• disease modifying antirheumatic drugs
• multidrug resistance
• sulfasalazine

Clinicians have the impression that patients may respond to a given disease modifying antirheumatic drug (DMARD) for some period of time, then become “resistant”, a situation in which these drugs seem to lose their clinical effect. In this month’s Ann Rheum Dis, Joost van der Heijden and colleagues describe acquired resistance to sulfasalazine (SSZ) through an effect on a drug efflux pump. They then go on to describe the kinetics of this mechanism and test the effect of this change on other DMARDs.

In general, the efficacy, or lack thereof, of DMARDs may be due to a very large number of factors. The mechanism of action of drugs in a given disease, of course, plays a major part in its efficacy and is dependent upon the pathophysiology and pathogenesis of the disease. In addition, the pharmacokinetics of the drug have a role in drug effects, which includes absorption and delivery of the drug to its site of action and its removal from the site by its distribution/transportation, metabolism, and/or excretion. In addition, the patient’s genetic background, comorbid diseases, and concomitant drugs may have effects on a drug’s efficacy.

The articles by Joost van de Heijden et al examined one …