Bromocriptine is an ergot-derived dopamine agonist, a drug that mimics dopamine at its receptors. Because dopamine is the brain’s main brake on prolactin release, bromocriptine lowers prolactin. It was the original dopamine agonist treatment for prolactin-secreting pituitary tumors (Inder & Jang, Medicina 2022). It is sold in the US in two very different forms: Parlodel, first approved in 1978 and now labeled for hyperprolactinemia, acromegaly and Parkinson’s disease (Parlodel label), and Cycloset, a low-dose tablet approved in 2009 for type 2 diabetes (Cycloset label).
The most important safety fact is historical. Bromocriptine was once used to stop breast milk after childbirth, and serious events in postpartum women, including stroke, seizures and heart attack, led the FDA to move to withdraw that use in 1994. Both current labels warn against it. In prolactinoma care, cabergoline has largely replaced bromocriptine because it works better and is better tolerated.
This page summarizes what the FDA labels, clinical trials and reviews report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Ergot-derived dopamine D2 receptor agonist |
| Brands / approval | Parlodel, NDA 017962, approved June 28, 1978; Cycloset, NDA 020866, approved May 5, 2009; generics available |
| Route | Oral tablet or capsule |
| Strengths | Parlodel 2.5 mg tablet and 5 mg capsule; Cycloset 0.8 mg tablet |
| Labeled daily dose | 2.5–15 mg (hyperprolactinemia, as studied); usually 20–30 mg (acromegaly); 1.6–4.8 mg (Cycloset) |
| Half-life (label) | 4.85 h (Parlodel, single dose); about 6 h (Cycloset) |
| Oral bioavailability | About 7% reaches the circulation after first-pass metabolism, mainly by CYP3A4 (Cycloset label) |
| US status | Prescription only; not listed in Schedule III (21 CFR 1308.13) |
| WADA status | Not named on the 2026 Prohibited List (WADA 2026 Prohibited List) |
What it is
Bromocriptine mesylate is an ergot derivative. As its chemical name (2-bromo-12′-hydroxy-…-ergotaman-3′,6′,18-trione) indicates, it carries a bromine atom on the ergot ring system. The labeled molecular formula of the salt is C₃₂H₄₀BrN₅O₅·CH₄SO₃, with a molecular weight of 750.72 (Cycloset label). Cabergoline is also an ergot derivative (cabergoline label).
The Parlodel label explains the two main actions (Parlodel label):
- Pituitary. Dopamine released by hypothalamic neurons inhibits prolactin secretion from the anterior pituitary. Bromocriptine activates the same receptors and lowers prolactin, with little or no effect on other pituitary hormones. The exception is acromegaly, where it lowers elevated growth hormone in most patients.
- Brain motor circuits. In Parkinson’s disease it stimulates dopamine receptors in the corpus striatum directly. Unlike levodopa, it does not need to be converted to dopamine by the dwindling neurons of the substantia nigra.
Cycloset uses a third, less intuitive action. The label describes it as a “sympatholytic” D2 agonist: taken in the morning, it is associated with better insulin sensitivity and lower glucose after meals, without raising insulin levels (Cycloset label).
Bromocriptine was found to inhibit prolactin shortly after prolactin was isolated in the early 1970s. By the end of that decade, CT imaging had shown that it shrinks large prolactinomas. It remained the treatment of choice until cabergoline arrived in the late 1980s and early 1990s (Inder & Jang, Medicina 2022).
Pharmacokinetics
The two products share an active ingredient but are formulated and timed differently.
| Parameter | Parlodel | Cycloset |
|---|---|---|
| Time to peak | 2.5 h (fasted, 5 mg, n = 5) | 53 min fasted; about 90–120 min after a high-fat meal |
| Peak level | 465 pg/mL after 5 mg; 628 pg/mL at steady state on 5 mg twice daily | About 80–125 pg/mL after 4.8 mg |
| Elimination half-life | 4.85 h | About 6 h |
| Effect of food | No significant change in exposure; taken with food to reduce vomiting | Exposure (AUC) about 55–65% higher when fed |
| Protein binding | 90–96% | 90–96% |
| Main route out | Feces (about 82% of a radiolabeled dose); urine 5.6% | Bile; urine about 2–6% |
Sources: Parlodel label; Cycloset label.
About 65–95% of an oral dose is absorbed, but about 93% is broken down on its first pass through the gut and liver, so only about 7% reaches the bloodstream. CYP3A4 is the main enzyme. That is why CYP3A4 inhibitors raise bromocriptine levels sharply (see Interactions). Exposure is 18–30% higher in women than in men. Neither label has pharmacokinetic data in liver or kidney disease. Because the drug is cleared mainly by the liver, both advise caution in hepatic impairment.
