Antibiotics Used for Treating Urinary Tract Infections (UTIs)

Key takeaways:

• Pathogens such as E. coli, S. saprophyticus, and P. mirabilis can cause urinary tract infections, affecting the kidneys, urethra, bladder, and ureters.  
• UTI symptoms may include burning sensations while urinating, frequent need to urinate, an irresistible urge to urinate, cloudy urine, and blood in your pee. 
• Common antibiotics used to treat UTIs include trimethoprim/sulfamethoxazole, fluoroquinolones, nitrofurantoin, aminopenicillins, and cephalosporins.

Urinary tract infection (UTI) is an infection that affects the urinary system, which includes the kidneys (pyelonephritis), urethra (urethritis), bladders (cystitis), and ureters. UTIs can cause symptoms like pain while peeing (dysuria), strong urgency to pee, and blood in urine.

The organisms that cause UTI are mostly those classified under gram-negative bacteria, which have strong multilayer outer shells and are highly resistant to antibiotics. Some gram-positive organisms can also cause UTIs.

Clinically, there are two types of UTIs: uncomplicated and complicated.

An uncomplicated UTI is a bacterial infection that occurs in healthy people and does not originate from existing medical conditions or structural abnormalities.

However, complicated UTIs result from medical conditions affecting the urinary tract, such as pregnancy, urinary blockage, and foreign bodies. 

Common antibiotics that doctors prescribe for treating urinary tract infections include the following:

1. Bactrim (Trimethoprim-sulfamethoxazole)

Trimethoprim-sulfamethoxazole, often known as co-trimoxazole, is an antibiotic used to treat various bacterial infections. It is especially beneficial for treating acute and recurrent UTIs. It works by stopping a necessary step in the growth of bacteria, thereby decreasing their growth. 

Compared to most antibiotics, co-trimoxazole is beneficial because of its low cost, efficacy, and tolerability.

Although it is unusual to experience side effects with this drug, some may experience various side effects that may go away after a few minutes or hours. Some side effects to note include loss of appetite, nausea, a painful /swollen tongue, dizziness, photosensitivity, rash, and anorexia.

The dosage of trimethoprim-sulfamethoxazole in treating UTIs is one tablet 800 mg of sulphamethoxazole and 160 trimethoprim every 12 hours for 14 days. The treatment may extend to 2 or 3 months, depending on the intensity of the infection.

Trimethoprim-sulfamethoxazole contains sulfur; you should not take it if you are allergic to this ingredient. Alternatively, your doctor may prescribe trimethoprim alone for the treatment, which is as successful as the combination. 

If you are in your first trimester of pregnancy and have an UTI, it is best that you avoid co-trimoxazole due to the risk of congenital abnormalities.

2. Fluoroquinolones

Fluoroquinolones are antibiotics that can treat different bacterial infections, (which means they are broad-spectrum antibiotics). They are effective against both gram-positive and gram-negative bacteria. 

Fluoroquinolones act by stopping the actions of enzymes responsible for bacterial survival—DNA gyrase and topoisomerase IV. The two most widely used broad-spectrum fluoroquinolones for treating UTIs are ciprofloxacin and levofloxacin. 

The dosage for ciprofloxacin tablets is 1000 mg once a day for complicated UTIs and 500 mg daily for uncomplicated UTIs, while the dosage for levofloxacin is 500 mg a day for 7–14 days, depending on the severity of the infection.

Although this class of antibiotics is not known to cause life-threatening side effects, you may look out for these side effects: nausea, vomiting, dyspepsia, dizziness, insomnia, and headache.

Fluoroquinolone is well tolerated, but you should not use it if you are pregnant due to possible side effects.

