Cimetidine
**Cimetidine** is a histamine (H2) receptor antagonist used for the management of idiopathic, uraemic, or drug-related erosive gastritis, gastric and duodenal ulcers, oesophagitis, and hypersecretory conditions secondary to gastrinoma, mast cell neoplasia, or short bowel syndrome. > **Clinical Warning:** Efficacy against NSAID-induced ulcers is controversial. It is less effective at reducing gastric acidity than more modern H2 blockers (e.g., famotidine) and proton pump inhibitors (e.g., omeprazole). It has minimal prokinetic effects and is not an antiemetic.
Mecanismo: Acts as a **Histamine (H2) receptor antagonist** → competitively inhibits histamine at H2 receptors of the gastric parietal cells → reduces histamine-induced gastric acid secretion. It also binds to microsomal **cytochrome P450** enzymes, retarding oxidative hepatic drug metabolism. It has weak anti-androgenic effects.
Dosificación por especie
- All uses (gastritis, ulcers, oesophagitis, hypersecretory conditions) · 2.5-5 mg/kg · PO/IV/IM · q12h · Taper upon cessation · Administer IV over 30 minutes. Reduce dose in renal impairment.
- All uses (gastritis, ulcers, oesophagitis, hypersecretory conditions) · 5 mg/kg · PO/IV/IM · q8h · Taper upon cessation · Administer IV over 30 minutes. Reduce dose in renal impairment.
Las dosis son una referencia clínica para médicos veterinarios. Confirme siempre con la información vigente del producto y el paciente individual.
Vías de administración
Contraindicaciones
- No specific contraindications available, but use with caution in patients with known hypersensitivity.
Efectos adversos
- Thrombocytopenia (reported in dogs)
- Transient and self-resolving slight swelling of mammary glands (female dogs)
- Hepatotoxicity (rare, reported in humans)
- Nephrotoxicity (rare, reported in humans)
- Headache (humans)
- Decreased libido (humans)
Interacciones farmacológicas
- Propranolol · Increases plasma levels of beta-blockers due to CYP450 inhibition · moderate
- Verapamil · Increases plasma levels of calcium-channel blockers · moderate
- Diazepam · Increases plasma levels of diazepam · moderate
- Lidocaine · Increases plasma levels of lidocaine · major
- Metronidazole · Increases plasma levels of metronidazole · moderate
- Pethidine · Increases plasma levels of pethidine · moderate
- Theophylline · Increases plasma levels of theophylline · major
- Myelosuppressive agents · May exacerbate leucopenia · moderate
- Sucralfate · May decrease cimetidine bioavailability; administer sucralfate at least 2 hours before · minor
- Antacids · May decrease absorption; stagger oral doses by 2 hours · minor
- Digoxin · Altered absorption/metabolism; stagger oral doses by 2 hours · moderate
- Itraconazole · Decreased absorption of itraconazole due to reduced gastric acidity; stagger oral doses by 2 hours · moderate
- Maropitant · Potential interaction; stagger oral doses by 2 hours · minor
Monitoreo
- Clinical signs of GI ulceration or bleeding
- Renal function (to guide dose reduction if impaired)
- Heart rate and blood pressure (if administering IV)
- Complete blood count (monitor for thrombocytopenia or leucopenia, especially if on concurrent myelosuppressive drugs)
Sobredosis
Adverse reactions are generally minor even at high doses. Supportive care should be provided if massive overdose occurs.
La referencia de fármacos de VetSheet está destinada a médicos veterinarios como apoyo a la decisión clínica; no sustituye el juicio profesional ni la información vigente del fabricante.