Trimethoprim dosage forms

Alert All dosage forms have same 5 1 ratio of sulfamethoxazole (SMX) to trimethoprim (TMP). 

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 Our studies on cotrimoxazole (unpublished results) revealed immediate formation of fine needle-shaped crystals irrespective of the initial shape of sulfamethoxazole and trimethoprim crystals as a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... 

Bonazzi, D. Andrisano, V. Di Pietra, A.M. Cavrini, V. Analysis of trimethoprim-sulfonamide drug combinations in dosage forms by UV spectroscopy and liquid chromatography (HPLC). Farmaco, 1994, 49, 381-386 [simultaneous sulfadiazine, sulfamethox3q>yridazine, trimethoprim]... 

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