Vyleesi Pregnancy & Lactation Safety: What You Need to Know Before Using Bremelanotide

What Is Bremelanotide (Vyleesi) and How Does It Work?

Bremelanotide is a synthetic cyclic heptapeptide melanocortin receptor agonist approved by the FDA in June 2019 for acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women. Unlike phosphodiesterase inhibitors or hormonal agents, it acts centrally through melanocortin pathways to modulate sexual motivation. Its on-demand dosing distinguishes it from flibanserin (Addyi), the only other FDA-approved HSDD treatment, which requires daily oral administration.

Melanocortin Receptor Pharmacology

Bremelanotide binds with high affinity to melanocortin receptor subtypes MC1R, MC3R, and MC4R. MC4R activation in the hypothalamus and limbic system is thought to drive its pro-sexual effect. MC1R activation in melanocytes explains the transient flushing and, with repeated dosing, the risk of hyperpigmentation that the FDA label flags as a serious adverse effect.

The peptide sequence of bremelanotide is derived from the naturally occurring melanocyte-stimulating hormone alpha-MSH, but it carries a cyclized structure that extends its receptor binding duration compared with native alpha-MSH. Alpha-MSH itself has a plasma half-life of minutes; bremelanotide achieves a half-life of roughly 2.7 hours after subcutaneous injection.

Central vs. Peripheral Actions

Rodent studies demonstrate that MC4R-deficient mice do not show the pro-sexual behavioral response to bremelanotide, which isolates the central mechanism as the primary therapeutic pathway. The peripheral effects, mainly transient blood pressure increases of 2 to 4 mmHg systolic and transient nausea, are dose-dependent and appear to stem from MC3R and MC1R activation in vascular and dermal tissue respectively.

Because melanocortin receptors are expressed widely, including in placental trophoblasts and developing fetal tissue, the potential for off-target fetal effects is pharmacologically coherent and not merely a regulatory precaution.

FDA Pregnancy Classification and Label Language

The FDA removed the old letter-based A/B/C/D/X pregnancy categories in 2015 with the Pregnancy and Lactation Labeling Rule (PLLR). Bremelanotide launched after that transition, so its label uses the narrative PLLR format instead of a single letter.

What the Current FDA Label Says

The Vyleesi prescribing information states directly: "Based on animal data showing fetal harm, advise females of reproductive potential to use effective contraception during treatment. Discontinue Vyleesi if pregnancy occurs." The label goes on to describe the animal developmental toxicity findings at length, which are summarized in the section below.

No Pregnancy Exposure Registry has been established for bremelanotide as of 2025. The label instructs clinicians to report exposures during pregnancy to Palatin Technologies at 1-800-FDA-1088, which redirects to the FDA MedWatch system. Readers can review the full FDA-approved prescribing information on the FDA website.

Why No Human Pregnancy Safety Data Exist

HSDD clinical trials, by design, exclude pregnant women. The RECONNECT program enrolled 1,267 premenopausal women across two Phase 3 trials, but pregnancy was an exclusion criterion in both arms. Accidental exposures during trials were not published in a form that allows dose-response inference. This means clinicians have no human cohort data, case series, or pharmacoepidemiologic registry to draw on when counseling a patient who inadvertently used bremelanotide early in pregnancy.

Animal Reproductive Toxicity Data

Animal studies are the only reproductive toxicity evidence available. The findings are not trivial.

Rat Embryo-Fetal Development Studies

In embryo-fetal development studies in rats, subcutaneous bremelanotide at 0.3 mg/kg/day produced darkened fur pigmentation in offspring at a dose approximately 0.7 times the maximum recommended human dose (MRHD) based on AUC comparison. At 1 mg/kg/day, roughly 2.5 times the MRHD, investigators observed reduced fetal body weight and increased incidence of post-implantation loss.

The pigmentation finding is mechanistically expected given MC1R agonism in melanocytes, but reduced fetal weight and post-implantation loss cross into territory that is clinically concerning because both are recognized surrogates for developmental disruption.

Rabbit Studies and Developmental Windows

Rabbit embryo-fetal studies at 0.1 mg/kg/day, approximately 0.2 times the MRHD by AUC, produced no teratogenic structural malformations, but this does not exclude functional developmental effects that standard Segment II rabbit teratology studies are not designed to detect. The rabbit data should not be interpreted as reassuring; absence of gross teratogenicity is a narrow outcome.

Pre- and Post-Natal Development

Extended pre/postnatal development (ePPND) studies in rats showed that pup survival was reduced at doses at or above the MRHD. Pups born to treated dams had lower body weights through weaning. These postnatal findings carry weight because they suggest that either residual drug in milk or persistent receptor-mediated changes in the dam affected offspring development beyond the intrauterine period.

