PEDIATRIC DOSAGE GUIDELINES FOR OTITIS MEDIA, ACUTE BACTERIAL SINUSITIS, AND COMMUNITY-ACQUIRED PNEUMONIA
(Age 6 months and above, [see Use in Specific Populations (8.4)])
Based on Body Weight
OTITIS MEDIA AND COMMUNITY-ACQUIRED PNEUMONIA: (5-Day Regimen)| Dosing Calculated on 10 mg/kg/day Day 1 and 5 mg/kg/day Days 2 to 5. |
|---|
| Weight | 100 mg/5 mL | 200 mg/5 mL | Total mL per Treatment Course | Total mg per Treatment Course |
|---|
| Kg | Day 1 | Days 2 to 5 | Day 1 | Days 2 to 5 |
|---|
5 | 2.5 mL; (½ tsp) | 1.25mL; (¼ tsp) | | | 7.5 mL | 150 mg |
10 | 5 mL; (1 tsp) | 2.5 mL; (½ tsp) | | | 15 mL | 300 mg |
20 | | | 5 mL; (1 tsp) | 2.5 mL; (½ tsp) | 15 mL | 600 mg |
30 | | | 7.5 mL; (1½ tsp) | 3.75 mL; (¾ tsp) | 22.5 mL | 900 mg |
40 | | | 10 mL; (2 tsp) | 5 mL; (1 tsp) | 30 mL | 1,200 mg |
50 and above | | | 12.5 mL; (2½ tsp) | 6.25 mL; (1¼ tsp) | 37.5 mL | 1,500 mg |
OTITIS MEDIA AND ACUTE BACTERIAL SINUSITIS: (3-Day Regimen)| Dosing Calculated on 10 mg/kg/day. |
|---|
| Weight | 100 mg/5 mL | 200 mg/5 mL | Total mL per Treatment Course | Total mg per Treatment Course |
|---|
| Kg | Days 1 to 3 | Days 1 to 3 |
|---|
5 | 2.5 mL; (½ tsp) | | 7.5 mL | 150 mg |
10 | 5 mL; (1 tsp) | | 15 mL | 300 mg |
20 | | 5 mL; (1 tsp) | 15 mL | 600 mg |
30 | | 7.5 mL; (1½ tsp) | 22.5 mL | 900 mg |
40 | | 10 mL; (2 tsp) | 30 mL | 1,200 mg |
50 and above | | 12.5 mL; (2½ tsp) | 37.5 mL | 1,500 mg |
OTITIS MEDIA: (1-Day Regimen)| Dosing Calculated on 30 mg/kg as a single dose. |
|---|
| Weight | 200 mg/5 mL | Total mL per Treatment Course | Total mg per Treatment Course |
|---|
| Kg | 1-Day Regimen |
|---|
5 | 3.75 mL; (3/4 tsp) | 3.75 mL | 150 mg |
10 | 7.5 mL; (1½ tsp) | 7.5 mL | 300 mg |
20 | 15 mL; (3 tsp) | 15 mL | 600 mg |
30 | 22.5 mL; (4½ tsp) | 22.5 mL | 900 mg |
40 | 30 mL; (6 tsp) | 30 mL | 1,200 mg |
50 and above | 37.5 mL; (7½ tsp) | 37.5 mL | 1,500 mg |
The safety of re-dosing azithromycin in pediatric patients who vomit after receiving 30 mg/kg as a single dose has not been established. In clinical studies involving 487 patients with acute otitis media given a single 30 mg/kg dose of azithromycin, 8 patients who vomited within 30 minutes of dosing were re-dosed at the same total dose.
Pharyngitis/Tonsillitis: The recommended dose of azithromycin for children with pharyngitis/tonsillitis is 12 mg/kg once daily for 5 days. (See chart below.)
