As many as 74 percent of patients on targeted cancer drugs have taken other medicines that may limit the cancer therapy’s effectiveness or cause toxic side effects, a study found.
Researchers at Medco Health Solutions Inc. (MHS) found that 23 percent to 57 percent of patients on targeted cancer drugs were also prescribed medicines that may have blunted the effect of the cancer treatment. Twenty-four percent to 74 percent of the patients received drugs that may have added toxic side effects when used at the same time as the cancer therapies.
“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,” said Steven Bowlin, an author of the study and senior director at Medco’s research division, in a statement.
The researchers examined drug claims data for 11,600 cancer patients who had taken one of nine targeted cancer pills, including the leukemia drug Gleevec from Basel, Switzerland- based Novartis AG (NOVN), during a 29-month period ending in mid-2010. A large range of possible interactions was reviewed and the research didn’t prove that patients were harmed by taking other medications such as certain heartburn drugs, antibiotics or steroids, Bowlin said in a telephone interview.
There are numerous ways drugs may interfere with one another and most possible interactions don’t cause harm, he said. The study results are being presented today at the American Society for Clinical Pharmacology and Therapeutics annual meeting.
For Gleevec, 43 percent of the 4,617 cancer patients taking the therapy got medicines that may reduce its effectiveness, while 68 percent received drugs that might increase toxicity. The doctors who prescribed the potentially interfering drugs were usually primary-care physicians and other noncancer specialists, the study found.
Anything that may reduce a cancer drug’s effectiveness “is obviously very concerning,” Eric Stanek, vice president of research at Medco and a study author, said in an interview. “You don’t want to wait and see if the cancer comes back” to realize there is a problem.
Other drugs examined included the kidney cancer drug Sutent from Pfizer Inc. (PFE) and the lung cancer drug Tarceva from Roche Holding AG. (ROG)
The next step in the Medco research will be to examine whether any of the Gleevec patients were harmed by the potentially interfering drug combinations, Bowlin said. Results from this follow-up may be ready in a year.
Medco, based in Franklin Lakes, New Jersey, manages pharmacy benefits for 65 million Americans and has agreed to be acquired by St. Louis-based Express Scripts Inc. (ESRX) The deal would create the largest U.S. manager of pharmacy benefits.
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