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Inodilator — Phosphodiesterase III Inhibitor Pregnancy: Limited data — use only if benefit outweighs risk in life-threatening cardiogenic shock

Milrinone

Brand names: Primacor

Adult dose

Dose: Loading: 50 mcg/kg over 10 min (optional); Maintenance: 0.375–0.75 mcg/kg/min
Route: IV infusion
Frequency: Continuous
Max: 1.13 mg/kg/day
Increases cAMP → inotropy + vasodilation. Useful post-cardiac surgery and in acute decompensated heart failure. Does not require beta-receptor stimulation — effective in beta-blocker treated or downregulated receptor states. Loading dose often omitted if haemodynamically unstable (causes hypotension).

Paediatric dose

Dose: 0.25–0.75 mcg/min/kg
Route: IV infusion
Frequency: Continuous
Max: 0.75 mcg/kg/min
Paediatric post-cardiac surgery low output syndrome: 0.25–0.75 mcg/kg/min. Loading dose 50–75 mcg/kg over 15 min under specialist guidance.

Dose adjustments

Renal

Significant renal excretion — reduce dose: 0.2 mcg/kg/min if eGFR <20 mL/min. Accumulation risk.

Hepatic

No specific adjustment required.

Paediatric weight-based calculator

Paediatric post-cardiac surgery low output syndrome: 0.25–0.75 mcg/kg/min. Loading dose 50–75 mcg/kg over 15 min under specialist guidance.

Clinical pearls

  • Milrinone acts downstream of beta-receptors — effective when beta-agonists (dobutamine) fail due to receptor downregulation in chronic heart failure or beta-blocker therapy
  • OPTIME-CHF trial: milrinone in acute decompensated HF — no mortality benefit; increased arrhythmias. Use reserved for cardiogenic shock, not routine decompensation.
  • Post-cardiac surgery: first-line inodilator in many centres — reduces pulmonary vascular resistance (useful in RV dysfunction)

Contraindications

  • Severe aortic/pulmonary valve stenosis (outflow obstruction)
  • Hypertrophic obstructive cardiomyopathy

Side effects

  • Hypotension (vasodilation — common)
  • Tachyarrhythmias (ventricular)
  • Thrombocytopenia (prolonged use)
  • Headache

Interactions

  • Other vasodilators/antihypertensives (additive hypotension)
  • Furosemide (precipitates if mixed in same line — flush between)

Monitoring

  • Cardiac output monitoring
  • BP (hypotension common)
  • ECG
  • Platelet count (prolonged use)
  • Renal function and dose adjustment

Reference: BNFc; BNF 90; OPTIME-CHF Trial (JAMA 2002); ESC Acute Heart Failure Guidelines 2021; BNFc. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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