candidate for brexanolone, and would zuranolone fit better?
• Who will care for my baby during the 60 hours?
• How do we plan around breastfeeding?
• What does insurance cover, and what does the total cost look like?
• What ongoing depression treatment happens after the infusion?

Sources

This guide draws on current prescribing information and public health references and current as of June 8, 2026. It is reviewed for clinical accuracy and updated as guidance changes.

• U.S. Food and Drug Administration. Brexanolone (Zulresso) prescribing information.
• Zulresso REMS program materials.
• MedlinePlus, U.S. National Library of Medicine. Brexanolone.
• American College of Obstetricians and Gynecologists. Screening for and treatment of perinatal depression.
• American Psychiatric Association. Practice Guideline for the Treatment of Patients with Major Depressive Disorder.