Inamrinone

DOSAGE AND ADMINISTRATION

Loading doses of inamrinone injection should be administered as supplied (undiluted). Infusions of inamrinone may be administered in normal or half normal saline solution to a concentration of 1 mg/mL to 3 mg/mL. Diluted solutions should be used within 24 hours.

Inamrinone injection may be administered into running dextrose (glucose) infusions through a Y-Connector or directly into the tubing where preferable.

Chemical Interactions

A chemical interaction occurs slowly over a 24-hour period when the intravenous solution of inamrinone is mixed directly with dextrose (glucose)-containing solutions. THEREFORE, INAMRINONE SHOULD NOT BE DILUTED WITH SOLUTIONS THAT CONTAIN DEXTROSE (GLUCOSE) PRIOR TO INJECTION.

A chemical interaction occurs immediately, which is evidenced by the formation of a precipitate when furosemide is injected into an intravenous line of an infusion of inamrinone. Therefore, furosemide should not be administered in intravenous lines containing inamrinone.

The following procedure is recommended for the administration of inamrinone injection:

1. Initiate therapy with a 0.75 mg/kg loading dose given slowly over 2 to 3 minutes.

2. Continue therapy with a maintenance infusion between 5 mcg/kg/min and 10 mcg/kg/min.

3. Based on clinical response, an additional loading dose of 0.75 mg/kg may be given 30 minutes after the initiation of therapy.

4. The rate of infusion usually ranges from 5 mcg/kg/min to 10 mcg/kg/min such that the recommended total daily dose (including loading doses) does not exceed 10 mg/kg. A limited number of patients studied at higher doses support a dosage regimen up to 18 mg/kg/day for shortened durations of therapy.

The following infusion rate chart may be used to assure that the calculations are made correctly.

To utilize the chart, the concentration of inamrinone infusion solution used must be 2.5 mg/mL (2500 mcg/mL). This concentration is prepared by mixing the inamrinone solution with an equal volume of diluent (normal or half normal saline).

Example: A 70 kg patient would require a loading dose of 10.5 mL of undiluted inamrinone. If the physician selects a dose of 7.5 mcg/kg/min for the infusion, the flow rate would be 13 mL/hr at the 2.5 mg/mL concentration of inamrinone.

5. The rate of administration and the duration of therapy should be adjusted according to the response of the patient. The physician may wish to reduce or titrate the infusion downward based on clinical responsiveness or untoward effects.

The above dosing regimens can be expected to place most patients’ plasma concentration of inamrinone at approximately 3 mcg/mL. Increases in cardiac index show a linear relationship to plasma concentration of a range of 0.5 mcg/mL to 7 mcg/mL. No observations have been made at greater plasma concentrations.

Patient improvement may be reflected by increases in cardiac output, reduction in pulmonary capillary wedge pressure, and such clinical responses as a lessening of dyspnea and an improvement in other symptoms of heart failure, such as orthopnea and fatigue.

Monitoring central venous pressure (CVP) may be valuable in the assessment of hypotension and fluid balance management. Prior correction or adjustment of fluid/electrolytes is essential to obtain satisfactory response with inamrinone.

Parenteral drug products should be inspected visually and should not be used if particulate matter or discoloration is observed.

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