milrinone

General

High Alert Medication: This medication bears a heightened risk of causing significant patient harm when it is used in error.

Pronunciation:
mill-ri-none

Trade Name(s)

• Primacor

Ther. Class.
inotropics

Indications

Short-term treatment of HF unresponsive to conventional therapy with digoxin, diuretics, and vasodilators.

Action

• Increases myocardial contractility.
• Decreases preload and afterload by a direct dilating effect on vascular smooth muscle.

Therapeutic Effect(s):

Increased cardiac output (inotropic effect).

Pharmacokinetics

Absorption: IV administration results in complete bioavailability.

Distribution: Unknown.

Metabolism and Excretion: 80–90% excreted unchanged by the kidneys.

Half-life: 2.3 hr (↑ in renal impairment).

TIME/ACTION PROFILE (hemodynamic effects)

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity;
• Severe aortic or pulmonic valvular heart disease;
• Hypertrophic subaortic stenosis (may ↑ outflow tract obstruction).

Use Cautiously in:

• History of arrhythmias, electrolyte abnormalities, abnormal digoxin levels, or insertion of vascular catheters (↑ risk of ventricular arrhythmias);
• Renal impairment (↓ infusion rate if CCr is <50 mL/min);
• OB:  Lactation: Pregnancy or lactation.

Adverse Reactions/Side Effects

CNS: headache, tremor

CV: VENTRICULAR ARRHYTHMIAS, angina pectoris, chest pain, hypotension, supraventricular arrhythmias

CV: skin rash

GI: ↑ liver enzymes

F and E: hypokalemia

Hemat: thrombocytopenia

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

None significant.

Route/Dosage

IV (Adults):  Loading dose– 50 mcg/kg followed by  continuous infusion  at 0.5 mcg/kg/min (range 0.375–0.75 mcg/kg/min).

IV (Infants and Children):  Loading dose– 50 mcg/kg over 10 min followed by  continuous infusion  at 0.5 mcg/kg/min (range 0.25–0.75 mcg/kg/min).

Availability (generic available)

Injection: 1 mg/mL

Premixed infusion: 20 mg/100 mL, 40 mg/200 mL

Assessment

• Monitor heart rate and BP continuously during administration. Slow or discontinue if BP drops excessively.
• Monitor intake and output and daily weight. Assess patient for resolution of signs and symptoms of HF (peripheral edema, dyspnea, rales/crackles, weight gain) and improvement in hemodynamic parameters (increase in cardiac output and cardiac index, decrease in pulmonary capillary wedge pressure). Correct effects of previous aggressive diuretic therapy to allow for optimal filling pressure.
• Monitor ECG continuously during infusion. Arrhythmias are common and may be life threatening. The risk of ventricular arrhythmias is increased in patients with a history of arrhythmias, electrolyte abnormalities, abnormal digoxin levels, or insertion of vascular catheters.

Lab Test Considerations:

Monitor electrolytes and renal function frequently during administration. Correct hypokalemia prior to administration to decrease the risk of arrhythmias.

• Monitor platelet count during therapy.

Toxicity Overdose:

High Alert: Overdose manifests as hypotension. Dose should be decreased or discontinued. Supportive measures may be necessary.

Potential Diagnoses

• Decreased cardiac output (Indications) 

Implementation

• High Alert: Accidental overdose of milrinone can cause patient harm or death. Have second practitioner independently check original order, dose calculations, and infusion pump settings.

Patient/Family Teaching

Inform patient and family of reasons for administration. Milrinone is not a cure but is a temporary measure to control the symptoms of HF.

Evaluation/Desired Outcomes

Decrease in the signs and symptoms of HF.

• Improvement in hemodynamic parameters.