Principles of cancer chemotherapy

Single-drug chemotherapy of canine transmissible venereal tumor with cyclophosphamide, methotrexate, or vincristine

During a 21-month period, 48 dogs with spontaneous canine transmissible venereal tumor (clinical stage, T1-T3) were presented to the Veterinary Teaching Hospital, Ahmadu Bello University, Zaria, Nigeria, and were divided into one control and four treatment groups to test the efficacy of single-agent chemotherapeutic drugs. The dogs were not randomly assigned to groups because each chemotherapeutic agent was not continuously available during the test period. Group I consisted of four dogs that received oral cyclophosphamide (50 mg/M2 body surface area [BSA]) on the first four days for six weeks. No therapeutic response was noted in any of the four dogs. Group II consisted of ten dogs that received intravenous (IV) cyclophosphamide (50 mg/M2 BSA) for four consecutive days per week for six weeks. Two of the ten had a partial remission. Group III consisted of eight dogs that received oral methotrexate (2.5 mg/M2 BSA) every other day for six weeks. No therapeutic response was noted in any of the eight dogs. Group IV consisted of 20 dogs that were administered IV vincristine sulfate (0.5 mg/M2 BSA) weekly until a response was noted. Complete remission occurred in each of the 20 dogs. One dog had recurrence within 12 months. Group V was the untreated control group, consisting of six dogs among which no spontaneous remission was seen. Instead, tumor progression was noted. Adverse responses to medication, anorexia, vomiting, diarrhea, and weight loss were seen only with dogs treated with cyclophosphamide and methotrexate.

Hepatic pharmacokinetics of glutaraldehyde-treated methotrexate-loaded carrier erythrocytes in dogs

Methotrexate-loaded glutaraldehyde-treated canine carrier erythrocytes were used to deliver a 1.6-mg/kg dosage of drug. About 90% of the drug-loaded cells disappeared from circulation within 1 h. Approximately 11 mg of drug reached the liver, and a substantial portion of the methotrexate entered the enterohepatic bile salt circulation. Biochemical tests of liver function, such as alkaline phosphatase and serum glutamine pyruvate transaminase, indicated mild hepatocellular necrosis which was attributed to the action of methotrexate on the hepatocytes. Bilirubin levels were unchanged during and following drug treatment. The plasma half-life of the drug was extended 2.4-fold in the first 24 h following injection.