Bromocriptine

Bromocriptine
Chemical structure of bromocriptine
Formula	C32H40BrN5O5
Administration	Oral (tablets, capsules)
Solubility	Practically insoluble in water; soluble in methanol, chloroform, ethanol
Legal status	Prescription only
Brand names	Parlodel, Cycloset
Bioavailability	28% (oral)
Recommended dose	2.5–15 mg/day (hyperprolactinemia); 20–30 mg/day (acromegaly); 1.25 mg BID increasing to 5–40 mg/day (Parkinson's); 1.6–4.8 mg/day (type 2 diabetes)
Upper limit	100 mg/day (maximum; varies by indication)
LD50	>2000 mg/kg (rat, oral)
Ray's verdict

Introduction

Bromocriptine is an ergot alkaloid derivative,part of the same chemical family as LSD, that emerged from research into serotonin antagonism. While pharmaceutical companies market it primarily as a "dopamine agonist," this framing deliberately obscures its equally important antiserotonin properties.

"When lysergic acid derivatives came onto the pharmaceutical market, the spirit of the times caused them to be described as dopamine agonists, rather than as serotonin antagonists, but the latter would be at least as descriptive of their effects. Bromocriptine fulfills many of the requirements of being a serotonin antagonist, for example by suppressing prolactin." - Ray Peat "Research on LSD and its derivatives led to drugs such as bromocriptine, which oppose the effects of histamine and estrogen. Some of bromocriptine's effects are clearly antagonistic to serotonin, though bromocriptine is usually called a dopamine agonist; dopamine is pretty generally a serotonin antagonist."- Ray Peat

Structure / Chemical properties

• Chemical class: Ergoline / ergot alkaloid derivative
• Related compounds: LSD, lisuride, cabergoline, metergoline, methysergide
• Key structural feature: Based on the same indole molecular structure as serotonin itself, but modified (e.g., with bromine) to produce antagonistic effects

"All of these are based on the same indole molecular structure that serotonin is, but they are tuned in a different way by additives. For example, adding bromine, bromocriptine, is one that's used to treat pituitary tumors." - Ray Peat

Function / Mechanism of action

1. Dopamine D2 receptor agonist:

Bromocriptine, a dopamine D2 agonist, inhibits seasonal fattening and improves seasonal insulin resistance in Syrian hamsters.

2. Serotonin antagonist: Bromocriptine causes non-competitive antagonism of serotonin, particularly on coronary arteries and smooth muscle.

Ergotamine, dihydroergotamine, bromocriptine, lisuride, ergometrine, ketanserin, trazodone, cyproheptadine and pizotifen caused non-competitive antagonism of serotonin concentration-response curves.

3. Prolactin inhibitor: Dopamine agonism directly suppresses prolactin secretion from the pituitary. Prolactin drives 5-alpha reductase activity and androgen receptor upregulation.

The rationale for bromocriptine is to inhibit prolactin. Prolactin interacts at the receptor level on the prostate cancer cell. Prolactin increases cell sensitivity to androgens by enhancing androgen receptors.

4. Inhibits serotonin synthesis (indirect): Dopamine and dopamine agonists inhibit tryptophan hydroxylase (TPH), reducing serotonin production.

Dopamine and dopaminergic drugs also have a direct inhibitory activity on serotonin synthesis by inhibiting the enzyme tryptophan hydroxylase (TPH).

Medical uses / Effects

FDA-approved indications:

• Hyperprolactinemia
• Prolactinomas (pituitary tumors)
• Parkinson's disease
• Type II diabetes (as Cycloset—timed-release bromocriptine)

Therapeutic applications from bioenergetic sources:

Pituitary tumors:

"Bromocriptine is another ergot-derived drug that cures pituitary tumors. And there's a family treating Cushing's disease and other pituitary-related problems." - Ray Peat

"Many of those tumors are curable by a chemical, bromocriptine or cabergoline are two of the chemicals that have been used to shrink pituitary tumors, and those tumors became extremely common after the birth control pill was introduced, so they're basically produced by an excess of estrogen." - Ray Peat, Patrick Timpone interview (March 2021)

Diabetes and obesity:

Bromocriptine treatment significantly reduced weight gain... and the areas under the GTT glucose and insulin curves by 29% and 48%, respectively. Basal plasma insulin concentration was markedly reduced throughout the day in bromocriptine-treated animals without influencing plasma glucose levels.

Cardiovascular disease:

Cycloset (bromocriptine) also reduced the CVD events for all type II diabetic patients, even in those with good blood sugar levels.

Ulcers (better than acid blockers):

The relapse rate in the cimetidine-treated group was significantly higher than in all the other test groups... dopaminergic drugs like bromocriptine are not only just as effective at healing ulcers, the relapse rate from dopaminergic drugs is much lower.

Cancer (breast):

Prolactin inhibiting drugs like bromocriptine not only stopped the progression of breast cancer but also induced complete remission in the majority of the animals.

Side / Adverse effects

• Nausea (common, especially initially)
• Constipation
• Postural hypotension (dizziness upon standing)
• Fatigue/drowsiness

Bromocriptine is considered safer than cabergoline, which carries higher fibrosis risk:

"Cabergoline is the most potent agonist on the 5-HT2B receptor and as such has the highest risk of fibrosis of the heart and the lungs and actually the gastrointestinal tract as well. So I would be very, very careful with cabergoline. I don't think there's any reason to use cabergoline considering that a safer version known as bromocriptine is also available."- Georgi Dinkov

Dosing

General therapeutic range: 2.5–5 mg daily, sometimes up to 7.5 mg

For prolactinoma/high prolactin:

"What would your doctors think about letting you try an antiserotonin drug, like lisuride or ondansetron or bromocriptine, now that your prolactin was measured so high? I think the prolactin should be around 9 to 12."- Ray Peat

For ulcers: 2.5 mg twice daily (study dose)

For breast cancer (research): ~`0.6 mg/kg` daily, 5 days/week for 4 weeks (animal-derived HED)

Metergoline comparison: Doses of 2–4 mg daily are clinically equivalent to bromocriptine for lowering prolactin

Brands and sources

Brand Name	Form	Indication
Parlodel	Tablets/capsules	Hyperprolactinemia, Parkinson's, acromegaly
Cycloset	Quick-release tablets	Type II diabetes (timed morning dosing)

Prescription required in most countries.

Alternatives in the ergot family:

• Lisuride - more potent, better safety profile, non-hallucinogenic LSD equivalent
• Metergoline - similar efficacy, also antifungal, may lower prolactin through non-dopaminergic mechanisms
• Cabergoline - more potent but higher fibrosis risk (avoid if possible)