Cabergoline is only found in individuals that have used or taken this drug. It is a long-acting dopamine agonist and prolactin inhibitor. It is used to treat hyperprolactinemic disorders and Parkinsonian Syndrome. Cabergoline possesses potent agonist activity on dopamine D2 receptors. The dopamine D2 receptor is a 7-transmembrane G-protein coupled receptor associated with Gi proteins. In lactotrophs, stimulation of dopamine D2 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. Cabergoline is a long-acting dopamine receptor agonist with a high affinity for D2 receptors. Receptor-binding studies indicate that cabergoline has low affinity for dopamine D1, alpha1,- and alpha2- adrenergic, and 5-HT1- and 5-HT2-serotonin receptors.
belongs to the class of organic compounds known as lysergic acids and derivatives. These are alkaloids with a structure based on the lysergic acid skeleton.
Oral (12)
First-pass effect is seen, however the absolute bioavailability is unknown.
Mechanism of Toxicity
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. (2, 3, 4, 12) The dopamine D2 receptor is a 7-transmembrane G-protein coupled receptor associated with Gi proteins. In lactotrophs, stimulation of dopamine D2 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. Cabergoline is a long-acting dopamine receptor agonist with a high affinity for D2 receptors. Receptor-binding studies indicate that cabergoline has low affinity for dopamine D1, α1,- and α2- adrenergic, and 5-HT1- and 5-HT2-serotonin receptors.
Metabolism
Hepatic. Cabergoline is extensively metabolized, predominately via hydrolysis of the acylurea bond of the urea moiety. Cytochrome P-450 mediated metabolism appears to be minimal. The main metabolite identified in urine is 6-allyl-8b-carboxy-ergoline (4-6% of dose). Three other metabolites were identified urine (less than 3% of dose).
Route of Elimination: After oral dosing of radioactive cabergoline to five healthy volunteers, approximately 22% and 60% of the dose was excreted within 20 days in the urine and feces, respectively. Less than 4% of the dose was excreted unchanged in the urine.
Half Life: The elimination half-life is estimated from urinary data of 12 healthy subjects to range between 63 to 69 hours.
No indication of carcinogenicity to humans (not listed by IARC).
Uses/Sources
For the treatment of hyperprolactinemic disorders, either idiopathic or due to prolactinoma (prolactin-secreting adenomas). May also be used to manage symptoms of Parkinsonian Syndrome as monotherapy during initial symptomatic management or as an adjunct to levodopa therapy during advanced stages of disease. Cabergoline is frequently used as a second-line agent in the management of prolactinomas when bromocriptine is ineffective. Ergoline alkaloids occurs in various species of vines of the Convolvulaceae (morning glory) family and in some species of lower fungi. (9, 12)
Minimum Risk Level
Not Available
Health Effects
Cabergoline use may cause valvular heart disease and fibrosis. Ingestion of ergoline alkaloids is known to cause the disease ergotism. Ergotism occurs in two forms, gangrenous and convulsive, likely depending on the different kinds and amounts of ergoline alkaloids present. (1, 12, 13)
Symptoms
Side effects of cabergoline include nausea, constipation, dry mouth, sleep disturbances, vertigo, depression, hypotension, and peripheral edema. Convulsive ergotism can cause painful seizures and spasms, diarrhea, paresthesias, itching, headaches, nausea and vomiting. Usually the gastrointestinal effects precede the central nervous system effects. As well as seizures there can be hallucinations and mental effects including mania or psychosis. Gangrenous ergotism causes dry gangrene as a result of vasoconstriction induced in the more poorly vascularized distal structures, such as the fingers and toes. Symptoms include desquamation, weak periphery pulse, loss of peripheral sensation, edema and ultimately the death and loss of affected tissues. (10, 13) Overdosage might be expected to produce nasal congestion, syncope, or hallucinations.
Treatment
Treatment for ergotism consists of vasodilators, anticoagulants and low molecular weight dextrans. If necessary, a sympathetic nerve blockade may be carried out, such as brachial plexus blockade. Temporary sedation (e.g. haloperidol) will be necessary in hallucination and diazepam is used for convulsions. There is no specific antidote. (11)