PEDIATRIC DOSAGE GUIDELINES FOR PHARYNGITIS/TONSILLITIS
(Age 2 years and above, [see Use in Specific Populations (8.4)])
Based on Body Weight
PHARYNGITIS/TONSILLITIS: (5-Day Regimen)| Dosing Calculated on 12 mg/kg/day for 5 days. |
|---|
| Weight | 200 mg/5 mL | Total mL per Treatment Course | Total mg per Treatment Course |
|---|
| Kg | Days 1 to 5 |
|---|
8 | 2.5 mL; (½ tsp) | 12.5 mL | 500 mg |
17 | 5 mL; (1 tsp) | 25 mL | 1,000 mg |
25 | 7.5 mL; (1½ tsp) | 37.5 mL | 1,500 mg |
33 | 10 mL; (2 tsp) | 50 mL | 2,000 mg |
40 | 12.5 mL; (2½ tsp) | 62.5 mL | 2,500 mg |
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.
Adults:
Clinically significant abnormalities (irrespective of drug relationship) occurring during the clinical trials were reported as follows: with an incidence of greater than 1%: decreased hemoglobin, hematocrit, lymphocytes, neutrophils, and blood glucose; elevated serum creatine phosphokinase, potassium, ALT, GGT, AST, BUN, creatinine, blood glucose, platelet count, lymphocytes, neutrophils, and eosinophils; with an incidence of less than 1%: leukopenia, neutropenia, decreased sodium, potassium, platelet count, elevated monocytes, basophils, bicarbonate, serum alkaline phosphatase, bilirubin, LDH, and phosphate. The majority of subjects with elevated serum creatinine also had abnormal values at baseline. When follow-up was provided, changes in laboratory tests appeared to be reversible.
In multiple-dose clinical trials involving more than 5,000 patients, four patients discontinued therapy because of treatment-related liver enzyme abnormalities and one because of a renal function abnormality.
Pediatric Patients:
One, Three, and Five Day Regimens
Laboratory data collected from comparative clinical trials employing two 3-day regimens (30 mg/kg or 60 mg/kg in divided doses over 3 days), or two 5-day regimens (30 mg/kg or 60 mg/kg in divided doses over 5 days) were similar for regimens of azithromycin and all comparators combined, with most clinically significant laboratory abnormalities occurring at incidences of 1% to 5%. Laboratory data for patients receiving 30 mg/kg as a single dose were collected in one single center trial. In that trial, an absolute neutrophil count between 500 cells/mm3 to 1,500 cells/mm3 was observed in 10/64 patients receiving 30 mg/kg as a single dose, 9/62 patients receiving 30 mg/kg given over 3 days, and 8/63 comparator patients. No patient had an absolute neutrophil count < 500 cells/mm3.
In multiple-dose clinical trials involving approximately 4,700 pediatric patients, no patients discontinued therapy because of treatment-related laboratory abnormalities.
Risk Summary
Available data from published literature and postmarketing experience over several decades with azithromycin use in pregnant women have not identified any drug-associated risks for major birth defects, miscarriage, or adverse maternal or fetal outcomes (see Data). Developmental toxicity studies with azithromycin in rats, mice, and rabbits showed no drug-induced fetal malformations at doses up to 4, 2, and 2 times, respectively, an adult human daily dose of 500 mg based on body surface area. Decreased viability and delayed development were observed in the offspring of pregnant rats administered azithromycin from day 6 of pregnancy through weaning at a dose equivalent to 4 times an adult human daily dose of 500 mg based on body surface area (see Data).
The estimated background risk of major birth defects and miscarriage for the indicated populations is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.
Data
Human Data
Available data from published observational studies, case series, and case reports over several decades do not suggest an increased risk for major birth defects, miscarriage, or adverse maternal or fetal outcomes with azithromycin use in pregnant women. Limitations of these data include the lack of randomization and inability to control for confounders such as underlying maternal disease and maternal use of concomitant medications.
Animal Data
Azithromycin administered during the period of organogenesis did not cause fetal malformations in rats and mice at oral doses up to 200 mg/kg/day (moderately maternally toxic). Based on body surface area, this dose is approximately 4 (rats) and 2 (mice) times an adult human daily dose of 500 mg. In rabbits administered azithromycin at oral doses of 10 mg/kg/day, 20 mg/kg/day, and 40 mg/kg/day during organogenesis, reduced maternal body weight and food consumption were observed in all groups; no evidence of fetotoxicity or teratogenicity was observed at these doses, the highest of which is estimated to be 2 times an adult human daily dose of 500 mg based on body surface area.
