Interactions With Cancer Drug Vincristine (ONCOVIN)

Vincristine (ONCOVIN), a drug derived from the flowering peri­winkle plant, is useful in the treat­ment of several cancers, particularly leukemias.

Unfortunately, patients who take this drug can experience signifi­cant adverse effects on the nervous system, particularly when vincristine blood levels get too high.

Drug safety experts have known for more than 15 years that combin­ing vincristine with certain other drugs can cause severe — even life-threatening — neurotoxicity. Still, case reports continue to appear in medical journals describing severe adverse outcomes from these well-documented drug interactions.

What are the signs and symptoms of vincristine neurotoxicity?

When vincristine blood levels get too high, one of the most common symptoms is severe constipation and abdominal pain. In some cases, this can lead to a condition called ileus, in which the bowels shut down completely. Ileus can be dangerous if it is not recognized and treated, because it can result in leakage of bacteria into the abdominal cavity, leading to life-threatening infection (peritonitis).

Other signs of vincristine-induced neurotoxicity include severe seizures, weakness of muscles (sometimes leading to temporary paralysis), muscle pain, drooping eyelids and reduced reflexes.

Some people need mechanical ventilation of their lungs during the acute reaction because of decreased ability to breathe. Other common findings of vincristine toxicity in­clude hypertension and Syndrome of Inappropriate AntiDiuretic Hor­mone Hypersecretion (SIADH), a condition that can produce danger­ously low blood sodium levels.

What drugs interact with vincristine?

Drugs that inhibit the enzyme CYP3A4 or P-glycoprotein can increase vincristine blood levels and the risk of toxicity because these en­zymes help the body to clear out the vincristine. See the Table for a list of these drugs.

Several anti-fungal drugs (e.g., flu­conazole, itraconazole, ketoconazole, posaconazole and voriconazole) interact with vincristine. Unfortu­nately, people taking vincristine may be more susceptible to fungal infec­tions. It may be necessary for your physician to temporarily decrease the amount of vincristine if you are also using these drugs.

What You Can Do

If you take vincristine (or care for someone who does), be alert for these interactions as manifested by the signs and symptoms of increased vincristine levels discussed in this article. This is especially important because patients with cancer often receive their anti-cancer drugs from one clinic and their other drugs from other prescribers, and both sets of physicians need to know what the other is prescribing.

Recognizing signs of toxicity from vincristine early is urgent because most of the side effects are reversible when the interacting drug is stopped and the patient receives corrective treatment.

Table. Drugs Likely to Increase Risk of Vincristine Toxicity

* Do Not Use on WorstPills.org
** Limited Use on WorstPills.org
*** Last Choice on WorstPills.org