3. Beta-lactams

Beta-lactam antibiotics are among the most commonly used antibiotics for treating UTIs. These antibiotics contain a special 4-membered ring in their structure (the beta-lactam ring). The presence of this ring enables them to kill bacteria by preventing the formation of cell walls. Antibiotics in this class include:

• Penicillins
• Cephalosporins
• Carbapenems
• Monobactam
• Beta-lactamase inhibitors

You may be familiar with amoxicillin, a penicillin under beta-lactam antibiotics. They are the most commonly used antibiotics, though their effectiveness has been reduced by drug resistance, which poses a public health risk. The innovation of beta-lactam inhibitors has resolved this problem. 

Beta-lactamase inhibitors now improve the efficacy of beta-lactam antimicrobial treatments and prevent antimicrobial resistance. Antibiotics under this class include avibactam, clavulanic acid, relebactam, sulbactam, tazobactam, vaborbactam, and tebipenem.

Compared to other antibiotics, Beta-lactams are well tolerated and usually safe. Penicillins are best not used to treat people with previous skin reactions, e.g., Stevens-Johnson syndrome.

4. Nitrofurantoin

This antibiotic medication is used to treat lower urinary tract infections. It is effective against both gram-positive and gram-negative bacteria and kills almost all traits of bacteria that cause urinary tract infections. 

The mechanism that nitrofurantoin uses to perform this action for years is not understood, but that may as well explain why there is no bacterial resistance to nitrofurantoin.

The recommended dosage for nitrofurantoin is 100 mg twice daily for 5-7 days. Prescribing nitrofurantoin for less than five days is less effective and not recommended. 

Nitrofurantoin is considered safe compared to alternatives, but common adverse reactions you may experience include nausea, vomiting, loss of appetite, and diarrhea. 

The use of nitrofurantoin is contraindicated in acute bacterial pyelonephritis (a type of UTI where one or two kidneys are affected) as it is not successful in the treatment of upper UTIs. Other cases where nitrofurantoin shouldn't be used include:

• In anuria (no urine)
• Oliguria (less urine output)
• Pregnant women at term (38 to 42 weeks gestation),
• During labor and delivery
• In neonates younger than one month of age
• Men with UTIs.

5. Fosfomycin tromethamine

Fosfomycin is a long-time drug that was effective in treating urinary tract infections. However, due to the innovation of new classes of antibiotics, its use declined.

With the issue of bacterial resistance to several antibiotics, fosfomycin is making a comeback as a viable alternative for treating UTIs. 

This bactericidal antibiotic is mainly active against E. coli, Citrobacter, Enterobacter, Klebsiella, Serratia, and Enterococcus species. It works by killing bacteria or preventing their growth.

The recommended dose of fosfomycin tromethamine for treating uncomplicated UTI is a 3 g single dose.

Generally, fosfomycin tromethamine is considered safe unless you have a known hypersensitivity to this drug. Also, you may notice mild gastrointestinal disturbances like diarrhea, nausea, abdominal pain, and indigestion while using this drug. 

Headaches, dizziness, infection of the upper respiratory tract (nose, nasal cavity, mouth, and throat), vaginitis (inflammation of the vagina resulting in discharge, itching, and pain), and bacterial/fungal superinfections have also been reported from the use of fosfomycin tromethamine.

The use of fosfomycin tromethamine in pregnancy should be under the supervision of a health professional and when there are no available options. 

6. Doxycycline

Doxycycline is among the class of antibiotics known as tetracycline. It is active against both classes of bacteria—gram-positive and gram-negative and works by preventing the growth of bacteria. 

Although there are not many studies supporting the use of doxycycline in the treatment of UTI, a 2023 study on the use of doxycycline in the treatment of UTI suggests that, despite the limited urinary penetration of doxycycline, it can be an alternative option for treating UTI. But, this is when patients lack oral options due to allergies or resistant organisms.

The recommended dose for doxycycline in treating UTI is 100 mg, to be taken twice daily for one week. Also, the drug is best taken on an empty stomach 1 hour before eating or 2 hours after a meal and taken with at least 8 ounces of water.

