Dosing and uses of Zithromax, Zmax (azithromycin)
Adult dosage forms and strengths
powder for solution
- 500mg
- 2.5g
suspension reconstituted
- 100mg/5mL
- 200mg/5mL
packet
- 1g
tablet
- 250mg
- 500mg
- 600mg
Acute Bacterial Exacerbations of Chronic Obstructive Pulmonary Disease
500 mg PO once, then 250 mg once daily for 4 days
Alternatively, 500 mg PO qDay for 3 days
Acute Otitis Media
500 mg PO once, then 250 mg once daily for 4 days
Genital Ulcer Disease (Chancroid)
1 g PO once
Acute Bacterial Sinusitis
500 mg/day PO for 3 days or 2 g PO once
Community-Acquired Pneumonia
500 mg PO once, then 250 mg once daily for 4 days
2 g extended release suspension PO once
500 mg IV as single dose for at least 2 days; follow with oral therapy with single dose of 500 mg to complete 7-10 days course of therapy
Pharyngitis/Tonsillitis
500 mg PO once, then 250 mg once daily for 4 days
Alternatively, 12 mg/kg PO; not to exceed 500 mg on day 1 followed by 6 mg/kg; not to exceed 250 mg on days 2 through 5
Uncomplicated Skin/Skin Structure Infections
500 mg PO once, then 250 mg once daily for 4 days
Cat Scratch Disease
>45.5 kg: 500 mg PO once, then 250 mg once daily for 4 days
Pertussis (Off-label)
500 mg PO once, then 250 mg once daily for 4 days
Acute Pelvic Inflammatory Disease
500 mg IV over 1 hour once daily for 1-2 days; follow therapy by oral route with 250 mg qDay for 5 days to complete a 7 day therapy
Uncomplicated Gonococcal Infections
Infection of pharynx, cervix, urethra, or rectum: Ceftriaxone 250 mg IM once plus azithromycin 1 g PO once (preferred) or alternatively doxycycline 100 mg PO q12hr for 7 days
CDC STD guidelines: MMWR Recomm Rep. June 5, 2015:64(RR3);1-137
Sexual assault
- Prophylaxis of sexually transmitted diseases (STDs) such as gonorrhea after sexual assault per CDC guidelines includes the following 3-drug regimen:
- Ceftriaxone 250 mg IM once PLUS
- Azithromycin 1 g PO once PLUS
- Metronidazole or tinidazole 2 g PO once
- If alcohol has been recently ingested or emergency contraception is provided, metronidazole or tinidazole can be taken by the victim at home rather than as directly observed therapy to avoid drug interactions
Mycobacterium Avium Complex Infection
Prevention
- Primary prophylaxis: 1.2 g PO once weekly or 600 mg PO twice weekly; with or without rifabutin 300 mg once daily
- Secondary prophylaxis: 500-600 mg PO qDay in combination with ethambutol
Treatment
- 250 mg PO once daily in combination with ethambutol 15 mg/kg/day with or without rifabutin 300 mg/day
- Alternative regimen: 500 mg PO 3 times weekly in combination with ethambutol 15 mg/kg/day with or without rifabutin 300 mg/day
Endocarditis (Off-label)
Prophylaxis
500 mg PO 30-60 min before procedure
Current American Heart Association (AHA) guidelines recommend only for high-risk patients
Dosing Considerations
Not for use in patients with pneumonia judged to be inappropriate for oral therapy because of moderate to severe illness or risk factors
Susceptible organisms
- Actinobacillus actinomycetemcomitans, Actinomyces israelii, Actinomyces naeslundii, Actinomyces odontolyticus, Afipia felis, Arachnia propionica, Arcanobacterium (Corynebacterium) haemolyticum, Bartonella henselae, Bartonella quintana, Bordetella pertussis, Borrelia burgdorferi, Borrelia recurrentis, Klebsiella granulomatis, Campylobacter jejuni, Chlamydia pneumoniae (TWAR agent), Chlamydia trachomatis, Haemophilus ducreyi, Haemophilus influenzae, Legionella spp, Mycobacterium simiae, Mycobacterium scrofulaceum, Mycobacterium xenopi, Mycoplasma pneumoniae, Moraxella (Branhamella) catarrhalis, Neisseria gonorrhoeae, Staphylococcus aureus, Streptococcus (group C and G), Streptococcus agalactiae (group B), Streptococcus bovis (group D), Streptococcus intermedius group (Streptococcus anginosus, Streptococcus intermedius, Streptococcus constellatus), Streptococcus pneumoniae, Streptococcus pyogenes (group A), viridans streptococci
