Adjuvant arthritis 50 years on: The impact of the 1956 article by C. M. Pearson, 'Development of arthritis, periarthritis and periostitis in rats given adjuvants'.

The Science Citation Index (Web of Science) has now accumulated over 700 citations to this report published in Proc Soc exp Biol Med 1956; 91: 95-101, including several in 2006. This memoire is a tribute to its author for revealing the opportunities for so much subsequent research in experimental pharmacology and toxicology. For half a century, the adjuvant disease in rats has enormously aided research on drugs to control arthritis and other chronic inflammatory disorders. The adjuvant also triggers many systemic responses beyond the articular tissues. So we are given simultaneously a window to explore the converse phenomenon: namely, how a chronic disease can affect drug efficacy and toxicity. This phenomenon has been variously described as patho-pharmacodynamics, conditional pharmacology/toxicology and 'a right nuisance' ! Nevertheless it has enormous heuristic value for clinical therapeutics.