Sulfamethoxazole-d4

Sulfamethoxazole-d4 is intended for use as an internal standard for the quantification of sulfamethoxazole (Item No. 23613) by GC- or LC-MS. Sulfamethoxazole is a sulfonamide antibiotic.{38582} It inhibits growth of E. coli (MIC = 10 ?g/ml) and clinical isolates of methicillin-resistant S. aureus (MRSA; MICs = 25-50 ?g/ml).{38583,38584} Sulfamethoxazole, in combination with trimethoprim (Item No. 16473) at a ratio of 20:1, inhibits growth of MRSA in vivo in mice (MIC = 0.8 ?g/ml; ED50s = 6.4 and 9.6 mg/kg for two MRSA strains).{38584} In a mouse model of urinary tract infection with E. coli, a combination of sulfamethoxazole and trimethoprim decreases recurrent infection when administered for 10 days.{38585} Sulfamethoxazole acts by inhibiting dihydropteroate synthase (DHPS), which converts pteridine and 4-aminobenzoic acid (PABA; Item No. 18659) to dihydropteroate, an intermediate in folate biosynthesis. It inhibits recombinant P. carinii DHPS (IC50 = 23 nM; Ki = 7.5 nM) and folate biosynthesis in situ by 48.6%. Formulations containing sulfamethoxazole and trimethoprim have been used to treat bronchitis, prostatitis, and urinary tract infections among other infectious conditions.