Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
In clinical trials, most of the reported side effects were mild to moderate in severity and were reversible upon discontinuation of the drug. Potentially serious adverse reactions of angioedema and cholestatic jaundice were reported. Approximately 0.7% of the patients (adults and pediatric patients) from the 5-day multiple-dose clinical trials discontinued azithromycin therapy because of treatment-related adverse reactions. In adults given 500 mg/day for 3 days, the discontinuation rate due to treatment-related adverse reactions was 0.6%. In clinical trials in pediatric patients given 30 mg/kg, either as a single dose or over 3 days, discontinuation from the trials due to treatment-related adverse reactions was approximately 1%. Most of the adverse reactions leading to discontinuation were related to the gastrointestinal tract, e.g., nausea, vomiting, diarrhea, or abdominal pain [see Clinical Studies (14.2)].
Adults
Multiple-dose regimens
Overall, the most common treatment-related adverse reactions in adult patients receiving multiple-dose regimens of azithromycin were related to the gastrointestinal system with diarrhea/loose stools (4 to 5%), nausea (3%), and abdominal pain (2 to 3%) being the most frequently reported.
No other adverse reactions occurred in patients on the multiple-dose regimens of azithromycin with a frequency greater than 1%. Adverse reactions that occurred with a frequency of 1% or less included the following:
Cardiovascular
Palpitations, chest pain.
Gastrointestinal
Dyspepsia, flatulence, vomiting, melena, and cholestatic jaundice.
Genitourinary
Monilia, vaginitis, and nephritis.
Nervous System
Dizziness, headache, vertigo, and somnolence.
General
Fatigue.
Allergic
Rash, pruritus, photosensitivity, and angioedema.
Single 1-gram dose regimen
Overall, the most common adverse reactions in patients receiving a single-dose regimen of 1 gram of azithromycin were related to the gastrointestinal system and were more frequently reported than in patients receiving the multiple-dose regimen.
Adverse reactions that occurred in patients on the single 1-gram dosing regimen of azithromycin with a frequency of 1% or greater included diarrhea/loose stools (7%), nausea (5%), abdominal pain (5%), vomiting (2%), dyspepsia (1%), and vaginitis (1%).
Single 2-gram dose regimen
Overall, the most common adverse reactions in patients receiving a single 2-gram dose of azithromycin were related to the gastrointestinal system. Adverse reactions that occurred in patients in this study with a frequency of 1% or greater included nausea (18%), diarrhea/loose stools (14%), vomiting (7%), abdominal pain (7%), vaginitis (2%), dyspepsia (1%), and dizziness (1%). The majority of these complaints were mild in nature.
Pediatric Patients
Single and Multiple-dose regimens: The types of adverse reactions in pediatric patients were comparable to those seen in adults, with different incidence rates for the dosage regimens recommended in pediatric patients.
Acute Otitis Media
For the recommended total dosage regimen of 30 mg/kg, the most frequent adverse reactions (≥1%) attributed to treatment were diarrhea, abdominal pain, vomiting, nausea, and rash [see Dosage and Administration (2) and Clinical Studies (14.2)].
The incidence, based on dosing regimen, is described in the table below:
| Dosage Regimen | Diarrhea % | Abdominal Pain % | Vomiting % | Nausea % | Rash % |
| 1-day | 4.3 % | 1.4 % | 4.9 % | 1.0 % | 1.0 % |
| 3-day | 2.6 % | 1.7 % | 2.3 % | 0.4 % | 0.6 % |
| 5-day | 1.8 % | 1.2 % | 1.1 % | 0.5 % | 0.4 % |
Community-Acquired Pneumonia
For the recommended dosage regimen of 10 mg/kg on Day 1 followed by 5 mg/kg on Days 2 to 5, the most frequent adverse reactions attributed to treatment were diarrhea/loose stools, abdominal pain, vomiting, nausea, and rash.
The incidence is described in the table below:
| Dosage Regimen | Diarrhea/Loose stools % | Abdominal Pain % | Vomiting % | Nausea % | Rash % |
| 5-day | 5.8 % | 1.9 % | 1.9 % | 1.9 % | 1.6 % |
Pharyngitis/Tonsillitis
For the recommended dosage regimen of 12 mg/kg on Days 1 to 5, the most frequent adverse reactions attributed to treatment were diarrhea, vomiting, abdominal pain, nausea, and headache.
The incidence is described in the table below:
| Dosage Regimen | Diarrhea % | Abdominal Pain % | Vomiting % | Nausea % | Rash % | Headache % |
| 5-day | 5.4 % | 3.4 % | 5.6 % | 1.8 % | 0.7 % | 1.1 % |
With any of the treatment regimens, no other adverse reactions occurred in pediatric patients treated with azithromycin with a frequency greater than 1%. Adverse reactions that occurred with a frequency of 1% or less included the following:
Cardiovascular
Chest pain.
Gastrointestinal
Dyspepsia, constipation, anorexia, enteritis, flatulence, gastritis, jaundice, loose stools, and oral moniliasis.
Hematologic and Lymphatic
Anemia and leukopenia.
Nervous System
Headache (otitis media dosage), hyperkinesia, dizziness, agitation, nervousness, and insomnia.
General
Fever, face edema, fatigue, fungal infection, malaise, and pain.
Allergic
Rash and allergic reaction.
Respiratory
Cough, pharyngitis, pleural effusion, and rhinitis.
Skin and Appendages
Eczema, fungal dermatitis, pruritus, sweating, urticaria, and vesiculobullous rash.
Special Senses
Conjunctivitis.