In a pre- and postnatal development study, azithromycin was administered orally to pregnant rats from day 6 of pregnancy until weaning at doses of 50 mg/kg/day or 200 mg/kg/day. Maternal toxicity (reduced food consumption and body weight gain; increased stress at parturition) was observed at the higher dose. Effects in the offspring were noted at 200 mg/kg/day during the postnatal development period (decreased viability, delayed developmental landmarks). These effects were not observed in a pre- and postnatal rat study when up to 200 mg/kg/day of azithromycin was given orally beginning on day 15 of pregnancy until weaning.
Risk Summary
Azithromycin is present in human milk (see Data). Non-serious adverse reactions have been reported in breastfed infants after maternal administration of azithromycin (see Clinical Considerations). There are no available data on the effects of azithromycin on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for azithromycin and any potential adverse effects on the breastfed infant from azithromycin or from the underlying maternal condition.
Clinical Considerations
Advise women to monitor the breastfed infant for diarrhea, vomiting, or rash.
Data
Azithromycin breastmilk concentrations were measured in 20 women after receiving a single 2 g oral dose of azithromycin during labor. Breastmilk samples collected on days 3 and 6 postpartum as well as 2 and 4 weeks postpartum revealed the presence of azithromycin in breastmilk up to 4 weeks after dosing. In another study, a single dose of azithromycin 500 mg was administered intravenously to 8 women prior to incision for cesarean section. Breastmilk (colostrum) samples obtained between 12 and 48 hours after dosing revealed that azithromycin persisted in breastmilk up to 48 hours.
Pharyngitis/Tonsillitis: Safety and effectiveness in the treatment of pediatric patients with pharyngitis/tonsillitis under 2 years of age have not been established.
Cardiac Electrophysiology
QTc interval prolongation was studied in a randomized, placebo-controlled parallel trial in 116 healthy subjects who received either chloroquine (1,000 mg) alone or in combination with oral azithromycin (500 mg, 1,000 mg, and 1,500 mg once daily). Co-administration of azithromycin increased the QTc interval in a dose- and concentration- dependent manner. In comparison to chloroquine alone, the maximum mean (95% upper confidence bound) increases in QTcF were 5 (10) ms, 7 (12) ms and 9 (14) ms with the co-administration of 500 mg, 1,000 mg and 1,500 mg azithromycin, respectively.
Absorption
The absolute bioavailability of azithromycin 250 mg capsules is 38%.
In a two-way crossover study in which 12 healthy subjects received a single 500 mg dose of azithromycin (two 250 mg tablets) with or without a high fat meal, food was shown to increase Cmax by 23% but had no effect on AUC.
When azithromycin oral suspension was administered with food to 28 adult healthy male subjects, Cmax increased by 56% and AUC was unchanged.
Distribution
The serum protein binding of azithromycin is variable in the concentration range approximating human exposure, decreasing from 51% at 0.02 mcg/mL to 7% at 2 mcg/mL.
The antibacterial activity of azithromycin is pH related and appears to be reduced with decreasing pH. However, the extensive distribution of drug to tissues may be relevant to clinical activity.
Azithromycin has been shown to penetrate into human tissues, including skin, lung, tonsil, and cervix. Extensive tissue distribution was confirmed by examination of additional tissues and fluids (bone, ejaculum, prostate, ovary, uterus, salpinx, stomach, liver, and gallbladder). As there are no data from adequate and well-controlled studies of azithromycin treatment of infections in these additional body sites, the clinical significance of these tissue concentration data is unknown.
Following a regimen of 500 mg on the first day and 250 mg daily for 4 days, very low concentrations were noted in cerebrospinal fluid (less than 0.01 mcg/mL) in the presence of noninflamed meninges.
Metabolism
In vitro and in vivo studies to assess the metabolism of azithromycin have not been performed.
Elimination
Plasma concentrations of azithromycin following single 500 mg oral and IV doses declined in a polyphasic pattern resulting in a mean apparent plasma clearance of 630 mL/min and terminal elimination half-life of 68 hr. The prolonged terminal half-life is thought to be due to extensive uptake and subsequent release of drug from tissues. Biliary excretion of azithromycin, predominantly as unchanged drug, is a major route of elimination. Over the course of a week, approximately 6% of the administered dose appears as unchanged drug in urine.
