Cipro beats amoxicillin-clavulanate in cystitis study: young women, uncomplicated cystitis

OB/GYN News, Nov 1, 2003 by Bruce Jancin

CHICAGO -- Amoxicillin-clavulanate is clearly inferior to ciprofloxacin for treatment of uncomplicated cystitis in young women--even in those infected with a uropathogen strain susceptible to amoxicillin-clavulanate, Dr. Thomas M. Hooten reported.

In an era when concern over the high rate of resistance to trimethoprim / sulfamethoxazole among the Escherichia coli responsible for most uncomplicated cystitis has led to increased use of alternative agents, amoxicillin-clavulanate is not the way to go, according to Dr. Hooten of the University of Washington, Seattle.

He presented a randomized trial in which 321 young women with uncomplicated cystitis received 3 days of ciprofloxacin at 250 mg b.i.d, or amoxicillin-clavulanate at 500 mg b.i.d, and were then followed for 4 months. The mean age of participants was 24 years; nearly three-quarters had a history of prior urinary tract infection. Compliance with all six doses of medication was 98% in both study arms, Dr. Hooten said at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.

Clinical cure rates were significantly better in the ciprofloxacin group at every time point during follow-up. (See chart.)

Laboratory studies demonstrated that while 98.2% of strains of the causative uropathogen were sensitive to ciprofloxacin and 0.3% were resistant to the fluoroquinolone, only 75.2% of isolates were sensitive to amoxicillin-clavulanate and 9.4% were resistant to the drug.

Even among amoxicillin-clavulanate-susceptible strains, however, the clinical cure rate after a course of amoxicillin-clavulanate ranged from a mere 76% at 2 weeks' follow-up to 57% at 8 weeks and 52% at 12 weeks. These rates of freedom from urinary tract infection were significantly lower than in the ciprofloxacin group at each time point.

"This is in keeping with the poor performance of other [beta]-lactams in the treatment of urinary tract infections," the physician said at the conference, which was sponsored by the American Society for Microbiology.

Amoxicillin-clavulanate was also much more likely to cause GI and vaginal side effects. Seventeen percent of women on the drug reported vaginal discomfort, compared with 7% in the ciprofloxacin group. Sixteen percent of amoxicillin-clavulanate--treated patients complained of loose stools, compared with 3% on ciprofloxacin.

Clinical Cure Rates in
Uncomplicated Cystitis

                           Amoxicillin-
           Ciprofloxacin   Clavulanate

2 weeks         98%            80%
4 weeks         90%            77%
8 weeks         84%            70%
12 weeks        79%            66%

Source: Dr. Thomas M. Hooten