A pain medication developed in St. Louis might become the substitute of choice for those who had been taking Vioxx. Merck and Company has pulled Vioxx from the shelves after a three-year study indicated those who took the drug for more than 18 months had a higher risk of cardiovascular disease or stroke than those taking a placebo. Patients take the drug to ease chronic pain, such as that brought on by arthritis. Doctors might have their patients switch to Celebrex, made by Pfizer. While studies questioned the effect of Vioxx on the heart, no such concerns have been raised about Celebrex.