Specific Populations
Patients with Renal Impairment
Azithromycin pharmacokinetics was investigated in 42 adults (21 to 85 years of age) with varying degrees of renal impairment. Following the oral administration of a single 1.0 g dose of azithromycin (4 × 250 mg capsules), mean Cmax and AUC0-120 increased by 5.1% and 4.2%, respectively, in subjects with mild to moderate renal impairment (GFR 10 mL/min to 80 mL/min) compared to subjects with normal renal function (GFR > 80 mL/min). The mean Cmax and AUC0-120 increased 61% and 35%, respectively, in subjects with severe renal impairment (GFR < 10 mL/min) compared to subjects with normal renal function (GFR > 80 mL/min).
Patients with Hepatic Impairment
The pharmacokinetics of azithromycin in subjects with hepatic impairment has not been established.
Male and Female Patients
There are no significant differences in the disposition of azithromycin between male and female subjects. No dosage adjustment is recommended based on gender.
Geriatric Patients
Pharmacokinetic parameters in older volunteers (65 to 85 years old) were similar to those in young adults (18 to 40 years old) for the 5-day therapeutic regimen. Dosage adjustment does not appear to be necessary for older patients with normal renal and hepatic function receiving treatment with this dosage regimen. [see Geriatric Use (8.5)]
Pediatric Patients
In two clinical studies, azithromycin for oral suspension was dosed at 10 mg/kg on day 1, followed by 5 mg/kg on days 2 through 5 in two groups of pediatric patients (aged 1 to 5 years and 5 to 15 years, respectively). The mean pharmacokinetic parameters on day 5 were Cmax = 0.216 mcg/mL, Tmax = 1.9 hr, and AUC0-24 = 1.822 mcg∙hr/mL for the 1- to 5-year-old group and were Cmax = 0.383 mcg/mL, Tmax = 2.4 hr, and AUC0-24 = 3.109 mcg∙hr/mL for the 5- to 15-year-old group.
In another study, 33 pediatric patients received doses of 12 mg/kg/day (maximum daily dose 500 mg) for 5 days, of whom 31 patients were evaluated for azithromycin pharmacokinetics following a low fat breakfast. In this study, azithromycin concentrations were determined over a 24 hr period following the last daily dose. Patients weighing above 41.7 kg received the maximum adult daily dose of 500 mg. Seventeen patients (weighing 41.7 kg or less) received a total dose of 60 mg/kg. The following table shows pharmacokinetic data in the subset of pediatric patients who received a total dose of 60 mg/kg.
Pharmacokinetic Parameter [mean (SD)] | 5-Day Regimen (12 mg/kg for 5 days ) |
|---|
| N | 17 |
|---|
Cmax (mcg/mL) | 0.5 (0.4) |
Tmax (hr) | 2.2 (0.8) |
AUC0–24 (mcg∙hr/mL) | 3.9 (1.9) |
Single dose pharmacokinetics of azithromycin in pediatric patients given doses of 30 mg/kg have not been studied. [see Dosage and Administration (2)]
Drug Interaction Studies
Drug interaction studies were performed with azithromycin and other drugs likely to be co-administered. The effects of co-administration of azithromycin on the pharmacokinetics of other drugs are shown in Table 1 and the effects of other drugs on the pharmacokinetics of azithromycin are shown in Table 2.
Co-administration of azithromycin at therapeutic doses had a modest effect on the pharmacokinetics of the drugs listed in Table 1. No dosage adjustment of drugs listed in Table 1 is recommended when co-administered with azithromycin.
