D2 receptor( Ki = 12.2 nM ); D3 receptor ( Ki = 12.2 nM ); D4 receptor ( Ki = 59.7 nM ); D1 receptor ( Ki = 1659 nM ); D5 receptor ( Ki = 1691 nM )

Bromocriptine stimulates [35S]-GTPγS binding at the D2 dopamine receptor expressed in CHO cells with pEC50 of 8.15±0.05[1]. Bromocriptine also is a strong inhibitor of brain nitric oxide synthase. Bromocriptine (BKT), an ergot alkaloid, is found to be weakly active against inducible macrophage NOS (IC50>100 μM), but it acts as a strong inhibitor of purified neuronal nitric oxide synthase (NOS) (IC50=10±2 μM) [2]. It has been discovered that at least one human cytochrome P450 enzyme is inhibited by bromocriptine. With an estimated IC50 value for the interaction of 1.69 μM, bromocriptine is a strong inhibitor of CYP3A4[3].

Bromocriptine mesylate (2 mg/kg, i.p.) is given for 7 days in groups of mice participating in the forced swimming test (FST) and tail suspension test (TST). Bromocriptine group exhibits a discernible anti-immobility effect in comparison to the control. The anti-immobility effect of MPE (200 mg/kg, p.o.) is significantly and dose-dependently potentiated when bromocriptine is given 30 minutes after the final dose of the seven-day MPE treatment and the subjects are exposed to FST, in contrast to MPE treatment alone. When compared to the control group, the group receiving bromocriptine treatment exhibits a notable decrease in immobility time. When bromocriptine (100 and 200 mg/kg, p.o.) is administered seven days after MPE pretreatment, the anti-immobility effect of MPE is significantly and dose-dependently enhanced, as compared to MPE treatment alone[4]. When bromocriptine is administered intraceremoniously, the static mechanical allodynia (SMA) score is significantly lower than in sham (saline-injected rats) and the effect lasts for 30 minutes. In the CCI-IoN group, intraperitoneal administration of bromocriptine resulted in a significant, dose-dependent (0.1 mg and 1 mg/kg) decrease in pain scores compared to sham, with a 6-hour duration of effect. The biggest reduction in score is induced by the highest dose (P<0.01). For 20 minutes, bromocriptine has an effect. When compared to a sham group, the CCI-IoN+6-OHDA lesioned group's SMA score significantly decreases upon intraperitoneal administration of bromocriptine. Its impact lasts for half an hour[5].

The assay for [35S]-GTPγS binding is performed. For 30 minutes at 30°C, cell membranes (25 ±75 ug) are incubated in Buffer B, which contains 0.1 mM dithiothreitol (DTT), 1 uM GDP, and medications in a volume of 0.9 mL. This preincubation guarantees that the tested agonists are in an equilibrium state when the final concentration of [35S]-GTPγS (50±150 pM) is added (in 100 uL of Buffer B) to start the reaction. Unless otherwise specified, the assay mixture is incubated for a further 20 minutes. Rapid filtration ends the assays, and bound radioactivity is measured as previously mentioned for the radio-ligand binding assays. Less than 20% of the added GTPγS is bound in total by [35S]-GTPγS[1].

Mice: There are 150 total Swiss mice (20–25 g) of either sex used. One such agonist for the dopamine receptor (D2) is bromocriptine mesylate. Distilled water is used to dilute the medication haloperidol, which is then injected. A single drop of glacial acetic acid is used to dissolve bromocriptine mesylate, which is then diluted with distilled water to the desired volume. Imipramine dissolves in 0.9% regular saline. In groups of mice undergoing the Forced Swimming Test (FST) and Tail Suspension Test (TST), haloperidol (0.1 mg/kg, i.p.) and bromocriptine mesylate (2 mg/kg, i.p.) are given for 7 days. As a standard, positive control groups receive imipramine (10 mg/kg, p.o.) for seven days.
Rats: The rats used are adult male Sprague-Dawleys (N=112, 275–325 g). A couple of weeks following the 6-OHDA injection, the animals undergo a brief (less than three minutes) mask-applied 2% halothane anesthesia before receiving either the vehicle (5 μL of 0.9% saline) or bromocriptine (7 μg/kg dissolved in 5 μL vehicle) intraperitoneally. We used concentrations of SKF81297 (3 mg/kg dissolved in 0.9% saline) and bromocriptine (1 mg/kg) for intraperitoneal injection. A blind experimenter places the rats in the observation field for a 40-minute period test after they have recovered for less than two minutes.

