Abstract
Thyroid hormone has unique actions that make it a novel and possibly useful agent for treatment of heart failure. Because of potential adverse effects of thyroid hormone, however, there has been interest in developing analogues with fewer undesirable side effects. Screening of compounds structurally related to levothyroxine identified 3,5-diiodothyropropionic acid (DITPA) as an analogue with inotropic selectivity and low metabolic activity in hypothyroid rats. When DITPA was administered alone or in combination with captopril in rat and rabbit postinfarction models of heart failure, cardiac output was increased and left ventricular end-diastolic pressure (LV EDP) was decreased without increasing heart rate. A pilot clinical study was undertaken to evaluate the safety and efficacy of DITPA. In a dose-ranging study in 7 normal volunteers the drug was well tolerated. A double-blind comparison then was made of DITPA versus placebo in a group of 19 patients with moderately severe heart failure. Patients were randomly assigned to receive either 1.875 mg/kg of DITPA or placebo daily. After 2 weeks the drug was increased to 3.75 mg/kg daily for an additional 2 weeks. In heart failure patients receiving the drug for 4 weeks, cardiac index was increased (p = 0.04) and systemic vascular resistance index was decreased (p = 0.02). Total serum cholesterol (p = 0.013) and triglycerides (p = 0.005) also were decreased significantly. These results indicate that DITPA is well tolerated and could represent a useful new agent for treatment of congestive heart failure.
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