VINCRISTINE Drug Interactions: What You Need to Know

Drug Interactions The simultaneous oral or intravenous administration of phenytoin and antineoplastic chemotherapy combinations that included vincristine sulfate has been reported to reduce blood levels of the anticonvulsant and to increase seizure activity. Dosage adjustment should be based on serial blood level monitoring. The contribution of vincristine sulfate to this interaction is not certain. The interaction may result from reduced absorption of phenytoin and an increase in the rate of its metabolism and elimination. Vincristine sulfate is a substrate for cytochrome P450 3A isozymes (CYP3A). Concurrent administration of vincristine sulfate with itraconazole or fluconazole (known inhibitors of the CYP3A metabolic pathway) has been reported to cause an earlier onset and/or an increased severity of neuromuscular side effects (see ADVERSE REACTIONS ). This interaction is presumed to be related to inhibition of the metabolism of vincristine. Therefore, the concomitant use of strong CYP3A inhibitors with vincristine sulfate should be avoided. Patients should be frequently monitored for adverse reactions with concomitant use of moderate CYP3A inhibitors (e.g., fluconazole) with vincristine sulfate. Concurrent use of strong CYP3A inducers (e.g., St. John's Wort) with vincristine sulfate should be avoided. Vincristine sulfate is also a substrate for P-glycoprotein (P-gp). Therefore, the concomitant use of P-gp inhibitors or inducers should be avoided.

Drug Interactions Vincristine Sulfate

Injection should not be diluted in solutions that raise or lower the pH outside the range of 3.5 to 5.5. It should not be mixed with anything other than 0.9% Sodium Chloride Injection USP. Whenever solution and container permit, parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration.

CONTRAINDICATIONS Patients with the demyelinating form of Charcot–Marie–Tooth syndrome should not be given Vincristine Sulfate Injection. Careful attention should be given to those conditions listed under WARNINGS and PRECAUTIONS .

WARNINGS This preparation is for intravenous use only. It should be administered by individuals experienced in the administration of Vincristine Sulfate Injection. The intrathecal administration of Vincristine Sulfate Injection usually results in death. To reduce the potential for fatal medication errors due to incorrect route of administration, Vincristine Sulfate Injection should be diluted in a flexible plastic container and prominently labeled as indicated "FOR INTRAVENOUS USE ONLY – FATAL IF GIVEN BY OTHER ROUTES." See OVERDOSAGE section for the treatment of patients given intrathecal Vincristine Sulfate Injection.

Pregnancy

Vincristine sulfate can cause fetal harm when administered to a pregnant woman. When pregnant mice and hamsters were given doses of vincristine sulfate that caused resorption of 23% to 85% of fetuses, fetal malformations were produced in those that survived. Five monkeys were given single doses of vincristine sulfate between days 27 and 34 of their pregnancies; 3 of the fetuses were normal at term, and 2 viable fetuses had grossly evident malformations at term. In several animal species, vincristine sulfate can induce teratogenesis as well as embryo death at doses that are nontoxic to the pregnant animal. There are no adequate and well–controlled studies in pregnant women. If this drug is used during pregnancy or if the patient becomes pregnant while receiving this drug, she should be apprised of the potential hazard to the fetus. Women of child–bearing potential should be advised to avoid becoming pregnant.