Approved medical use
Parlodel (and generic bromocriptine)
The Parlodel label covers three indications (Parlodel label):
- Hyperprolactinemia-associated dysfunctions: amenorrhea (absent periods) with or without galactorrhea (milk discharge), infertility or hypogonadism, including prolactin-secreting adenomas. Tumor shrinkage has been shown in men and women with macroadenomas, and a course may be used to shrink a tumor before surgery.
- Acromegaly: alone or alongside pituitary radiation or surgery. Growth hormone falls by 50% or more in about half of patients, though usually not to normal.
- Parkinson’s disease: idiopathic or postencephalitic, mainly as an add-on to levodopa. Continued efficacy beyond 2 years has not been established.
| Indication | Labeled starting dose | Titration | Labeled range or limit |
|---|---|---|---|
| Hyperprolactinemia (adults) | 1.25–2.5 mg daily | Add 2.5 mg every 2–7 days as tolerated | 2.5–15 mg/day in adults studied |
| Prolactinoma (ages 11–15) | 1.25–2.5 mg daily | Increase as tolerated | 2.5–10 mg/day in reported cases |
| Acromegaly | 1.25–2.5 mg at bedtime with food for 3 days | Add 1.25–2.5 mg every 3–7 days | Usually 20–30 mg/day; not over 100 mg/day |
| Parkinson’s disease | 1.25 mg twice daily with meals | Add 2.5 mg/day every 14–28 days | Safety not shown above 100 mg/day |
The label recommends taking every dose with food.
Cycloset
Cycloset is approved as an adjunct to diet and exercise to improve blood sugar control in adults with type 2 diabetes. It should not be used for type 1 diabetes or diabetic ketoacidosis, efficacy with insulin has not been confirmed, and data with thiazolidinediones are limited (Cycloset label).
The labeled dose starts at one 0.8 mg tablet once daily, taken within 2 hours of waking with food. It rises by one tablet per week to 1.6–4.8 mg (2–6 tablets), as tolerated. Cycloset is not approved for prolactin disorders, and its doses are far lower than those used in acromegaly or Parkinson’s disease.
The withdrawn lactation indication
FDA approved Parlodel to prevent physiological lactation (milk production after birth) in 1980. By 1989 the agency had received 85 serious adverse event reports linked to this use, including 10 deaths, with hypertension, seizures and strokes. An FDA advisory committee concluded that the risks outweighed a limited benefit in a self-resolving condition. When Sandoz declined to remove the indication voluntarily, FDA published a proposal to withdraw it in August 1994 (Federal Register 1994). The current Cycloset label states that the indication was withdrawn from bromocriptine products.
What the research shows
Prolactinoma and hyperprolactinemia
In the Parlodel label’s clinical data, about 75% of women with amenorrhea and galactorrhea had galactorrhea fully or almost fully suppressed and regular ovulatory cycles restored. Periods returned after 6–8 weeks on average, but the range ran from a few days to 8 months (Parlodel label).
The key head-to-head trial randomized 459 women with hyperprolactinemic amenorrhea to cabergoline (0.5–1.0 mg twice weekly) or bromocriptine (2.5–5.0 mg twice daily), double-blind for 8 weeks and then open-label to 24 weeks (Webster et al., NEJM 1994):
| Outcome | Cabergoline (n = 223) | Bromocriptine (n = 236) |
|---|---|---|
| Stable normal prolactin | 83% | 59% |
| Ovulatory cycles or pregnancy | 72% | 52% |
| Persistent amenorrhea | 7% | 16% |
| Any adverse effect | 68% | 78% |
| Stopped for intolerance | 3% | 12% |
The differences in prolactin control, ovulation or pregnancy, side effects and dropouts were statistically significant. A 2022 review notes that bromocriptine is “rarely used these days.” Some experts still prefer it for women trying to conceive because of its longer pregnancy safety record (Inder & Jang, Medicina 2022). The same review puts the rate of dopamine-agonist resistance (defined as no response at 15 mg/day or more) at 20–30% for bromocriptine. For cabergoline, it is under 10% for microadenomas and up to 20% for macroadenomas. A 2023 JAMA review still lists either drug as first-line therapy for prolactinomas, which make up about 53% of pituitary adenomas (Tritos & Miller, JAMA 2023). The cabergoline page covers the comparison in more depth.
Pregnancy outcomes
The Parlodel label collected data on 1,276 pregnancies in women taking the drug, mostly stopped within the first 8 weeks (mean 28.7 days). It reported a spontaneous abortion rate of 11.4%, and birth defects in 3.3% of 1,109 live births, against a general-population range of 2–4.5%. The label found no suggestion that Parlodel contributed to birth defects (Parlodel label). The label still directs that treatment for hyperprolactinemia be stopped once pregnancy is confirmed.
Acromegaly
The evidence here is mainly the label’s: growth hormone falls by 50% or more in about half of patients, usually not to normal levels (Parlodel label). The usual effective dose (20–30 mg/day) is much higher than in hyperprolactinemia, which matters for the dose-related risks below.
Parkinson’s disease
A Cochrane review of 6 trials (850 participants) compared bromocriptine alone with levodopa in early Parkinson’s disease (van Hilten et al., Cochrane 2007). The trials were of low quality and too heterogeneous to pool. Longer trials suggested fewer dyskinesias (involuntary movements) and less dystonia with bromocriptine, but the differences were significant only in the largest trial. More patients dropped out on bromocriptine for poor response or side effects.
The Parlodel label itself says data are insufficient to support treating newly diagnosed Parkinson’s disease, and that bromocriptine caused more nausea, hallucinations, confusion and low blood pressure than levodopa/carbidopa. Other dopamine agonists, such as pramipexole, are also used in Parkinson’s disease.
Type 2 diabetes (Cycloset)
The Cycloset label reports four placebo-controlled trials in 3,723 patients (Cycloset label):
| Trial (24 weeks unless noted) | Patients | Baseline HbA1c | HbA1c difference vs placebo |
|---|---|---|---|
| Monotherapy | 159 | 9.0% vs 8.8% | −0.4 points (p = 0.05) |
| Add-on to sulfonylurea, Study K | 245 | 9.3% vs 9.4% | −0.5 points (p ≤ 0.001) |
| Add-on to sulfonylurea, Study L | 249 | 9.3% vs 9.4% | −0.6 points |
| Safety trial subgroup, HbA1c ≥ 7.5% on 1–2 oral drugs | 559 | 8.3% vs 8.4% | −0.5 points (p under 0.001) |
HbA1c is the average blood sugar marker over about 3 months. In the safety-trial subgroup, 25% on Cycloset vs 9% on placebo reached an HbA1c of 7.0% or less. Weight changed little (+0.2 kg vs +0.1 kg over 52 weeks in the whole safety trial).
The 52-week Cycloset Safety Trial randomized patients 2:1 to Cycloset or placebo on top of usual care, with serious adverse events as the primary endpoint (Gaziano et al., Diabetes Care 2010). The label reports these results:
| Endpoint | Cycloset (n = 2,054) | Placebo (n = 1,016) | Effect |
|---|---|---|---|
| Any serious adverse event | 8.5% | 9.6% | HR 1.02 (one-sided 96% upper bound 1.27) |
| Composite cardiovascular endpoint | 1.5% | 3.0% | HR 0.58 (95% CI 0.35–0.96) |
| Stopped treatment early | 47% | 32% | — |
The composite included heart attack, stroke, coronary revascularization and hospitalization for angina or heart failure. The published paper reports slightly different counts (37 vs 32 events, HR 0.60) and later had an erratum. Its primary test was noninferiority for serious adverse events (margin HR 1.5). The cardiovascular composite was a secondary, prespecified analysis, so it shows no excess risk rather than proven benefit.
Relevance to prolactin control alongside anabolic steroids
Bromocriptine is sometimes discussed online, like cabergoline, as a way to control prolactin in people using 19-nortestosterone steroids such as nandrolone or trenbolone. We found no controlled human trial of bromocriptine in anabolic steroid users for any outcome.
The human data on prolactin in steroid users are themselves thin. One cross-sectional study of 60 gym-goers in Baghdad found higher prolactin in the 30 who used anabolic steroids than in 30 non-users (Qasim Ali et al., Steroids 2024). It could not show which compound was responsible or whether symptoms followed. The Parlodel label also stresses that hyperprolactinemia can come from a pituitary tumor and calls for a complete pituitary evaluation before treatment.
