Urinary tract infections

Drug Store News, Dec 11, 1989

A third generation cephalosporin or extended spectrum penicillin as a single agent therapy may be a reasonable choice if an aminoglycoside needs to be avoided. Appropriate therapy can be initiated once the organism is identified.

Within 12 to 24 hours effective therapy should stabilize the patient. The best way to assess therapy is to examine the urine. The urine should be sterile in 48 hours or a very small number of bacteria may be present. The general rule is for intravenous therapy to continue until the patient has been afebrile for a least 24 to 48 hours.

The patient may then be discharged from the hospital on an appropriate oral antibiotic for 2-6 weeks. The traditional 10-14 day course of antibiotic therapy for pyelonephritis is usually not adequate. Turck et al have shown that extending therapy an additional six weeks after a culture confirmed relapse produced a 50 percent reduction in the relapse rate. Two weeks after completion of antibiotic therapy is the recommended time to do follow up cultures to detect possible relapse.

Prostatic Infections

The therapeutic approach to acute and chronic prostatitis is distinctly different. This is due to differences in the ability of the antibiotic to penetrate from the plasma into prostate fluids. Acute prostatitis is an acute inflammatory process which allows for antibiotic penetration. Bacteria in chronic prostatitis are protected because the ability of the antibiotic to diffuse from the plasma into the prostatic fluid is restricted. The prostatic bacteria are not resistant organisms but they cannot be reached by most antibiotics in adequate concentrations.

Acute prostatitis frequently responds dramatically to a 10-14 day course of an antibiotic such as an aminoglycoside or ampicillin.

Antibiotics that achieve high prostatic concentration include erythromycin, clindamycin, trimethoprim, carbenicillin, norfloxacin and ciprofloxacin. Erythromycin is not effective because it lacks activity against the gram negative organisms found in the prostate. Clindamycin is limited in usefulness because of its ability to cause intestinal superinfections.

Trimethoprim did appear to be a safe and logical choice but three separate studies only resulted in a cure rate of 33 percent. Patients in the three studies received twice-a-day doses of 160 mg of trimethoprim and 800 mg of sulfamethoxazole for periods ranging from 4-12 weeks. The apparent reason for this high failure rate is that prostatic fluid which is normally acidic becomes increasingly alkaline. This change occurs in males over 50 and in the presence of bacterial prostatitis. At these pH changes trimethoprim, a weak base, passes into the prostatic fluid becoming more ionized, remains unionized and diffuses back out of the prostatic fluid and into the blood.

More promising developments in the treatment of chronic prostatitis include carbenicillin, norfloxacin and ciprofloxacin. Oral carbenicillin has received FDA approval for treatment of acute and chronic prostatitis. This approval was based largely on a study conducted by Mobley in which 12 chronic bacterial prostatitis patients received two 500 mg tablets of carbenicillin indanyl sodium four times a day for 28 consecutive days. At the 4-week post treatment follow up exam a success rate of 67 percent was determined based on a negative culture and the absence of symptoms.