AMOXICILLIN

AMOXICILLIN (a-mox-i-sill'in) Amoxil, Apo-Amoxi , Larotid, Novamoxin, Trimox, DisperMox Classifications: antibiotic; aminopenicillin; Therapeutic:antibiotic Prototype: Ampicillin Pregnancy Category: B

Availability

125 mg, 250 mg, 500 mg tablets; 250 mg, 500 mg capsules; 50 mg/mL, 125 mg/5 mL, 250 mg/5 mL powder for suspension; 200 mg, 400 mg, 600 mg dispersible tablets

Action

Broad-spectrum semisynthetic aminopenicillin and analog of ampicillin. Like other penicillins, amoxicillin inhibits the final stage of bacterial cell wall synthesis by binding to specific penicillin-binding proteins (PBPs) located inside the cell wall of rapidly multiplying bacteria. It results in bacterial cell lysis and death.

Therapeutic Effect

Active against both aerobic gram-positive and aerobic gram-negative bacteria.

Uses

Infections of ear, nose, throat, GU tract, skin, and soft tissue caused by susceptible bacteria. Also used in uncomplicated gonorrhea.

Contraindications

Hypersensitivity to penicillins; infectious mononucleosis.

Cautious Use

History of or suspected atopy or allergy (hives, eczema, hay fever, asthma); history of cephalosporin or carbapenem hypersensitivity; colitis, dialysis, diarrhea, GI disease; viral infection, syphilis, renal impairment or failure, diabetes mellitus, leukemia, pregnancy (category B); infants, neonates.

Route & Dosage

Mild to Moderate Infections Adult: PO 250–500 mg q8h Child: PO 25–50 mg/kg/d (max: 60–80 mg/kg/d) divided q8h or 200–400 mg q12h Gonorrhea Adult: PO 3 g as single dose with 1 g probenecid Child (≥2 y): PO 50 mg/kg as single dose with probenecid 25 mg/kg

Administration

Oral

• Ensure that chewable tablets are chewed or crushed before being swallowed with a liquid.
• Place reconstituted pediatric drops directly on child's tongue or add to formula, milk, fruit juice, water, ginger ale, or other soft drink. Have child drink all the prepared dose promptly.
• Store in tightly covered containers at 15°–30° C (59°–86° F) unless otherwise directed. Reconstituted oral suspensions are stable for 7 d at room temperature.

Adverse Effects (≥1%)

Body as a Whole: As with other penicillins. Hypersensitivity (rash, anaphylaxis), superinfections. GI: Diarrhea, nausea, vomiting, pseudo-membranous colitis (rare). Hematologic: Hemolytic anemia, eosinophilia, agranulocytosis (rare). Skin: Pruritus, urticaria, or other skin eruptions. Special Senses: Conjunctival ecchymosis.

Interactions

tetracyclines may inhibit activity of amoxicillin; probenecid prolongs the activity of amoxicillin.

Pharmacokinetics

Absorption: Nearly complete absorption. Peak: 1–2 h. Distribution: Diffuses into most tissues and body fluids, except synovial fluid and CSF (unless meninges are inflamed); crosses placenta; distributed into breast milk in small amounts. Metabolism: In liver. Elimination: 60% of dose in urine in 6–8 h. Half-Life: 1–1.3 h.

Nursing Implications

Assessment & Drug Effects

• Determine previous hypersensitivity reactions to penicillins, cephalosporins, and other allergens prior to therapy.
• Lab tests: Baseline C&S tests prior to initiation of therapy, start drug pending results; periodic assessments of renal, hepatic, and hematologic functions should be made during prolonged therapy.
• Monitor for S&S of an urticarial rash (usually occurring within a few days after start of drug) suggestive of a hypersensitivity reaction. If it occurs, look for other signs of hypersensitivity (fever, wheezing, generalized itching, dyspnea), and report to physician immediately.
• Report onset of generalized, erythematous, maculopapular rash (ampicillin rash) to physician. Ampicillin rash is not due to hypersensitivity; however, hypersensitivity should be ruled out.
• Closely monitor diarrhea to rule out pseudomembranous colitis.

Patient & Family Education

• Take drug around the clock, do not miss a dose, and continue therapy until all medication is taken, unless otherwise directed by physician.
• Report onset of diarrhea and other possible symptoms of superinfection to physician (see Appendix F).

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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