Drug Guide

Generic Name

Milrinone Lactate

Brand Names Primacor, Primacor In Dextrose 5% In Plastic Container, Milrinone Lactate In Dextrose 5% In Plastic Container, Milrinone Lactate In Dextrose 5% In Plastic Container, Milrinone Lactate In Plastic Container

Classification

Therapeutic: Inotropic Agent

Pharmacological: Phosphodiesterase 3 Inhibitor

FDA Approved Indications

Short-term management of acute heart failure and cardiogenic shock to improve cardiac output

Mechanism of Action

Milrinone inhibits phosphodiesterase type 3, leading to increased intracellular cyclic AMP levels in cardiac and vascular tissue. This results in positive inotropic effects and vasodilation, decreasing preload and afterload, thereby improving cardiac output.

Dosage and Administration

Adult: Loading dose of 50 mcg/kg IV over 10 minutes, followed by continuous infusion of 0.375-0.75 mcg/kg/min. Dose adjustments may be necessary based on response and renal function.

Pediatric: Dosing guidelines are similar, with adjustments based on weight and clinical response. Usually, a loading dose is given cautiously, followed by continuous infusion.

Geriatric: Start at lower end of dosing range due to increased risk of hypotension and renal impairment. Monitor closely.

Renal Impairment: Reduce dose and infusion rate; clearance is decreased in renal impairment.

Hepatic Impairment: Use with caution; no specific dose adjustment recommended.

Pharmacokinetics

Absorption: Rapid onset with IV infusion.

Distribution: Widely distributed; volume of distribution approximately 4 L/kg.

Metabolism: Minimal hepatic metabolism; primarily excreted unchanged by the kidneys.

Excretion: Renally excreted; renal clearance approximately 70 mL/min.

Half Life: Approximately 2-3 hours in healthy adults; prolonged in renal impairment.

Contraindications

Hypersensitivity to milrinone or phosphodiesterase inhibitors.

Precautions

Use with caution in patients with arrhythmias, hypotension, severe aortic or mitral stenosis, or impaired renal function. Monitor blood pressure, renal function, and cardiac status regularly. Caution in pregnancy; safety not established. Use during lactation not established; decision should weigh benefits versus potential risks.

Adverse Reactions - Common

Hypotension (Frequent)
Arrhythmias (e.g., ventricular arrhythmias, atrial fibrillation) (Frequent)
Headache, nausea, tremor (Less frequent)

Adverse Reactions - Serious

Severe hypotension (Less common)
Life-threatening arrhythmias (Rare)
Myocardial ischemia (Rare)

Drug-Drug Interactions

Other vasodilators, diuretics, beta-blockers, or antiarrhythmic agents may increase risk of hypotension or arrhythmias.

Drug-Food Interactions

None significant.

Drug-Herb Interactions

Limited data; use caution with herbal supplements affecting blood pressure or cardiac function.

Nursing Implications

Assessment: Monitor blood pressure, heart rate, rhythm, and renal function regularly. Assess for signs of hypotension or arrhythmia.

Diagnoses:

Risk for decreased cardiac output
Risk for hypotension
Risk for electrolyte imbalance

Implementation: Administer IV infusion as prescribed, using infusion pump. Ensure continuous cardiac and blood pressure monitoring. Adjust dose based on clinical response and renal function.

Evaluation: Evaluate cardiovascular response, blood pressure stability, renal parameters, and adverse effects.

Patient/Family Teaching

Report any symptoms of chest pain, dizziness, palpitations, or unexplained fatigue immediately.
Notify healthcare provider if symptoms worsen or new symptoms develop.
Follow infusion administration instructions carefully. Be aware of potential side effects like hypotension and arrhythmias.

Special Considerations

Black Box Warnings:

Use with caution due to risk of arrhythmias and hypotension.

Genetic Factors: No specific genetic testing required.

Lab Test Interference: May interfere with certain laboratory assays but generally not significant.

Overdose Management

Signs/Symptoms: Severe hypotension, arrhythmias, myocardial ischemia.

Treatment: Discontinue infusion immediately. Provide supportive care, including vasopressors for hypotension and antiarrhythmics for arrhythmias. Monitor cardiovascular status closely.

Storage and Handling

Storage: Store at controlled room temperature (20-25°C/68-77°F). Protect from light.

Stability: Stable for 24 hours in unopened containers; discard unused portions. Follow manufacturer’s recommendations for beyond-use dates.