Pseudoephedrine
Pseudoephedrine is an oral **sympathomimetic amine**. In veterinary medicine, it is primarily utilized as a second-line agent for **urethral sphincter mechanism incompetence (USMI)** in dogs when phenylpropanolamine (PPA) is unavailable or contraindicated. It also serves as a nasal decongestant and a treatment for retrograde ejaculation. > **Clinical Pearl:** Pseudoephedrine is generally considered less efficacious and more prone to causing adverse effects (like agitation and hypertension) compared to PPA for urinary incontinence. Due to its status as a precursor for illicit methamphetamine synthesis, its sale is heavily restricted in many regions (e.g., Combat Methamphetamine Epidemic Act in the US), making procurement challenging.
Mecanismo: Pseudoephedrine acts as an **indirect-acting sympathomimetic**. * Enters sympathetic nerve terminals → stimulates the release of endogenous **norepinephrine** from storage vesicles. * Norepinephrine binds to **alpha-1 adrenergic receptors** in the smooth muscle of the urethra and blood vessels → **vasoconstriction** and **increased urethral sphincter tone** (preventing urine leakage). * Also weakly stimulates **beta-adrenergic receptors** → positive chronotropic effects (increased heart rate) and mild bronchodilation.
Dosificación por especie
- As a decongestant · 1 mg/kg · PO · q8h
- For use when an antihistamine/decongestant may be useful using the pyrilamine/pseudoephedrine oral granules · ½ ounce (1 tablespoonful) per 1,000 lb body weight. May mix with feed and repeated at 12 our intervals if needed. · PO · q12h · Do not use at least 72 hours before sporting events. ARCI UCGFS CLASS 3 DRUG.
- For urinary incontinence, or as a decongestant · 0.2-0.4 mg/kg [or practically, 15-60 mg (total dose) per dog] · PO · q8-12h
- To increase urethral tone · 1.5 mg/kg · PO · two to three times a day
- For retrograde ejaculation · 4-5 mg/kg · PO · three times daily or 1 to 3 hours before semen collection or attempted breeding may be tried.
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Glaucoma
- Prostatic hypertrophy
- Hyperthyroidism
- Diabetes mellitus
- Cardiovascular disorders
- Hypertension
Efectos adversos
- Panting
- Decreased appetite
- Lethargy
- Tachycardia
- CNS excitement
- Restlessness
- Insomnia
- Hypertension
- Arrhythmias
Interacciones farmacológicas
- Monoamine Oxidase (MAO) Inhibitors (e.g., amitraz, selegiline) · Should not be given within two weeks of receiving MAOIs; risk of severe hypertension and toxicity.
- Reserpine · Increased chance of hypertension if given concomitantly.
- Other Sympathomimetic Agents (e.g., ephedrine, phenylpropanolamine) · Increased toxicity may result; should not be administered together.
- Tricyclic Antidepressants (e.g., clomipramine, amitriptyline) · Increased chance of hypertension if given concomitantly.
Monitorización
- Efficacy (improvement in incontinence or congestion)
- Heart rate
- CNS stimulation (restlessness, agitation)
- Appetite
Sobredosis
Overdoses of pseudoephedrine can cause **hyperthermia, mydriasis, tachycardia, hypertension, vomiting, disorientation, and seizures**. * **Toxicity Thresholds:** In small animals, adverse reactions may develop at doses of 5-6 mg/kg. Deaths have occurred at doses >10-12 mg/kg. * **Clinical Signs:** Common findings in dogs include hyperactivity, tachycardia, agitation, mydriasis, restlessness, head bobbing, and panting. Cats commonly present with tachycardia. * **Treatment:** Large overdoses should be treated with gastric evacuation (if not contraindicated). Treat supportively and symptomatically (e.g., propranolol for tachycardia). Phenothiazines are preferred to treat hyperactivity, agitation, and tremors as diazepam may worsen dysphoria. Contact an animal poison control center for further guidance.
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.