Treatment of Urinary Tract Infections

TREATMENT OF URINARY TRACT INFECTIONS

The general principles of use of AMAs for urinary tract infections (UTIs) remain the same as for any other infection. Some specific considerations are highlighted below.

Most UTIs are caused by gram-negative bacteria, especially coliforms. Majority of acute infections involve a single organism (commonest is E. coli); chronic and recurrent infections may be mixed infections. Acute infections are largely self limiting; high urine flow rates with frequent bladder voiding may suffice. Many single dose antimicrobial treatments have been successfully tried, but a three day regimen is considered optimal for lower UTIs. Upper UTIs require more aggressive and longer treatment. In any case, treatment for more than 2 weeks is seldom warranted.

Bacteriological investigations are very important to direct the choice of drug. Though, treatment may not wait till report comes, urine sample must be collected for bacteriology before commencing therapy. Most AMAs attain high concentrations in urine, smaller than usual doses may be effective in lower UTIs—antibacterial action in urine is sufficient, mucosa takes care of itself. In upper UTI (pyelonephritis) antimicrobial activity in kidney tissue is needed—doses are similar to any systemic infection.

The least toxic and cheaper AMA should be used just long enough to eradicate the pathogen. It is advisable to select a drug which does not disrupt normal gut and perineal flora. If recurrences are frequent, chronic suppressive treatment with cotrimoxazole, nitrofurantoin, methenamine, cephalexin or norfloxacin may be given.

The commonly used antimicrobial regimens for empirical therapy of uncomplicated acute UTI are given in the box.

The status of AMAs (other than urinary antiseptics) in urinary tract infections is summarized below:

Sulfonamides

Dependability in acute UTIs has decreased: not used now as single drug. May occasionally be employed for suppressive and prophylactic therapy.

Cotrimoxazole

Though response rate and use have declined, it may be employed empirically in acute UTI without bacteriological data, because majority of urinary pathogens, including C. trachomatis, are covered by cotrimoxazole. It should not be used to treat UTI during pregnancy.

Quinolones

The first generation FQs, especially norfloxacin and ciprofloxacin are highly effective and currently the most popular drugs, because of potent action against gram-negative bacilli and low cost. Nalidixic acid is also employed. However, to preserve their efficacy, use should be restricted. FQs are particularly valuable in complicated cases, those with prostatitis or indwelling catheters and for bacteria resistant to cotrimoxazole/ampicillin. The FQs should not be given to pregnant women.

Ampicillin/Amoxicillin

Frequently used in the past as first choice drug for initial treatment of acute infections without bacteriological data, but higher failure and relapse rates have made them unreliable for empirical therapy. Many E. coli strains are now ampicillin-resistant. Amoxicillin + clavulanic acid is more frequently employed.

Cloxacillin

Use is restricted to penicillinase producing staphylococcal infection, which is uncommon in urinary tract.

Piperacillin/Carbenicillin

Only in serious Pseudomonas infection in patients with indwelling catheters or chronic obstruction, and in hospitalized patients.

Cephalosporins

Use is increasing, especially in women with nosocomial Klebsiella and Proteus infections; should normally be used only on the basis of sensitivity report, but empirical use for community acquired infection is also common. Some guidelines recommend them as alternative drugs.

Gentamicin

Very effective against most urinary pathogens including Pseudomonas. However, because of narrow margin of safety and need for parenteral administration, it is generally used only on the basis of in vitro bacteriological sensitivity testing. The newer aminoglycosides may be needed for hospital-acquired infections.

Chloramphenicol

 Though effective in many cases, use should be restricted, for fear of toxicity, to pyelonephritis in cases where the causative bacteria is sensitive only to this antibiotic.

Tetracyclines

They are seldom effective now, because most urinary pathogens have become resistant. Though broad spectrum, they are used only on the basis of sensitivity report and in Ch. No. trachomatis cystitis.

Urinary pH In Relation To Use Of AMAs

Certain AMAs act better in acidic urine, while others in alkaline urine. However, specific intervention to produce urine of desired reaction (by administering acidifying or alkalinizing agents) is seldom required (except for methenamine), because most drugs used in UTI attain high concentration in urine and minor changes in urinary pH do not affect clinical outcome. In case of inadequate response or in complicated cases, measurement of urinary pH and appropriate corrective measure may help.

In certain urease positive Proteus (they split urea present in urine into NH₃) infections it is impossible to acidify urine. In such cases, acidification should not be attempted and drugs which act better at higher pH should be used.

Urinary Infection In Patients With Renal Impairment

This is relatively difficult to treat because most AMAs attain lower urinary concentration. Methenamine mandelate, tetracyclines (except doxycycline) and certain cephalosporins are contraindicated.

Nitrofurantoin, nalidixic acid and aminoglycosides are better avoided. Still, every effort must be made to cure the infection, because if it persists, kidneys may be further damaged. Bacteriological testing and followup cultures are a must to select the appropriate drug and to ensure eradication of the pathogen. Potassium salts and acidifying agents are contraindicated.

Prophylaxis For Urinary Tract Infection

This may be given when:

·     Catheterization or instrumentation inflicting trauma to the lining of the urinary tract is performed; bacteremia frequently occurs and injured lining is especially susceptible.

·     Indwelling catheters are placed.

·     Uncorrectable abnormalities of the urinary tract are present.

·  Inoperable prostate enlargement or other chronic obstruction causes urinary stasis.