title: Stability of trimethoprim-sulfamethoxazole injection in five infusion fluids.
abstract: The stability of an intravenous dosage form of trimethoprim-sulfamethoxazole (Bactrim; Hoffmann-La Roche) was studied in five i.v. fluids at four dilutions. Trimethoprim-sulfamethoxazole injection was diluted 1:25 v/v, 1:20 v/v, 1:15 v/v and 1:10 v/v in 5% dextrose injection, lactated Ringer's injection, 0.45% sodium chloride injection, 0.9% sodium chloride injection, and 5% dextrose and 0.45% sodium chloride injection in quadruplicate. Solutions were mixed in 150-ml glass containers and stored at 23-25 degrees C; 5-ml samples were withdrawn at 0, 1, 2, 4, 6, 8, 12, and 24 hours and filtered with a 0.22-micron filter. Trimethoprim and sulfamethoxazole concentrations in the filtrates were assayed with high-performance liquid chromatography, and the pH of filtrates was measured. Trimethoprim and sulfamethoxazole were stable for 24 hours in all fluids and at all dilutions with one exception. Trimethoprim concentration fell more than 10% in lactated Ringer's injection at 24 hours because of precipitation in one container. There was no consistent change in pH of solutions. It is concluded that trimethoprim-sulfamethoxazole admixtures are stable in glass containers of the five solutions at the dilutions studied for 12 hours at ambient room temperature.
mesh_terms: D004338:Drug Combinations / Q000008:administration & dosage; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D007263:Infusions, Parenteral; D013420:Sulfamethoxazole / Q000008:administration & dosage; D014295:Trimethoprim / Q000008:administration & dosage; D015662:Trimethoprim, Sulfamethoxazole Drug Combination
chemical_list: D004338:Drug Combinations; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D014295:Trimethoprim; D013420:Sulfamethoxazole