Antibiotics for UTI, such as nitrofurantoin, trimethoprim-sulfamethoxazole, fosfomycin or ciprofloxacin, may be prescribed to treat urinary tract infections caused by bacteria. These medicines work by eliminating or stopping the growth of bacteria in the urinary tract, helping to relieve symptoms like pain or burning when urinating.
The type of antibiotic recommended by the doctor can vary depending on the severity of the infection, the part of the urinary tract affected, previous urine culture results and local antibiotic resistance. Simple bladder infections are usually treated with oral antibiotics, while kidney infections or complicated UTIs may require stronger antibiotics or treatment in the hospital.
Antibiotics should only be used as prescribed by a doctor, as using them incorrectly can increase the risk of bacterial resistance and make future infections harder to treat. It is also important to complete the full course of treatment, even if symptoms improve before finishing the antibiotic.
List of antibiotics
The main antibiotics that may be prescribed for a UTI include:
1. Nitrofurantoin
Nitrofurantoin is one of the most commonly prescribed antibiotics for uncomplicated bladder infections, especially when the infection is limited to the lower urinary tract. It is usually not recommended for kidney infections, as it does not reach high enough levels in kidney tissue.
Dosing: The usual adult dose is 100 mg twice a day for 5 days, although the dose and duration may vary depending on the formulation prescribed.
Side effects: Nausea, vomiting, loss of appetite, diarrhea, headache, dizziness, gas, stomach pain, dark yellow or brown urine, rash or itching. Rare but serious side effects can include lung problems, liver injury, nerve damage or severe allergic reactions.
Contraindications: Nitrofurantoin is contraindicated for people who are allergic to this medicine, have severe kidney disease, have difficulty urinating or are unable to urinate, or have a history of liver problems caused by nitrofurantoin. It is also usually avoided at the end of pregnancy and should be used with caution in people with G6PD deficiency.
2. Trimethoprim-sulfamethoxazole
Trimethoprim-sulfamethoxazole, also called TMP-SMX or co-trimoxazole, may be prescribed for uncomplicated UTIs when the bacteria are likely to be sensitive to this antibiotic. It may also be used after urine culture results confirm that the bacteria causing the infection can be treated with this medicine.
Dosing: The usual adult dose is 160 mg trimethoprim/800 mg sulfamethoxazole twice a day for 3 days for uncomplicated cystitis, or for longer periods in some complicated infections, as prescribed by a doctor.
Side effects: Nausea, vomiting, diarrhea, loss of appetite, headache, dizziness, rash, itching or increased sensitivity to sunlight. Serious side effects can include severe skin reactions, blood disorders, liver problems, kidney problems or high potassium levels.
Contraindications: Trimethoprim-sulfamethoxazole is contraindicated for people who are allergic to sulfonamides or trimethoprim, or who have had severe reactions to these medicines. It is generally avoided in certain cases of severe liver or kidney disease, some blood disorders, pregnancy, breastfeeding young infants, or in babies under 2 months old, unless specifically recommended by a doctor.
3. Fosfomycin
Fosfomycin is an antibiotic that may be prescribed for uncomplicated bladder infections, especially when a simple single-dose treatment is preferred or when resistance to other antibiotics is a concern. It works by preventing bacteria from forming a protective cell wall, which helps eliminate the infection.
Dosing: The usual adult dose for uncomplicated cystitis is one 3 g sachet taken as a single dose, dissolved in water, as directed by a doctor.
Side effects: Diarrhea, nausea, headache, dizziness, indigestion, stomach pain, vaginal itching, runny nose or back pain. Serious allergic reactions are rare but may include swelling, difficulty breathing or widespread rash.
Contraindications: Fosfomycin is contraindicated for people who are allergic to fosfomycin or any component of the formula. It should be used with medical guidance in pregnancy, breastfeeding or significant kidney disease.
4. Ciprofloxacin
Ciprofloxacin is a fluoroquinolone antibiotic that may be prescribed for more serious UTIs, kidney infections or complicated urinary infections when the bacteria are sensitive to it. It is generally not the first choice for simple bladder infections because of the risk of side effects and antibiotic resistance.
Dosing: The usual adult dose may range from 250 to 500 mg twice a day for 3 to 7 days for some UTIs, or longer for complicated infections, depending on medical evaluation and culture results.
