Patients with inflammatory diseases such as rheumatoid arthritis now have many more treatment options than in the past, including biologic disease-modifying antirheumatic drugs (DMARDs). These drugs, derived by modifying substances found in humans or animals, slow progression of the disease rather than simply treating the symptoms. The cost of biologic DMARDs is a major concern because a one month's supply may cost 100 times more than a year's supply of older, non-biologic DMARDs.