Why are the antibiotics my doctor prescribed for me not what I expected?
After your doctor has diagnosed you with a urinary tract infection (UTI) the next task is to find out which bacteria has caused the infection. In ~80% of cases the troublemaker is E. coli, but there are about 45 recognized strains of that bacteria species and only about ten of those cause UTIs. Each strain responds in its own way to different antibiotics. Therefore, your doctor will have you do a urine sample test which will be sent to a lab for a urine culture.
This requires a couple of days of waiting for the urine culture to grow, be tested against different antibiotics, and the lab results to return to your doctor. However, it’s well worth the wait and you can use OTC painkillers like ibuprofen to ease the pain during the waiting period. Testing is the only method that can determine the bacteria strain with certainty and it allows your doctor to choose the antibiotic that will be most effective against it.
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Due to decades of antibiotics treatment for UTIs, many E. coli strains already are resistant against the longest-standing antibiotics, such as ampicillin. Nowadays there are databases that doctors can check to see what bacteria strain is resistant to what medication. As doctors say, you need to match the “drug with the bug.”
So, when you first went to the doctor you probably expected to get a certain antibiotic. Something that you heard a friend say works well or even — if you previously had a UTI — an antibiotic you had been prescribed in the past. Well, as you now know, it doesn’t work this way. The bacteria strains that caused your friend’s UTI or your last UTI probably are different from the one behind your current UTI. Each UTI needs to be evaluated individually and requires customized antibiotic treatment, although in most cases it still comes down to Macrobid and Bactrim.
Aside from considering the bacteria, there are several other factors doctors have to weigh in order to decide which antibiotic to describe. This includes:
- The severity of your UTI (whether there’s immediate risk of kidney infections)
- Your past history with UTIs (is it a recurring or chronic UTI?)
- Your recent antibiotics use
- Allergies and your general medical history
- Any recent overseas travels you did
- The antibiotic’s side effects
- Whether you’re pregnant
All of these are important factors to include when considering antibiotics prescriptions.
What are the most common UTI antibiotics?
In the U.S. market, the FDA has approved several antibiotics for treating UTs and the most commonly prescribed are:
- Macrobid (nitrofurantoin) often is the first choice, because it specifically targets UTI bacteria and its side effects are well understood and mostly mild. It wipes out the bad bacteria but doesn’t hurt good bacteria. Macrobid also is a safe option for pregnant females in the second and third trimesters. Nitrofurantoin resistance is on the rise though, i.e., it’s becoming less effective against bacteria. However, according to the New York City Health Department, it still works well in about 95% of treatment cases. That said, the drug is not very effective against kidney inflammation, which means that if your doctor sees a high risk for your UTI to spread from the bladder to the kidneys Macrobid may not be the first choice any longer.
- Cipro (ciprofloxaxin) in the recent past was one of the most prescribed treatments for UTIs, but bacterial resistance has become a problem. The drug no longer works in 10-20% of cases, depending on region and country. There also can be unpleasant side effects such as heart problems and tendon rupture. Because of these issues, ciprofloxaxin no longer is a first choice for simple UTIs. However, it’s still used for treating kidney infections, because it gets faster to the kidneys than other medications.
- Bactrim is a composite drug made from two antibiotics: sulfamethoxazole and trimethoprim. It’s a broad antibiotic used for treating everything from respiratory infections to UTIs. This is because it has an extensive track record and side effects tend to be moderate. However, its widespread use over decades has taught more and more bacteria to become resistant against it, so that 33% of E. coli triggered UTIs don’t respond to the antibiotic anymore.
- Monurol (fosfomycyin) has been developed to target bladder and prostate infections. Bacterial resistance isn’t a big problem yet with this antibiotic but it’s only effective against simple UTIs; it won’t help with kidney infections.
- Keflex (cephalexin) has been around since 1967 and has been used for treating a wide range of ailments, such as skin and ear infections. Recently it has become more popular for treating UTIs, especially complicated UTIs (kidney infections and recurring UTIs). For example, it’s used to treat kidney infections when bacteria have proved resistant against cirpofloxaxin. Diarrhea, nausea and other stomach issues are common side effects, though.
As you can see, there’s a wide range of antibiotic options and none of them are perfect or universally applicable to all UTIs. Therefore, it’s highly recommended that you talk to your doctor about doing a urine culture, even if it costs you more money and requires 2-3 days of painful waiting. Only such a test can help you find the right antibiotic treatment.
- Vejborg, Rebecca Munk, et al. “Comparative Genomics of Escherichia Coli Strains Causing Urinary Tract Infections.” Applied and Environmental Microbiology, vol. 77, no. 10, 15 May 2011, pp. 3268–3278, aem.asm.org/content/77/10/3268, 10.1128/AEM.02970-10. Accessed 22 Feb. 2020.
- Gardiner, Bradley J, et al. “Nitrofurantoin and Fosfomycin for Resistant Urinary Tract Infections: Old Drugs for Emerging Problems.” Australian Prescriber, vol. 42, no. 1, 1 Feb. 2019, pp. 14–19, www.ncbi.nlm.nih.gov/pmc/articles/PMC6370609/, 10.18773/austprescr.2019.002. Accessed 22 Feb. 2020.
- The Lancet. “Balancing Treatment with Resistance in UTIs.” The Lancet, vol. 391, no. 10134, May 2018, p. 1966, www.thelancet.com/journals/lancet/article/PIIS0140-6736(18)31077-8/fulltext, 10.1016/s0140-6736(18)31077-8. Accessed 22 Feb. 2020.