Dopamine Agonists
Dopamine Agonists in Pediatric Medicine
Key Points
- Primary agents: Cabergoline, Bromocriptine
- Act on D2 receptors to inhibit prolactin secretion
- Used in hyperprolactinemia and prolactinomas
- Require careful titration and monitoring
Overview
Dopamine agonists are crucial medications in pediatric endocrinology, primarily used to manage disorders related to elevated prolactin levels and certain types of pituitary tumors. These agents effectively mimic dopamine's natural inhibitory effect on prolactin secretion.
Mechanism of Action
Physiological Basis
- Receptor Interaction
- Selective activation of D2 dopamine receptors
- Direct action on lactotroph cells in anterior pituitary
- Inhibition of prolactin gene transcription
- Reduction in lactotroph cell proliferation
- Additional Effects
- Tumor shrinkage in prolactinomas
- Restoration of gonadal function
- Improvement in visual field defects
Pharmacological Characteristics
- Cabergoline
- Long half-life (65-109 hours)
- Higher D2 receptor affinity
- Better tolerability profile
- Bromocriptine
- Shorter half-life (3-7 hours)
- More frequent dosing required
- First-generation dopamine agonist
Clinical Indications
Primary Indications
- Hyperprolactinemia
- Microprolactinomas
- Macroprolactinomas
- Idiopathic hyperprolactinemia
- Drug-induced hyperprolactinemia
- Specific Clinical Presentations
- Galactorrhea
- Delayed puberty
- Primary amenorrhea
- Growth disorders associated with hyperprolactinemia
Special Considerations
- Visual field defects from macroadenomas
- Fertility preservation in adolescents
- Growth potential optimization
- Quality of life impact
Administration & Dosing
Cabergoline Dosing
- Initial Dose
- Start: 0.25-0.5 mg/week
- Divided into 1-2 doses per week
- Take with meals to improve tolerance
- Titration
- Increase by 0.25-0.5 mg/week monthly
- Maximum dose: 2-4 mg/week
- Based on prolactin levels and tolerance
Bromocriptine Dosing
- Initial Dose
- Start: 0.625-1.25 mg/day
- Evening dose with food
- Gradual titration essential
- Maintenance
- Typical range: 2.5-15 mg/day
- Divided into 2-3 doses
- Individual response-based adjustment
Monitoring & Safety
Initial Assessment
- Baseline Evaluation
- Prolactin levels
- Pituitary MRI
- Visual field examination
- Growth and pubertal status
- Cardiovascular assessment
Ongoing Monitoring
- Laboratory Monitoring
- Prolactin levels every 4-8 weeks initially
- Then every 3-6 months once stable
- Liver function tests periodically
- Clinical Monitoring
- Growth velocity every 3-6 months
- Pubertal development assessment
- Visual field checks in macroadenomas
- Cardiac evaluation annually
Side Effects Management
- Common Side Effects
- Nausea and vomiting
- Postural hypotension
- Headache
- Fatigue
- Management Strategies
- Gradual dose titration
- Evening administration
- Taking with food
- Adequate hydration
- Regular monitoring for impulse control disorders