Absorption, Distribution and Excretion
Approximately 28% of the oral dose is absorbed; however due to a substantial first pass effect, only 6% of the oral dose reaches the systemic circulation unchanged. Bromocriptine and its metabolites appear in the blood as early as 10 minutes following oral administration and peak plasma concentration are reached within 1-1.5 hours. Serum prolactin may be decreased within 2 hours or oral administration with a maximal effect achieved after 8 hours. Growth hormone concentrations in patients with acromegaly is reduced within 1-2 hours with a single oral dose of 2.5 mg and decreased growth hormone concentrations persist for at least 4-5 hours.
Parent drug and metabolites are almost completely excreted via the liver, and only 6% eliminated via the kidney.

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Metabolism / Metabolites
Completely metabolized by the liver, primarily by hydrolysis of the amide bond to produce lysergic acid and a peptide fragment, both inactive and non-toxic. Bromocriptine is metabolized by cytochrome P450 3A4 and excreted primarily in the feces via biliary secretion.
Bromocriptine has known human metabolites that include 5-bromo-N-[2,10-dihydroxy-7-(2-methylpropyl)-5,8-dioxo-4-propan-2-yl-3-oxa-6,9-diazatricyclo[7.3.0.02,6]dodecan-4-yl]-7-methyl-6,6a,8,9-tetrahydro-4H-indolo[4,3-fg]quinoline-9-carboxamide and 5-bromo-N-[2,11-dihydroxy-7-(2-methylpropyl)-5,8-dioxo-4-propan-2-yl-3-oxa-6,9-diazatricyclo[7.3.0.02,6]dodecan-4-yl]-7-methyl-6,6a,8,9-tetrahydro-4H-indolo[4,3-fg]quinoline-9-carboxamide.
Completely metabolized by the liver, primarily by hydrolysis of the amide bond to produce lysergic acid and a peptide fragment, both inactive and non-toxic. Bromocriptine is metabolized by cytochrome P450 3A4 and excreted primarily in the feces via biliary secretion.
Route of Elimination: Parent drug and metabolites are almost completely excreted via the liver, and only 6% eliminated via the kidney.
Half Life: 2-8 hours

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Biological Half-Life
2-8 hours

Toxicity Summary
The dopamine D₂ receptor is a 7-transmembrane G-protein coupled receptor associated with G_i proteins. In lactotrophs, stimulation of dopamine D₂ receptor causes inhibition of adenylyl cyclase, which decreases intracellular cAMP concentrations and blocks IP3-dependent release of Ca²⁺ from intracellular stores. Decreases in intracellular calcium levels may also be brought about via inhibition of calcium influx through voltage-gated calcium channels, rather than via inhibition of adenylyl cyclase. Additionally, receptor activation blocks phosphorylation of p42/p44 MAPK and decreases MAPK/ERK kinase phosphorylation. Inhibition of MAPK appears to be mediated by c-Raf and B-Raf-dependent inhibition of MAPK/ERK kinase. Dopamine-stimulated growth hormone release from the pituitary gland is mediated by a decrease in intracellular calcium influx through voltage-gated calcium channels rather than via adenylyl cyclase inhibition. Stimulation of dopamine D₂ receptors in the nigrostriatal pathway leads to improvements in coordinated muscle activity in those with movement disorders.

Ergoline alkaloids have been shown to have the significant affinity towards the 5-HT1 and 5-HT2 serotonin receptors, D1 and D2 dopamine receptors, and alpha-adrenergic receptors. This can result in a number of different effects, including vasoconstriction, convulsions, and hallucinations. Bromocriptine acts by directly stimulating the dopamine receptors in the corpus striatum. (A2914, A2915, A2916, A2941)

[1]. Agonist action at D2(long) dopamine receptors: ligand binding and functional assays. Br J Pharmacol. 1998 Jul;124(5):978-84.

[2]. Bromocriptine is a strong inhibitor of brain nitric oxide synthase: possible consequences for the origin of its therapeutic effects.FEBS Lett. 1997 Apr 7;406(1-2):33-6.

[3]. Assessment of potential interactions between dopamine receptor agonists and various human cytochrome P450 enzymes using a simple in vitro inhibition screen. Drug Metab Dispos. 1997 Oct;25(10):1211-4.

[4]. Dopamine mediated antidepressant effect of Mucuna pruriens seeds in various experimental models of depression. Ayu. 2014 Jan;35(1):90-7.

[5]. Nigrostriatal dopaminergic depletion increases static orofacial allodynia. J Headache Pain. 2016;17:11.

