Patients and healthcare professionals alike overestimate the safety of drug patches, according to a report in today's LA Times.
Pain patches containing fentanyl, including Ortho-McNeil's Duragesic, have caused overdoses, prompting the FDA to order a black box warning in 2005 that the patches should be prescribed at the lowest dose possible and not for short-term pain or post-operative pain. But other transdermal patches have also come in for questioning, including the Ortho Evra birth control patch, which may increase risk of blood clots due to its higher-than-usual estrogen boost, and Daytrana for ADD, which has caused skin irritation in some users.
One issue common to patches, the article notes, is that while delivering a drug more steadily, they can also ultimately deliver more of it. Another is that because heat affects the rate of absorption, sunbathing or a hot shower could cause overdose. Moreover, skin thickness varies from patient to patient, and thicker skins may mean lower uptake.
Kenneth Sloan, a medicinal chemist at the University of Florida who has researched absorption from patches, told the paper: “Patches are not innocuous. One patch does not fit all.”