Side effects: Nausea, diarrhea, vomiting, stomach pain, headache, dizziness, insomnia, rash or increased sensitivity to sunlight. Serious side effects can include tendon inflammation or rupture, nerve damage, mood changes, seizures, heart rhythm changes, low blood sugar or severe allergic reactions.
Contraindications: Ciprofloxacin is contraindicated for people who are allergic to ciprofloxacin or other fluoroquinolones, and it should not be taken with tizanidine. It is generally avoided in pregnancy, breastfeeding, children and people with a history of tendon problems related to fluoroquinolones, unless the doctor considers it necessary.
5. Levofloxacin
Levofloxacin is another fluoroquinolone antibiotic that may be used for kidney infections or complicated UTIs, especially when oral treatment is possible and the bacteria are susceptible. Like ciprofloxacin, it is usually reserved for specific cases because of safety concerns and the risk of bacterial resistance.
Dosing: The usual adult dose may be 250 to 750 mg once a day for 3 to 7 days, or longer in some complicated infections, depending on the type and severity of the UTI.
Side effects: Nausea, diarrhea, headache, dizziness, insomnia, constipation, stomach pain, rash or sensitivity to sunlight. Serious side effects can include tendon rupture, nerve damage, mental health changes, seizures, heart rhythm changes, blood sugar changes or severe allergic reactions.
Contraindications: Levofloxacin is contraindicated for people who are allergic to levofloxacin or other fluoroquinolones. It is generally avoided in pregnancy, breastfeeding, children, people with previous fluoroquinolone-related tendon problems or those at high risk of serious adverse effects, unless specifically prescribed by a doctor.
6. Cephalexin
Cephalexin is a cephalosporin antibiotic that may be prescribed as an alternative for some lower UTIs, especially when first-choice antibiotics cannot be used or when urine culture results show the bacteria are sensitive to it. It may also be considered in some cases during pregnancy, depending on medical evaluation.
Dosing: The usual adult dose may be 500 mg every 6 to 12 hours for 5 to 7 days, although the dose can vary depending on the infection and the doctor’s instructions.
Side effects: Diarrhea, nausea, vomiting, stomach pain, indigestion, dizziness, tiredness, rash, itching or vaginal yeast infection. Serious side effects can include severe allergic reactions, severe diarrhea caused by C. difficile or blood changes.
Contraindications: Cephalexin is contraindicated for people who are allergic to cephalexin or other cephalosporin antibiotics. It should be used with caution in people with a history of severe penicillin allergy, kidney disease or previous antibiotic-associated colitis.
7. Amoxicillin-clavulanate
Amoxicillin-clavulanate may be prescribed for UTIs when the bacteria are sensitive to this antibiotic, especially when other first-line options are not appropriate. It combines amoxicillin with clavulanate, which helps block enzymes that some bacteria use to resist treatment.
Dosing: The usual adult dose may be 500/125 mg every 8 hours or 875/125 mg every 12 hours for 5 to 7 days, depending on the infection and the doctor’s prescription.
Side effects: Diarrhea, nausea, vomiting, stomach pain, indigestion, rash, itching, headache or vaginal yeast infection. Serious side effects can include liver problems, severe allergic reactions or severe diarrhea caused by C. difficile.
Contraindications: Amoxicillin-clavulanate is contraindicated for people who are allergic to penicillins, amoxicillin, clavulanate or related antibiotics. It should not be used by people with a history of jaundice or liver problems caused by amoxicillin-clavulanate, and should be used with caution in kidney disease or a history of severe antibiotic-associated diarrhea.
8. Ceftriaxone
Ceftriaxone is an injectable cephalosporin antibiotic that may be used for more serious UTIs, kidney infections or complicated infections, especially in emergency or hospital settings. It may be given before switching to an oral antibiotic once symptoms improve and culture results are available.
Dosing: The usual adult dose is often 1 g once a day by injection, but the dose and duration can vary depending on the severity of the infection, kidney involvement and medical assessment.
Side effects: Pain or swelling at the injection site, diarrhea, nausea, rash, itching, increased liver enzymes or changes in blood tests. Serious side effects can include severe allergic reactions, severe diarrhea, gallbladder problems or blood disorders.
Contraindications: Ceftriaxone is contraindicated for people who are allergic to ceftriaxone or other cephalosporins. It should be used with caution in people with a history of severe penicillin allergy, liver or kidney problems, gallbladder disease, or previous antibiotic-associated colitis.