Depression of Muscle Spindle Function with Vincristine

Abstract

VINCRISTINE sulphate, a purified indole alkaloid of the periwinkle plant, has been used widely in clinical and experimental cancer chemotherapy since its activity in acute leukaemia was first described in 1962 (ref. 1). A prominent side effect which often limits therapy with this drug is a dose-related peripheral neuropathy, presenting with depression of the deep tendon reflexes and paraesthesias, and progressing to flaccid paralysis in advanced cases². Careful monitoring of the early effects of vincristine and appropriate adjustment of the dosage schedule may reduce the incidence of neurological complications. In fact, the only prominent neurological effect which remains at the controlled dose levels used is markedly depressed or absent deep tendon reflexes. This change is so characteristic that we have quantitated the amplitude of the Achilles reflex in order to govern the use of the drug and in order to indicate the onset of its action³.