Zithromax vs. Bactrim for Pneumonia and Ear Infection: Important Differences and Potential Risks.

Key takeaways

Azithromycin (Zithromax) and sulfamethoxazole/trimethoprim (Bactrim, Septra) are both antibiotics, but they belong to different classes and treat different types of infections. Azithromycin is a macrolide antibiotic taken once daily, typically for 3 to 5 days, and is used for infections like strep throat, sinus infections, and pneumonia. It works by stopping bacteria from making certain proteins. On the other hand, sulfamethoxazole/trimethoprim is a combination of a sulfonamide and an antifolate, taken twice daily, and is used for urinary tract infections, ear infections, and certain types of pneumonia. It works by stopping bacteria from making folic acid. Both are available as generic and come in tablet, liquid, and injectable forms. Azithromycin can cause side effects like diarrhea and stomach pain, whereas sulfamethoxazole/trimethoprim can cause nausea, rash, and increased sensitivity to sunlight. Both medications have serious side effects, but sulfamethoxazole/trimethoprim is not recommended during pregnancy and can cause low sodium and high potassium levels.

Azithromycin

(Zithromax)

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Sulfamethoxazole/trimethoprim

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Summary for Zithromax

Prescription only

Azithromycin (Zithromax) is a macrolide antibiotic. It's used to treat many types of infections in children and adults, including strep throat, sinus infection, and pneumonia. Azithromycin (Zithromax) is taken by mouth once daily. Typically, the length of treatment ranges from 3 to 5 days, depending on the type of infection you have. For convenience, azithromycin (Zithromax) also comes pre-packaged as Z-Pak. Some of the more common side effects of azithromycin (Zithromax) include diarrhea, stomach pain, and nausea.

Indications for Zithromax

Adults

Azithromycin (Zithromax) can treat certain types of:

Sudden worsening of chronic obstructive pulmonary disease (COPD) from a bacterial infection
Bronchitis
Sinus infections
Pneumonia
Strep throat
Tonsil infections
Skin infections (e.g., cellulitis)
Urethra or cervix infections
Genital ulcer disease (chancroid)

Children

Azithromycin (Zithromax) can treat certain types of:

Ear infections (ages 6 months and older)
Pneumonia (ages 6 months and older)
Strep throat (ages 2 years and older)
Tonsil infections (ages 2 years and older)

Pros and Cons for Zithromax

Pros

Taken by mouth once daily
Treatment typically lasts only 3 to 5 days
Comes as a liquid; good option for people who've trouble swallowing tablets
Available as a lower-cost generic

Cons

Might not be the best choice for people with severe liver problems or certain heart problems
Can cause stomach-related side effects, like diarrhea and stomach pain
Some bugs might be resistant to azithromycin (Zithromax)

Common Side Effects for Zithromax

Adults

Diarrhea (4-5%)
Nausea (3%)
Stomach pain (2-3%)

Children

Diarrhea (2-6%)
Vomiting (1-6%)
Stomach pain (1-3%)

Warnings for Zithromax

Severe allergic and skin reactions
Liver damage
Heart rhythm problems (QT prolongation)
Possible higher risk of death from heart problems
Diarrhea from Clostridioides difficile infection
Worsening of certain muscle problems (myasthenia gravis)
Doesn't treat syphilis

Summary for Bactrim

Prescription only

Sulfamethoxazole/trimethoprim (sometimes known as SMZ/TMP) is a combination medication containing an antifolate and sulfa antibiotic. It's used to treat different types of infections, such as urinary tract infections (UTIs), ear infections, and lung infections. This antibiotic has two different brand names, Bactrim and Septra, and it's also available as a lower-cost generic. It's a tablet that's taken by mouth, typically twice daily for most types of infections. This antibiotic also comes as a suspension under the brand name Sulfatrim for people who can't swallow tablets and as an injection for people in the hospital. Common side effects include nausea, diarrhea, and rash.

Indications for Bactrim

Urinary tract infection (UTI)
Lower respiratory tract infection (e.g., Pneumocystis pneumonia, infections related to bronchitis)
Diarrhea caused by Shigella (shigellosis)
Travelers' diarrhea - tablet or liquid only
Ear infections - tablet or liquid only

Pros and Cons for Bactrim

Pros

Treats many types of bacterial infections
Can be given to children as young as 2 months old to treat certain infections
Available as a lower-cost generic

Cons

Can upset your stomach and make your skin more sensitive to the sun
Not the best choice for people with liver or kidney problems
Not recommended if you're pregnant
Can't take if you have a sulfa allergy

Common Side Effects for Bactrim

Nausea
Vomiting
Diarrhea
Loss of appetite
Rash
Hives
Skin sensitivity to sun or light

Warnings for Bactrim

Not for use during pregnancy
Severe allergic reactions and skin reactions
Low platelet counts and risk for bleeding
Diarrhea from Clostridioides difficile infection
Low sodium levels and high potassium levels
Blood cell-related problems
Problems with processing phenylalanine - for people with phenylketonuria (PKU) only