Milrinone

ADMINISTRATION ROUTES:

IV

ALTERNATIVE NAMES:

Primacor

ICU INDICATIONS:

1. Low cardiac output state due to impaired myocardial contractility
2. Demonstrated vasospasm on CTA after aneurysmal subarachnoid haemorrhage

PRESENTATION AND ADMINISTRATION:

Milrinone 1 mg/mL (10 mL vial)

Dilute 10 mg up to 50 mL using compatible IV fluid

Compatible in the following IV fluids:

0.45% saline, 0.9% saline, 5% dextrose

Store at room temperature. Preparations not used in 24 hours should be discarded.

DOSAGE:

Low cardiac output state after cardiac surgery

IV infusion:

0.375 - 0.75 mcg/kg/min

Note: a loading dose of up to 50 mcg/kg may sometimes be used. This is not standard policy in Wellington ICU due to sometimes profound hypotension. During cardiothoracic surgery, patients may receive a loading dose in theatre prior to coming off bypass

Demonstrated vasospasm on CTA after aneurysmal subarachnoid haemorrhage

IV loading dose:

0.1 mg/kg given over 30 min

followed by

IV infusion:

1 mcg/kg/min

Milrinone should be weaned over 48 hours after resolution of vasospasm

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

Dose in renal impairment

Dose in renal replacement therapy

Note: renal impairment significantly increases the terminal elimination half life of milrinone. Patients with renal impairment on milrinone infusions may develop progressive vasodilation leading to escalating noradrenaline requirements. If noradrenaline requirement is increasing consider whether it is appropriate to cease milrinone.

DOSAGE IN PAEDIATRICS:

IV infusion:

Weight < 30kg:

1.5 mg/kg in 50 mL 5% dextrose run at 0.5 - 1.5 mL/hr (0.25 - 0.75 mcg/kg/min)

Weight ≥30kg:

1.5 mg/kg in 100 mL 5% dextrose run at 1 - 3 mL/hr (0.25 - 0.75 mcg/kg/min)

CLINICAL PHARMACOLOGY:

Milrinone lactate is a positive inotrope and vasodilator, with little chronotropic activity different in structure and mode of action from either the digitalis glycosides or catecholamines.

Milrinone lactate, at relevant inotropic and vasorelaxant concentrations, is a selective inhibitor of peak III cAMP phosphodiesterase isozyme in cardiac and vascular muscle. This inhibitory action is consistent with cAMP mediated increases in intracellular ionised calcium and contractile force in cardiac muscle, as well as with cAMP dependent contractile protein phosphorylation and relaxation in vascular muscle.

CONTRAINDICATIONS:

1. Hypersensitivity to milrinone

WARNINGS:

Milrinone is an inodilator. Significant hypotension due to peripheral vasodilation is common and is generally treated with noradrenaline.

PRECAUTIONS:

General:

The use of milrinone has been associated with increased frequency of ventricular and atrial arrhythmias. Milrinone may aggravate outflow tract obstruction in hypertrophic subaortic stenosis.

Laboratory Tests:

No tests in addition to routine ICU tests are indicated

Drug/Laboratory Test Interactions:

None noted

IMPORTANT DRUG INTERACTIONS IN ICU:

None of note

ADVERSE REACTIONS:

Cardiovascular:

SVT, VT, VF, hypotension

Respiratory:

Bronchospasm

CNS:

Headaches, tremor

Haematological:

Thrombocytopaenia

Metabolic:

Hypokalaemia