AZITHROMYCIN

AZITHROMYCIN (a-zi-thro-mye'sin) AzaSite, Zithromax, Zmax Classifications: antibiotic; macrolide antibiotic; Therapeutic: antibiotic Prototype: Erythromycin Pregnancy Category: B

Availability

500 mg, 600 mg tablets; 100 mg/5 mL, 200 mg/5 mL, 1 g/packet oral suspension; 500 mg injection; 1% ophthalmic; Zmax extended release: 176 mg/5 mL oral suspension

Action

A macrolide antibiotic that reversibly binds to the 50S ribosomal subunit of susceptible organisms and consequently inhibits protein synthesis.

Therapeutic Effect

Effective for treatment of mild to moderate infections caused by pyogenic organisms.

Uses

Pneumonia, lower respiratory tract infections, pharyngitis/tonsillitis, gonorrhea, nongonococcal urethritis, skin and skin structure infections due to susceptible organisms, otitis media, Mycobacterium avium–intracellulare complex infections, acute bacterial sinusitis. Zmax: acute bacterial sinusitis and community acquired pneumonia. AzaSite: bacterial conjunctivitis.

Unlabeled Uses

Bronchitis, Helicobacter pylori gastritis.

Contraindications

Hypersensitivity to azithromycin, erythromycin, or any of the macrolide antibiotics; viral infections.

Cautious Use

Older adults or debilitated persons, hepatic or renal impairment; GI disease; ventricular arrhythmias, QT prolongation; UV exposure; pregnancy (category B), and lactation.

Route & Dosage

Bacterial Infections Adult: PO 500 mg on day 1, then 250 mg q24h for 4 more d IV 500 mg q.d. for at least 2 d, administer 1 mg/mL over 3 h or 2 mg/mL over 1 h Child (≥6 mo): PO 10 mg/kg on day 1, then 5 mg/kg for 4 more d (max: 250 mg/d) Acute Bacterial Sinusitis Adult: PO 500 mg once daily x 3 d. Zmax: single one-time dose of 2 g. Child ( ≥6 mo): PO 10 mg/kg once daily x 3 d Otitis Media Child (>6 mo): PO 30 mg/kg as a single dose or 10 mg/kg once daily (not to exceed 500 mg/d) for 3 d or 10 mg/kg as a single dose on day 1 followed by 5 mg/kg/d on days 2–5 Gonorrhea Adult: PO 2 g as a single dose Chancroid Adult: PO 1 g as a single dose Child: PO 20 mg/kg as single dose (max: 1 g) Bacterial Conjunctivitis Adult: Ophthalmic 1 drop b.i.d x 2 d then daily x 5d Renal Impairment Clcr <10 mL/min: use with caution

Administration

Oral

• Give capsule at least 1 h before or 2 h after a meal. Tablets may be taken without regard to food.
• Do not give within 2 h of an aluminum or magnesium-containing antacid.

Intravenous PREPARE: Intermittent: Reconstitute 500-mg vial with 4.8 mL of sterile water for injection and shake until dissolved. Final concentration is 100 mg/mL. Solution must be further diluted to 1.0 or 2.0 mg/mL by adding 5 mL of the 100-mg/mL solution to 500 mL or 250 mL, respectively, of D5W, D5/NS, 0.45NaCl, or other compatible solution.   ADMINISTER: Intermittent: Administer 1 mg/mL over 3 h. Infuse 2 mg/mL over 1 h. Note: Do not give a bolus dose.   INCOMPATIBILITIES Y-site: Amikacin, aztreonam, cefotaxime, ceftazidime, ceftriaxone, cefuroxime, ciprofloxacin, clindamycin, famotidine, fentanyl, furosemide, gentamicin, imipenem/cilastatin, ketorolac, levofloxacin, morphine, ondansetron, piperacillin/tazobactam, potassium, ticarcillin/clavulanate, tobramycin.

• Store drug when diluted as directed for 24 h at or below 30° C (86° F) or for 7 d under 5° C (41° F).

Adverse Effects (≥1%)

CNS: Headache, dizziness. GI: Nausea, vomiting, diarrhea, abdominal pain; hepatotoxicity, mild elevations in liver function tests.

Diagnostic Test Interference

Liver function tests: reversible, asymptomatic elevations in liver enzymes (AST, ALT, gamma glutamyl transferase, alkaline phosphatase) have been reported in some patients treated with azithromycin.

Interactions

Drug: antacids may decrease peak level of azithromycin; may increase toxicity of dihydroergotamine, ergotamine. Food: Food will decrease the amount of azithromycin absorbed by 50%.

Pharmacokinetics

Absorption: 37% of dose reaches the systemic circulation. Onset: 48 h. Peak: 2.5–4 h. Distribution: Extensively into tissues including sputum, blister, and vaginal secretions; tissue concentrations are often higher than serum concentrations. Metabolism: In liver. Elimination: 5–12% of dose in urine. Half-Life: 60–70 h.

Nursing Implications

Assessment & Drug Effects

• Monitor for and report loose stools or diarrhea, since pseudomembranous colitis (see Appendix F) must be ruled out.
• Monitor PT and INR closely with concurrent warfarin use.

Patient & Family Education

• Direct sunlight (UV) exposure should be minimized during therapy with drug.
• Take aluminum or magnesium antacids 2 h before or after drug.
• Report onset of loose stools or diarrhea.

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Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug