Vasopressin
**Vasopressin**, also known as antidiuretic hormone (ADH), is an endogenous peptide hormone synthesized in the hypothalamus and stored in the posterior pituitary gland. In veterinary medicine, it serves several critical roles: * **Diagnostic Agent**: Used primarily in the water deprivation test to differentiate between central and nephrogenic diabetes insipidus. * **Emergency & Critical Care**: Increasingly utilized as an adjunctive treatment for vasodilatory shock and during cardiopulmonary cerebral resuscitation (CPCR). > **Clinical Pearl**: In states of severe shock or cardiac arrest (ventricular asystole/pulseless electrical activity), vasopressin offers distinct advantages over epinephrine. It induces profound vasoconstriction even in acidotic environments, spares coronary and renal vasculature (improving myocardial perfusion), and lacks the arrhythmogenic and chronotropic effects associated with catecholamines. Historically used to treat central diabetes insipidus, it has largely been replaced by the synthetic analog **desmopressin (DDAVP)** for long-term management due to the discontinuation of long-acting oil-based formulations.
Mecanismo: Vasopressin exerts its effects via multiple receptor subtypes: * **V1 Receptors (Vascular Smooth Muscle)**: Mediates profound vasoconstriction. At high doses, it causes contraction of capillaries and small arterioles, increasing systemic vascular resistance and blood pressure. It also stimulates smooth muscle in the bladder, gallbladder, and GI tract. * **V2 Receptors (Renal Collecting Ducts)**: Mediates antidiuretic effects. Vasopressin binds to V2 receptors → activates adenylate cyclase → increases **cAMP** → promotes the insertion of **aquaporin-2 channels** into the luminal membrane → increases water permeability and reabsorption of solute-free water → concentrates urine and decreases urine flow. * **V3 Receptors (Pituitary)**: Stimulates the release of corticotropin (ACTH). * **Oxytocin & Purinergic (P2) Receptors**: Minimal oxytocic effects at standard doses, but massive doses can stimulate uterine contraction.
Dosificación por especie
- Diagnostic agent (after water deprivation test) · 0.5 U/kg IM · IM · Once · Empty bladder and determine specific gravity at 30, 60, and 120 minutes after administration.
- Adjunctive treatment of vasodilatory shock (unresponsive to fluids/catecholamines) · 0.01-0.04 Units/minute IV · IV · CRI
- CPCR (pulseless electrical activity or ventricular asystole) · 0.2-0.8 Units/kg, IV once · IV · Once · May be beneficial for myocardial and cerebral blood flow.
- Diagnostic agent (Exogenous vasopressin test after water deprivation test) · 2.5 mU/kg IV over one hour · IV · Once · 1 hour · Give aqueous vasopressin in D5W. Empty bladder and collect urine at 30, 60, and 90 minutes.
- Adjunctive treatment of vasodilatory shock (unresponsive to fluids/catecholamines) · 0.01-0.04 Units/minute IV · IV · CRI · Dose is not dependent upon patient weight. DO NOT exceed 0.04 Units/minute (risk of myocardial ischemia). DO NOT use in cardiogenic shock.
- CPCR (pulseless electrical activity or ventricular asystole) · 0.2-0.8 Units/kg, IV once · IV · Once · May be beneficial for myocardial and cerebral blood flow.
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Known hypersensitivity to vasopressin
- Chronic nephritis until nitrogen retention is resolved to reasonable levels
- Cardiogenic shock (due to risk of myocardial ischemia)
Efectos adversos
- Local irritation at the injection site
- Sterile abscesses
- Skin reactions
- Platelet aggregation
- Bilirubinemia
- Abdominal pain
- Hematuria
- Hypersensitivity (urticarial) reactions
- Water intoxication (with overdosage)
Interacciones farmacológicas
- Alcohol · May inhibit the antidiuretic activity of vasopressin
- Demeclocycline · May inhibit the antidiuretic activity of vasopressin
- Epinephrine (large doses) · May inhibit the antidiuretic activity of vasopressin
- Heparin · May inhibit the antidiuretic activity of vasopressin
- Norepinephrine (large doses) · May inhibit the antidiuretic activity of vasopressin
- Antidepressants, Tricyclic · May potentiate the antidiuretic effects of vasopressin
- Carbamazepine · May potentiate the antidiuretic effects of vasopressin
- Chlorpropamide · May potentiate the antidiuretic effects of vasopressin
- Clofibrate · May potentiate the antidiuretic effects of vasopressin
- Fludrocortisone · May potentiate the antidiuretic effects of vasopressin
- Phenformin · May potentiate the antidiuretic effects of vasopressin
- Urea · May potentiate the antidiuretic effects of vasopressin
Monitorización
- Urine output and frequency
- Water consumption
- Urine specific gravity
- Urine osmolality
- Blood pressure and ECG (when used for shock/CPCR)
Sobredosis
### Water Intoxication Overdosage of vasopressin leads to excessive water retention and subsequent **water intoxication** (dilutional hyponatremia). * **Early Signs**: Listlessness, depression, and lethargy. * **Severe Signs**: Coma, seizures, and eventually death due to cerebral edema. **Treatment**: * *Mild Intoxication*: Discontinue vasopressin therapy and strictly restrict water access until clinical signs resolve. * *Severe Intoxication*: May require the administration of osmotic diuretics (e.g., mannitol, urea, or dextrose) with or without a loop diuretic like furosemide to rapidly excrete excess free water.
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.