Azithromycin (Zithromax, Z-Pak): Uses, Dosage, Side Effects and Cost in Canada

Azithromycin is a prescription antibiotic used to treat certain bacterial infections, including some cases of pneumonia, strep throat, skin infections, ear infections in children and sexually transmitted infections such as chlamydia. Zithromax is the original brand, often dispensed as the 6-tablet Z-Pak, and generic azithromycin tablets and liquid are widely available in Canada.

For many infections, azithromycin is not the first choice. For example, penicillin is the usual first treatment for strep throat. Antibiotics should be used only when a bacterial infection is proven or strongly suspected, because unnecessary use does not help and leads to resistant bacteria.

Whether you need an antibiotic depends on your symptoms and sometimes on test results. BC residents can speak with a BC-licensed doctor by phone through Avee Health about their symptoms and whether testing or a prescription is needed.

In Canada, azithromycin by mouth is authorized for mild to moderate infections caused by susceptible bacteria, including:

• Strep throat and tonsillitis, in people who cannot use first-choice treatment
• Community-acquired pneumonia that can be treated at home with tablets
• Bacterial flare-ups of chronic obstructive pulmonary disease (COPD)
• Uncomplicated skin infections
• Infections of the urethra or cervix caused by chlamydia or gonorrhea, and chancroid in men
• Middle ear infections in children 6 months and older

It is also used to prevent a serious infection called MAC in people with advanced HIV. People with pneumonia who are moderately or severely ill, or need hospital care, should not be treated with azithromycin tablets alone.

Azithromycin belongs to the macrolide group of antibiotics. It attaches to the part of the bacterial cell that builds proteins (the ribosome) and stops it from working, so the bacteria cannot grow and multiply. It does not work against viruses.

After it is absorbed, azithromycin moves quickly from the blood into body tissues, where levels can reach up to 50 times the highest level in the blood. It is released slowly, with an average half-life of about 68 hours, which allows once-daily dosing and short courses.

Some bacteria are resistant to azithromycin. When possible, prescribers use test results to confirm that it will work.

Take azithromycin exactly as your prescriber directs. The dose and number of days depend on the infection. The Canadian Zithromax product monograph gives these usual adult tablet doses:

• Mild pneumonia, uncomplicated skin infections and strep throat (when first-choice treatment cannot be used): 500 mg on day 1, then 250 mg once a day on days 2 to 5. This is the 6-tablet Z-Pak.
• Flare-ups of COPD caused by bacteria (age 16 and older): 500 mg once a day for 3 days, or the 5-day schedule above
• Chlamydia infection of the urethra or cervix: a single 1000 mg dose

Treatment of sexually transmitted infections depends on testing and current Canadian guidelines, so your prescriber may choose a different medicine or combination. Children receive a liquid form dosed by body weight, set by the prescriber.

Tablets can be taken with or without food. Do not take aluminum or magnesium antacids at the same time as azithromycin. Finish the full course even if you feel better. Because azithromycin stays in the body for a long time, a short course keeps working for several days after the last dose.

Missed dose: do not double the next dose. If you are not sure what to do, ask your pharmacist.