Dopamine
Dopamine is an endogenous **catecholamine** and the immediate metabolic precursor to norepinephrine. In veterinary critical care, it is primarily utilized as a continuous rate infusion (CRI) to manage hemodynamic instability, particularly hypotensive shock and acute heart failure, *after* adequate fluid resuscitation. ### Clinical Highlights * **Dose-Dependent Effects**: Dopamine's receptor affinity shifts dramatically based on the infusion rate, progressing from dopaminergic (vasodilation) to beta-1 (inotropic) to alpha-1 (vasopressor) effects. * **Renal Dose Controversy**: Historically, "low-dose" dopamine was used to promote diuresis in oliguric acute kidney injury. Modern evidence suggests it does not significantly improve Glomerular Filtration Rate (GFR) and is largely considered unproven or controversial in dogs, and potentially detrimental in cats. * **Strict Administration Rules**: Must be given via a dedicated IV line with a syringe pump or fluid pump. **Extravasation** causes severe tissue necrosis. > **Clinical Pearl**: Dopamine is ineffective and potentially dangerous if administered to a hypovolemic patient. Always restore intravascular volume before initiating vasopressor or inotropic therapy.
Mechanism: Dopamine acts directly on **dopaminergic**, **ฮฒ1-adrenergic**, and **ฮฑ1-adrenergic** receptors, and indirectly by stimulating the release of endogenous norepinephrine from sympathetic nerve terminals. Its effects are highly dose-dependent: * **Low Dose (0.5โ2 ยตg/kg/min)**: Primarily stimulates **D1 and D2 dopaminergic receptors** โ vasodilation of renal, mesenteric, coronary, and intracerebral vascular beds. Increases renal blood flow and urine output, but does not appreciably increase GFR. * **Medium Dose (2โ10 ยตg/kg/min)**: Stimulates **ฮฒ1-adrenergic receptors** in the myocardium โ increases intracellular cAMP โ positive inotropic (increased contractility) and mild chronotropic (increased heart rate) effects. Improves cardiac output and organ perfusion. * **High Dose (>10โ12 ยตg/kg/min)**: Overrides dopaminergic effects and strongly stimulates **ฮฑ1-adrenergic receptors** in the vasculature โ profound vasoconstriction โ increases systemic vascular resistance (SVR) and blood pressure. Renal and peripheral blood flows are decreased at these rates.
Dosing by species
- Vasodilatory shock if fluid resuscitation and dobutamine is not successful ยท 2.5-10 micrograms/kg/min ยท IV ยท CRI ยท Titrated to effect ยท If not successful may try adding norepinephrine.
- Treatment of severe hypotension/shock ยท 1-3 micrograms/kg/minute CRI; higher dosages of 3-10 micrograms/kg/min CRI are indicated if greater cardiotonic and BP support are indicated ยท IV ยท CRI ยท Titrated to effect ยท Not a substitute for adequate volume replacement therapy.
- Treatment of severe hypotension/shock after fluid correction and if dobutamine does not give desired effect ยท 1-10 micrograms/kg/min ยท IV ยท CRI ยท Titrated to effect
- Vasodilatory shock if fluid resuscitation and dobutamine is not successful ยท 2.5-10 micrograms/kg/min ยท IV ยท CRI ยท Titrated to effect ยท If not successful may try adding norepinephrine.
- Adjunctive therapy for acute heart failure ยท 1-10 micrograms/kg/min ยท IV ยท CRI ยท Titrated to effect ยท Initially, a dose of 2 micrograms/kg/min is usually used and titrated upward to desired clinical effect. Doses higher than 10 may increase peripheral vascular resistance and heart rate.
- Treatment of severe hypotension/shock ยท 1-3 micrograms/kg/minute CRI; higher dosages of 3-10 micrograms/kg/min CRI are indicated if greater cardiotonic and BP support are indicated ยท IV ยท CRI ยท Titrated to effect ยท Not a substitute for adequate volume replacement therapy.
- Treatment of severe hypotension/shock after fluid correction and if dobutamine does not give desired effect ยท 1-10 micrograms/kg/min ยท IV ยท CRI ยท Titrated to effect
Routes of administration
Contraindications
- Pheochromocytoma
- Ventricular fibrillation
- Uncorrected tachyarrhythmias
- Uncorrected hypovolemia (must replace fluids first)
Adverse effects
- Nausea and vomiting
- Ectopic beats (arrhythmias)
- Tachycardia
- Palpitations
- Hypotension (at low doses) or Hypertension (at high doses)
- Dyspnea
- Vasoconstriction (reduced peripheral circulation)
- Severe tissue necrosis and sloughing (if extravasated)
Drug interactions
- Alpha-adrenergic blockers (e.g., prazosin) ยท May antagonize the vasoconstrictive properties of high-dose dopamine.
- Halogenated hydrocarbon anesthetics (e.g., halothane) ยท May result in increased incidences of ventricular arrhythmias.
- Tricyclic antidepressants ยท May potentiate adverse cardiovascular effects.
- Beta-blockers (e.g., propranolol, metoprolol) ยท May antagonize the cardiac (inotropic/chronotropic) effects of dopamine.
- Diuretics ยท May potentiate urine production effects of low-dose dopamine.
- Monoamine oxidase inhibitors (MAOIs) ยท Can significantly prolong and enhance the effects of dopamine.
- Oxytocic drugs ยท May cause severe hypertension when used concurrently.
- Phenothiazines ยท May antagonize the renal and mesenteric vasodilatation effects of dopamine.
- Vasopressors/Vasoconstrictors ยท Concurrent use may cause severe hypertension.
Monitoring
- Continuous electrocardiogram (ECG) for cardiac rate and rhythm
- Direct or indirect blood pressure
- Urine output/flow
- IV catheter site (frequent checks for patency and signs of extravasation)
Overdose
Accidental overdosage is primarily manifested by **excessive blood pressure elevation** (severe hypertension) and arrhythmias. * **Treatment**: Because dopamine's half-life is extremely short (~2 minutes), treatment usually consists only of temporarily discontinuing the IV infusion or reducing the rate until parameters normalize. * If the patient's condition fails to stabilize rapidly after discontinuation, the alpha-adrenergic antagonist **phentolamine** may be administered.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.