Slow infusion of vinca alkaloids in the treatment of idiopathic thrombocytopenic purpura.

Vinca alkaloids are useful in the treatment of idiopathic thrombocytopenic purpura, a disorder in which macrophages remove platelets sensitized with antibody. Because vinca alkaloids avidly bind to platelets, drugs can be delivered selectively to macrophages. However, drugs given by bolus injection are cleared too rapidly to bind optimally to autologous platelets, and the use of allogeneic platelets loaded with drug in vitro is cumbersome, expensive, and dangerous. Therefore, slow infusions were devised to prolong the duration of enhanced plasma drug concentrations, thereby providing better conditions for in-vivo drug loading into autologous platelets. Twenty-four patients with refractory idiopathic thrombocytopenic purpura were given slow infusions; 17 had good to excellent responses. Eleven of eighteen patients who had been treated with bolus injections had better results when treated with slow infusions. Patients with improved responses had slower plasma clearance rates than did patients with poor responses. Slow infusion therapy had fewer side effects than bolus injection therapy. Slow infusions are the best method for long-term management.