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 | Lbs. | Day 1–5 |
|---|
| 8 | 18 | 2.5 mL; (½ tsp) | 12.5 mL | 500 mg |
| 17 | 37 | 5 mL; (1 tsp) | 25 mL | 1000 mg |
| 25 | 55 | 7.5 mL; (1½ tsp) | 37.5 mL | 1500 mg |
| 33 | 73 | 10 mL; (2 tsp) | 50 mL | 2000 mg |
| 40 | 88 | 12.5 mL; (2½ tsp) | 62.5 mL | 2500 mg |
Constituting instructions for AZITHROMYCIN Oral Suspension 300, 600, 900, 1200 mg bottles. The table below indicates the volume of water to be used for constitution:
| Amount of water to be added | Total volume after constitution (azithromycin content) | Azithromycin concentration after constitution |
|---|
| Shake well before each use. Oversized bottle provides shake space. Keep tightly closed. |
| 9 mL (300 mg) | 15 mL (300 mg) | 100 mg/5 mL |
| 9 mL (600 mg) | 15 mL (600 mg) | 200 mg/5 mL |
| 12 mL (900 mg) | 22.5 mL (900 mg) | 200 mg/5 mL |
| 15 mL (1200 mg) | 30 mL (1200 mg) | 200 mg/5 mL |
After mixing, store suspension at 5° to 30°C (41° to 86°F) and use within 10 days. Discard after full dosing is completed.
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 2–5, 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 1–5, 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 5000 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 1–5%. 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 500–1500 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 4700 pediatric patients, no patients discontinued therapy because of treatment-related laboratory abnormalities.
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 (1000 mg) alone or in combination with oral azithromycin (500 mg, 1000 mg, and 1500 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, 1000 mg and 1500 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 µg/mL to 7% at 2 µg/mL.
The antibacterial activity of azithromycin is pH related and appears ro 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 µg/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 hours. 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
Renal Insufficiency
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 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).
Hepatic Insufficiency
The pharmacokinetics of azithromycin in subjects with hepatic impairment has not been established.
Gender
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 1–5 years and 5–15 years, respectively). The mean pharmacokinetic parameters on day 5 were Cmax=0.216 µg/mL, Tmax=1.9 hours, and AUC0–24=1.822 µg∙hr/mL for the 1- to 5-year-old group and were Cmax=0.383 µg/mL, Tmax=2.4 hours, and AUC0–24=3.109 µg∙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 hour 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 (µg/mL) | 0.5 (0.4) |
| Tmax (hr) | 2.2 (0.8) |
| AUC0–24(µg∙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 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 6–8 | 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 16–18 | 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 8–11 | 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 | 1200 mg/day orally on days 8–21 | 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 - 90% Confidence interval not reported | 0.95 |
| Fluconazole | 200 mg orally single dose | 1200 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 | 1200 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 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 8–11 | 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 7–10 | 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 | 1200 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 for14 days | 5 | 1.12 (0.42 to 3.02) | 0.94 (0.52 to 1.70) |
| Zidovudine | 500 mg/day orally for 21 days | 1200 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 - 90% Confidence interval not reported |
| 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) |
Cross Resistance
Azithromycin demonstrates cross resistance with erythromycin resistant Gram positive isolates.
Azithromycin has been shown to be active against most isolates of the following bacteria, both in vitro and in clinical [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. Azithromycin exhibits in vitro minimal inhibitory concentrations (MICs) of 4.0 mcg/ml or less against most (≥ 90%) isolates of the following bacteria; however, the safety and effectiveness of azithromycin in treating clinical infections due to these bacteria have not been established in adequate and well-controlled 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 Methods
When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility test results for antibacterial drugs used in resident hospitals to the physician as periodic reports that describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting an antibacterial drug product for treatment.
Dilution Techniques
Quantitative methods are used to determine minimal inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antibacterial compounds. The MICs should be determined using a standardized test method 1,2,3 (broth or agar). The MIC values should be interpreted according to criteria provided in Table 1.
Diffusion Techniques
Quantitative methods that require measurement of zone diameters can also provide reproducible estimates of the susceptibility of bacteria to antibacterial compounds. The zone size provides an estimate of the susceptibility of bacteria to antibacterial compounds. The zone size should be determined using a standardized method2,3. This procedure uses paper disk impregnated with 15 mcg azithromycin to test the susceptibility of bacteria to azithromycin. The disk diffusion interpretive criteria are provided in Table 1.
| Table 1: Susceptibility Test Interpretive Criteria for Azithromycin Clarithromycin is used for susceptibility testing due to its better solubility |
|---|
| Pathogen | Minimum Inhibitory Concentrations (mcg/mL) | Disk Diffusion (zone diameter in mm) |
|---|
| S | I | R | S | I | R |
|---|
| Haemophilus influenzae Insufficient information is available to determine Intermediate or Resistant interpretive criteria | ≤4 | - | - | ≥12 | | |
| Staphylococcus aureus | ≤2 | 4 | ≥8 | ≥18 | 14–17 | ≤13 |
| Streptococci including S. pneumoniae | ≤0.5 | 1 | ≥2 | ≥18 | 14–17 | ≤13 |
The ability to correlate MIC values and plasma drug levels is difficult as azithromycin concentrates in macrophages and tissues. [see Clinical Pharmacology (12)]
A report of "Susceptible" indicates that the pathogen is likely to inhibit growth of the pathogen if the antibacterial compound reaches the concentration at the infection site necessary to inhibit growth of the pathogen. A report of "Intermediate" indicates that the result should be considered equivocal, and if the microorganism is not fully susceptible to alternative clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug is physiologically concentrated. This category also provides a buffer zone that prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of "Resistant" indicates that the antibacterial is not likely to inhibit growth of the pathogen if the antibacterial compound reaches the concentrations usually achievable at the infection site; other therapy should be selected.
Quality Control
Standardized susceptibility test procedures require the use of laboratory controls to monitor and ensure the accuracy and precision of supplies and reagents used in the assay, and the techniques of the individuals performing the test 1,2,3. Standard azithromycin powder should provide the following range of MIC values provided in Table 2. For the diffusion technique using the 15-mcg azithromycin disk the criteria provided in Table 2 should be achieved.
Table 2: Acceptable Quality Control Ranges for Susceptibility Testing| Quality Control Organism | Minimum Inhibitory Concentrations (mcg/mL) | Disk Diffusion (zone diameters in mm) |
|---|
Staphylococcus aureus ATCCATCC = American Type Culture Collection 25923 | Not Applicable | 21–26 |
Staphylococcus aureus ATCC 29213 | 0.5–2 | Not Applicable |
Haemophilus Influenzae ATCC 49247 | 1.0–4.0 | 13–21 |
| Streptococcus pneumoniae ATCC 49619 | 0.06–0.25 | 19–25 |
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– 24. For the 304 patients analyzed in the modified intent-to-treat analysis at the Days 21–24 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 21–24 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 | Day28 |
|---|
| 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 2–5).
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 2–5) 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 2–5).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 24–28 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 12–16) and Test of Cure (Days 28–32). 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 24–28, the clinical success rate (cure) was 85%.
| Presumed Bacteriologic Eradication |
|---|
| Day 10 | Days 24–28 |
|---|
| 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%) |