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Bromocriptine and Dopaminergic Ergots
Module 4 — Mechanism, Indications, and Adverse Effects
Mechanism and Indications
Core Mechanism
Dopamine Type 2 Receptor Agonism
  • Anterior pituitary: suppresses prolactin secretion from lactotrophs
  • Basal ganglia: compensates for dopamine loss in Parkinson’s disease
  • Pituitary somatotrophs: reduces growth hormone in acromegaly (less effective than octreotide)
Clinical Indications
When to Use Bromocriptine
  • Hyperprolactinemia — first-line pharmacological treatment
  • Prolactinoma — suppresses prolactin and shrinks tumor
  • Parkinson’s disease — adjunct or early monotherapy
  • Neuroleptic malignant syndrome — restores dopaminergic tone
  • Acromegaly — second-line after somatostatin analogs
Neuroleptic Malignant Syndrome
Treatment Protocol
Neuroleptic Malignant Syndrome: Hyperthermia, Rigidity, Altered Mental Status, Autonomic Instability
  • Cause: dopamine type 2 receptor blockade by antipsychotic drugs
  • Step 1: Discontinue offending antipsychotic immediately
  • Step 2: Bromocriptine — activates dopamine type 2 receptors, reverses blockade, reduces rigidity
  • Step 3: Dantrolene — blocks sarcoplasmic reticulum calcium release, reduces muscle contraction and heat
Adverse Effects
Dopaminergic
Common Adverse Effects
  • Nausea and vomiting — chemoreceptor trigger zone
  • Orthostatic hypotension
  • Dyskinesias — high doses in Parkinson’s disease
  • Hallucinations and confusion — dose-dependent
Ergot Backbone — Class Effect
Cardiac Valvulopathy
  • Mechanism: serotonin type 2B agonism on valve cells
  • Fibrosis and thickening of cardiac valve leaflets
  • Dose-dependent — highest risk at Parkinson’s disease doses
  • Pergolide withdrawn 2007 due to this risk
  • Not seen with non-ergot dopamine agonists
Step 1 Rules
Bromocriptine = dopamine type 2 agonist. First-line for hyperprolactinemia and prolactinoma. Used in neuroleptic malignant syndrome with dantrolene. Cardiac valvulopathy via serotonin type 2B receptor is a class effect of ergot dopamine agonists — not seen with pramipexole or ropinirole. Cabergoline preferred over bromocriptine for hyperprolactinemia.