Antibiotic, Antifungal, Antiviral Drugs

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.

Lomefloxacin hydrochloride is administered orally. Lomefloxacin hydrochloride may be administered without regard to meals. Food decreases the rate of GI absorption of the drug, but only decreases the extent of absorption by 12%. Dosage of lomefloxacin, which is available for oral use as the hydrochloride, is expressed in terms of lomefloxacin.

Gemifloxacin is used for the treatment of acute bacterial exacerbation of chronic bronchitis caused by susceptible strains of Streptococcus pneumoniae, Haemophilus influenzae, H. parainfluenzae, or Moraxella catarrhalis. In several randomized, double-blind, active-controlled studies in patients with acute exacerbation of chronic bronchitis, clinical response (defined as sufficient improvement in or resolution of signs and symptoms at day 13-24 without further need for anti-infectives) was achieved in 86-94% of those receiving oral gemifloxacin (320 mg once daily for 5 days) and in 93, 85, or 85% of those receiving oral amoxicillin and clavulanate potassium (500 mg of amoxicillin 3 times daily for 7 days), oral clarithromycin (500 mg twice daily for 7 days), or oral levofloxacin (500 mg once daily for 7 days), respectively. In several controlled and uncontrolled studies in patients with clinically and radiographically documented CAP, clinical response was achieved in 89-92% of patients receiving oral gemifloxacin (320 mg once daily) for 7 days.

Pharmacokinetic interaction (decreased absorption of gemifloxacin). Gemifloxacin should be taken at least 2 hours before or 3 hours after antacids that contain aluminum or magnesium. (See Dosage and Administration: Administration.) Antacids containing calcium or calcium supplements have no clinically important pharmacokinetic interaction with gemifloxacin. Didanosine Pharmacokinetic interaction; didanosine chewable/dispersible buffered tablets, buffered powder for oral solution, or pediatric powder for oral solution prepared as an admixture with antacid may substantially decrease gemifloxacin absorption.

Gemifloxacin Mesylate: Cautions. Musculoskeletal Effects, Nervous System Effects, Sensitivity Reactions, Major Toxicities Dermatologic Reactions, Hepatic Effects, Specific Populations Pregnancy Category C. Lactation.

The oral LD50 of the drug is greater than 5 g/kg in mice and rats and approximately 2.5 g/kg in rabbits. In mice, rats, rabbits, and dogs, significant toxicity (including tonic/clonic convulsions) was observed with IV ciprofloxacin doses between 125 and 300 mg/kg.

In vitro on a weight basis, the activity of ciprofloxacin is approximately equal to or slightly greater than that of ofloxacin against most susceptible organisms and is at least 2 times greater than that of norfloxacin against most susceptible organisms. Ciprofloxacin is active in vitro against most gram-negative aerobic bacteria, including Enterobacteriaceae and Pseudomonas aeruginosa. Ciprofloxacin also is active in vitro against many gram-positive aerobic bacteria, including penicillinase-producing, nonpenicillinase-producing, and oxacillin-resistant staphylococci (previously known as methicillin-resistant staphylococci), although many strains of streptococci are relatively resistant to the drug. The drug generally is less active against gram-positive than gram-negative bacteria.