Co-administration of azithromycin with efavirenz or fluconazole had a modest effect on the pharmacokinetics of azithromycin. Nelfinavir significantly increased the Cmax and AUC of azithromycin. No dosage adjustment of azithromycin is recommended when administered with drugs listed in Table 2. [see Drug Interactions (7.3)]
Table 1. Drug Interactions: Pharmacokinetic Parameters for Co-administered Drugs in the Presence of Azithromycin| Co-administered Drug | Dose of Co-administered Drug | Dose of Azithromycin | n | Ratio (with/without azithromycin) of Co-administered Drug Pharmacokinetic Parameters (90% CI); No Effect = 1.00 |
|---|
| Mean Cmax | Mean AUC |
|---|
Atorvastatin | 10 mg/day for 8 days | 500 mg/day orally on days 6 to 8 | 12 | 0.83 (0.63 to 1.08) | 1.01 (0.81 to 1.25) |
Carbamazepine | 200 mg/day for 2 days, then 200 mg twice a day for 18 days | 500 mg/day orally for days 16 to 18 | 7 | 0.97 (0.88 to 1.06) | 0.96 (0.88 to 1.06) |
Cetirizine | 20 mg/day for 11 days | 500 mg orally on day 7, then 250 mg/day on days 8 to 11 | 14 | 1.03 (0.93 to 1.14) | 1.02 (0.92 to 1.13) |
Didanosine | 200 mg orally twice a day for 21 days | 1,200 mg/day orally on days 8 to 21 | 6 | 1.44 (0.85 to 2.43) | 1.14 (0.83 to 1.57) |
Efavirenz | 400 mg/day for 7 days | 600 mg orally on day 7 | 14 | 1.04 | 0.95 |
Fluconazole | 200 mg orally single dose | 1,200 mg orally single dose | 18 | 1.04 (0.98 to 1.11) | 1.01 (0.97 to 1.05) |
Indinavir | 800 mg three times a day for 5 days | 1,200 mg orally on day 5 | 18 | 0.96 (0.86 to 1.08) | 0.90 (0.81 to 1.00) |
Midazolam | 15 mg orally on day 3 | 500 mg/day orally for 3 days | 12 | 1.27 (0.89 to 1.81) | 1.26 (1.01 to 1.56) |
Nelfinavir | 750 mg three times a day for 11 days | 1,200 mg orally on day 9 | 14 | 0.90 (0.81 to 1.01) | 0.85 (0.78 to 0.93) |
Sildenafil | 100 mg on days 1 and 4 | 500 mg/day orally for 3 days | 12 | 1.16 (0.86 to 1.57) | 0.92 (0.75 to 1.12) |
Theophylline | 4 mg/kg IV on days 1, 11, 25 | 500 mg orally on day 7, 250 mg/day on days 8 to 11 | 10 | 1.19 (1.02 to 1.40) | 1.02 (0.86 to 1.22) |
Theophylline | 300 mg orally twice a day for 15 days | 500 mg orally on day 6, then 250 mg/day on days 7 to 10 | 8 | 1.09 (0.92 to 1.29) | 1.08 (0.89 to 1.31) |
Triazolam | 0.125 mg on day 2 | 500 mg orally on day 1, then 250 mg/day on day 2 | 12 | 1.06 | 1.02 |
Trimethoprim/ Sulfamethoxazole | 160 mg/800 mg/day orally for 7 days | 1,200 mg orally on day 7 | 12 | 0.85 (0.75 to 0.97)/ 0.90 (0.78 to 1.03) | 0.87 (0.80 to 0.95)/ 0.96 (0.88 to 1.03) |
Zidovudine | 500 mg/day orally for 21 days | 600 mg/day orally for 14 days | 5 | 1.12 (0.42 to 3.02) | 0.94 (0.52 to 1.70) |
Zidovudine | 500 mg/day orally for 21 days | 1,200 mg/day orally for 14 days | 4 | 1.31 (0.43 to 3.97) | 1.30 (0.69 to 2.43) |
Table 2. Drug Interactions: Pharmacokinetic Parameters for Azithromycin in the Presence of Co-administered Drugs. [see Drug Interactions (7)]| Co-administered Drug | Dose of Co-administered Drug | Dose of Azithromycin | n | Ratio (with/without co-administered drug) of Azithromycin Pharmacokinetic Parameters (90% CI); No Effect = 1.00 |
|---|
| Mean Cmax | Mean AUC |
|---|
Efavirenz | 400 mg/day for 7 days | 600 mg orally on day 7 | 14 | 1.22 (1.04 to 1.42) | 0.92 |
Fluconazole | 200 mg orally single dose | 1,200 mg orally single dose | 18 | 0.82 (0.66 to 1.02) | 1.07 (0.94 to 1.22) |
Nelfinavir | 750 mg three times a day for 11 days | 1,200 mg orally on day 9 | 14 | 2.36 (1.77 to 3.15) | 2.12 (1.80 to 2.50) |
Mechanism of Action
Azithromycin acts by binding to the 23S rRNA of the 50S ribosomal subunit of susceptible microorganisms inhibiting bacterial protein synthesis and impeding the assembly of the 50S ribosomal subunit.