- First-line therapy: A felis, B henselae, B quintana, B pertussis, C jejuni, C pneumoniae (TWAR agent), C trachomatis, H ducreyi, H influenzae, Legionella spp, M scrofulaceum, M simiae, M xenopi, N gonorrhoeae
Pediatric dosage forms and strengths
oral suspension
- 100mg/5mL
- 200mg/5mL
powder for solution
- 500mg
- 2.5g
suspension reconstituted
- 100mg/5mL
- 200mg/5mL
packet
- 1g
tablet
- 250mg
- 500mg
- 600mg
Acute Otitis Media
<6 months: Safety and efficacy not established
≥6 months: 30 mg/kg of oral suspension once or 10 mg/kg PO once daily for 3 days or 10 mg/kg once on day 1 followed by 5 mg/kg on days 2-5
Community-Acquired Pneumonia
<6 months: Safety and efficacy not established
≥6 months: 10 mg/kg PO on day 1, followed by 5 mg/kg PO on days 2 through 5
≥6 months (Zmax): 60 mg/kg PO once; not to exceed 2 g
Cat Scratch Disease (Off-label)
<45.5 kg: 10 mg/kg PO as single dose; then 5 mg/kg PO qDay on days 2 through 5
>45.5 kg: 500 mg PO once, then 250 mg once daily for 4 days
Acute Bacterial Sinusitis
Zmax: 2g PO once
10 mg/kg of oral suspension PO once daily for 3 days
Pharyngitis/Tonsillitis
<2 years: Safety and efficacy not established
≥2 years: 12 mg/kg PO once daily for 5 days; not to exceed 500 mg/day
Chlamydia Trachomatis Infection (Off-label)
>45 mg/kg: 1 g PO as single dose
Mycobacterium Avium Complex Infection
Prophylaxis
<6 years: Safety and efficacy not established
≥6 years primary prophylaxis: 20 mg/kg PO once weekly; not to exceed 1200 mg or 5mg/kg/day qDay; not to exceed 250 mg/day
≥6 years secondary prophylaxis: 5 mg/kg/day PO qDay; not to exceed 250 mg/day in cimbination with ethambutol with or without rifabutin
Treatment: 10-12 mg/kg/day PO; not to exceed 500 mg; used in combination with ethambutol; if severe disease patient should also receive rifabutin
Zithromax, Zmax (azithromycin) adverse (side) effects
>10%
High single dose therapy
- Diarrhea (52.8%)
- Nausea (32.6%)
- Abdominal pain (27%)
- Loose stool (19.1%)
1-10%
Cramping (2-10%)
Vaginitis (2-10%)
Dyspepsia (9% with single high dose therapy)
Flatulence (9% with single high dose therapy)
Vomiting (6.7% with single high dose therapy)
Malaise (1.1%)
<1%
Agitation
Allergic reaction
Anemia
Anorexia
Candidiasis
Chest pain
Conjunctivitis
Constipation
Dermatitis (fungal)
Dizziness
Eczema
Edema
Enteritis
Facial edema
Fatigue
Gastritis
Headache
Hyperkinesia
Hypotension
Increased cough
Insomnia
Leukopenia
Malaise
Melena
Mucositis
Nervousness
Oral candidiasis
Pain
Palpitations
Pharyngitis
Pleural effusion
Pruritus
Pseudomembranous colitis
Rash
Rhinitis
Seizures
Somnolence
Urticaria
Vertigo
Postmarketing Reports
Anaphylaxis
Angioedema
Anorexia
Bronchospasm
Constipation
Dermatologic reactions
Dyspepsia
Elevated liver enzymes
Erythema multiforme
Flatulence
Oral candidiasis
Pancreatitis
Pseudomembranous colitis
Pyloric stenosis, rare reports of tongue discoloration
Stevens-Johnson syndrome
Torsades de pointes
Toxic epidermal necrolysis
Vomiting/diarrhea, rarely resulting in dehydration
Neutropenia
Elevated bilirubin, AST, ALT, BUN, creatinine
Alterations in potassium
Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)
Warnings
Contraindications
Documented hypersensitivity
History of cholestatic jaundice or hepatic impairment associated with prior azithromycin use
Coadministration with pimozide
Cautions
Use with caution in abnormal liver function, hepatitis, cholestatic jaundice, hepatic necrosis, and hepatic failure have been reported, some of which have resulted in death; discontinue azithromycin immediately if signs and symptoms of hepatitis occur
Injection-site reactions can occur with IV route
In treatment of gonorrhea or syphilis, perform susceptibility culture tests before initiating azithromycin therapy; may mask or delay symptoms of incubating gonorrhea or syphilis.
