2.1 Adults

Zmax should be taken as a single 2 g dose. Zmax provides a full course of antibacterial therapy in a single oral dose. It is recommended that Zmax be taken on an empty stomach (at least 1 hour before or 2 hours following a meal).

2.2 Pediatric patients

For pediatric patients 6 months and older, Zmax should be taken as a single dose of 60 mg/kg (equivalent to 27 mg/lb) body weight. The Zmax dose in mL is equivalent to the child's weight in lb (1 mL/lb dose, see Table 1 below), for a body weight of less than 75 lb (34 kg). It is recommended that Zmax be taken on an empty stomach (at least 1 hour before or 2 hours following a meal).

Pediatric patients weighing 75 lb (34 kg) or more should receive the adult dose (2 g).

2.3 Additional treatment after vomiting with Zmax

In the event that a patient vomits within 5 minutes of administration, the health care provider should consider additional antibiotic treatment since there would be minimal absorption of azithromycin. Since insufficient data exist on absorption of azithromycin if a patient vomits between 5 and 60 minutes following administration, alternative therapy should be considered. Neither a second dose of Zmax nor alternative treatment is warranted if vomiting occurs ≥60 minutes following administration, in patients with normal gastric emptying. In patients with delayed gastric emptying, alternative therapy should be considered.

2.4 Instructions for the pharmacist

Constitute with 60 mL of water and replace cap. Shake bottle well before dispensing. Do not refrigerate. Constituted suspension should be consumed within 12 hours.

For pediatric dosing in patients weighing less than 75 lb (34 kg), use of a dosing device is recommended. The pharmacist should inform the patient's caregiver that any suspension remaining after dosing MUST be discarded.

5.1 Allergic and skin reactions

Serious allergic reactions, including angioedema, anaphylaxis, Stevens Johnson syndrome and toxic epidermal necrolysis have been reported rarely in patients on azithromycin therapy using other formulations. Although rare, fatalities have been reported. Despite initially successful symptomatic treatment of the allergic symptoms, when symptomatic therapy was discontinued, the allergic symptoms recurred soon thereafter in some patients without further azithromycin exposure. These patients required prolonged periods of observation and symptomatic treatment. The relationship of these episodes to the long tissue half-life of azithromycin and subsequent exposure to antigen has not been determined.

If an allergic reaction occurs, appropriate therapy should be instituted. Physicians should be aware that reappearance of the allergic symptoms may occur when symptomatic therapy is discontinued.

5.2 Clostridium difficile-associated diarrhea

Clostridium difficile-associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including Zmax, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.

C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.

If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated.

5.3 Exacerbation of myasthenia gravis

Exacerbation of symptoms of myasthenia gravis and new onset of myasthenic syndrome have been reported in patients receiving azithromycin therapy.

5.4 Gastrointestinal Disturbances

A higher incidence of gastrointestinal adverse events (8 of 19 subjects) was observed when Zmax was administered to a limited number of subjects with GFR< 10 mL/min [See USE IN SPECIFIC POPULATIONS (8.6)]

5.5 Prolongation of the QT interval

Prolonged cardiac repolarization and QT interval, imparting a risk of developing cardiac arrhythmia and torsades de pointes, have been seen in treatment with other macrolides. A similar effect with azithromycin cannot be completely ruled out in patients at increased risk for prolonged cardiac repolarization.

5.6 Development of drug resistant bacteria

Prescribing Zmax in the absence of a proven or strongly suspected bacterial infection is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

6.1 Clinical studies experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

6.2 Postmarketing experience with other azithromycin products

Because these reactions are reported voluntarily from a population of uncertain size, reliably estimating their frequency or establishing a causal relationship to drug exposure is not always possible.

Adverse events reported with azithromycin immediate release formulations during the postmarketing period for which a causal relationship may not be established include:

Allergic: arthralgia, edema, urticaria and angioedema
Cardiovascular: palpitations and arrhythmias including ventricular tachycardia and hypotension
There have been rare reports of QT prolongation and torsades de pointes.
Gastrointestinal: anorexia, constipation, dyspepsia, flatulence, vomiting/diarrhea rarely resulting in dehydration, pseudomembranous colitis, pancreatitis, oral candidiasis and rare reports of tongue discoloration
General: asthenia, paresthesia, fatigue, malaise and anaphylaxis (rarely fatal)
Genitourinary: interstitial nephritis, acute renal failure, moniliasis and vaginitis
Hematopoietic: thrombocytopenia, mild neutropenia
Liver/Biliary: abnormal liver function including hepatitis and cholestatic jaundice, as well as rare cases of hepatic necrosis and hepatic failure, some of which have resulted in death
Nervous System: convulsions, dizziness/vertigo, headache, somnolence, hyperactivity, nervousness, agitation and syncope
Psychiatric: aggressive reaction and anxiety
Skin/Appendages: pruritus, rash, photosensitivity, rarely serious skin reactions including erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis
Special Senses: hearing disturbances including hearing loss, deafness and/or tinnitus and rare reports of taste/smell perversion and/or loss