Resistance
Azithromycin demonstrates cross resistance with erythromycin. The most frequently encountered mechanism of resistance to azithromycin is modification of the 23S rRNA target, most often by methylation. Ribosomal modifications can determine cross resistance to other macrolides, lincosamides, and streptogramin B (MLSB phenotype).
Antimicrobial Activity
Azithromycin has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections. [see Indications and Usage (1)]
Gram-Positive Bacteria
Staphylococcus aureus
Streptococcus agalactiae
Streptococcus pneumoniae
Streptococcus pyogenes
Gram-Negative Bacteria
Haemophilus ducreyi
Haemophilus influenzae
Moraxella catarrhalis
Neisseria gonorrhoeae
Other Bacteria
Chlamydophila pneumoniae
Chlamydia trachomatis
Mycoplasma pneumoniae
The following in vitro data are available, but their clinical significance is unknown. At least 90 percent of the following bacteria exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for azithromycin against isolates of similar genus or organism group. However, the efficacy of azithromycin in treating clinical infections caused by these bacteria has not been established in adequate and well-controlled clinical trials.
Gram-Positive Bacteria
Beta-hemolytic streptococci (Groups C, F, G)
Viridans group streptococci
Gram-Negative Bacteria
Bordetella pertussis
Legionella pneumophila
Anaerobic Bacteria
Prevotella bivia
Peptostreptococcus species
Other Bacteria
Ureaplasma urealyticum
Susceptibility Testing
For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for azithromycin tablets, please see: https://www.fda.gov/STIC.
Acute Bacterial Exacerbations of Chronic Bronchitis
In a randomized, double-blind controlled clinical trial of acute exacerbation of chronic bronchitis (AECB), azithromycin (500 mg once daily for 3 days) was compared with clarithromycin (500 mg twice daily for 10 days). The primary endpoint of this trial was the clinical cure rate at Days 21 to 24. For the 304 patients analyzed in the modified intent-to-treat analysis at the Days 21 to 24 visit, the clinical cure rate for 3 days of azithromycin was 85% (125/147) compared to 82% (129/157) for 10 days of clarithromycin.
The following outcomes were the clinical cure rates at the Days 21 to 24 visit for the bacteriologically evaluable patients by pathogen:
| Pathogen | Azithromycin (3 Days ) | Clarithromycin (10 Days ) |
|---|
S. pneumoniae | 29/32 (91%) | 21/27 (78%) |
H. influenzae | 12/14 (86%) | 14/16 (88%) |
M. catarrhalis | 11/12 (92%) | 12/15 (80%) |
Acute Bacterial Sinusitis
In a randomized, double-blind, double-dummy controlled clinical trial of acute bacterial sinusitis, azithromycin (500 mg once daily for 3 days) was compared with amoxicillin/clavulanate (500/125 mg three times a day for 10 days). Clinical response assessments were made at Day 10 and Day 28. The primary endpoint of this trial was prospectively defined as the clinical cure rate at Day 28. For the 594 patients analyzed in the modified intent to treat analysis at the Day 10 visit, the clinical cure rate for 3 days of azithromycin was 88% (268/303) compared to 85% (248/291) for 10 days of amoxicillin/clavulanate. For the 586 patients analyzed in the modified intent to treat analysis at the Day 28 visit, the clinical cure rate for 3 days of azithromycin was 71.5% (213/298) compared to 71.5% (206/288), with a 97.5% confidence interval of -8.4 to 8.3, for 10 days of amoxicillin/clavulanate.