While using this drug, you may experience some side effects, although compared to its tetracycline counterparts, doxycycline is highly tolerated and may not cause serious side effects. But some side effects you may experience include mild diarrhea, nausea, vomiting, skin rash, headache, and tooth discoloration.  

Doxycycline is contraindicated in pregnancy and breastfeeding, in children under the age of 12, those with an allergy to doxycycline, and when in use with penicillin and isotretinoin.

7. Plazomicin

Plazomicin is a new antibiotic among the class of antibiotics known as aminoglycosides, which has been recently approved for treating complicated UTIs and pyelonephritis (an UTI that affects the kidneys) in adults with limited or no alternative treatment options. 

The purpose of producing this drug was to target strains of enterobacter that have become very resistant to all antibiotics (multidrug-resistant Enterobacteriaceae).

There are other drugs under the aminoglycoside class —gentamicin, amikacin, and tobramycin, but their activities amongst some bacteria strains that are capable of producing an enzyme that inactivates the function of antibiotics known as aminoglycoside-modifying enzymes are minimal, and this is an advantage that plazomicin has over other aminoglycosides. 

Plazomicin acts by gluing to the bacteria’s ribosome, thereby killing the bacteria. Also, plazomicin is poorly absorbed, just like every other aminoglycoside, and healthcare providers should administer it parenterally.

Some side effects you may experience while using this drug are diarrhea, hypertension, headache, nausea, vomiting, and hypotension, but this can only be seen in 1% of patients. During this treatment, the health professional may monitor you closely in case of any severe adverse effects.

8. Recarbio (Imipenem/Cilastatin/Relebactam)

Recarbio is a combination of three different drugs (imipenem, cilastatin, and relebactam) that have recently passed approval for treating complicated urinary tract infections and pyelonephritis due to the increase in multidrug-resistant pathogens.

It is recommended for those who are 18 years of age and older who have limited or no alternative treatment options.

Recarbio acts by disrupting bacterial cell wall synthesis, thereby causing the death of the bacteria.

Some side effects associated with the drug include diarrhea, nausea, headache, vomiting, alanine aminotransferase increase (enzyme found in the liver and kidney), aspartate aminotransferase increase (enzyme associated with liver health), infusion site reactions, fever, and hypertension.

Recarbio is administered as an intravenous (IV) infusion, and the approved dosage for complicated urinary tract infections is 1.25 g (imipenem 500 mg, cilastatin 500 mg, relebactam 250 mg) once every 6 hours, administered over 30 minutes for 4–14 days. 

Are there available over-the-counter antibiotics for treating UTIs?

No, there are no available over-the-counter antibiotics for treating UTIs. Health professionals advise against self-medicating with antibiotics because of antibiotic misuse, abuse, or resistance. To prevent this, consult a physician or other healthcare provider for a proper prescription.

Although there are no over-the-counter antibiotics for UTI, there are some over-the-counter medications that can help relieve pain and discomfort, and they include; 

• Phenazopyridine (Puridium)
• Methenamine (Hiprex)
• Ascorbic acid
• Cranberry
• Probiotics
• Sodium salicylate
• Benzoic acid
• D-Mannose

At-home remedies that may work for UTI?

As aforementioned, antibiotics are the recommended treatment for UTIs, but there are at-home therapies that may help prevent, eliminate, reduce recurrence, or reduce the symptoms of UTIs. Some of these remedies include:

• Staying hydrated always.
• Urinating after sexual activity
• Wiping bottom from front to back after using the toilet
• Consumption of cranberry supplements

When to seek medical attention?

If you have recurring UTIs (three UTIs with three positive urine cultures within 12 months, or two infections within 6 months), consult your doctor or health care provider.

Final words

Urinary tract infections (UTIs) can be discomforting and may cause permanent kidney damage. The good news is that they can be treated with the help of a healthcare provider and the proper antibiotic treatment regimen.

Over-the-counter medications, such as cranberry, probiotics, benzoic acid, phenazopyridine, and ascorbic acid, are also available to help ease the discomfort of UTIs.