Vasopressors & Inotropes

Dopamine

Patient-specific bag-prep worksheet for a 100 mL dopamine drip. The 6×kg shortcut adds 6 mg/kg of stock to a 100 mL bag, yielding a concentration where the pump rate in mL/hr equals the dose in µg/kg/min. No further math at the bedside. Used for inotropic and vasopressor support in hypotension and shock once fluid status is adequate.

Stock: 40 mg/mL (40 000 µg/mL)

High-alert medication. Do NOT confuse DOPamine with DOBUTamine or DOXapram (Doprap).
Volume status first. Volume depletion should be corrected before dopamine administration. Vasopressors are not a substitute for adequate fluid replacement.

How this calculator works

Uses the 6 × kg method: add (6 × patient weight in kg) mg of dopamine to a 100 mL bag of compatible IV fluid. Once mixed, the pump rate in mL/hr is equal to the dose in µg/kg/min, no further math at the bedside.

Don't have a 100 mL bag? The 6×kg shortcut requires a 100 mL bag specifically (the elegant pump-rate-equals-dose identity is bag-size dependent). If you only have 250 mL or 500 mL bags available, use the standard dopamine CRI calculator →

Species

Dog Cat

Patient weight

lb kg

Target dose (µg/kg/min)

Dogs: 3–20 µg/kg/min (start 2.5–5, titrate +2.5–5 every ~30 min). Cats: 5–20 µg/kg/min, same titration.

Awaiting input

Enter a patient weight to see the result.

Reference

How the calculation works

The 6 × kg method produces a bag where pump rate (mL/hr) equals dose (µg/kg/min). The bag concentration is derived as:

$$\text{concentration} = \frac{6 \times \text{BW}_{\text{kg}} \times 1000\,\mu g/mg}{100\,\text{mL}} = 60 \times \text{BW}_{\text{kg}}\;\mu g/\text{mL}$$

At that concentration, a dose of D µg/kg/min requires:

$$\text{mL/hr} = \frac{\text{BW}_{\text{kg}} \times D_{\mu g/kg/min} \times 60}{60 \times \text{BW}_{\text{kg}}} = D$$

So pump rate (mL/hr) and dose (µg/kg/min) are numerically equal, no further bedside math needed.

Worked example with current inputs

Enter a patient weight to see the worked example.

Reference

The 6 × kg method

The preparation worksheet specifies:

Multiply patient weight in kg by 6, that's the milligrams of dopamine to add.
From a 40 mg/mL stock vial, draw the equivalent volume.
Remove that same volume from a 100 mL bag of compatible IV fluid first, then add the dopamine.
Run the pump at mL/hr = dose in µg/kg/min.

Worked example

For a 10 kg patient: 6 × 10 = 60 mg of dopamine, which is 1.5 mL of 40 mg/mL stock. Remove 1.5 mL from a 100 mL bag, then add 1.5 mL of dopamine. To dose at 5 µg/kg/min, run the pump at 5 mL/hr.

Why this works

A 100 mL bag with (6 × BW) mg of dopamine has concentration (6 × BW × 1000) ÷ 100 = 60 × BW µg/mL. For a dose D µg/kg/min, total drug needed per hour is BW × D × 60 µg. Divided by the concentration: (60 × BW × D) ÷ (60 × BW) = D mL/hr.

Limits and stability

The final dopamine concentration is capped at 3,200 µg/mL (3.2 mg/mL). The 6 × kg method exceeds this for patients above ~53 kg; at that point, switch to a 250 mL or 500 mL bag with proportionally more dopamine.
Stable for 24 hours at 20–25°C after dilution. Discard if discolored beyond slightly yellow.
Administer through a dedicated IV line into a large vein. Extravasation causes tissue necrosis.
Stepwise dose reduction prior to discontinuation reduces rebound hypotension risk.

Compatible fluids

5% / 10% dextrose, lactated Ringer's, 5% dextrose in LRS or 0.9% NaCl, 6% hetastarch, Plasma-Lyte, 0.9% NaCl.

Contraindications and cautions

Contraindicated: pheochromocytoma, ventricular fibrillation, uncorrected tachyarrhythmias.
Caution: ischemic or occlusive vascular disease; weaning from mechanical ventilation; oliguric acute kidney injury (low-dose dopamine is unlikely to benefit and may worsen renal vasoconstriction).
Discontinue or reduce dose if PVCs occur or if there are signs of reduced peripheral or cardiac perfusion.

Notable drug interactions

α-antagonists (acepromazine, prazosin): may decrease pressor effects.
β-antagonists (propranolol, metoprolol): combination causes unopposed α stimulation, raising SVR.
Inhalant anesthetics (isoflurane, sevoflurane): may increase arrhythmia risk.
MAOIs (amitraz, selegiline, linezolid): start dopamine at 1/10 the usual dose if MAOI given within 2–3 weeks.
Other sympathomimetics (dobutamine, terbutaline, etc.): toxicity risk if combined.

Sources

Primary: Plumb's Veterinary Drugs, dopamine monograph (Prescriber Highlights, Pharmacology/Actions, Pharmacokinetics, Contraindications/Precautions/Warnings, Adverse Effects, Drug Interactions, Dosages, Preparation/Stability, Administration sections).
Secondary (cat HCM/PVC concern): Lumb and Jones' Veterinary Anesthesia and Analgesia, 6th ed. Chapter 21 (Cardiovascular Drugs). Editor and full bibliographic details pending.
Secondary (clinical positioning): Hart S, Silverstein DC. Catecholamines. In: Silverstein DC, Hopper K, eds. Small Animal Critical Care Medicine. 3rd ed. St. Louis, MO: Elsevier; 2023:855–859 (Chapter 147, Table 147.1). Confirms the receptor-effect dose tiers (1–4 µg/kg/min dopaminergic; 5–10 µg/kg/min β; >10 µg/kg/min α) and provides the clinical context that dopamine is currently recommended as an alternative to norepinephrine only in highly selected patients (low risk of tachyarrhythmias, or absolute/relative bradycardia), its use in critically ill humans has been associated with significantly poorer outcomes and higher arrhythmic-event incidence than norepinephrine.