Zithromax

Action

Bactericidal and bacteriostatic; inhibits protein synthesis after binding with 50S ribosomal subunit of susceptible organisms. Demonstrates cross-resistance to erythromycin-resistant gram-positive strains and resistance to most strains of Enterococcus faecalis and methicillin-resistant Staphylococcus aureus.

Availability

Oral suspension: 100 mg/5 ml in 15-ml bottles; 200 mg/5 ml in 15-ml, 22.5-ml, and 30-ml bottles

Oral suspension (Zmax extended-release): 2-g bottle

Powder for injection: 500 mg in 10-ml vials

Powder for oral suspension: 100 mg/5 ml, 200 mg/5 ml, 1,000 mg/packet

Solution (ophthalmic): 1% in 5-ml bottle filled with 2.5 ml solution

Tablets: 250 mg, 500 mg, 600 mg

Tablets (Tri-Pak): three 500-mg tablets

Tablets (Z-Pak): six 250-mg tablets

Indications and dosages

➣ Bacterial conjunctivitis caused by CDC coryneform group G, H. influenzae, S. aureus, Streptococcus mitis group, and S. pneumoniae

Adults: Instill 1 drop in affected eye(s) b.i.d., 8 to 12 hours apart for first 2 days; then instill 1 drop in affected eye(s) once daily for next 5 days

➣ Mild community-acquired pneumonia

Adults: 500 mg P.O. on first day, then 250 mg/day for next 4 days. Or, 2 g P.O. as single dose (extended-release oral suspension).

Children ages 6 months and older: 10 mg/kg P.O. (no more than 500 mg/dose) on day 1, then 5 mg/kg (no more than 250 mg/dose) for 4 more days

➣ Community-acquired pneumonia caused by Chlamydia pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Streptococcus pneumoniae, Legionella pneumophila, Moraxella catarrhalis, and S. aureus

Adults and adolescents ages 16 and older: 500 mg I.V. daily for at least two doses, then 500 mg P.O. daily for a total of 7 to 10 days

Children ages 6 months to 16 years: 10 mg/kg P.O. as a single dose on day 1, then 5 mg/kg P.O. on days 2 through 5

➣ Pharyngitis and tonsillitis

Adults: 500 mg P.O. on day 1, then 250 mg/day for next 4 days, to a total dosage of 1.5 g

Children ages 2 and older: 12 mg/kg P.O. daily for 5 days. Maximum dosage is 500 mg.

➣ Skin and skin-structure infections

Adults: 500 mg P.O. on first day, then 250 mg/day for next 4 days, to total dosage of 1.5 g

➣ Acute bacterial sinusitis

Adults: 500 mg P.O. daily for 3 days; or, 2 g P.O. as single dose (extended-release oral suspension)

Children ages 6 months and older: 10 mg/kg (maximum, 500 mg) P.O. daily for 3 days

➣ Mild to moderate acute exacerbation of chronic obstructive pulmonary disease

Adults: 500 mg/day for 3 days or 500 mg P.O. on day 1, then 250 mg P.O. daily on days 2 through 5; or, 2 g P.O. (extended-release oral suspension) as single dose

➣ Pelvic inflammatory disease caused by Chlamydia trachomatis, Neisseria gonorrhoeae, or Mycoplasma hominis

Adults: 500 mg I.V. daily on days 1 and 2, then 250 mg P.O. daily for a total of 7 days. If anaerobes are suspected, give continually with appropriate anti-anaerobic antibiotic, as ordered.

➣ Nongonococcal urethritis or cervicitis caused by C. trachomatis; genital ulcers caused by Haemophilus ducreyi (chancroid)

Adults: 1 g P.O. as a single dose

➣ Urethritis and cervicitis caused by N. gonorrhoeae

Adults: 2 g P.O. as a single dose

➣ To prevent disseminated Mycobacterium avium complex disease in patients with advanced human immunodeficiency virus

Adults: 1.2 g P.O. once weekly (given alone or with rifabutin)

➣ Acute otitis media

Children ages 6 months and older: 30 mg/kg as a single dose or 10 mg/kg once daily for 3 days; or 10 mg/kg as a single dose on day 1, followed by 5 mg/kg on days 2 through 5

Off-label uses

• Uncomplicated gonococcal infections of cervix, urethra, rectum, and pharynx

Contraindications

• Hypersensitivity to drug, erythromycin, or other macrolide antiinfectives

• None (ophthalmic solution)

Precautions

Use cautiously in:

• severe hepatic impairment, severe renal insufficiency, prolonged QT interval

• breastfeeding patients.

Administration

• Obtain specimens for culture and sensitivity testing before starting therapy.

• Administer tablets and single-dose packets with or without food.

• Give oral suspension 1 hour before meals or 2 hours afterward. With 1-g packet, or single 2-g bottles, mix entire contents in 2 oz of water.

☞ Don't administer as I.V. bolus or I.M. injection.

• For I.V. use, reconstitute 500-mg vial with 4.8 ml of sterile water for injection.

• As appropriate, dilute solution further using normal or half-normal saline solution, dextrose 5% in water, or lactated Ringer's solution.

• Infuse injection over no less than 60 minutes. Infuse 1 mg/ml over 3 hours or 2 mg/2 ml over 1 hour.

• Know that 1,000-mg packet and extended-release oral suspension aren't for pediatric use.

Adverse reactions

CNS: dizziness, drowsiness, fatigue, headache, vertigo

CV: chest pain, palpitations

EENT: eye irritation (with ophthalmic use)

GI: nausea, diarrhea, abdominal pain, cholestatic jaundice, dyspepsia, flatulence, melena, pseudomembranous colitis

GU: nephritis, vaginitis, candidiasis

Metabolic: hyperglycemia, hyperkalemia

Skin: photosensitivity, rashes, angioedema

Other: overgrowth of nonsusceptible organisms (with prolonged use)

Interactions

Drug-drug. Antacids containing aluminum or magnesium: decreased peak azithromycin blood level

Arrhythmias (such as amiodarone, quinidine): increased risk of life-threatening arrhythmias

Carbamazepine, cyclosporine, digoxin, dihydroergotamine, ergotamine, hexobarbital, phenytoin, theophylline, triazolam: increased blood levels of these drugs

HMG-CoA reductase inhibitors (such as atorvastatin, lovastatin): increased risk of myopathy or rhabdomyolysis

Pimozide: prolonged QT interval, ventricular tachycardia

Warfarin: increased International Normalized Ratio

Drug-food. Any food: decreased absorption of multidose oral suspension

Drug-behaviors. Sun exposure: photosensitivity

Patient monitoring

• Monitor temperature, white blood cell count, and culture and sensitivity results.

• Assess for signs and symptoms of infection.

• Monitor patients at risk for cardiac arrhythmia.

Patient teaching

• Tell patient he may take tablets with or without food.

• Advise patient to take suspension 1 hour before or 2 hours after meals.

• Remind patient to complete entire course of therapy as ordered, even after symptoms improve.

• Advise patient not to wear contact lenses if signs or symptoms of bacterial conjunctivitis exist.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, foods, and behaviors mentioned above.