Sulfa methoxypyridazine

It is important to consider the influence of interaction between functional groups of drugs that leads to their habit modification when formulated in suspension dosage form. Proton transfer from the N atom of sulfamethoxazole to the pyrimidine basic N1 atom of trimethoprim has been reported to occur in their equimolar complexes. Bettinetti et al. have reported nucleation of the complex of trimethoprim and sulfa-methoxypyridazine (1 1) to be accelerated by water or wet granulation. Our studies on cotrimoxazole (unpublished results) revealed immediate formation of fine needle-shaped crystals irrespective of the initial shape of sulfamethoxazole and trimethoprim crystals as a result of the interaction between the two drugs in suspension form. Small needles (Fig. 6A) were... 

Age-related changes in drug distribution have been reported. The apparent volume of distribution is somewhat larger in newborns and infants than in adults. The estimated volume of distribution of sulfa-methoxypyridazine in newborns and infants is 0.47 and 0.36 L/kg, respectively, whereas the values are 0.20-0.26 L/kg in children, adults, and elderly subjects. The volume of distribution of chlordiazepoxide is substantially larger in the elderly (0.52 L/kg) than in the young (0.42 L/kg). The age-related difference in the volume of distribution may be due to a difference in plasma protein binding and/or in the relative size of body compartments. 

---