inamrinone lactate
Inocor

Available forms
Available by prescription only
Injection: 5 mg/ml

Indications and dosages
 Short-term management of heart failure. Adults: Initially, 0.75 mg/kg I.V. bolus over 2 to 3 minutes; then begin maintenance infusion of 5 to 10 mcg/kg/minute. Additional bolus of 0.75 mg/kg may be given 30 minutes after therapy is initiated. Maximum daily dose is 10 mg/kg.
 Cardiac life support in patients for whom other preferred drugs can’t be used for pump failure and acute pulmonary edema. Adults: 0.75 mg/kg I.V. bolus over 2 to 3 minutes, then 5 to 15 mcg/kg/ minute.

Pharmacodynamics
Vasodilating action: The primary vasodilating effect of inamrinone seems to stem from a direct effect on peripheral vessels.
Inotropic action: The mechanism of action responsible for the apparent inotropic effect isn’t fully understood; however, it may be linked to inhibition of phosphodiesterase activity, resulting in increased cellular levels of adenosine 3′,5′-cyclic phosphate; this, in turn, may alter intracellular and extracellular calcium levels. The role of calcium homeostasis hasn’t been determined. Clinical effects include increased cardiac output mediated by reduced afterload and, possibly, inotropism.

Pharmacokinetics
Absorption: Administered I.V.
Distribution: Distribution volume is 1.2 L/kg. Distribution sites are unknown. Protein-binding ranges from 10% to 49%. Therapeutic steady state serum levels range from 0.5 to 7 mcg/ml (ideal concentration: 3 mcg/ml).
Metabolism: Metabolized in the liver to several metabolites of unknown activity.
Excretion: In normal patients, inamrinone is excreted in the urine, with a terminal elimination half-life of about 4 hours. Half-life may be prolonged slightly in patients with heart failure.

Contraindications and precautions
Contraindicated in patients hypersensitive to inamrinone or bisulfites. Don’t use in patients with severe aortic or pulmonic valvular disease in place of surgical intervention or during an acute phase of MI.

Interactions
Drug-drug. Cardiac glycosides: Increases inotropic effect. This is a benefit in certain conditions.
Disopyramide: May cause severe hypotension. Avoid use together.

Adverse reactions
CV: arrhythmias, hypotension, fever, chest pain.
GI: nausea, vomiting, anorexia, abdominal pain.
Hematologic: thrombocytopenia.
Metabolic: decreased serum potassium.
Other: burning at injection site, hypersensitivity reactions (pericarditis, ascites, myositis vasculitis, pleuritis).

Effects on lab test results
• May increase liver enzyme levels. May decrease potassium levels.
• May decrease platelet count.

Overdose and treatment
Overdose may cause severe hypotension.
 Treatment may include administration of a potent vasopressor, such as norepinephrine, as well as other general supportive measures, including cautious fluid volume replacement.

Special considerations
• Inamrinone is prescribed primarily for patients who haven’t responded to therapy with cardiac glycosides, diuretics, and vasodilators.
• Dispense drug as supplied or dilute in normal or half-normal saline solution to concentration of 1 to 3 mg/ml. Don’t dilute drug with solutions containing dextrose because a slow chemical reaction occurs over 24 hours. However, amrinone can be injected into running dextrose infusions through Y-connector or directly into tubing. Use diluted solution within 24 hours.
• Don’t administer furosemide in I.V. lines containing amrinone because a chemical reaction occurs immediately.
• Monitor blood pressure and heart rate throughout infusion. Slow or stop infusion if patient’s blood pressure decreases or if arrhythmias (ventricular or supraventricular) occur. Dosage may need to be reduced.
• A platelet count below 150,000/mm³ usually necessitates dosage reduction. Thrombocytopenia usually occurs after prolonged treatment.
• Monitor electrolyte levels (especially potassium) because drug increases cardiac output, which may cause diuresis.
• Hemodynamic monitoring may be useful in guiding therapy.
• Observe patient for adverse GI effects (such as nausea, vomiting, and diarrhea); reduce dosage or discontinue drug.
Breast-feeding patients
• Drug may appear in breast milk. Safety in breast-feeding women hasn’t been established.
Pediatric patients
• Safety and efficacy in children younger than age 18 haven’t been established.

Patient education
• Warn patient that burning may occur at the injection site.
• Tell patient to report adverse reactions promptly.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use