Concentrations of sulphadiazine and trimethoprim in nasal secretion after co-trimazine administration.

Co-trimazine (1 g) was given once daily to 20 healthy volunteers during four days. Serum and nasal secretion concentrations were measured after the fourth dose. Secretion levels exceeded those in serum by a factor of 1.36 (sulphadiazine) and 2.96 (trimethoprim) (as expressed by the ratio of the AUC of secretion and serum concentrations). The average ratios of the concentrations of sulphadiazine to trimethoprim were 11.6-15.3 and 4.8-10.3 in serum and secretion respectively. During the dosage interval of 24 h, sulphadiazine and trimethoprim concentrations exceeded the MIC values of the common respiratory pathogens in serum and secretion.