AMRINONE

Amrinone is a phosphodiesterase inhibitor that has both positive inotropic and vasodilator actions. Despite the potential benefit of its combined actions (i.e., greater augmentation of cardiac output with less cardiac work), amrinone has not proven superior to single-action cardiotonic agents such as dobutamine.

ACTIONS

The combined actions of amrinone produce an increase in cardiac stoke output without an increase in cardiac stroke work. The effects of amrinone on cardiac performance are roughly equivalent to those of dobutamine. However, because amrinone does not stimulate adrenergic receptors, its effects can add to the effects of dobutamine. Unlike dobutamine, the actions of amrinone are not attenuated by b-receptor antagonists.

Indications

Amrinone is effective as single-agent therapy in the management of low output states caused by systolic heart failure. However, it is most often used as a second agent that is added to dobutamine in cases of refractory heart failure.

DRUG ADMINISTRATION

Amrinone is degraded by dextrose and by light. Therefore, amrinone should not be infused in dextrose-containing fluids, and the infusion solution should be protected from light. An initial loading dose is used for amrinone therapy. The usual dose is 0.75 mg/kg but can be as high as 1.5 mg/kg. This is followed by a continuous infusion, usually in the range of 5 to 10 ug/kg/min. A dose rate of 10 ug/kg/min will achieve the desired hemodynamic response in over 80% of patients.

Incompatabilities

Furosemide should not be injected into intravenous lines carrying amrinone infusions because the drug forms a precipitate when added to amrinone solutions (see Handbook of Injectable Drugs).

ADVERSE EFFECTS

Although the oral form of the drug was discontinued by the FDA because of a high incidence of complications, short-term therapy with intravenous amrinone is relatively free of adverse effects. Thrombocytopenia caused by nonimmunogenic platelet destruction was a common side effect of chronic therapy with oral amrinone, but this complication is reported in only 2 to 3% of patients receiving short-term intravenous amrinone. The problem resolves when the drug is discontinued, and no cases of abnormal bleeding have been reported. Hypotension caused by excessive vasodilation has been a common complication of amrinone therapy in some reports, but it seems to occur mostly in hypovolemic patients.

Contraindications

Amrinone is contraindicated in patients with hypertrophic cardiomyopathy. Thrombocytopenia is not a contraindication to intravenous amrinone, but it is probably wise to avoid the drug if possible in patients with platelet counts below 50,000/mL.

Related Post :

Hemodynamic Drug