Bacterial or fungal superinfection may result from prolonged use
Prolonged QT interval: Cases of torsades de pointes have been reported during postmarketing surveillance; use with caution in patients with known QT prolongation, history of torsades de pointes, congenital long QT syndrome, bradyarrhythmias, or uncompensated heart failure; also use with caution if coadministering with drugs that prolong QT interval or proarrhythmic conditions (eg, hypokalemia, hypomagnesemia); elderly patients may be more susceptible to drug-associated effects on QT intervaL
Pneumonia: PO azithromycin is safe and effective only for community-acquired pneumonia (CAP) due to C pneumoniae, H influenzae, M pneumoniae, or S pneumoniae
Cases of Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) reported; despite successful symptomatic treatment of allergic symptoms, when symptomatic therapy was discontinued, allergic symptoms recurred soon thereafter in some patients without further azithromycin exposure; if allergic reaction occurs, the drug should be discontinued and appropriate therapy instituted; physicians should be aware that allergic symptoms may reappear when symptomatic therapy discontinued
Endocarditis prophylaxis: Indicated only for high-risk patients, per current AHA guidelines
Use caution in renal impairment (CrCl <10 mL/min)
Use with caution in patients with myasthenia gravis (exacerbation may occur)
Immediate release and extended release suspensions are not interchangeable
Use extended release suspension only for treatment of infections that are proven or strongly suspected to be caused by susceptible bacteria
Clostridium difficile associated diarrhea (CDAD) reported and may range in severity from mild diarrhea to fatal colitis; treatment with antibacterial agents alters the normal flora of colon leading to overgrowth of Clostridium difficile
Serious allergic reactions, including angioedema, anaphylaxis, and dermatologic reactions including Stevens-Johnson Syndrome, and toxic epidermal reported ; if allergic reaction occurs, drug should be discontinued and appropriate therapy instituted; physicians should be aware that allergic symptoms may reappear after symptomatic therapy has been discontinued
Following use in neonates (treatment up to 42 days of life), infantile hypertrophic pyloric stenosis reported; direct parents and caregivers to contact physician if vomiting or irritability with feeding occurs
Prescribing antibiotics in absence of a proven or strongly suspected bacterial infection is unlikely to provide benefit to patient and increases risk of development of drug-resistant bacteria
Pregnancy and lactation
Pregnancy category: B
Lactation: Unknown whether drug is excreted into breast milk; use with caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Zithromax, Zmax (azithromycin)
Mechanism of action
Binds to 50S ribosomal subunit of susceptible microorganisms and blocks dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest; does not affect nucleic acid synthesis
Concentrates in phagocytes and fibroblasts, as demonstrated by in vitro incubation techniques; in vivo studies suggest that concentration in phagocytes may contribute to drug distribution to inflamed tissues
Absorption
Rapidly absorbed
Bioavailability: 37%; variable effect with food (increased with oral suspension, unchanged with tablet)
Peak serum time: 2-3 hr (immediate release); 5 hr (extended release)
Distribution
Extensively distributed into skin, lungs, sputum, tonsils, and cervix; penetrates cerebrospinal fluid (CSF) poorly
Protein bound: 7-50% (concentration dependent)
Vd: 33.3 L/kg (PO); 31.1 L/kg (IV)
Metabolism
Metabolized in liver
Elimination
Half-life: ~70 hr (immediate release); 59 hr (extended release)
Excretion: Feces (50% as unchanged drug), urine (5-12%)
Administration
IV Incompatibilities
Y-site: Amikacin, aztreonam, cefotaxime, ceftazidime, ceftriaxone, cefuroxime, ciprofloxacin, clindamycin, droperidol, famotidine, fentanyl, furosemide, gentamicin, imipenem, cilastatin, ketorolac, levofloxacin, morphine, piperacillin-tazobactam, ondansetron(?), potassium chloride, ticarcillin-clavulanate, tobramycin
IV Compatibilities
Solution (partial list): SWI, D5W, LR, D5/LR, D5/½NS, NS, ½Ns
Y-site: Bivalirudin, dexmedetomidine, diphenhydramine, dolasetron, droperidoL
IV Preparation
Dilute 500-mg vial in 4.8 mL of SWI (100 mg/mL)
Dilute further in NS to 1 mg/mL (500 mL) or 2 mg/mL (250 mL)
IV Administration
Use standard syringe
1 mg/mL solution: Infuse over 3 hours
2 mg/mL solution: Infuse over 1 hour
Oral Administration
Tablet: Take tablets without regard to food; however, food may enhance tolerability
Oral suspension
- Conventional oral suspension (100 mg/5 mL, 200 mg/5 mL) may be stored for 10 days after reconstitution and taken without regard to food
- Conventional 1 g package must be taken immediately after reconstitution
- Extended-release oral suspension must be taken on empty stomach within 12 hours of reconstitution; given only in single dose; not interchangeable with immediate release formulation