Side effects and risks
Common side effects
Side effect rates differ by indication and dose (Parlodel label; Cycloset label):
| Side effect | Hyperprolactinemia (Parlodel) | Acromegaly (Parlodel) | Cycloset 52-week trial | Placebo, same trial |
|---|---|---|---|---|
| Nausea | 49% | 18% | 32.2% | 7.6% |
| Headache | 19% | under 2% | 11.4% | 8.3% |
| Dizziness | 17% | under 2% | 14.8% | 9.2% |
| Fatigue | 7% | 3% (drowsiness/tiredness) | 13.9% | 6.7% |
| Vomiting | 5% | 2% | 8.1% | 3.1% |
| Constipation | 3% | 14% | 5.8% | 5.1% |
In hyperprolactinemia, 69% had at least one side effect, mostly mild to moderate, and about 5% stopped treatment because of them. On Cycloset, common side effects lasted a median of 14 days and clustered during dose titration.
Postpartum use
This is the drug’s most serious documented risk. The Parlodel label lists postmarketing US reports in postpartum women of 72 seizures (4 with status epilepticus), 30 strokes and 9 heart attacks. Many seizures and strokes were preceded by a constant, often worsening headache, sometimes with visual disturbance. Most of these women had no hypertensive disorder of pregnancy. A causal link has not been established, but the label does not recommend bromocriptine to prevent lactation (Parlodel label).
The labels differ in how far they go:
- Parlodel: should not be used postpartum in women with coronary artery disease or other severe cardiovascular conditions unless withdrawal is medically contraindicated. It should not be used during lactation.
- Cycloset: contraindicated in all postpartum and all lactating patients.
Low blood pressure, fainting and sudden sleep
In postpartum studies, almost 30% of women had drops of more than 20 mm Hg systolic and 10 mm Hg diastolic, sometimes as much as 50–59 mm Hg systolic. In the Cycloset safety trial, syncope (fainting) occurred in 1.6% vs 0.7% on placebo, and somnolence in 4.3% vs 1.3%. Parlodel also carries a warning for sudden sleep onset during daily activities, mostly in Parkinson’s disease, sometimes without warning signs.
Fibrosis and heart valves
With long-term, high-dose Parlodel, the label reports pleural and pericardial effusions, pleural and pulmonary fibrosis, constrictive pericarditis and retroperitoneal fibrosis. Retroperitoneal fibrosis has been seen after 2–10 years at 30–140 mg/day. Its early signs include back pain, leg swelling and reduced kidney function. The label says the changes slowly reverted toward normal when the drug was stopped (Parlodel label). The Cycloset label adds that fibrotic complications do not always resolve after stopping.
Cardiac valve fibrosis is listed among Parlodel’s postmarketing reports. The Cycloset label states that studies have not established a definitive link between bromocriptine and clinically significant (moderate to severe) valve disease. In Cycloset’s controlled trials, there was one case of pulmonary fibrosis among 2,500 treated patients (Cycloset label).
Impulse control disorders and psychiatric effects
Both labels warn of intense urges to gamble, spend money or have sex that people may not recognize as abnormal. Cycloset’s patient counseling also lists binge or compulsive eating. In some cases the urges stopped after the dose was lowered or the drug stopped. The labels tell prescribers to ask about them specifically. In studies of dopamine agonists for prolactinoma generally, the prevalence of impulse control disorders has been reported at 8–25% (Inder & Jang, Medicina 2022).
The Parlodel label also lists:
- hallucinations, confusion and, rarely, psychosis, especially at high doses;
- caution in people with a history of psychosis;
- a syndrome resembling neuroleptic malignant syndrome (fever, rigidity, altered consciousness) after rapid dose reduction or withdrawal;
- withdrawal symptoms on tapering, such as apathy, anxiety, depression, fatigue, insomnia, sweating and pain.
Pituitary-specific risks
In patients with large prolactinomas, the Parlodel label notes:
- stopping the drug has been associated with rapid tumor regrowth in most cases;
- cerebrospinal fluid can leak from the nose (CSF rhinorrhea) as tumors shrink;
- vision can worsen even when prolactin is controlled, when the optic chiasm is pulled down into the emptied pituitary fossa.
Interactions
| Interacting drug or class | Effect (label) |
|---|---|
| Erythromycin and other macrolides | Bromocriptine AUC up 2.8–3.7-fold and peak up 4.6-fold; Cycloset capped at 1.6 mg/day with moderate CYP3A4 inhibitors |
| Strong CYP3A4 inhibitors (azole antifungals, HIV protease inhibitors) | Avoid with Cycloset; caution with Parlodel |
| Octreotide | Bromocriptine AUC up about 38% in acromegaly |
| Dopamine antagonists (antipsychotics, metoclopramide) | Each drug may blunt the other; not recommended |
| Other ergot alkaloids, sympathomimetics, triptans | More ergot-type effects, or reports of hypertension; combination not recommended |
| Alcohol | May worsen side effects |
| Blood pressure–lowering drugs | Added risk of low blood pressure |
Who should not take it
Per the labels, bromocriptine is contraindicated in people with:
- hypersensitivity to bromocriptine or other ergot alkaloids;
- uncontrolled hypertension (Parlodel);
- syncopal migraine (Cycloset);
- postpartum status or breastfeeding (Cycloset).
