Azithromycin vs. Bactrim

See how Azithromycin and Bactrim compare on approved uses, dosing, side effects, and cost.

Key Takeaways

  • Azithromycin is a macrolide antibiotic usually given as a short 3-to-5-day course or a single dose, while Bactrim is a sulfonamide combination typically taken twice daily for 10 to 14 days.

  • Azithromycin treats respiratory infections, skin infections, and several sexually transmitted infections, while Bactrim is a go-to choice for urinary tract infections and pneumocystis pneumonia prevention.

  • Both can cause nausea and stomach upset, but azithromycin carries a heart-rhythm warning while Bactrim carries a higher risk of serious skin reactions and should be avoided in pregnancy.

Azithromycin vs. Bactrim Drug Summary

Azithromycin

Azithromycin is a macrolide (azalide) antibiotic used to treat respiratory infections, skin infections, and several sexually transmitted infections. It is typically taken as a short 3-to-5-day oral course or a single dose, and is also available as an intravenous infusion for more severe infections.

Bactrim

Bactrim is a combination sulfonamide antibiotic that blocks two steps in bacterial folate production, used for urinary tract infections, traveler's diarrhea, and pneumocystis pneumonia. It is usually taken as an oral tablet twice daily for 10 to 14 days, with an intravenous form available for hospitalized patients.

Azithromycin vs. Bactrim Side Effects

Azithromycin

Most common
nausea (up to 18%)
vomiting (up to 7%)
diarrhea (up to 14%)
abdominal pain (up to 7%)

Bactrim

Most common
nausea (rate not quantified in label)
vomiting (rate not quantified in label)
anorexia (rate not quantified in label)
rash (rate not quantified in label)

Azithromycin vs. Bactrim Dosage

Azithromycin

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 500 mg once Day 1
Maximum dose 5 mg/kg once daily Days 2-5
Dose changes 4 increases As tolerated

Bactrim

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 800 mg/160 mg every 12h At the start
Maximum dose 8-10 mg/kg/day TMP q6-12h If needed
Dose changes 3 increases As tolerated

Azithromycin vs. Bactrim Indications

Azithromycin

Azithromycin is FDA-approved for a wide range of bacterial infections, including community-acquired pneumonia, sinusitis, and skin infections. It also treats certain sexually transmitted infections such as chlamydia-related urethritis and cervicitis. Its short dosing course makes it a common choice when adherence is a concern.

  • Community-acquired pneumonia

  • Acute bacterial sinusitis

  • Pharyngitis and tonsillitis

  • Skin and skin structure infections

  • Urethritis, cervicitis, and pelvic inflammatory disease

Bactrim

Bactrim is FDA-approved for urinary tract infections, traveler's diarrhea, and pneumocystis pneumonia, both to treat active infection and to prevent it in immunocompromised patients. It also treats shigellosis and certain ear infections in children. It is not approved for strep throat, unlike some other antibiotics.

  • Urinary tract infections

  • Pneumocystis jirovecii pneumonia (treatment and prevention)

  • Shigellosis

  • Acute otitis media in children

  • Traveler's diarrhea in adults

Azithromycin vs. Bactrim Pros and Cons

Azithromycin

Azithromycin's short 3-to-5-day or single-dose regimens make it easy to complete without missing doses. It covers a broader range of respiratory, skin, and sexually transmitted infections than Bactrim, but it carries a heart-rhythm warning that Bactrim does not share.

Pros

  • Short 3-to-5-day or single-dose regimens

  • Covers respiratory and skin infections plus several STIs

  • Long tissue half-life keeps drug levels up after the course ends

  • Not affected by G6PD deficiency

Cons

  • Carries an FDA warning for QT prolongation and abnormal heart rhythm

  • Can cause rare, serious liver injury

  • Not approved for urinary tract infections

  • Bacterial resistance to macrolides is increasingly common

Bactrim

Bactrim is inexpensive and effective against urinary tract infections and pneumocystis pneumonia, infections azithromycin is not approved to treat. It requires a longer 10-to-14-day course and carries added precautions around pregnancy and certain blood conditions.

Pros

  • Effective for urinary tract infections

  • Used to prevent and treat pneumocystis pneumonia

  • One of the least expensive commonly prescribed antibiotics

  • Long track record dating back to the 1970s

Cons

  • Requires a longer 10-to-14-day course in most cases

  • Higher risk of severe skin reactions like Stevens-Johnson syndrome

  • Contraindicated in pregnancy and in infants under 2 months

  • Can trigger hemolytic anemia in G6PD-deficient patients

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