Dosage of salicylates for children with juvenile rheumatoid arthritis. A prospective clinical trial with three different preparations of acetylsalicylic acid.

41 children with juvenile rheumatoid arthritis (JRA) and 6 with postinfectious arthropathies, aged 3--15 years, were treated with acetylsalicylic acid for 14 days during which time the patients were hospitalized. Three different acetylsalicylic acid preparations were used: a microencapsulated form, an enteric-coated form and standard acetylsalicylic acid tablets. Serum salicylate concentrations were measured by Trinder's photometric method. With doses of 90--120 mg/kg/day symptoms of salicylism appeared in about 50% of the cases. Daily doses of 2 g/m2 (not exceeding 70 mg/kg) proved relatively safe in this study, whereas symptoms and signs of intoxication appeared at doses exceeding 3 g/m2/day. In this respect there were no significant differences between the three acetylsalicylic acid preparations used. The results of this study also suggest that the serum salicylate concentrations should not exceed 2000 mumol/l (about 27 mg/100 ml). The symptoms of salicylism correlated closely with serum salicylate levels, which, in turn, correlated well with the dosage in g/m2. Elevation of serum aspartate aminotransferase was noted in 1/3 of the cases. All of these had a dose exceeding 2 g/m2, and the frequency of elevated enzyme activities increased with increasing dosage. In the group receiving enteric coated form of acetylsalicylic acid, there were fewer positive benzidine tests (12%) than in the two other groups (22--28%).