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bromocriptine

Discussion in 'Medical Students - MD' started by HiddenTruth, Apr 23, 2004.

  1. HiddenTruth

    HiddenTruth Senior Member
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    Why does bromocriptine treatment for hyperprolactinemia produce CSD rhinorrhea as a rare complication? What is the pathology and pharmacology associated with such treatment? thanks
     
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  3. idq1i

    Physician 15+ Year Member

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    Bromocriptine mesylate is a dopamine receptor agonist, which activates post-synaptic dopamine receptors. The dopaminergic neurons in the tuberoinfundibular process modulate the secretion of prolactin from the anterior pituitary by secreting a prolactin inhibitory factor (thought to be dopamine); in the corpus striatum the dopaminergic neurons are involved in the control of motor function. Clinically, bromocriptine mesylate significantly reduces plasma levels of prolactin in patients with physiologically elevated prolactin as well as in patients with hyperprolactinemia. The inhibition of physiological lactation as well as galactorrhea in pathological hyperprolactinemic states is obtained at dose levels that do not affect secretion of other tropic hormones from the anterior pituitary. Experiments have demonstrated that bromocriptine induces long lasting stereotyped behavior in rodents and turning behavior in rats having unilateral lesions in the substantia nigra. These actions, characteristic of those produced by dopamine, are inhibited by dopamine antagonists and suggest a direct action of bromocriptine on striatal dopamine receptors.

    Bromocriptine mesylate is a nonhormonal, nonestrogenic agent that inhibits the secretion of prolactin in humans, with little or no effect on other pituitary hormones, except in patients with acromegaly, where it lowers elevated blood levels of growth hormone in the majority of patients. In about 75% of cases of amenorrhea and galactorrhea, bromocriptine mesylate therapy suppresses the galactorrhea completely, or almost completely, and reinitiates normal ovulatory menstrual cycles.

    Menses are usually reinitiated prior to complete suppression of galactorrhea; the time for this on average is 6-8 weeks. However, some patients respond within a few days, and others may take up to 8 months.

    Galactorrhea may take longer to control depending on the degree of stimulation of the mammary tissue prior to therapy. At least a 75% reduction in secretion is usually observed after 8-12 weeks. Some patients may fail to respond even after 12 months of therapy.

    In many acromegalic patients, bromocriptine mesylate produces a prompt and sustained reduction in circulating levels of serum growth hormone.

    Bromocriptine mesylate produces its therapeutic effect in the treatment of Parkinson?s disease, a clinical condition characterized by a progressive deficiency in dopamine synthesis in the substantia nigra, by directly stimulating the dopamine receptors in the corpus striatum. In contrast, levodopa exerts its therapeutic effect only after conversion to dopamine by the neurons of the substantia nigra, which are known to be numerically diminished in this patient population.

    Pharmacokinetics

    The pharmacokinetics and metabolism of bromocriptine in human subjects were studied with the help of radioactively labeled drug. Twenty-eight percent of an oral dose was absorbed from the gastrointestinal tract. The blood levels following a 2? mg dose were in the range of 2-3 ng equivalents/mL.

    Plasma levels were in the range of 4-6 ng equivalents/mL indicating that the red blood cells did not contain appreciable amounts of drug and/or metabolites. In vitro experiments showed that the drug was 90%-96% bound to serum albumin.

    Bromocriptine was completely metabolized prior to excretion. The major route of excretion of absorbed drug was via the bile. Only 2.5%-5.5% of the dose was excreted in the urine. Almost all (84.6%) of the administered dose was excreted in the feces in 120 hours

    Hyperprolactinemic Indications

    The incidence of adverse effects is quite high (69%) but these are generally mild to moderate in degree. Therapy was discontinued in approximately 5% of patients because of adverse effects. These in decreasing order of frequency are: nausea (49%), headache (19%), dizziness (17%), fatigue (7%), lightheadedness (5%), vomiting (5%), abdominal cramps (4%), nasal congestion (3%), constipation (3%), diarrhea (3%) and drowsiness (3%). A slight hypotensive effect may accompany bromocriptine mesylate treatment. The occurrence of adverse reactions may be lessened by temporarily reducing dosage to 1,2 tablet 2 or 3 times daily. A few cases of cerebrospinal fluid rhinorrhea have been reported in patients receiving bromocriptine mesylate for treatment of large prolactinomas. This has occurred rarely, usually only in patients who have received previous transsphenoidal surgery, pituitary radiation, or both, and who were receiving bromocriptine mesylate for tumor recurrence. It may also occur in previously untreated patients whose tumor extends into the sphenoid sinus.
     
  4. HiddenTruth

    HiddenTruth Senior Member
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    So where did you copy and paste this from :laugh:
     
  5. idq1i

    Physician 15+ Year Member

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    rxlist. I found it when I was trying to determine the answer for myself. I don't know if it was of any use to you, though.
     
  6. ericdamiansean

    ericdamiansean High Profiler
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    where is this RX list?
    btw, anyone know of a really good pathophysio book? seems like every doc I know nowadays when I'm in the hospital wants to know about the pathophysio of every single darn thing..and they get tested in the exams as well..and not that lange book..doesn't work too well
     
  7. punjabiMD

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    Pathophysiology for the Wards and Boards by Carlos Ayala.
     
  8. idq1i

    Physician 15+ Year Member

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    www.rxlist.com Quite useful
     
  9. ericdamiansean

    ericdamiansean High Profiler
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