Parkinsonism bromocriptine/dopamine agonists

Anti-Parkinson Drugs, Dopamine Agonists (bromocriptine, pergolide, cabergoline)... 

Bromocriptine is a dopamine agonist acting by direct stimulation of the dopamine receptors. In Parkinson s disease, it is reserved for use in patients who are intolerant to levodopa or in whom levodopa alone is not sufficient. Orphenadrine is an antimuscarinic indicated in Parkinson s disease. Antimuscarinics tend to be more effective than levodopa in targeting tremor rather than rigidity and bradykinesia. Moclobemide is an antidepressant referred to as a reversible monoamine oxidase inhibitor (RIAAA) type A. 

Pharmacology Bromocriptine, a dopamine agonist, may relieve akinesia, rigidity, and tremor in patients with Parkinson s disease. It produces its therapeutic effect by directly stimulating the dopamine receptors in the corpus striatum. 

Bromocriptine is a D2 agonist its structure is shown in Table 16-6. This drug has been widely used to treat Parkinson s disease in the past, but is now rarely used for this purpose, having been superseded by the newer dopamine agonists. Bromocriptine is absorbed to a variable extent from the gastrointestinal tract peak plasma levels are reached within 1-2 hours after an oral dose. It is excreted in the bile and feces. The usual daily dose of bromocriptine for parkinsonism varies between 7.5 and 30 mg. To minimize adverse effects, the dose is built up slowly over 2 or 3 months from a starting level of 1.25 mg twice daily after meals the daily dose is then increased by 2.5 mg every 2 weeks, depending on the response or the development of adverse reactions. 

Dopamine agonists suppress prolactin release very effectively in patients with hyperprolactinemia. GH release is reduced in patients with acromegaly, although not as effectively. Cabergoline and bromocriptine are also used in Parkinson s disease to improve motor function and reduce levodopa requirements (see Chapter 28). Newer, nonergot D2 agonists... 

Dopamine agonists Bromocriptine Cabergoline Pergolide Pramipexole Ropinirole Directly stimulates dopamine receptors in basal ganglia. May produce fewer side effects (dyskinesias, fluctuations in response) than levodopa preliminary evidence suggests that early use may also delay the progression of Parkinson disease. 

Dopamine agonists include bromocriptine, cabergoline, lysuride, pergolide, apomorphine, pramipexole and ropinirole. These drugs are not converted into dopamine but have a direct effect on dopamine receptors in the brain. Dopamine agonists are used both as adjuncts to co-careldopa and co-beneldopa therapy and also initially in early Parkinson s disease, especially in younger adults. 

Pramipexole is a non-ergot dopamine agonist similar to bromocriptine, used in the management of Parkinson s disease as an adjunct to levodopa. 

Terguride is an ergot derivative, a partial dopamine agonist with properties similar to those of bromocriptine. It has been used in the treatment of Parkinson s disease and hyperprolactinaemia. 

Dopamine agonists. Recent studies point to the possibility of neuroprotection from aging and parkinsonism by the administration of dopamine receptor agonists. Agents showing some promise include bromocriptine, a-dihydroergocryptine, lisuride and pergolide. 

An alternative approach to the treatment with L-DOPA is the use of drugs that mimic the action of dopamine. Treatment with dopamine-agonists, such as bromocriptine (15),137 pergolide, and lisuride, has some advantages over treatment with L-DOPA. Dopamine agonists are effective in patients in the advanced stages of Parkinson s disease, unlike L-DOPA, because their action at postsynaptic dopamine receptors is unaffected by the lack of dopamine producing nerve cells. 

Bromocriptine - dopamine receptor agonist Parkinson s disease... 

The combined use of levodopa and dopamine agonists can increase efficacy and adverse effects in Parkinson s disease, therefore doses of both drugs should be slowly adjusted to optimise therapy. A study suggests that bromocriptine can moder-... 

The answer is b. (Hardman, pp 282—283J Central dopamine receptors are divided into Dt and D2 receptors. Antipsychotic activity is better correlated to blockade of D2 receptors. Haloperidol, a potent antipsychotic, selectively antagonizes at Dz receptors. Phenothiazine derivatives, such as chlorpromazine, fluphenazine, and promethazine, are not selective for D2 receptors. Bromocriptine, a selective D2 agonist, is useful in the treatment of parkinsonism and hyperprolactinemia. It produces fewer adverse reactions than do nonselective dopamine receptor agonists... 

Bromocriptine, a dopaminomimetic that is a dopamine D2 receptor agonist, possesses expressed antiparkinsonian activity. It is used for treating all phases of idiopathic and post-encephalic Parkinsonism. However, it has a number of undesirable side effects, even causing mental disturbances in long-term use. The most common synonyms are parlodel, bromergon, and others. 

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