Pharmacodynamics
Bromocriptine stimulates centrally-located dopaminergic receptors resulting in a number of pharmacologic effects. Five dopamine receptor types from two dopaminergic subfamilies have been identified. The dopaminergic D1 receptor subfamily consists of D₁ and D₅ subreceptors, which are associated with dyskinesias. The dopaminergic D2 receptor subfamily consists of D₂, D₃ and D₄ subreceptors, which are associated with improvement of symptoms of movement disorders. Thus, agonist activity specific for D2 subfamily receptors, primarily D₂ and D₃ receptor subtypes, are the primary targets of dopaminergic antiparkinsonian agents. It is thought that postsynaptic D₂ stimulation is primarily responsible for the antiparkinsonian effect of dopamine agonists, while presynaptic D₂ stimulation confers neuroprotective effects. This semisynthetic ergot derivative exhibits potent agonist activity on dopamine D₂-receptors. It also exhibits agonist activity (in order of decreasing binding affinity) on 5-hydroxytryptamine (5-HT)_1D, dopamine D₃, 5-HT_1A, 5-HT_2A, 5-HT_1B, and 5-HT_2C receptors, antagonist activity on α_2A-adrenergic, α_2C, α_2B, and dopamine D₁ receptors, partial agonist activity at receptor 5-HT_2B, and inactivates dopamine D₄ and 5-HT₇ receptors. Parkinsonian Syndrome manifests when approximately 80% of dopaminergic activity in the nigrostriatal pathway of the brain is lost. As this striatum is involved in modulating the intensity of coordinated muscle activity (e.g. movement, balance, walking), loss of activity may result in dystonia (acute muscle contraction), Parkinsonism (including symptoms of bradykinesia, tremor, rigidity, and flattened affect), akathesia (inner restlessness), tardive dyskinesia (involuntary muscle movements usually associated with long-term loss of dopaminergic activity), and neuroleptic malignant syndrome, which manifests when complete blockage of nigrostriatal dopamine occurs. High dopaminergic activity in the mesolimbic pathway of the brain causes hallucinations and delusions; these side effects of dopamine agonists are manifestations seen in patients with schizophrenia who have overractivity in this area of the brain. The hallucinogenic side effects of dopamine agonists may also be due to 5-HT_2A agonism. The tuberoinfundibular pathway of the brain originates in the hypothalamus and terminates in the pituitary gland. In this pathway, dopamine inhibits lactotrophs in anterior pituitary from secreting prolactin. Increased dopaminergic activity in the tuberoinfundibular pathway inhibits prolactin secretion making bromocriptine an effective agent for treating disorders associated with hypersecretion of prolactin. Pulmonary fibrosis may be associated bromocriptine’s agonist activity at 5-HT_1B and 5-HT_2B receptors.

C33H44BRN5O8S

750.700160000001

749.209

C, 52.80; H, 5.91; Br, 10.64; N, 9.33; O, 17.05; S, 4.27

22260-51-1

Bromocriptine; 25614-03-3

31101

White to off-white solid powder

891.3ºC at 760 mmHg

215-218

492.8ºC

0mmHg at 25°C

3.982

3

6

5

43

1230

6

[H][C@@]12CC3=C(Br)NC4=CC=CC(C1=C[C@@H](C(N[C@@]5(C(C)C)C(N6[C@@H](CC(C)C)C(N7CCC[C@]7([C@]6(O)O5)[H])=O)=O)=O)CN2C)=C43.OS(=O)(C)=O

NOJMTMIRQRDZMT-GSPXQYRGSA-N

InChI=1S/C32H40BrN5O5.CH4O3S/c1-16(2)12-24-29(40)37-11-7-10-25(37)32(42)38(24)30(41)31(43-32,17(3)4)35-28(39)18-13-20-19-8-6-9-22-26(19)21(27(33)34-22)14-23(20)36(5)15-18;1-5(2,3)4/h6,8-9,13,16-18,23-25,34,42H,7,10-12,14-15H2,1-5H3,(H,35,39);1H3,(H,2,3,4)/t18-,23-,24+,25+,31-,32+;/m1./s1

(6aR,9R)-5-bromo-N-[(1S,2S,4R,7S)-2-hydroxy-7-(2-methylpropyl)-5,8-dioxo-4-propan-2-yl-3-oxa-6,9-diazatricyclo[7.3.0.02,6]dodecan-4-yl]-7-methyl-6,6a,8,9-tetrahydro-4H-indolo[4,3-fg]quinoline-9-carboxamide;methanesulfonic acid

CB154; CB-154; CB 154; Bromocriptine Mesylate; 2-Bromoergocryptine Mesylate

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture and light.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: ~100~250 mg/mL (133.2~333.0 mM)
H2O: ~1.1 mg/mL (~1.5 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (2.77 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (2.77 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (2.77 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)