Dimenhydrinate
Dimenhydrinate is a first-generation **H1-receptor antagonist** widely known by the human brand name Dramamine®. It is an ethanolamine derivative consisting of a salt complex of **diphenhydramine** (approx. 54%) and **8-chlorotheophylline** (approx. 46%), a mild stimulant added to counteract the sedative effects of the antihistamine. In veterinary medicine, it is primarily utilized for its **antiemetic** properties to prevent and treat **motion sickness** in dogs and cats. **Clinical Pearls:** * Because histamine is not considered a primary mediator of vomiting in cats, other antiemetics (e.g., maropitant, prochlorperazine) may be more efficacious for feline motion sickness. * It is often considered "half-strength diphenhydramine" and can be used whenever an H1-blocker is indicated. * It may be used as an adjunctive treatment for feline pancreatitis to reduce histamine-mediated microvascular permeability.
Mecanismo: Dimenhydrinate exhibits antihistaminic (H1), antiemetic, anticholinergic, CNS depressant, and local anesthetic effects, primarily driven by the **diphenhydramine** moiety. * **H1-Receptor Antagonism**: Competitively blocks histamine at **H1 receptors** → prevents histamine-mediated responses in the GI tract, blood vessels, and respiratory tract. * **Antiemetic/Vestibular Effect**: Blocks **muscarinic acetylcholine receptors** → inhibits acetylcholine stimulation of the vestibular and reticular systems → reduces motion sickness. * **Pancreatitis Application**: H1 blockade → reduces histamine-mediated increases in microvasculature permeability → potentially limits hemorrhagic necrosis in feline pancreatitis.
Dosificación por especie
- Prevention and treatment of motion sickness/vomiting · 8 mg/kg · PO · q8h
- Prevention and treatment of motion sickness/vomiting · 4-8 mg/kg · PO · q8h
- Antihistamine · 4 mg per cat · PO · q8h
- Adjunctive treatment of pancreatitis · 8 mg/kg · PO · q8h
- Prevention and treatment of motion sickness (antiemetic) · 4-8 mg/kg · PO · three times daily
- Prevention and treatment of motion sickness · 4-8 mg/kg · PO · q8h
- Antihistamine · 4-8 mg/kg · PO · q8-12h
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Hypersensitivity to dimenhydrinate or other antihistamines in its class
- Angle closure glaucoma (use with caution)
- Prostatic hypertrophy (use with caution)
- Pyloroduodenal or bladder neck obstruction (use with caution)
- COPD if mucosal secretions are a problem (use with caution)
- Hyperthyroidism, seizure disorders, cardiovascular disease, or hypertension (use with caution)
Efectos adversos
- CNS depression (lethargy, somnolence)
- Anticholinergic effects (dry mouth, urinary retention)
- GI effects (diarrhea, vomiting, anorexia - less common)
Interacciones farmacológicas
- Anticholinergic drugs (e.g., tricyclic antidepressants) · May potentiate the anticholinergic effects of other anticholinergic drugs.
- CNS Depressant Drugs · Increased sedation can occur if combined with other CNS depressants.
- Ototoxic Drugs (e.g., aminoglycosides) · May mask the clinical signs of ototoxicity; use with caution when administering concomitantly.
Monitorización
- Clinical efficacy (reduction in vomiting/motion sickness)
- Adverse effects (sedation, anticholinergic signs such as dry mouth or urinary retention)
Sobredosis
Overdosage may cause **CNS stimulation** (excitement to seizures) or **depression** (lethargy to coma), anticholinergic effects, respiratory depression, and death. **Treatment:** * Empty the gut if ingestion was oral. Induce emesis if the patient is alert and CNS status is stable. * Administration of a saline cathartic and/or activated charcoal may be given after emesis or gastric lavage. * Symptomatic and supportive therapies. * **Phenytoin (IV)** is recommended in the treatment of seizures caused by antihistamine overdose in humans; use of barbiturates and diazepam are avoided.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.