What Are the Best Antibiotics for a UTI?
You’ve got a UTI and your doctor prescribed you antibiotics. How did your doctor decide what to prescribe? Is there a best antibiotic for you? This post discusses the treatment of simple bladder infections in women who are not pregnant only and is meant solely for your information. Infections in men, complicated UTI’s or infections of the kidney (pyelonephritis) are not discussed. As always, speak with your physician about medical advice that is pertinent to you and your unique healthcare needs.
How Does Your Doctor Decide if You Need Treatment?
Your doctor will determine if you have a UTI based on the symptoms you describe, your physical exam and testing your urine for the presence of blood, white cells and nitrites. Sometimes he or she will also send your urine to the microbiology lab for a culture. Unfortunately, that can take 2-3 days and by then you could be done with treatment and already feeling better!
Which Drugs Do We Pick and Why?
To quickly get you back on your feet, we make an educated guess and start treatment with an “empiric” course of antibiotics. This is based on your prior history of UTI’s, the local resistance patterns of common UTI causing bacteria, your personal medical history, allergies, and medications. We also choose antibiotics that will effectively treat a simple bladder infection, but avoid antibiotics intended for more serious infections. Many physicians rely on guidelines from the Infectious Disease Society of America (IDSA) and the medications discussed are part of those guidelines.1
The A-Team: First line antibiotics for UTI that are well tolerated and have low resistance.
Nitrofurantoin
Usually this is given as a 3-5 days course twice a day, though some formulations require it to be taken 4 times daily. This drug is well tolerated; it causes minimal GI upset and allergies are rare. Some people get nausea or a headache from nitrofurantoin. This only works in people with normal kidney function, so it is limited for use in older women. Recently it was tested head to head against fosfomycin and nitrofurantoin had a 10% better cure rate.2
Trimethoprim-sulfamethoxazole
This is often called by its brand name, Bactrim. This is a sulfa antibiotic and very popular for treating UTI’s; however, many people have allergies to sulfa drugs. Common side effects include a rash, hives, itching, nausea and vomiting. Sulfa drugs interact with many other drugs, so it is important that your doctor and pharmacist know everything you take, including supplements and OTC products. In some locales resistance to sulfa can be high, so your doctor should check local resistance patterns before prescribing a sulfa drug.
Fosfomycin trometamol
This is an old antibiotic making a comeback, primarily because it has low resistance. Its brand name is Monurol and it is given as a single oral dose that concentrates in the urine. A few drawbacks: it is not routinely included in urine culture testing, so your doctor needs to specifically request this, and it has a slightly lower cure rate than nitrofurantoin and sulfa.2
Second line antibiotics for UTI: These should be used if first line agents can’t be used or fail.
Fluoroquinolones: ofloxacin, ciprofloxacin, and levofloxacin.
Quinolones are a potent group of antibiotics; however, they are best reserved for more serious infections than simple UTI’s. They have been widely overused and now there is increasing resistance to them. In addition, the FDA has issued a black box warning on the use of quinolones, as they can cause serious muscle and tendon injury, and are not be used for simple infections. Unless there is a compelling reason your UTI needs to be treated with a quinolone, this should not the be first line for a simple UTI.
Beta-lactams/cephalosporins: amoxicillin, cefpodoxime, cephalexin, etc….
This is a broad class of antibiotics and includes some of the oldest available antibiotics. The older and less expensive drugs in this class often have resistance to UTI causing bacteria, thus limiting their use. All of these can cause stomach upset, especially diarrhea and rash and/or allergies are common. If you have a history of UTI’s that are sensitive to a beta-lactam or cephalosporin, empiric therapy with a drug such as amoxicillin or cephalexin is often a choice your doctor will make.
Hopefully, this post explained a little more about how your doctor chooses the best antibiotic for your UTI. As always, speak with your doctor about your unique needs.
References:
- International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: A 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clin Infect Dis, 2011.
- Effect of 5-Day Nitrofurantoin vs Single-Dose Fosfomycin on Clinical Resolution of Uncomplicated Lower Urinary Tract Infection in Women: A Randomized Clinical Trial. JAMA 2018.
