[1] Dopamine agonists are primarily used in the treatment of the motor symptoms of Parkinson's disease, and to a lesser extent, in hyperprolactinemia and restless legs syndrome.

[4] In Parkinson's disease dopaminergic neurons that produce the neurotransmitter dopamine in the brain slowly break down and can eventually die.

[5] There are two fundamental ways of treating Parkinson's disease, either by replacing dopamine or mimicking its effect.

[6][7] Depressive symptoms and disorders are common in patients with Parkinson's disease and can affect their quality of life.

Instead of conventional antidepressant medication in treating depression, treatment with dopamine agonists has been suggested.

Although preliminary evidence of clinical trials has shown interesting results, further research odds crucial to establish the anti-depressive effects of dopamine agonists in treating depressive symptoms and disorders in those with Parkinson's.

Research shows that these agents reduce the size of prolactinomas by suppressing the hypersecretion of prolactin resulting in normal gonadal function.

[13] Numerous clinical trials have been performed to assess the use of dopamine agonists for the treatment of restless legs syndrome (RLS).

[14] Dopamine agonists are mainly used to treat Parkinson's disease, but also hyperprolactinemia and restless legs syndrome.

[15] The side effects are predominantly collected from studies of Parkinson's disease, where dopamine agonists are commonly used as a first-line treatment with levodopa.

[16] Dopamine agonists are divided into two subgroups or drug classes, first-generation and newer agents.

Other serious side effects are hallucinations, peripheral edema, gastrointestinal ulcers, pulmonary fibrosis and psychosis.

[1] A high risk for valvular heart disease has been established in association with ergot-derived agonists especially in elderly patients with hypertension.

[1][18][19] Impulse control disorder, which manifests in behaviors such as gambling, hypersexuality, compulsive shopping or binge eating, can be another serious adverse effect of dopamine agonists.

[15] After long-term use of dopamine agonists a withdrawal syndrome may occur when discontinuing the drug or reducing the dose.

The following side effects are possible: anxiety, panic attacks, dysphoria, depression, agitation, irritability, suicidal ideation, fatigue, orthostatic hypotension, nausea, vomiting, diaphoresis, generalised pain and drug cravings.

[21] There is evidence that suggests that since ergot dopamine agonists are metabolized by CYP3A4 enzyme concentration rises with the use of CYP3A4 inhibitors.

[16] Pharmacokinetics is the study of how a drug moves through the body, involving four main processes: absorption, distribution, metabolism, and excretion.

Finally, excretion is how the drug or its metabolites are eliminated from the body, often through urine or feces (Gibaldi & Perrier, 1982).

[22] Absorption of bromocriptine oral dose is approximately 28%; however, only 6% reaches the systemic circulation unchanged, due to a substantial first-pass effect.

[1] Ropinirole is rapidly absorbed after a single oral dose, reaching plasma concentration in approximately 1–2 hours.

Bromocriptine stimulates Na+, K+-ATPase activity and/or cytosolic Ca2+ elevation and therefore reduction of prolactin which leads to no production of cAMP.

The mechanism of action of pramipexole is mostly unknown, it is thought to be involved in the activation of dopamine receptors in the area of the brain where the striatum and the substantia nigra is located.

In the second stage L-DOPA (levodopa) is formed by adding a phenol group to the benzene ring of L-tyrosine.

The third stage is the formation of dopamine by removing the carboxylic acid group from L-DOPA, catalysed by the enzyme dopa decarboxylase.

Two conformers of dopamine have been identified as alpha- and beta-conformers in which the catechol ring is coplanar with the plane of the ethylamine side chain.

Central dopaminergic agonist properties of semisynthetic ergoline derivatives lergotrile, pergolide, bromocriptine and lisuride have been established.

Some studies suggest that ergot alkaloids have the properties of mixed agonist-antagonist with regards to certain presynaptic and postsynaptic receptors.

[37]Apomorphine has a catechol element and belongs to a class called β-phenylethylamines and its main components are similar to the dopamine structure.

[48] When using the two drug classes together there is a possibility to reduce the amount of L-DOPA by 20-30% and thus keeping the fluctuating motor responses to a minimum.