Warfarin

Although, in a study of 22 healthy men, a 5-day course of azithromycin did not affect the prothrombin time from a subsequently administered dose of warfarin, spontaneous post-marketing reports suggest that concomitant administration of azithromycin may potentiate the effects of oral anticoagulants. Prothrombin times should be carefully monitored while patients are receiving azithromycin and oral anticoagulants concomitantly.

8.1 Pregnancy

8.3 Nursing Mothers

It is not known whether azithromycin is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when azithromycin is administered to a nursing woman.

8.4 Pediatric Use

Safety and effectiveness in the treatment of pediatric patients under 6 months of age have not been established.

8.5 Geriatric Use

Data collected from the azithromycin capsule and tablet formulations indicate that a dosage adjustment does not appear to be necessary for older patients with normal renal function (for their age) and hepatic function receiving treatment with Zmax.

In clinical trials of Zmax, 17% of subjects were at least 65 years of age (214/1292) and 5% of subjects (59/1292) were at least 75 years of age. No overall differences in safety or effectiveness were observed between these subjects and younger subjects.

8.6 Renal Impairment

No dosage adjustment is recommended for patients GFR >10 mL/min. Caution should be exercised when Zmax is administered to patients with GFR <10 mL/min, due to a higher incidence of gastrointestinal adverse events (8 of 19 subjects) observed in a limited number of subjects with GFR <10 mL/min. [See CLINICAL PHARMACOLOGY (12)]

8.7 Gender

The impact of gender on the pharmacokinetics of azithromycin has not been evaluated for Zmax. However, previous studies have demonstrated no significant differences in the disposition of azithromycin between male and female subjects. No dosage adjustment of Zmax is recommended based on gender.

12.1 Mechanism of Action

Azithromycin is an antimicrobial agent [See Clinical Pharmacology (12.4)]

12.2 Pharmacodynamics

Based on animal models of infection, the antimicrobial activity of azithromycin appears to correlate with the ratio of area under the concentration-time curve to minimum inhibitory concentration (AUC/MIC) for certain pathogens (S. pneumoniae and S. aureus). The principal pharmacokinetic/pharmacodynamic parameter best associated with clinical and microbiological cure has not been elucidated in clinical trials with Zmax.

12.3 Pharmacokinetics

Zmax is an extended release microsphere formulation. Based on data obtained from studies evaluating the pharmacokinetics of azithromycin in healthy adult subjects a higher peak serum concentration (Cmax) and greater systemic exposure (AUC 0–24) of azithromycin are achieved on the day of dosing following a single 2 g dose of Zmax versus 1.5 g of azithromycin tablets administered over 3 days (500 mg/day) or 5 days (500 mg on day 1, 250 mg/day on days 2–5) [Table 2]. Consequently, due to these different pharmacokinetic profiles, Zmax is not interchangeable with azithromycin tablet 3-day and 5-day dosing regimens.

12.4 Microbiology

13. 1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term studies in animals have not been performed to evaluate carcinogenic potential. Azithromycin has shown no mutagenic potential in standard laboratory tests: mouse lymphoma assay, human lymphocyte clastogenic assay, and mouse bone marrow clastogenic assay. No evidence of impaired fertility due to azithromycin was found in rats given daily doses up to 10 mg/kg (approximately 0.05 times the single 2 g oral adult human dose on a mg/m2 basis).

13. 2 Animal Toxicology and/or Pharmacology

Phospholipidosis (intracellular phospholipid accumulation) has been observed in some tissues of mice, rats, and dogs given multiple doses of azithromycin. It has been demonstrated in numerous organ systems (e.g., eye, dorsal root ganglia, liver, gallbladder, kidney, spleen, and/or pancreas) in dogs treated with azithromycin at doses which, expressed on the basis of mg/m2, are approximately one-sixth the recommended adult dose, and in rats treated at doses approximately one-fourth the recommended adult dose. This effect has been shown to be reversible after cessation of azithromycin treatment. Based on the pharmacokinetic data, phospholipidosis has been seen in the rat (50 mg/kg/day dose) at the observed maximal plasma concentration of 1.3 µg/mL (1.6 times the observed Cmax of 0.821 µg/mL at the adult dose of 2 g.) Similarly, it has been shown in the dog (10 mg/kg/day dose) at the observed maximal serum concentration of 1 µg/mL (1.2 times the observed Cmax of 0.821 µg/mL at the adult dose of 2 g).

