CLARITHROMYCIN

CLARITHROMYCIN (clar'i-thro-my-sin) Biaxin Filmtabs, Biaxin XL Classifications: macrolide antibiotic; Therapeutic: antibiotic, macrolide Prototype: Erythromycin Pregnancy Category: C

Availability

250 mg, 500 mg tablets; 500 mg sustained-release tablets; 125 mg/5 mL, 250 mg/5 mL suspension

Action

A semisynthetic macrolide antibiotic that binds to the 50S ribosomal subunit of susceptible bacterial organisms and, thereby, blocks RNA-mediated bacterial protein synthesis of the bacteria.

Therapeutic Effect

It is active against both aerobic and anaerobic gram-positive and gram-negative organisms.

Uses

Treatment of upper respiratory, lower respiratory infections; acute maxillary sinusitis; otitis media; and skin and soft tissue infections caused by clinically significant aerobic and anaerobic gram-negative and gram-positive organisms, including S. aureus, H. influenzae, S. pneumoniae, M. catarrhalis, S. pyogenes, M. pneumoniae. Prevention and treatment of Mycobacterium avium complex (MAC) infections in patients with HIV. Used in combination for Helicobacter pylori.

Contraindications

Hypersensitivity to clarithromycin, erythromycin, or any other macrolide antibiotics; patients receiving pimozide; suspected or potential bacteremias; acute porphyria; severe hepatic or biliary disease; congenital QT prolongation, torsades de pointes; viral infections; pregnancy (category C). Safety and efficacy in infants <20 mo not established.

Cautious Use

Renal impairment, older adults, GI disease, colitis; lactation.

Route & Dosage

Mild to Moderate Infections Adult: PO 250–500 mg b.i.d. or 500 mg XL q.d. for 10–14 d Child: PO 7.5 mg/kg q12h Mycobacterial Infections Adult: PO 500 mg q12h Child: PO 7.5 mg/kg q12h H. pylori Infections Adult: PO 500 mg b.i.d. to t.i.d. Renal Impairment Clcr <30 mL/min: decrease dose by ? or double the dosing interval

Administration

Oral

• Ensure that sustained-release form of drug is not chewed or crushed. It must be swallowed whole.
• Shake suspension well before use.
• Store at 15°–30° C (59°–86° F).

Adverse Effects (≥1%)

GI: Diarrhea, abdominal discomfort, nausea, abnormal taste, dyspepsia. Hematologic: Eosinophilia. CNS: Headache. Skin: Rash, urticaria.

Diagnostic Test Interference

May increase serum AST and ALT levels.

Interactions

Drug: May increase theophylline levels; drugs known to interact with erythromycin (i.e., digoxin, carbamazepine, triazolam, warfarin, ergotamine, dihydroergotamine) should be monitored carefully for increased levels and toxicity; pimozide may increase risk of arrhythmias.

Pharmacokinetics

Absorption: Readily absorbed from GI tract; 50% reaches the systemic circulation. Peak: 2–4 h. Distribution: Widely distributes into most body tissue (excluding CNS); high pulmonary tissue concentrations. Metabolism: Partially metabolized in the liver; active 14-OH metabolite acts synergistically with the parent compound against H. influenzae. Elimination: 20% excreted unchanged in urine; 10–15% of 14-OH metabolite excreted in urine. Half-Life: 3–5 h.

Nursing Implications

Assessment & Drug Effects

• Inquire about previous hypersensitivity to other macrolides (e.g., erythromycin) before treatment.
• Withhold drug and notify physician, if hypersensitivity occurs (e.g., rash, urticaria).
• Monitor for and report loose stools or diarrhea, since pseudomembranous colitis must be ruled out.
• When clarithromycin is given concurrently with anticoagulants, digoxin, or theophylline, blood levels of these drugs may be elevated. Monitor appropriate serum levels and assess for S&S of drug toxicity.

Patient & Family Education

• Complete prescribed course of therapy.
• Report rash or other signs of hypersensitivity immediately.
• Report loose stools or diarrhea even after completion of drug therapy.

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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