Clinical Pharmacokinetics of Slow-Acting Antirheumatic Drugs

The pharmacokinetics of the slow acting antirheumatic drugs (SAARDs), hydroxychloroquine, chloroquine, penicillamine, the gold complexes and sulphasalazine, in humans have been studied. For all these drugs, both in controlled clinical trials and in empirical observations from rheumatological practice, delays of several months are reported before full clinical effects are achieved. Variability in response is also characteristic of these agents. Pharmacokinetic factors may partially explain these clinical observations. Delays in the achievement of steady-state concentrations or of concentrations likely to have a therapeutic benefit may occur because of slow drug accumulation. Variable concentrations may arise after standard administered doses because of interindividual pharmacokinetic variability. These factors are likely to contribute to the delay in response and the variable response, respectively