WASHINGTON, March 16, 2012 /PRNewswire/ -- Oral cancer drugs that target key enzymes in tumor cells have made significant contributions to oncology care, freeing many patients from spending long hours at infusion centers to receive their chemotherapy treatments. But new research shows that many patients using these oral medications are also on other drugs that may prevent patients from getting the full benefit from their cancer treatment, or increase the risk of side effects. (Logo: http://photos.prnewswire.com/prnh/20100609/MEDCOLOGO ) The study by the Medco Research Institute™, the research subsidiary of Medco Health Solutions, Inc. (NYSE:MHS), is being presented today at the 2012 American Society for Clinical Pharmacology and Therapeutics (ASCPT) Annual Meeting. The research found that 23-74 percent of patients taking one of nine oral oncology medications were also on a drug that had the potential to reduce the effectiveness of the cancer treatment or increase its toxicity. The cancer therapies studied are in a class known as oral kinase inhibitors which include the medications imatinib (Gleevec®) and erlotinib (Tarceva®). Medications that may cause drug-drug interactions include proton pump inhibitors (PPIs), steroids, calcium channel blockers and certain antibiotics and antifungal agents. "Oral cancer drugs represent a huge advancement in oncology treatment, but make no mistake these are powerful drugs. These high costs medications can have severe side effects and need to be actively monitored for proper use and adherence," said Dr. Milayna Subar, national practice leader at the Medco Oncology Therapeutic Resource Center®. "What's as important is knowing what other medications the patient is on. The fact that about one quarter to 75 percent of patients on these oral drugs may not be getting the full benefit of their treatment or may in fact be putting their health at further risk because of another medication they are taking is concerning. Our oncology pharmacists are able to alert doctors about potential medication interactions through our Drug Utilization Review programs that have a complete picture of their prescription drugs." The study reviewed the pharmacy claims of about 11,600 patients taking one of nine kinase inhibitors that treat different forms of cancer and evaluated the number of patients who were taking at least one other drug that had the potential to cause a drug interaction with their cancer treatment. In addition to imatinib and erlotinib, the cancer drugs studied included dasatinib (Sprycel®), everolimus (Afinitor®), lapatinib (Tykerb®), nilotinib (Tasigna®), pazopanib (Votrient®), sorafenib (Nexavar®), and sunitinib (Sutent®).