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Inodilator / Acute Heart Failure Pregnancy: Avoid — no adequate data; use only for life-threatening maternal cardiac failure under specialist supervision

Milrinone

Brand names: Primacor

Adult dose

Dose: Loading: 50 mcg/kg IV over 10 minutes (optional — omit if hypotensive). Maintenance: 0.375-0.75 mcg/kg/min IV infusion.
Route: Intravenous infusion
Frequency: Continuous infusion
Max: 1.13 mg/kg/day
Phosphodiesterase-3 (PDE3) inhibitor — increases intracellular cAMP → positive inotropy AND vasodilation (inodilator). Used in acute decompensated HF, especially post-cardiac surgery. Unlike dobutamine, does NOT cause tachycardia at clinical doses and is NOT antagonised by beta-blockers — useful in patients on chronic beta-blocker therapy.

Paediatric dose

Dose: 0.25-0.75 mcg/min/kg
Route: IV infusion
Frequency: Continuous
Max: 0.75 mcg/kg/min
Specialist paediatric intensive care. Used post-congenital heart disease surgery. Loading dose 50-75 mcg/kg over 30-60 min if tolerated.

Dose adjustments

Renal

eGFR 10-50: reduce maintenance to 0.2-0.43 mcg/kg/min. eGFR <10: 0.2 mcg/kg/min. Milrinone is 80% renally excreted — significant accumulation in CKD.

Hepatic

No dose adjustment required

Paediatric weight-based calculator

Specialist paediatric intensive care. Used post-congenital heart disease surgery. Loading dose 50-75 mcg/kg over 30-60 min if tolerated.

Clinical pearls

  • Beta-blocker compatibility: milrinone works DISTAL to the beta-receptor (on PDE3 enzyme), so its effects are not antagonised by beta-blockers. In patients on chronic carvedilol or bisoprolol who need inotropic support, milrinone is preferred over dobutamine (which requires beta-receptor stimulation and may have attenuated effect).
  • Levosimendan vs milrinone: levosimendan (calcium sensitiser) is preferred in some guidelines for acute HF when 'inodilator' effect needed — particularly post-cardiac surgery and in cardiogenic shock with preserved myocardial viability. SURVIVE trial: levosimendan not superior to dobutamine for mortality.
  • OPTIME-CHF trial: milrinone vs placebo in decompensated HF — no mortality benefit; increased hypotension and new-onset AF. Evidence for milrinone in acute HF is not strong — used mainly as bridge to decision (transplant/VAD) or post-cardiac surgery.
  • Thrombocytopenia: platelets should be monitored during prolonged milrinone infusion — rare but platelet counts <100 x10^9/L have been reported. Stop if significant thrombocytopenia develops.
  • Renal accumulation: milrinone half-life (2.3h in normal renal function) extends to >20h in severe CKD. Dose reduction is essential — accumulation causes refractory vasodilation and arrhythmias.

Contraindications

  • Severe hypotension (vasodilation worsens)
  • Severe aortic or pulmonic valvular disease (obstructive pathology)
  • Hypovolaemia (treat first)
  • Hypersensitivity to milrinone

Side effects

  • Hypotension (vasodilation — most common; avoid loading dose if hypotensive)
  • Ventricular arrhythmias (VT, VF — particularly at higher doses)
  • Tachycardia (less than dobutamine)
  • Thrombocytopenia (rare — platelet monitoring)
  • Headache

Interactions

  • Other inotropes/vasopressors — additive haemodynamic effects
  • Diuretics — additive hypotension; ensure adequate filling before use

Monitoring

  • Continuous ECG (arrhythmia monitoring)
  • Blood pressure (arterial line preferred)
  • Platelet count
  • eGFR (dose adjustment)
  • Cardiac output/haemodynamic parameters

Reference: BNFc; BNF 90; BNFc; OPTIME-CHF Trial (Cuffe et al. JAMA 2002); ESC Acute HF Guidelines 2021; SPC Primacor. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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