In an open label, non-comparative study requiring baseline transantral sinus punctures, the following outcomes were the clinical success rates at the Day 7 and Day 28 visits for the modified intent to treat patients administered 500 mg of azithromycin once daily for 3 days with the following pathogens:
Clinical Success Rates of Azithromycin (500 mg per day for 3 Days)| Pathogen | Day 7 | Day 28 |
|---|
S. pneumoniae | 23/26 (88%) | 21/25 (84%) |
H. influenzae | 28/32 (87%) | 24/32 (75%) |
M. catarrhalis | 14/15 (93%) | 13/15 (87%) |
Pharyngitis/Tonsillitis
In three double-blind controlled studies, conducted in the United States, azithromycin (12 mg/kg once a day for 5 days) was compared to penicillin V (250 mg three times a day for 10 days) in the treatment of pharyngitis due to documented Group A β-hemolytic streptococci (GABHS or S. pyogenes). Azithromycin was clinically and microbiologically statistically superior to penicillin at Day 14 and Day 30 with the following clinical success (i.e., cure and improvement) and bacteriologic efficacy rates (for the combined evaluable patient with documented GABHS):
Three U.S. Streptococcal Pharyngitis Studies Azithromycin vs. Penicillin V EFFICACY RESULTS | Day 14 | Day 30 |
|---|
Bacteriologic Eradication: | | |
Azithromycin | 323/340 (95%) | 255/330 (77%) |
Penicillin V | 242/332 (73%) | 206/325 (63%) |
Clinical Success (cure plus improvement): | | |
Azithromycin | 336/343 (98%) | 310/330 (94%) |
Penicillin V | 284/338 (84%) | 241/325 (74%) |
Approximately 1% of azithromycin-susceptible S. pyogenes isolates were resistant to azithromycin following therapy.
Acute Otitis Media
Efficacy using azithromycin given over 5 days (10 mg/kg on Day 1 followed by 5 mg/kg on Days 2 to 5).
Trial 1
In a double-blind, controlled clinical study of acute otitis media performed in the United States, azithromycin (10 mg/kg on Day 1 followed by 5 mg/kg on Days 2 to 5) was compared to amoxicillin/clavulanate potassium (4:1). For the 553 patients who were evaluated for clinical efficacy, the clinical success rate (i.e., cure plus improvement) at the Day 11 visit was 88% for azithromycin and 88% for the control agent. For the 521 patients who were evaluated at the Day 30 visit, the clinical success rate was 73% for azithromycin and 71% for the control agent.
Trial 2
In a non-comparative clinical and microbiologic trial performed in the United States, where significant rates of beta-lactamase producing organisms (35%) were found, 131 patients were evaluable for clinical efficacy. The combined clinical success rate (i.e., cure and improvement) at the Day 11 visit was 84% for azithromycin. For the 122 patients who were evaluated at the Day 30 visit, the clinical success rate was 70% for azithromycin.
Microbiologic determinations were made at the pre-treatment visit. Microbiology was not reassessed at later visits. The following clinical success rates were obtained from the evaluable group:
| Pathogen | | |
|---|
| Day 11 | Day 30 |
|---|
| Azithromycin | Azithromycin |
|---|
S. pneumoniae | 61/74 (82%) | 40/56 (71%) |
H. influenzae | 43/54 (80%) | 30/47 (64%) |
M. catarrhalis | 28/35 (80%) | 19/26 (73%) |
S. pyogenes | 11/11 (100%) | 7/7 (100%) |
Overall | 177/217 (82%) | 97/137 (73%) |
Trial 3
In another controlled comparative clinical and microbiologic study of otitis media performed in the United States, azithromycin (10 mg/kg on Day 1 followed by 5 mg/kg on Days 2 to 5) was compared to amoxicillin/clavulanate potassium (4:1). This study utilized two of the same investigators as Protocol 2 (above), and these two investigators enrolled 90% of the patients in Protocol 3. For this reason, Protocol 3 was not considered to be an independent study. Significant rates of beta-lactamase producing organisms (20%) were found. Ninety-two (92) patients were evaluable for clinical and microbiologic efficacy. The combined clinical success rate (i.e., cure and improvement) of those patients with a baseline pathogen at the Day 11 visit was 88% for azithromycin vs. 100% for control; at the Day 30 visit, the clinical success rate was 82% for azithromycin vs. 80% for control.
