Bromocriptine
Bromocriptine is a semisynthetic ergot alkaloid derivative that acts as a **dopamine agonist** and **prolactin inhibitor**. - **Dogs**: Used for pregnancy termination or pseudopregnancy (pseudocyesis). However, newer dopamine agonists like cabergoline are often preferred due to a much lower incidence of gastrointestinal side effects. - **Cats**: Occasionally used as an adjunctive treatment for acromegaly to help reduce insulin requirements. - **Horses**: Historically used for pituitary pars intermedia dysfunction (PPID/Equine Cushing's disease) or pituitary adenomas, though pergolide is the modern standard of care. > **Clinical Pearl**: Bromocriptine is notorious for causing significant emesis in dogs, which severely limits its clinical utility compared to cabergoline. Administering with food or using antiemetics may be required.
Mecanismo: Bromocriptine acts primarily by stimulating **postsynaptic dopamine (D2) receptors** in the hypothalamus and anterior pituitary gland. - **Prolactin Inhibition**: Dopamine receptor stimulation → release of prolactin-inhibitory factor (PIF) → direct inhibition of prolactin secretion from the anterior pituitary. - **Acromegaly**: In certain pituitary adenomas, paradoxical suppression of growth hormone (GH) secretion occurs via dopaminergic stimulation. - **CNS Effects**: Activates dopaminergic receptors in the neostriatum of the brain, which can influence motor control and behavior.
Dosificación por especie
- Adjunctive treatment of acromegaly · Initial dose of 0.2 mg (total dose) · Unspecified · Unspecified · May reduce insulin requirements.
- Treatment of pituitary adenoma · 0.03-0.09 mg/kg (30-90 micrograms/kg) twice daily PO or SC · PO/SC · twice daily · Its use is limited. Note: ARCI UCGFS Class 2 Drug.
- Treatment of pituitary adenoma · 5 mg (total dose) IM q12h · IM · q12h · To prepare an injectable formulation for IM use from oral dosage forms: Bromocriptine mesylate 70 mg is added to 7 mL of a solution of 80% normal saline and 20% absolute alcohol (v/v). Final concentration is 1% (10 mg/mL).
- Treatment of pseudocyesis (pseudopregnancy) · 10-100 micrograms/kg PO daily in divided doses until lactation ceases · PO · daily in divided doses · until lactation ceases · Vomiting, depression and anorexia are common side effects, usually more problematic than the lactation.
- Treatment of pseudocyesis (pseudopregnancy) · 10-100 micrograms/kg PO twice daily for 10-14 days · PO · twice daily · 10-14 days · Vomiting is very common; reducing dose and administering after meals may help.
- Treatment of pseudocyesis (pseudopregnancy) · 10-50 micrograms/kg PO at least twice a day · PO · at least twice a day
- Pregnancy termination after mismating · 50-100 micrograms/kg PO or IM twice daily for 4-7 days · PO/IM · twice daily · 4-7 days · From day 35-45 after LH surge. Not uniformly effective and may cause vomiting at this dosage (a peripheral acting antiemetic 30 minutes before dose may be helpful).
Vías de administración
Contraindicaciones
- Hypertension
- Pregnancy (in humans, documented teratogenicity not established but contraindicated)
- Nursing/lactating animals (interferes with lactation)
Efectos adversos
- Nausea
- Vomiting (highly prevalent in dogs)
- Sedation
- Fatigue
- Hypotension
- Anorexia
- Depression
- Trembling
- Diarrhea
- Tachycardia
Interacciones farmacológicas
- Alcohol · May cause a disulfiram-type reaction
- Butyrophenones (e.g., haloperidol, azaperone) · May increase prolactin concentrations; bromocriptine doses may need to be increased
- Amitriptyline · May increase prolactin concentrations; bromocriptine doses may need to be increased
- Phenothiazines · May increase prolactin concentrations; bromocriptine doses may need to be increased
- Reserpine · May increase prolactin concentrations; bromocriptine doses may need to be increased
- Cyclosporine · May elevate cyclosporine levels
- Erythromycin · May increase bromocriptine levels
- Clarithromycin · May increase bromocriptine levels
- Estrogens or Progestins · May interfere with the effects of bromocriptine
- Ergot Alkaloids · Not recommended; concurrent use has caused severe hypertension and myocardial infarction in humans
- Hypotensive Medications · May cause additive hypotension
- MAO Inhibitors (including amitraz, selegiline) · Avoid use of bromocriptine with these compounds
- Metoclopramide · May cause prolactin release in dogs, negating the effects of bromocriptine for treating pseudopregnancy
Monitorización
- Clinical efficacy (dependent upon the reason for use)
- Blood pressure (especially if patients exhibit clinical signs associated with hypotension)
Sobredosis
Overdosage may cause **vomiting, severe nausea, and profound hypotension**. - **Clinical Signs in Dogs**: Common findings recorded in decreasing frequency include vomiting, trembling, diarrhea, subdued behavior, and tachycardia. - **Treatment**: Standardized gut removal techniques should be employed when applicable, though emesis often occurs spontaneously. Institute cardiovascular monitoring (blood pressure, heart rate) and provide supportive care as needed.
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