Common cancer treatments nowadays include not just radiation, surgery, and infusion chemotherapy treatments, but also pills that patients take every day for weeks, months, or even years. Many of these pills, however, interact with common medications such as acid blockers and antihistamines, rendering the cancer drugs less effective or dangerously potent.

The majority of cancer patients prescribed a particular kind of oral cancer drug, known as kinase inhibitors, were taking other medications that interacted negatively with these drugs, according to a new survey released Friday by the nonprofit Medco Research Institute.

Reviewing pharmacy claims of about 11,600 patients on kinase inhibitors -- including imatinib (Gleevec) and erlotinib (Tarceva) -- the study researchers found that many patients were also taking proton pump inhibitors, steroids, calcium channel blockers, and certain antibiotics and antifungal agents that either made their cancer-fighting drugs more potent or lessened their effectiveness.