Clinical Trials Experience in Adults
Multiple-dose regimens: Overall, the most common treatment-related adverse reactions in adult patients receiving multiple-dose regimens of ZITHROMAX 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 ZITHROMAX 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 ZITHROMAX 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 ZITHROMAX 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 ZITHROMAX 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.
Clinical Trials Experience in 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 table 8 below:
| Table 8. Incidence of Adverse Reactions in Pediatric Patients Treated for Acute Otitis Media |
|---|
| 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 table 9 below:
| Table 9. Incidence of Adverse Reactions in Pediatric Patients Treated for Community-Acquired Pneumonia |
|---|
| 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 table 10 below:
| Table 10. Incidence of Adverse Reactions in Pediatric Patients Treated for Pharyngitis/Tonsillitis |
|---|
| 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 ZITHROMAX 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.
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, 20, 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 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 ZITHROMAX and any potential adverse effects on the breastfed infant from ZITHROMAX 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 (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 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.
Elimination
Metabolism
In vitro and in vivo studies to assess the metabolism of azithromycin have not been performed.
Excretion
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 GFR 10 to 80 mL/min compared to subjects with GFR >80 mL/min. The mean Cmax and AUC0–120 increased 61% and 35%, respectively, in subjects with GFR <10 mL/min compared to subjects with 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 1–5 years and 5–15 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 table 12 shows pharmacokinetic data in the subset of pediatric patients who received a total dose of 60 mg/kg.
| Table 12. Pharmacokinetic Parameters for Pediatric Patients Receiving 12 mg/kg/day (5-day Regimen) |
|---|
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 13 and the effects of other drugs on the pharmacokinetics of azithromycin are shown in Table 14.
Co-administration of azithromycin at therapeutic doses had a modest effect on the pharmacokinetics of the drugs listed in Table 13. No dosage adjustment of drugs listed in Table 13 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 14. [see Drug Interactions (7.3)]
| Table 13. 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 11 days | 1200 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 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 | 1200 mg/day orally for 14 days | 4 | 1.31
(0.43 to 3.97) | 1.30
(0.69 to 2.43) |
| Table 14. 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 | 1200 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 | 1200 mg orally on day 9 | 14 | 2.36
(1.77 to 3.15) | 2.12
(1.80 to 2.50) |
Oral Antacids (Aluminum Hydroxide, Magnesium Hydroxide) | 1350 mg aluminum hydroxide and 1200 mg of magnesium hydroxide single dose on day 1 or day 8 | 500 mg orally on day 1 and day 8 | 10 | 0.765 | 0.984 |
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 this drug, please see: https://www.fda.gov/STIC.
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.
Clinical Cure Rates at Days 21-24 Bacteriologically Evaluable Patients by Pathogen:
| Table 15. Clinical Cure Rates at Days 21-24 in Adult Patients with AECB 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%) |
Important Administration Instructions
ZITHROMAX tablets and oral suspension can be taken with or without food.
Concomitant Administration with Aluminum and Magnesium Containing Antacids
Advise patients not to take aluminum and magnesium containing antacids and azithromycin simultaneously.
Allergic Reactions
Direct patients to discontinue azithromycin immediately and contact a physician if any signs of an allergic reaction occur [see warnings and Precautions (5.1)].
Vomiting, Irritability, Diarrhea or Rash with Feeding in Infants
Direct parents or caregivers to contact their physician if vomiting, irritability, diarrhea or rash with feeding occurs in the infant [see Warnings and Precautions (5.3) and Use in Specific Population (8.2)].
Antibacterial Resistance
Patients should be counseled that antibacterial drugs including ZITHROMAX should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When ZITHROMAX 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 ZITHROMAX or other antibacterial drugs in the future.
Diarrhea
Diarrhea is a common problem caused by antibacterials, including ZITHROMAX 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 Warnings and Precautions (5.6)].
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