In a murine model system, pyridoxine has demonstrated protective properties during administration of lethal doses of vincristine (VCR). Subsequently, pyridoxine has been evaluated in patients receiving VCR during an adjuvant chemotherapy program for stage II carcinoma of the breast. The toxicities, cumulative VCR dosage, and percentage of ideal dosage observed in 24 patients receiving pyridoxine have been compared to those observed in 88 patients who previously received VCR without pyridoxine in the same chemotherapy program. All patients ideally were to receive VCR 1.0 mg/m2 weekly for 6-weeks with dose modification for neurotoxicity. Treatment patients received pyridoxine 1.5 grams p.o. daily in three divided doses during the 6-week course. The degree of neurotoxic manifestations of VCR was similar in the treatment and comparison patients. Absent to mild neurotoxicity was observed in approximately 70% of patients in both groups; moderate or greater neurotoxicity occurred in about 30% of patients in both groups. Full dosage (6.0 mg/m2) was attained in 8 (33%) treatment patients and 18 (24%) comparison patients (p = 0.28). The mean percentage of ideal dosage of VCR was 84.6 +/- 10.8 in patients receiving pyridoxine and 81.9 +/- 21.6 in those given only VCR (p = 0.59). Gastrointestinal and hematologic toxicities were similar in both groups. Pyridoxine in this dose and schedule afforded no protection from the neurotoxic side effects of VCR.

A phase 2 trial of vincristine infusion was conducted in a group of 21 patients with refractory multiple myeloma. Patients were generally heavily pretreated with radiotherapy and chemotherapy. Vincristine was given intravenously (IV) as a 0.5 mg bolus and followed immediately by infusion of 0.25 to 0.50 mg/m2/d for 5 days. Courses were repeated every 3 weeks in the absence of disease progression or prohibitive toxicity. Objective responses (partial) were noted in two patients (10%), both of whom were administered 0.5 mg/m2/d infusions. Response durations were brief (2.2 and 1.2 months). Toxicity consisted of neurotoxicity and myelosuppression. In addition to the occurrence of paresthesias and myalgias, ileus (two cases) and moderately severe loss of motor function (two cases) were observed. The mean lowest WBC count following treatment was 2.67 X 10(3)/microL v 3.96 X 10(3)/microL pretreatment (P = .008). The mean lowest platelet count was 75.0 X 10(3)/microL v 106.8 X 10(3)/microL pretreatment (P = .008). Vincristine infusion appears to have limited activity in the treatment of refractory multiple myeloma. Additionally, response durations were short lived and toxicity, both neurologic and hematologic, was appreciable.

In a murine model system, folinic acid demonstrated host-protective properties during administration of repetitive and lethal doses of vincristine (VCR). Subsequently, folinic acid was evaluated in patients receiving VCR during an adjuvant chemotherapy program for stage II carcinoma of the breast. The toxicities, cumulative VCR dosage, and percentage of ideal dosage observed in 18 patients receiving folinic acid have been compared with those observed in 70 patients who previously received VCR without folinic acid in the same chemotherapy program. All patients ideally were intended to receive VCR 1.0 mg/m2 weekly for 6 weeks, with dose modification for neurotoxicity. Treatment patients received folinic acid 800 mg PO daily in three divided doses during the 6-week course. The degree of neurotoxic manifestations of VCR was similar in the treatment and comparison patients. Absent to mild neurotoxicity was observed in approximately 70% of patients in both groups; moderate or greater neurotoxicity occurred in about 30% of patients in both groups. Full dosage (6.0 mg/m2) was attained in 7 (39%) treatment patients and 17 (24%) comparison patients (P = 0.21). The mean percentage of the ideal dosage of VCR was 73.7 +/- 28.7 in patients receiving folinic acid and 76.1 +/- 20.5 in those given only VCR (P = 0.69). Hematologic toxicities were similar in both groups, but nausea occurred more frequently in the folinic acid group. Folinic acid in this dose and schedule afforded no protection from the neurotoxic side effects of VCR.