Bromocriptine

Absorption

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.

Toxicity

Symptoms of overdosage include nausea, vomiting, and severe hypotension. The most common adverse effects include nausea, headache, vertigo, constipation, light-headedness, abdominal cramps, nasal congestion, diarrhea, and hypotension.

Chemical properties

Crystals.

Originator

Parlodel,Sandoz,UK,1975

The Uses of Bromocriptine

Bromocriptine, a dopaminomimetic that is a dopamine D2 receptor agonist, possesses expressed antiparkinsonian activity. It is used for treating all phases of idiopathic and postencephalic Parkinsonism.

The Uses of Bromocriptine

Enzyme inhibitor (prolactin).

Background

Bromocriptine mesylate is a semisynthetic ergot alkaloid derivative with potent dopaminergic activity. It inhibits prolactin secretion and may be used to treat dysfunctions associated with hyperprolactinemia. Bromocriptine is also indicated for the management of signs and symptoms of Parkinsonian Syndrome, as well as the treatment of acromegaly. Bromocriptine has been associated with pulmonary fibrosis, and can also cause sustained suppression of somatotropin (growth hormone) secretion in some patients with acromegaly.
In 1995, the FDA withdrew the approval of bromocriptine mesylate for the prevention of physiological lactation after finding that bromocriptine was not shown to be safe for use. It continues to be used for the indications mentioned above.

Indications

For the treatment of galactorrhea due to hyperprolactinemia, prolactin-dependent menstrual disorders and infertility, prolactin-secreting adenomas, prolactin-dependent male hypogonadism, as adjunct therapy to surgery or radiotherapy for acromegaly or as monotherapy is special cases, as monotherapy in early Parksinsonian Syndrome or as an adjunct with levodopa in advanced cases with motor complications. Bromocriptine has also been used off-label to treat restless legs syndrome and neuroleptic malignant syndrome.

What are the applications of Application

Bromocriptine is a dopaminergic agonist which inhibits release of prolactin

Definition

An semisynthetic ergotamine alkaloid derivative and powerful dopamine D2 agonist. It inhibits prolactin secretion and release from the pituitary and retards tumor growth.

Manufacturing Process

A solution of 3.4 grams of N-bromosuccinimide in 60 cc of absolute dioxane is added drop wise in the dark, during the course of 5 minutes, to a stirred solution, heated to 60°C, of 9.2 grams of ergocryptine in 180 cc of absolute dioxane. The reaction mixture is stirred at this temperature for 70 minutes and is concentrated to a syrup-like consistency in a rotary evaporator at a bath temperature of 50°C. The reaction mixture is subsequently diluted with 300 cc of methylene chloride, is covered with a layer of about 200 cc of a 2 N sodium carbonate solution in a separating funnel and is shaken thoroughly. The aqueous phase is extracted thrice with 100 cc amounts of methylene chloride. The combined organic phases are washed once with 50 cc of water, are dried over sodium sulfate and the solvent is removed under a vacuum.
The resulting brown foam is chromatographed on a 50-fold quantity of aluminum oxide of activity II-III with 0.2% ethanol in methylene chloride as eluant, whereby the compound indicated in the heading is eluted immediately after a secondary fraction which migrates somewhat more rapidly than the fractions containing the heading compound. The last fractions to leave the aluminum oxide contain varying amounts of starting material together with the heading compound, and may be subjected directly, as mixed fractions, to an afterbromination in accordance with the method described above. The fractions containing the pure heading compound are combined and crystallized from methyl ethyl ketonehopropy1 ether. Melting point 215°-218°C (decomp.), [α]D 20-195° (c = 1 in methylene chloride).

brand name

Parlodel (Novartis);Bromed;Lactismine;Parilac;Umprel.

Therapeutic Function

Prolactin inhibitor

World Health Organization (WHO)

Bromocriptine, a semisynthetic ergot alkaloid derivative and prolactin inhibitor was introduced into medicine in 1976. It is used in the prevention of lactation, but because of the risk of rebound effect and since only 10% of women benefit therapeutically from such intervention, the United States Food and Drug Administration has requested manufacturers to no longer indicate preparations containing bromocriptine for this purpose. The World Health Organization is not aware of similar action having been taken elsewhere.

Hazard

Poison; teratogen; developmental abnor- malities of the respiratory system,musculoskeletal system, rogenital system, craniofacial area, and body wall; teratogen; mutagen; questionable car- cinogen; tumorigen; causes nausea, vomiting, orthostatic hypotension; constipation, dyskinesias, psychoses, digital spasm, erythromelalgia.

Mechanism of action

Bromocriptine is absorbed after oral administration, but approximately 90% of a dose undergoes extensive first-pass hepatic metabolism, with the remainder hydrolyzed in the liver to inactive metabolites that are eliminated mostly in the bile. The half-life is relatively short (~3 hours).

Pharmacokinetics

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-HT1A, 5-HT2A, 5-HT1B, and 5-HT2C receptors, antagonist activity on α2A-adrenergic, α2C, α2B, and dopamine D1 receptors, partial agonist activity at receptor 5-HT2B, 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-HT2A 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-HT1B and 5-HT2B receptors.

Clinical Use

Bromocriptine is an ergot peptide derivative that is a partial agonist at D1-type and a full agonist at D2-type postsynaptic dopamine receptors, usually given in combination with levodopa therapy. It was the first direct dopamine receptor agonist used in treatment of Parkinson's disease after its development as an inhibitor of prolactin release (via activation of anterior pituitary D2 receptors). At low doses (typically 1–5 mg/day), bromocriptine is an effective prolactin inhibitor, and at higher doses (typically 10–20 mg/day), the antiparkinsonism and mood-elevating effects of bromocriptine become apparent.

Side Effects

Bromocriptine has a number of undesirable side effects, even causing mental disturbances in long-term use.

Synthesis

Bromocriptine, 2-bromoergocriptine (10.1.13), is a semisynthetic derivative of a natural ergot alkaloid, ergocriptin (a derivative of lysergic acid), which is synthesized by bromination of ergocriptin using N-bromosuccinimide [18,19].

Drug interactions

Potentially hazardous interactions with other drugs
Increased risk of toxicity with bromocriptine and isometheptene.

Metabolism

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.

Metabolism

Bromocriptine is extensively metabolised. It undergoes extensive first-pass biotransformation in the liver, reflected by complex metabolite profiles and by almost complete absence of parent drug in urine and faeces. In plasma the elimination half life is 3-4 hours for the parent drug and 50 hours for the inactive metabolites.The parent drug and its metabolites are also completely excreted via the liver with only 6% being eliminated via the kidney.