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[×] COMT inhibitors
 BRAND NAMES
 MECHANISM OF ACTION
Bromocriptine, an ergot derivative, is a potent dopamine receptor agonist on D2 receptors. It acts by direct stimulation of the D2-dopamine receptors on pituitary lactotrophs, thus inhibiting prolactin secretion.
The mechanism by which Bromocriptine improves glycemic control is unknown. Morning administration of Bromocriptine improves glycemic control in patients with type 2 diabetes without increasing plasma insulin concentrations. Bromocriptine significantly reduced the HbA1c approximately by 0.5%.
- Treatment of dysfunctions associated with hyperprolactinemia, including amenorrhea (absence of menstruation), oligomenorrhea (infrequent menstruation), anovulation and galactorrhea (inappropriate production of milk). Hyperprolactinaemia is an endocrine disorder seen in men and women, which is associated with impaired gonadal function. The most common symptoms in women are secondary amenorrhea, reduced libido, menstrual disorders, and galactorrhea. In men, symptoms generally include reduced libido and/or impotence.
- Treatment of acromegaly (abnormal production of growth hormone (GH) after epiphyseal plate closure at puberty). Bromocriptine therapy, alone or as adjunctive therapy with pituitary irradiation or surgery, reduces serum growth hormone by 50% or more in approximately half of patients treated, although not usually to normal levels. Since the effects of external pituitary radiation may not become maximal for several years, adjunctive therapy with Parlodel offers potential benefit before the effects of irradiation are manifested.
- Patients with prolactin-secreting pituitary adenomas: Reduction in tumor size has been demonstrated in both male and female patients with macroadenomas. In cases where adenectomy is elected, a course of Bromocriptine therapy may be used to reduce the tumor mass prior to surgery.
- Parkinson’s disease: As adjunctive treatment to levodopa or to levodopa/Carbidopa, Bromocriptine therapy may provide additional therapeutic benefits in those patients who are currently maintained on optimal dosages of levodopa, those who are beginning to deteriorate (develop tolerance) to levodopa therapy, and those who are experiencing “end of dose failure’’ on levodopa therapy. Bromocriptine therapy may permit a reduction of the maintenance dose of levodopa and, thus may ameliorate the occurrence and/or severity of adverse reactions associated with long-term levodopa therapy such as abnormal involuntary movements (e.g., dyskinesias) and the marked swings in motor function (“on-off’’ phenomenon)
- Type 2 diabetes: Bromocriptine (Cycloset) is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. (FDA approved)
- Parkinson's disease: In order to ensure optimal tolerability, treatment should be started with a low dose of 1.25 mg/day, given preferably in the evening, for the first week. Bromocriptine should be titrated slowly in order to arrive at the minimal effective dose for each patient. The daily dosage should be increased gradually by 1.25 mg/day each week, and given as 2 to 3 divided doses. An adequate therapeutic response may be reached within 6 to 8 weeks; if it is not, the daily dose may be further increased by 2.5 mg/day each week. The usual therapeutic range for monotherapy or combined therapy is 10-40 mg/day, but higher doses may be required in some patients. Should undesirable reactions occur during the titration phase, the daily dose should be reduced and maintained at the lower level for at least a week. If the adverse reactions disappear, the dose can be increased again.
For patients exhibiting motor disorders on levodopa therapy, it is suggested that the levodopa dosage should be reduced before Bromocriptine treatment is initiated. When a satisfactory response to Bromocriptine has been obtained, a further stepwise reduction in levodopa dosage can be made. In certain patients, levodopa may be withdrawn completely.
- Prolactinomas: 1.25 mg, 2 or 3 times daily, gradually increasing to several tablets daily as required to keep plasma prolactin adequately suppressed.
- Acromegaly: Initially 1.25 mg, 2 or 3 times daily, gradually increasing to 10 to 20 mg daily, depending on clinical response and side effects.
- Prolactin dependent subfertility, gallactorrhea, amenorrhea: 1.25 mg, 2 or 3 times daily; if this proves inadequate, gradually increase to 2.5 mg 2 or 3 times daily. Continue treatment until the menstrual cycle has returned to normal and/or ovulation is restored. If required, treatment may be continued over several cycles to prevent relapse.
- Type 2 diabetes (cycloset): Initial dose is 0.8 mg daily increased weekly by one tablet until maximal tolerated daily dose of 1.6 to 4.8 mg is achieved. cycloset is administered once daily within two hours after waking in the morning, with food, to potentially reduce gastrointestinal side effects such as nausea.
- Hypersensitivity to bromocriptine, to any of the excipients or to ergot-related drugs.
- Uncontrolled hypertension
- Severe heart disease
- Mental illness now or in the past
 WARNINGS AND PRECAUTIONS
- Bromocriptine may cause hypotension. Care should be exercised when administering Bromocriptine concomitantly with other drugs known to lower blood pressure
- Psychotic disorders: In patients with severe psychotic disorders, treatment with a dopamine receptor agonist such as Bromocriptine may exacerbate the disorder or may diminish the effectiveness of drugs used to treat the disorder. Therefore, the use of Bromocriptine in patients with severe psychotic disorders in not recommended.
- Bromocriptine has been associated with somnolence.Patients should be made aware of this potential side effect, particularly when initiating therapy. Patients experiencing somnolence should refrain from driving or operating heavy machinery.
- Dopamine antagonists such as medicines to treat mental illness and prevent nausea (e.g. Clozapine, Olanzapine, Ziprasidone, Metoclopramide): Since Bromocriptine exerts its therapeutic effect by direct stimulation of dopamine receptors, it should not be concurrently administered with drugs that have dopamine-antagonist activity since these might reduce the the effectiveness of Bromocriptine. Bromocriptine may also reduce the effectiveness of these agents.
- Bromocriptine is extensively metabolized by CYP3A4. Use caution when coadministering strong inhibitors (e.g. Itraconazole, Clarithromycin), inducers, or substrates for CYP3A4.
- Concomitant use of Bromocriptine with other ergot alkaloids (e.g., to treat migraine headache: ergotamine, dihydroergotamine) is not recommended.
 PREGNANCY AND LACTATION
- Pregnancy Category B (US)
- Nursing mothers: Do not use in nursing women. May inhibit lactation. Postmarketing reports of stroke in this patient population
 SIDE EFFECTS
Common adverse events include: nausea, fatigue, dizziness, orthostatic hypotension, vomiting, drowsiness and headache.
Postmarketing reports with higher doses of bromocriptine include psychotic disorders, hallucinations, and pulmonary fibrosis
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