Microbiologic determinations were made at the pre-treatment visit. Microbiology was not reassessed at later visits. At the Day 11 and Day 30 visits, the following clinical success rates were obtained from the evaluable group:
| Day 11 | Day 30 |
|---|
| Pathogen | Azithromycin | Control | Azithromycin | Control |
|---|
S. pneumoniae | 25/29 (86%) | 26/26 (100%) | 22/28 (79%) | 18/22 (82%) |
H. influenzae | 9/11 (82%) | 9/9 (100%) | 8/10 (80%) | 6/8 (75%) |
M. catarrhalis | 7/7 (100%) | 5/5 (100%) | 5/5 (100%) | 2/3 (66%) |
S. pyogenes | 2/2 (100%) | 5/5 (100%) | 2/2 (100%) | 4/4 (100%) |
Overall | 43/49 (88%) | 45/45 (100%) | 37/45 (82%) | 30/37 (81%) |
Efficacy using azithromycin given over 3 days (10 mg/kg/day).
Trial 4
In a double-blind, controlled, randomized clinical study of acute otitis media in pediatric patients from 6 months to 12 years of age, azithromycin (10 mg/kg per day for 3 days) was compared to amoxicillin/clavulanate potassium (7:1) in divided doses q12h for 10 days. Each patient received active drug and placebo matched for the comparator.
For the 366 patients who were evaluated for clinical efficacy at the Day 12 visit, the clinical success rate (i.e., cure plus improvement) was 83% for azithromycin and 88% for the control agent. For the 362 patients who were evaluated at the Days 24 to 28 visit, the clinical success rate was 74% for azithromycin and 69% for the control agent.
Efficacy using azithromycin 30 mg/kg given as a single dose
Trial 5
A double-blind, controlled, randomized trial was performed at nine clinical centers. Pediatric patients from 6 months to 12 years of age were randomized 1:1 to treatment with either azithromycin (given at 30 mg/kg as a single dose on Day 1) or amoxicillin/clavulanate potassium (7:1), divided q12h for 10 days. Each child received active drug, and placebo matched for the comparator.
Clinical response (Cure, Improvement, Failure) was evaluated at End of Therapy (Days 12 to 16) and Test of Cure (Days 28 to 32). Safety was evaluated throughout the trial for all treated subjects. For the 321 subjects who were evaluated at End of Treatment, the clinical success rate (cure plus improvement) was 87% for azithromycin, and 88% for the comparator. For the 305 subjects who were evaluated at Test of Cure, the clinical success rate was 75% for both azithromycin and the comparator.
Trial 6
In a non-comparative clinical and microbiological trial, 248 patients from 6 months to 12 years of age with documented acute otitis media were dosed with a single oral dose of azithromycin (30 mg/kg on Day 1).
For the 240 patients who were evaluable for clinical modified Intent-to-Treat (MITT) analysis, the clinical success rate (i.e., cure plus improvement) at Day 10 was 89% and for the 242 patients evaluable at Days 24 to 28, the clinical success rate (cure) was 85%.
Presumed Bacteriologic Eradication | Day 10 | Days 24 to 28 |
|---|
S. pneumoniae | 70/76 (92%) | 67/76 (88%) |
H. influenzae | 30/42 (71%) | 28/44 (64%) |
M. catarrhalis | 10/10 (100%) | 10/10 (100%) |
Overall | 110/128 (86%) | 105/130 (81%) |
General Patient Counseling
Azithromycin tablets can be taken with or without food.
Patients should also be cautioned not to take aluminum- and magnesium-containing antacids and azithromycin simultaneously.
The patient should be directed to discontinue azithromycin immediately and contact a physician if any signs of an allergic reaction occur.
Direct parents or caregivers to contact their physician if vomiting and irritability with feeding occurs in the infant.
Patients should be counseled that antibacterial drugs including azithromycin should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When azithromycin is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of the therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by azithromycin or other antibacterial drugs in the future.
Diarrhea is a common problem caused by antibacterials which usually ends when the antibacterial is discontinued. Sometimes after starting treatment with antibacterials patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibacterial drug. If this occurs, patients should contact their physician as soon as possible.
See FDA-approved Patient Labeling
Manufactured by:
CSPC Ouyi Pharmaceutical Co., Ltd.
Shijiazhuang, Hebei, China, 052160
Manufactured for:
TAGI Pharma, Inc.
South Beloit, IL 61080