Pharmacology
The activity profile of pramipexole at various sites has been characterized as follows:

While pramipexole is used clinically (see below), its D3-preferring receptor binding profile has made it a popular tool compound for preclinical research. For example, pramipexole has been used (in combination with D2- and or D3-preferring antagonists) to discover the role of D3 receptor function in rodent models and tasks for neuropsychiatric disorders. Of note, it appears that pramipexole, in addition to having effects on dopamine D3 receptors, may also affect mitochondrial function via a mechanism that remains less understood. A pharmacological approach to separate dopaminergic from non-dopaminergic (e.g. mitochondrial) effects of pramipexole has been to study the effects of the R-stereoisomer of pramipexole (which has much lower affinity to the dopamine receptors when compared to the S-isomer) side by side with the effects of the S-isomer.Parkinsons disease is a neurodegenerative disease affecting the substantia nigra, a component of the basal ganglia. The substantia nigra has a high quantity of dopaminergic neurons, which are nerve cells that release the neurotransmitter known as dopamine. When dopamine is released, it may activate dopamine receptors in the striatum, which is another component of the basal ganglia. When neurons of the substantia nigra deteriorate in Parkinsons disease, the striatum no longer properly receives dopamine signals. As a result, the basal ganglia can no longer regulate body movement effectively and motor function becomes impaired.
Although a modest statistically significant benefit of pramipexole over placebo was detected, neither the response rates (40% compared with 33%) nor the remission rates (27% compared with 23%) differed significantly between groups. Dosages were modest (mean=1.35 mg/day; maximum=2.0 mg/day) ... To our knowledge, this is the first case series of adjunctive pramipexole in patients with treatment-resistant depression for whom at least four previous treatments in the current episode had failed. Overall, 76% of the patients showed a meaningful clinical response that persisted, while 24% were intolerant or nonresponsive to pramipexole. Effective pramipexole dosages ranged from 0.75 to 5.0 mg/day. The mean effective dosage of pramipexole in responders and remitters (N=32) was 2.46 mg/day". Side effects
Common side effects of pramipexole may include:
Headache
Peripheral edema
Hyperalgesia (body aches and pains)
Nausea and vomiting
Sedation and somnolence
Decreased appetite and subsequent weight loss
Orthostatic hypotension (resulting in dizziness, lightheadedness, and possibly fainting, especially when standing up)
Insomnia
Hallucinations (seeing, hearing, smelling, tasting or feeling things that are not there), amnesia and confusion
Twitching, twisting, or other unusual body movements
Unusual tiredness or weakness
Impulsive-compulsive behaviors: pramipexole (and related D3-preferring dopamine agonist medications such as ropinirole) can induce "impulsive-compulsive spectrum disorders" such as compulsive gambling, punding,  hypersexuality, and overeating, even in people without any prior history of these behaviours. Augmentation: Especially when used to treat restless legs syndrome, long-term pramipexole treatment may exhibit drug augmentation, which is "an iatrogenic worsening of RLS symptoms following treatment with dopaminergic agents" and may include an earlier onset of symptoms during the day or a generalized increase in symptoms.