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Patients taking oral cancer drugs may risk drug interactions, study finds

Taking other drugs can reduce efficacy, increase toxicity of oral kinase inhibitors

WASHINGTON — Pills for treating cancer have created numerous alternatives to spending hours in a clinic or at home receiving chemotherapy infusions, but risks of drug interactions remain, according to a new survey by the research arm of pharmacy benefit manager Medco Health Solutions.

The survey, released Friday by the Medco Research Institute, found that 23% to 74% of patients taking one of nine oral cancer drugs also were on a drug that had the potential to reduce the cancer drugs' effectiveness or increase its toxicity. The drugs studied belong to a class known as oral kinase inhibitors and included Novartis' Gleevec (imatinib) and Tarceva (erlotinib), made by Roche and Astellas Pharma.

"Oral cancer drugs represent a huge advancement in oncology treatment, but make no mistake — these are powerful drugs," Medco Oncology Therapeutic Research Center national practice leader Milayna Subar said. "These high-cost medications can have severe side effects and need to be actively monitored for proper use and adherence."

The study also found that 43% of the 4,617 patients receiving Gleevec were prescribed a drug that might diminish its efficacy, while 68% were taking a drug that could raise its level of toxicity. The other drugs were found to have their efficacy potentially impaired 23% to 57% of the time, and 24% to 74% of patients were using medicines that might raise their toxicity.

"Since these are drugs launched in the past decade for fairly small patient populations, we are learning more bout how they are used in real-world settings as compared to traditional clinical trials that test safety and efficacy in a tightly controlled environment," Medco Research Institute senior director and therapeutic area research lead and study co-author Steve Bowlin said. "Oncologists are not always aware of other medications prescribed by other doctors and vice-versa, which can pose a real hazard for their patients on oral cancer therapies."

The study was based on pharmacy claims from about 11,600 patients using one of nine oral kinase inhibitors.


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