Monitoring
The labels recommend the following checks:
| What | Why |
|---|---|
| Blood pressure, especially in the first weeks | Low blood pressure early; hypertension in postpartum reports |
| Pregnancy tests every 4 weeks while periods are absent (hyperprolactinemia) | Pregnancy can occur before periods return |
| Visual fields (macroprolactinoma) | Secondary vision loss despite tumor shrinkage |
| Growth hormone, monthly during titration (acromegaly) | Guides dose |
| Breathing symptoms, back pain, leg swelling, kidney function (long-term, high dose) | Early detection of fibrosis |
| New urges to gamble, spend, have sex or eat | Impulse control disorders |
| Regular skin checks | Melanoma risk is higher in Parkinson’s disease; the Parlodel label advises checks for any indication |
Key takeaways
- One molecule, two products. Parlodel (labeled doses up to 100 mg/day) treats prolactin disorders, acromegaly and Parkinson’s disease. Cycloset (0.8–4.8 mg once each morning) treats type 2 diabetes.
- Effective, but second to cabergoline for prolactin. In a 459-woman trial, prolactin normalized in 59% on bromocriptine vs 83% on cabergoline, and 12% vs 3% stopped for side effects.
- Never for stopping breast milk. Seizures, strokes and heart attacks in postpartum women led FDA to move to withdraw that use in 1994. Cycloset is contraindicated postpartum.
- Nausea is the defining side effect. It affected about half of hyperprolactinemia patients and a third of Cycloset patients.
- Long-term, high-dose risks. Pleural, pericardial and retroperitoneal fibrosis and impulse control disorders are labeled risks.
- No evidence in steroid users. No controlled trial has tested bromocriptine for prolactin-related effects of anabolic steroids.
Sources
- Validus Pharmaceuticals. Parlodel (bromocriptine mesylate) tablets and capsules, prescribing information (revised July 2021). DailyMed; Drugs@FDA, NDA 017962.
- VeroScience. Cycloset (bromocriptine mesylate tablets), prescribing information (revised August 2020). DailyMed; Drugs@FDA, NDA 020866.
- Food and Drug Administration. Sandoz Pharmaceuticals Corp.; Bromocriptine Mesylate (Parlodel) for the Prevention of Physiological Lactation; Opportunity for a Hearing on a Proposal To Withdraw Approval of the Indication. Federal Register. August 23, 1994;59(162). Docket No. 94N-0304. Federal Register.
- Webster J, Piscitelli G, Polli A, et al. A comparison of cabergoline and bromocriptine in the treatment of hyperprolactinemic amenorrhea. Cabergoline Comparative Study Group. N Engl J Med. 1994;331(14):904–909. PubMed.
- Inder WJ, Jang C. Treatment of prolactinoma. Medicina (Kaunas). 2022;58(8):1095. PubMed; PMC.
- Tritos NA, Miller KK. Diagnosis and management of pituitary adenomas: a review. JAMA. 2023;329(16):1386–1398. PubMed.
- van Hilten JJ, Ramaker CC, Stowe R, Ives NJ. Bromocriptine versus levodopa in early Parkinson’s disease. Cochrane Database Syst Rev. 2007;(4):CD002258. PubMed.
- Gaziano JM, Cincotta AH, O’Connor CM, et al. Randomized clinical trial of quick-release bromocriptine among patients with type 2 diabetes on overall safety and cardiovascular outcomes. Diabetes Care. 2010;33(7):1503–1508. PubMed; PMC.
- Qasim Ali L, Alshammary RAA, Ghazi Alshammary A, Jouda J. A hormonal side effect of anabolic steroids among a sample of Baghdad male bodybuilders. Steroids. 2024;209:109465. PubMed.
- World Anti-Doping Agency. The 2026 Prohibited List. WADA 2026 Prohibited List.
- US Code of Federal Regulations. 21 CFR 1308.13, Schedule III. 21 CFR 1308.13.
- Teva Pharmaceuticals USA. Cabergoline tablets, prescribing information. DailyMed.