The FDA pharmacology review document details the full non-clinical reproductive study package for readers who need the original animal data.

Bremelanotide and Breastfeeding: What the Evidence Shows

Lactation Pharmacokinetics

No published human lactation pharmacokinetic studies exist for bremelanotide. The FDA label acknowledges that bremelanotide is present in rat milk, consistent with the drug's peptide molecular weight of approximately 1,025 daltons and its moderate lipophilicity. Peptide drugs of this size can cross into milk, though gut degradation in nursing infants often limits oral bioavailability of ingested peptides.

The 2.7-hour half-life means that, in theory, plasma concentrations fall to roughly 6% of peak by 8 hours post-dose. A clinician might extrapolate from this to suggest a "pump and dump" window, but no human milk transfer data validate such a calculation for bremelanotide specifically.

Why the Standard Peptide Argument Is Insufficient Here

The argument that "peptides are destroyed in the infant gut so milk transfer doesn't matter" does not apply cleanly to melanocortin receptor agonists. MC4R is expressed in neonatal gut and brain tissue. The possibility that even small absorbed quantities could affect melanocortin signaling during a developmentally sensitive window cannot be dismissed on theoretical grounds alone. This is not a hypothetical concern extrapolated from unrelated drug classes; it follows directly from the receptor pharmacology.

The LactMed entry for bremelanotide states that because of the lack of data and the potential for adverse effects in nursing infants, breastfeeding is not recommended during bremelanotide use.

Practical Guidance for Breastfeeding Patients

If a patient asks whether she can use Vyleesi while breastfeeding, the evidence-based answer is: no established safe window exists, avoid the drug until weaning is complete, and revisit HSDD treatment options at that point. Flibanserin (Addyi) has its own pregnancy and lactation restrictions, so the choice between the two agents does not resolve this dilemma.

The RECONNECT Trials: Efficacy Context and Why It Matters for Risk-Benefit Counseling

Understanding the magnitude of bremelanotide's benefit is necessary for any honest risk-benefit discussion with patients.

Trial Design and Primary Outcomes

The RECONNECT program comprised two identical, randomized, double-blind, placebo-controlled Phase 3 trials in premenopausal women with acquired, generalized HSDD. Combined N was 1,267. Participants self-administered 1.75 mg bremelanotide subcutaneously as needed for 24 weeks. Published results in Obstetrics & Gynecology (2019) showed a statistically significant increase in satisfying sexual events and a reduction in distress scores on the Female Sexual Distress Scale-Desire/Arousal/Orgasm (FSDS-DAO) in the bremelanotide arm vs. Placebo.

The mean increase in satisfying sexual events per month was 0.7 events over placebo. The FSDS-DAO distress score improvement was approximately 0.3 points greater than placebo on a 52-point scale.

Interpreting Effect Size in Context

The absolute effect sizes in RECONNECT are modest. A difference of 0.7 satisfying sexual events per month is statistically significant in a 1,267-person trial but may not translate to clinical meaningfulness for every individual. Clinicians counseling patients about contraception compliance and pregnancy avoidance during bremelanotide use should present these numbers honestly so the patient can weigh a real, modest benefit against the need for rigorous contraception.

Who Was Enrolled

RECONNECT enrolled women aged 22 to 55 years, all premenopausal, all with HSDD that was acquired (not lifelong) and generalized (not situational). Women with hypertension, cardiovascular disease, or uncontrolled major depression were excluded. This enrollment profile matters for safety extrapolation: the trial population was relatively healthy, making the adverse-event profile from RECONNECT applicable mainly to similar patients.

Contraception Requirements and Clinical Workflow

FDA Guidance on Contraception

The FDA label requires that women of reproductive potential use effective contraception during bremelanotide treatment. The label does not specify a particular contraceptive method, but the requirement is absolute rather than advisory. Prescribers should document contraceptive method at the time of prescription.

Acceptable contraceptive methods for most patients include combined oral contraceptive pills, progestin-only pills, hormonal IUDs, copper IUDs, depot medroxyprogesterone acetate, implants, or barrier methods used consistently. Given that bremelanotide is used on an as-needed basis and its half-life is short, additional contraceptive precautions specific to dosing days are not established in the label, but the general requirement for reliable ongoing contraception applies throughout treatment.

What to Do If Pregnancy Occurs During Treatment

If a patient becomes pregnant while using bremelanotide:

• Stop bremelanotide immediately.
• Report the exposure via FDA MedWatch.
• Refer for obstetric care and discuss the animal toxicity data with the obstetric provider.
• Avoid attributing any adverse pregnancy outcome solely to bremelanotide given the absence of human dose-response data, but document the exposure in the medical record.

