Preventing Urinary Tract Infections
Annette N. Pellegrino is a clinical assistant professor at the University of Illinois at Chicago College of Pharmacy.
Urinary tract infections (UTIs) are a common and often recurring complaint, especially among sexually active women. Escherichia coli is the causative agent in 85% of community-acquired UTIs occurring in the United States each year; it is estimated that 6 million to 8 million episodes of UTIs in this patient population cause $1 billion in direct health care costs and >8 million physician visits per year.1,2 UTIs can be broken down into a number of categories, depending on site of infection and whether they are considered complicated or uncomplicated. For the purpose of this article, UTI will be synonymous with acute, uncomplicated cystitis.
Risk FactorsThe majority of UTIs occur in sexually active women. Risk increases at least 3-fold in this patient population when diaphragms are used for contraception. Failure to void the bladder shortly after sexual intercourse, as well as the use of spermicides, also increase the risk for acquiring a UTI.3
DiagnosisThe most common presenting symptoms of a UTI are dysuria, along with urgency or polyuria. These characteristic symptoms can predict the diagnosis of a UTI in 70% to 80% of all cases.3 The gold standard for diagnosis is a urine analysis, preferably captured mid-stream to avoid contaminants. OTC dipstick tests are available; however, unless the infecting bacteria are gram-negative, this test could lead to a false negative. Given the high percentage of diagnoses from symptomatic presentations, further questioning of patients about symptoms is warranted for potential referral to their primary care provider.
Antibiotic TherapyThe Table provides a summary of the most common agents and typical dosing used in the treatment of UTIs.4 One important factor to consider in the choice of agents for UTIs is drug inter-actions. Sulfonamides' main interactions include oral anticoagulants, sulfonylurea hypoglycemic agents, and hydantoin anticonvulsants. The mechanism for these interactions is believed to be inhibition of metabolism, thus potentiating the effect of the other agent.5 Dosage adjustment most likely will be necessary when a sulfonamide is given concomitantly with these agents.
Interactions with the fluoroquinolone class and oral anticoagulants also exist, but to a lesser extent than the sulfonamides. For the majority of the antibiotic agents, gastrointestinal (GI) upset is the main set of adverse drug reactions that occur with therapy.
Other TherapiesPhenazopyridine hydrochloride displays an analgesic action on the urinary tract and alleviates the common presentation symptoms of UTIs: dysuria, polyuria, burning, and urgency. This agent can be found in a variety of OTC products in dosages <100 mg. The usual prescription dose is 200 mg, 3 times daily. An important patient counseling point for this medication is that it can dye the urine an orange/red color. The most common adverse effect is GI upset, which can be avoided if administered with food. Some clinical controversy does exist with the use of this medication, as it can mask the symptoms of a UTI in an infection that may not be responding to antibiotic therapy.5
Cranberry products have been debated in current literature without much consensus on their utility. One proposed mechanism for their use in preventing UTIs is by decreasing the ability of the infecting pathogen to adhere to the bladder.4 Lactobacillus probiotics also have been theorized to help reduce the risk of acquiring UTIs. The theory is that the Lactobacillus lowers the vaginal pH, thus decreasing the chance of bowel flora (E coli) colonization.4
ProphylaxisMore than 20% of women who initially were diagnosed with a UTI will develop frequent recurrences.4 Frequent recurrences can be defined as a symptomatic episode that occurs at least 3 times in a year. Women who fall into this category can be classified as candidates for long-term administration of low-dose prophylactic antibiotic therapy.4 These women should receive proper education to avoid spermicide use and to void their bladder shortly after intercourse to help decrease the risk of a UTI. Medications of choice for prophylactic therapy include daily or 3-times-a-week low-dose administration of the following agents: trimethoprim-sulfamethoxazole (single strength), trimethoprim, or nitrofurantoin.5
Patient EducationPatient education in minimizing behaviors associated with an increased risk of acquiring UTIs plays an important role in reducing the occurrence of these community-acquired infections. When dispensing antibiotic prescriptions for the treatment of UTIs, pharmacists can use the opportunity to remind patients of risk factors for recurrence. Pharmacists also are well-positioned to help identify patients needing referral to their primary health care provider for assessment, as well as those who might benefit from prophylactic therapy.
1. Russo TA, Johnson JR. Diseases Caused by Gram-Negative Enteric Bacilli. In: Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL, Isselbacher KJ, eds. Harrison's Principles of Internal Medicine. 17th ed. New York, NY: McGraw-Hill; 2008:937.
2. Warren JW, Abrutyn E, Hebel JR, et al. Guidelines for antimicrobial treatment of uncomplicated acute bacterial cystitis and acute pyelonephritis in women. Clin Infect Dis. 1999;29(4):745-758.
3. Gonzales R, Kutner JS. CURRENT Practice Guidelines in Primary Care 2009. New York, NY: McGraw-Hill; 2008:179.
4. Coyle EA, Prince RA. Urinary Tract Infections and Prostatitis. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 7th ed. New York, NY: McGraw-Hill; 2008:1899.
5. Petri WA. Sulfonamides, Trimethoprim-Sulfamethoxazole, Quinolones, and Agents for Urinary Tract Infections. In: Brunton LL, Lazo JS, Parker KL, eds. Goodman & Gilman's The Pharmacological Basis of Therapeutics. 11th edition. New York, NY: McGraw-Hill; 2005:1111.