Makindo Medical Notes

💊 Milrinone is a phosphodiesterase-3 inhibitor (PDE3i) used in acute or refractory heart failure to improve cardiac output by enhancing myocardial contractility and reducing afterload. It has both inotropic and vasodilator effects — sometimes referred to as an “inodilator.”

📘 About

• Always refer to the BNF prescribing guidance for up-to-date dosing and monitoring advice.
• Used as a short-term intravenous therapy for severe heart failure unresponsive to standard treatment.
• Particularly useful in low-output states such as post-cardiac surgery or cardiogenic shock.

⚙️ Mode of Action

• Milrinone selectively inhibits phosphodiesterase type-3 (PDE3), increasing intracellular cyclic AMP (cAMP) in cardiac and vascular smooth muscle cells.
• In the myocardium, increased cAMP enhances calcium influx → positive inotropy (increased contractility).
• In vascular smooth muscle, it causes vasodilation → reduced preload and afterload.
• Overall effect: improved cardiac output with reduced systemic and pulmonary vascular resistance.

🩺 Indications

• Short-term treatment of severe congestive heart failure unresponsive to conventional therapy (except immediately post-MI).
• Low-output states following cardiac surgery or decompensated heart failure.
• Adjunct in cardiogenic shock when conventional inotropes (e.g. dobutamine) are insufficient.

💉 Dose Range (always verify in BNF or datasheet)

Always titrate cautiously and monitor for hypotension or arrhythmia during administration.

🚫 Contraindications

• Severe hypovolaemia (must be corrected before use).
• Significant valvular obstruction (e.g. aortic stenosis).
• Known hypersensitivity to milrinone or excipients.

⚠️ Cautions

• Use with caution in severe renal impairment — adjust dose and monitor closely.
• Risk of arrhythmia increases with concurrent digoxin or electrolyte disturbances.
• Monitor blood pressure, ECG, renal function, and electrolytes throughout infusion.
• Prolonged use associated with increased mortality in chronic heart failure — limit to short-term use.

💢 Side Effects

• 💓 Arrhythmias (ventricular or supraventricular).
• 💧 Hypotension due to vasodilation.
• 🫀 Angina or chest pain.
• 🧠 Headache, dizziness.
• 🧪 Hypokalaemia and thrombocytopenia.
• Rarely: raised liver enzymes or allergic reactions.

📚 References

• BNF: Milrinone
• Levy JH, Bailey JM. Milrinone: pharmacology and clinical applications. J Cardiothorac Vasc Anesth. 1992;6(5):691–705.
• Packer M et al. Effect of long-term oral milrinone therapy on mortality in severe chronic heart failure. N Engl J Med. 1991;325(21):1468–1475.

💡 Teaching tip: Milrinone is most effective for short-term bridge therapy in decompensated heart failure or post-cardiac surgery. Always correct hypovolaemia and electrolytes before starting, and avoid prolonged use due to pro-arrhythmic risk.