Phospholipidosis was also observed in neonatal rats dosed for 18 days at 30 mg/kg/day, which is less than the pediatric dose of 60 mg/kg on a mg/m2 basis, but was not observed in neonatal rats treated for 10 days at 40 mg/kg/day with mean maximal serum concentrations of 1.86 µg/ml, approximately 1.5 times the Cmax of 1.27 µg/ml at the pediatric dose. Phospholipidosis has been observed in neonatal dogs (10 mg/kg/day) at maximum mean whole blood concentrations of 3.54 µg/ml, approximately 3 times the pediatric dose Cmax.

The significance of the finding for animals and for humans is unknown.

Acute Bacterial Maxillary Sinusitis

Adult subjects with a diagnosis of acute bacterial maxillary sinusitis were evaluated in a randomized, double-blind, multicenter study; a maxillary sinus tap was performed on all subjects at baseline. Clinical evaluations were conducted for all subjects at the TOC visit, 7 to 14 days post-treatment. Two hundred seventy (270) subjects were treated with a single 2 g oral dose of Zmax and 268 subjects were treated with levofloxacin, 500 mg orally QD for 10 days. A subject was considered a cure if signs and symptoms related to the acute infection had resolved, or if clinical improvement was such that no additional antibiotics were deemed necessary. The clinical response for the primary population, Clinical Per Protocol Subjects, is presented below.

Clinical response by pathogen in the Bacteriologic Per Protocol population is presented below.

Community-Acquired Pneumonia

Adult subjects with a diagnosis of mild-to-moderate community-acquired pneumonia were evaluated in two, randomized, double-blind, multicenter studies. In both studies, clinical and microbiologic evaluations were conducted for all subjects at the Test of Cure (TOC) visit, 7 to 14 days post-treatment. In the first study, 247 subjects were treated with a single 2 g oral dose of Zmax and 252 subjects were treated with clarithromycin extended release, 1 g orally QD for 7 days. In the second study, 211 subjects were treated with a single 2.0 g oral dose of Zmax and 212 subjects were treated with levofloxacin, 500 mg orally QD for 7 days. A patient was considered a cure if signs and symptoms related to the acute infection had resolved, or if clinical improvement was such that no additional antibiotics were deemed necessary; in addition, the chest x-ray performed at the TOC visit was to be either improved or stable. The clinical response at TOC for the primary population, Clinical Per Protocol Subjects, is presented in the table below.

Clinical response by pathogen in the Bacteriologic Per Protocol population, across both studies, is presented below:

Storage

Before constitution, store dry powder at or below 30°C (86°F).

After constitution, store suspension at 25°C (77°F); excursions permitted to 15–30°C (59–86°F) [see USP Controlled Room Temperature]. Do not refrigerate or freeze.

Constituted suspension should be consumed within 12 hours. For adult patients, the entire bottle should be consumed. For pediatric patients, any suspension remaining after dosing MUST be discarded.

17.1 General Patient Counseling

• Patients should be instructed to take Zmax on an empty stomach (at least 1 hour before or 2 hours following a meal).
• To ensure accurate dosing for children, use of a dosing spoon, medicine syringe, or cup is recommended.
• Patients should be told that Zmax needs time to work, so the patient may not feel better right away. If the patient's symptoms do not improve in a few days, the patient or their guardian should call their doctor.
• Patients should be instructed to immediately contact a physician if any signs of an allergic reaction occur.
• Diarrhea is a common problem caused by antibiotics which usually ends when the antibiotic is discontinued. Sometimes after starting treatment with antibiotics, 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 antibiotic. If this occurs, patients should contact their physician as soon as possible.
• Patients who vomit within the first hour should contact their health care provider about further treatment.
• Keep bottle tightly closed. Store at room temperature. Use within 12 hours of constitution. Shake bottle well before use. Adult patients should consume the entire contents of the bottle; pediatric patients should take the recommended dose and MUST discard any unused portion.
• Patients should be advised that Zmax may be taken without regard to antacids containing magnesium hydroxide and/or aluminum hydroxide.

Patients should be counseled that antibacterial drugs including Zmax should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). Not taking the complete prescribed dose 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 Zmax or other antibacterial drugs in the future.

17.2 FDA-approved patient labeling