170: Factors influencing an optimal salicylate dosage regimen in children with rheumatoid arthritis

Abstract

Plasma salicylate levels were monitored in 31 children with rheumatoid arthritis in order to elucidate a series of problems concerning the establishment of an optimal drug regimen. In 6 of these children 24-hour urinary excretion of acetylsalicylic acid, salicyluric acid and total salicylate metabolites were also measured. Our results may be summarized as follows. 1) Monitoring, per se, is very effective in improving the compliance of patients. 2) Inter-individual variability of plasma levels at approximately equal dosage per kilo is very consistent: when only those children who had taken 78.6 ± 1.8 mg/kg/day were considered, plasma salicylate concentrations were found to be 16.5 ± 5-5 mg%. 3) Relationship was found between the administered salicylate dosage and the apparent plasma half-life (T1/2) but not between plasma levels and the T1/2. 4) A direct relationship between plasma salycilate levels and the per cent of the administered dose that was excreted as free or total salicylic acid was demonstrated. 5) Concomitant administration of corticosteroids seemed to significantly lower the plasma levels of salicylate.