Antibacterial drugs

Sulfasalazine conventional and delayed-release tablets are administered orally. The total daily dosage should be divided into equally divided doses, and, if possible, doses should be administered after meals. The delayed-release tablets should be swallowed whole. For the treatment of ulcerative colitis, the interval between doses of sulfasalazine given as conventional or delayed-release tablets should not exceed 8 hours.

Sulfamethizole shares the actions and uses of the other antibacterial sulfonamides. Sulfamethizole is used principally in the treatment of urinary tract infections caused by sulfonamide-susceptible organisms.

Sulfadiazine is administered orally. Patients should be instructed to drink one full glass (250 mL) of water with each dose of the drug and at frequent intervals throughout the day while they are receiving sulfadiazine. The usual adult dosage of sulfadiazine is 2-4 g initially, followed by 2-4 g daily administered in 3-6 equally divided doses.

Co-trimoxazole is used for the treatment of urinary tract infections (UTIs) caused by susceptible strains of E. coli, Proteus (indole-positive or -negative), Klebsiella, Morganella morganii, or Enterobacter. Co-trimoxazole, given in single doses, as 3-day therapy, or for 7-10 days, is effective in the treatment of acute uncomplicated UTIs. Some clinicians consider a 3-day regimen of co-trimoxazole the treatment of choice for the empiric treatment of acute uncomplicated UTIs. Co-trimoxazole also is used for the treatment of acute complicated UTIs (e.g., UTIs associated with abnormalities of the urinary tract or neurogenic bladder), but other anti-infectives are preferred by most clinicians.

Sulfonamides, synthetic derivatives of p-aminobenzenesulfonamide (sulfanilamide), are classified as anti-infectives if they possess antibacterial activity that is antagonized by p-aminobenzoic acid or p-aminobenzoyl glutamic acid.

Norfloxacin is administered orally. The drug should be given with a glass of water at least 1 hour before or at least 2 hours after a meal or ingestion of milk or other dairy products.

Antacids containing magnesium hydroxide or aluminum hydroxide may decrease absorption of oral norfloxacin, and the drugs probably should not be administered concomitantly. Patients should be instructed not to ingest antacids concomitantly with or within 2 hours of a norfloxacin dose. The mechanism of this interaction has not been fully elucidated to date, but studies using ciprofloxacin indicate that antacids containing magnesium and aluminum ions may bind to, and form insoluble complexes with, quinolones in the GI tract. 

Adverse effects have occurred in about 7% of patients receiving a single 800-mg oral dose of norfloxacin for the treatment of uncomplicated gonorrhea. Dizziness, nausea, and abdominal cramping are the adverse effects reported most frequently in patients receiving this single-dose regimen, and these effects have been reported in 2-3.5% of patients.

Norfloxacin also has been used in adults for the treatment of various GI infections caused by susceptible organisms. Because only low serum concentrations of norfloxacin are attained after oral administration of usual dosages, use of the drug is generally limited to genitourinary or GI tract infections. Prior to initiation of norfloxacin therapy, appropriate specimens should be obtained for identification of the causative organism and in vitro susceptibility tests.

Lomefloxacin is used orally in adults for the treatment of mild to moderate lower respiratory tract infections (acute bacterial exacerbations of chronic bronchitis) and uncomplicated or complicated urinary tract infections caused by susceptible organisms. The drug also is used orally for perioperative prophylaxis in patients undergoing transrectal prostate biopsy or transurethral surgical procedures.