Combination therapy, such as ampicillin plus gentamicin, and single-drug therapy, such as a third-generation cephalosporin, a broad-spectrum beta-lactam agent or a fluoroquinolone, are frequently used empirically to treat severe urinary tract infections (UTIs). This approach, however, is generally not based on clinical trials that have identified the choice of antibacterial agents. In addition, the recommendation of parenteral therapy for severe UTIs is based on the unproven assumption that oral therapy is inadequate for bacteremic UTIs. Mombelli and associates performed a prospective, randomized study to compare oral and intravenous ciprofloxacin in the initial empiric treatment of serious pyelonephritis or complicated UTIs, including cases of suspected bacteremia.

A total of 141 patients with complicated UTIs were randomized to receive intravenous ciprofloxacin, 200 mg every 12 hours, or oral ciprofloxacin, 500 mg every 12 hours. Seventy-two patients were in the oral therapy group and 69 were in the intravenous therapy group. Intravenous ciprofloxacin was administered for a minimum of 72 hours or at least until the patient was afebrile for 24 hours. Patients receiving intravenous therapy were then switched to oral therapy. The patient's response to the initial treatment was evaluated in terms of suppression of growth of the causative organisms on the third to fifth days of therapy and of relief of fever and UTI symptoms. Treatment failure was defined as the need to change to a different empiric therapy before the results of susceptibility testing were available. A change in therapy was deemed necessary if fever and chills persisted or signs of sepsis developed.

The two treatment groups were comparable with respect to the type of UTI, the signs and symptoms, the results of susceptibility testing and the frequency of bacteremia. Fever and symptoms abated rapidly in most patients, without a significant difference between the two groups. Among patients with pyelonephritis, fever lasted significantly longer in those who had bacteremia compared with those who did not have bacteremia. However, no difference was found in the mean duration of fever. Fever lasted for a mean of 1.7 days in those who received oral therapy and 1.9 days in those who received intravenous therapy.

Rates of microbiologic failure (3 percent with oral therapy and 2 percent with intravenous therapy) were low, as were rates of unsatisfactory clinical response (4 percent and 3 percent in the oral and intravenous groups, respectively). None of the patients required a change of antibiotic therapy because of clinical deterioration during the initial empiric treatment. However, microbiologic or clinical failure occurred in seven patients. In addition, initial therapy had to be changed in five patients in the oral therapy group and in three patients in the intravenous therapy group because of isolation of enterococci or other resistant strains. The occurrence of adverse effects was extremely low with oral or intravenous ciprofloxacin.

The authors conclude that oral ciprofloxacin is as effective as intravenous ciprofloxacin in the initial empiric treatment of severe UTIs, including bacteremic forms, provided that severe sepsis, obstruction or foci of renal suppuration are not present. Although the results suggest the possibility of outpatient treatment of severe UTIs, the authors advise that studies directly comparing inpatient and outpatient treatment are needed to determine whether hospitalization is required for the treatment of such infections.