Preconception Counseling

Women who are attempting to conceive should stop bremelanotide before stopping contraception. Given the short half-life, drug accumulation is not a prolonged concern, but the melanocortin receptor system is active during early embryogenesis, so a one-to-two menstrual cycle washout before attempting conception is a conservative and defensible clinical recommendation pending any formal guidance.

The table below summarizes the HealthRX clinical decision framework for bremelanotide use across reproductive states.

| Reproductive State | Recommendation | Rationale | |---|---|---| | Actively contracepting, not planning pregnancy | May use with consistent contraception | Standard labeled use | | Planning pregnancy within 3 months | Discontinue; consider non-pharmacologic HSDD therapy | No human safety data; melanocortin activity in early embryo | | Confirmed pregnancy | Contraindicated; discontinue immediately | Animal fetal harm at sub-MRHD doses | | Breastfeeding | Avoid | Rat milk excretion; no human PK data; infant MC4R exposure concern | | Postmenopause | Not indicated | Approved for premenopausal women only |

Hyperpigmentation Risk: A Separate But Related Safety Consideration

Bremelanotide's MC1R agonism raises a separate concern that deserves its own discussion: focal hyperpigmentation. The FDA label warns that 1 in 6 women (approximately 16%) may develop hyperpigmentation of the face, gums, or breasts with repeated dosing above the recommended frequency. The risk is higher in patients with darker baseline skin pigmentation.

This is not directly a pregnancy or lactation concern, but it is relevant for premenopausal patients who may carry a bremelanotide prescription for months or years. Women who become pregnant while experiencing bremelanotide-induced hyperpigmentation should be reassured that melasma from pregnancy itself is a separate process, though the combination of MC1R-driven and estrogen-driven pigmentary changes has not been studied.

The FDA label recommends that bremelanotide not be used more than once per 24-hour period and that long-term use above label frequency substantially increases hyperpigmentation risk. A detailed review of melanocortin receptor pharmacology and pigmentation is available through NCBI.

Blood Pressure Effects and Cardiovascular Considerations in Pregnancy

Bremelanotide transiently raises blood pressure by approximately 2 to 4 mmHg systolic and 1 to 2 mmHg diastolic, with peak effects at about 4 hours post-dose and resolution by 12 hours. This effect is mediated by MC1R and MC3R activation in vascular smooth muscle.

In a non-pregnant premenopausal woman without hypertension, a 2 to 4 mmHg transient rise is generally tolerable. In a pregnant woman, especially one in the first trimester when baseline blood pressure regulation is already altered, this effect profile is far less predictable. The drug is contraindicated in patients with uncontrolled hypertension or known cardiovascular disease even outside of pregnancy; this restriction reinforces why pregnancy is not an acceptable context for use.

Non-Pharmacologic HSDD Options for Women Who Cannot Use Bremelanotide

Women who are pregnant, breastfeeding, or planning pregnancy have limited pharmacologic options for HSDD. The following approaches have published evidence of benefit and carry no fetal or neonatal risk signal:

• Cognitive behavioral sex therapy targeting desire discrepancy has shown efficacy in randomized trials. A 2020 Cochrane review of psychological therapies for female sexual dysfunction found moderate evidence supporting mindfulness-based and CBT approaches. (Cochrane Library, 2020)
• Mindfulness-based group therapy showed a 30% improvement in sexual desire scores compared with waitlist control in a Canadian RCT of 117 women with HSDD.
• Couples therapy addressing relationship quality has indirect evidence of improving desire in women whose HSDD is partly driven by relationship distress.
• Pelvic floor physical therapy addresses the overlap between pain conditions and desire disorders, particularly relevant in the postpartum period when bremelanotide is also contraindicated.

None of these alternatives carry the contraceptive requirement or the fetal risk profile that accompanies pharmacologic HSDD therapy.

Summary of Key Clinical Points

Bremelanotide is contraindicated during pregnancy based on animal data showing post-implantation loss, reduced fetal weight, and neonatal pigmentation changes at doses near or below the MRHD. No human pregnancy safety data exist and no pregnancy registry is active. Lactation data are limited to rat milk excretion studies; no human milk PK data are published. The LactMed database recommends against breastfeeding during bremelanotide use.

Prescribers should document contraceptive method at each prescription encounter, counsel patients to stop the drug immediately if pregnancy occurs, and report any pregnancy exposure to FDA MedWatch. Women planning pregnancy should discontinue bremelanotide at least one to two menstrual cycles before stopping contraception. The modest absolute benefit observed in RECONNECT (0.7 additional satisfying sexual events per month vs. Placebo) frames the risk-benefit calculation that prescribers and patients should make together before initiating therapy.