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Reference calculator for pediatric azithromycin (Z-Pack) dosing
| Indication | Day 1 | Days 2-5 | Duration |
|---|---|---|---|
| Otitis Media | 10 mg/kg (max 500mg) | 5 mg/kg (max 250mg) | 5 days |
| Strep Pharyngitis | 12 mg/kg (max 500mg) | 12 mg/kg (max 250mg) | 5 days |
| Sinusitis | 10 mg/kg (max 500mg) | 5 mg/kg (max 250mg) | 5 days |
| CAP Pneumonia | 10 mg/kg (max 500mg) | 5 mg/kg (max 250mg) | 5 days |
| Pertussis | 10 mg/kg (max 500mg) | 5 mg/kg (max 250mg) | 5 days |
| Single-Dose Option | 30 mg/kg (max 1500mg) | - | 1 day |
While best absorbed on an empty stomach, if your child has significant stomach upset, giving azithromycin with a small amount of food is acceptable and may help reduce nausea.
The higher 'loading dose' on day 1 helps azithromycin quickly reach effective levels in your child's tissues. Because azithromycin has a long half-life (68 hours) and concentrates in tissues, the loading dose followed by smaller maintenance doses maintains therapeutic levels throughout the treatment course.
For best absorption, azithromycin suspension should be taken on an empty stomach (1 hour before or 2 hours after meals). However, tablets can be taken with food. If your child experiences stomach upset with the liquid, taking it with a light snack is acceptable—absorption is reduced but still adequate.
Azithromycin has a very long half-life and continues working in tissues for 5-7 days after you stop taking it. This means the '5-day' course actually provides about 10 days of antimicrobial activity. This is why it's called a 'Z-Pack' - the short course is equally effective.
If vomiting occurs within 30 minutes of taking the dose, give another full dose. If it's been longer than 30 minutes, most medication was likely absorbed—don't re-dose. If vomiting is persistent, contact your doctor as they may need to consider alternative antibiotics.
Yes! Azithromycin (a macrolide antibiotic) is chemically unrelated to penicillins and is commonly used as an alternative for children with penicillin or amoxicillin allergies. There is no cross-reactivity between these antibiotic classes.
Amoxicillin remains first-line for strep because: (1) it's more effective at eradicating Group A Strep, (2) resistance to azithromycin is increasing (up to 15% in some areas), and (3) azithromycin failures have been reported. However, it's a good alternative when penicillin allergy exists.
Probiotics may help reduce antibiotic-associated diarrhea. If using them, give the probiotic 2-3 hours apart from the azithromycin dose. Lactobacillus and Saccharomyces strains have shown benefit. Continue probiotics for a few days after completing the antibiotic.