Cabergoline

Indications

Cabergoline is primarily indicated for the treatment of hyperprolactinemic disorders, which can be idiopathic or associated with prolactin-secreting adenomas, known as prolactinomas. Additionally, cabergoline is utilized in the management of symptoms associated with Parkinsonian Syndrome. In this context, it can serve as monotherapy during the initial phase of symptomatic management or as an adjunct therapy to levodopa in advanced stages of the disease.

Pharmacodynamics

The pharmacological action of cabergoline is attributed to its ability to stimulate centrally located dopaminergic receptors. This compound is distinguished by its potent agonist activity at dopamine D2 and D3 receptors, which play a pivotal role in alleviating symptoms of movement disorders. Postsynaptic stimulation of D2 receptors is primarily responsible for its antiparkinsonian effects, while presynaptic D2 stimulation offers neuroprotective benefits. Beyond its primary targets, cabergoline also demonstrates agonist activity at several other receptors, including 5-HT2A, 5-HT2B, and others, alongside antagonist activity at specific alpha receptors. Such a broad spectrum of activity contributes to both its therapeutic impact and potential side effects, including hallucinations linked to the mesolimbic pathway and its role in the tuberoinfundibular pathway, where it inhibits prolactin secretion from the anterior pituitary gland.

Absorption

The absorption profile of cabergoline is influenced by a first-pass effect; however, its absolute bioavailability remains undetermined. This aspect necessitates consideration of potential variations in individual drug response.

Metabolism

Cabergoline undergoes extensive hepatic metabolism, primarily through the hydrolysis of the acylurea bond within the urea moiety. The involvement of cytochrome P-450 enzymes in its metabolism is minimal. In terms of excretion, 6-allyl-8b-carboxy-ergoline is the principal metabolite identified in urine, comprising 4-6% of the administered dose, along with three additional metabolites found at lower concentrations.

Mechanism of Action

Cabergoline functions as a long-acting agonist with high affinity for dopamine D2 receptors, playing a crucial role in modulating various physiological processes. In lactotroph cells, activation of these D2 receptors by cabergoline leads to the inhibition of adenylyl cyclase, resulting in reduced intracellular cAMP levels and suppression of IP3-mediated calcium release from intracellular stores. This reduction in intracellular calcium concentration can also occur through the inhibition of calcium influx via voltage-gated calcium channels. Furthermore, the activation of D2 receptors by cabergoline inhibits the phosphorylation of p42/p44 MAPK and reduces the activity of MAPK/ERK kinase, primarily via c-Raf and B-Raf-dependent pathways. Within the pituitary gland, dopamine-induced growth hormone release is facilitated by decreased calcium influx through voltage-gated channels, independent of adenylyl cyclase activity. In the nigrostriatal pathway, D2 receptor stimulation enhances coordinated muscle activity, proving beneficial for individuals with movement disorders. Notably, cabergoline exhibits low affinity for dopamine D1, α1-, and α2-adrenergic, as well as 5-HT1- and 5-HT2-serotonin receptors, as evidenced by receptor-binding studies.