amoxicillin trihydrate
(a mox i sill' in)
Amoxil, Amoxil Pediatric Drops, Apo-Amoxi (CAN), Novamoxin (CAN), Nu-Amoxi (CAN), Trimox, Trimox Pediatric Drops, Wymox

Pregnancy Category B

Drug class
Antibiotic, penicillin–ampicillin type

Therapeutic actions
Bactericidal: inhibits synthesis of cell wall of sensitive organisms, causing cell death.

Indications
· Infections due to susceptible strains of Haemophilus influenzae, E. coli, Proteus mirabilis, Neisseria gonorrhoeae, Streptococcus pneumoniae, streptococci, nonpenicillinase-producing staphylococci
· Helicobacter pylori infection in combination with other agents
· Post-exposure prophylaxis against Bacillus anthracis
· Unlabeled use: Chlamydia trachomatis in pregnancy

Contraindications and cautions
· Contraindicated with allergies to penicillins, cephalosporins, or other allergens.
· Use cautiously with renal disorders, lactation.

Available forms
Chewable tablets--125, 250 mg; tablets--500, 875 mg; capsules--250, 500 mg; powder for oral suspension--50 mg/mL; 125 mg/5 mL, 200 mg/5 mL, 250 mg/5 mL, 400 mg/5 mL
Available in oral preparations only.

Dosages
ADULTS AND PEDIATRIC PATIENTS > 20 KG
· URIs, GU infections, skin and soft-tissue infections: 250–500 mg PO q 8 hr or 875 mg PO bid.
· Post-exposure anthrax prophylaxis: 500 mg PO tid.
· Lower respiratory infections: 500 mg PO q 8 hr or 875 mg PO bid.
· Uncomplicated gonococcal infections: 3 g amoxicillin with 1 g probenecid PO.
· C. trachomatis in pregnancy: 500 mg PO tid for 7 days or 875 mg PO bid.
· Prevention of SBE: Dental, oral, or upper respiratory procedures: 2 g 1 hr before procedure.
· GI or GU procedures: 2 g ampicillin plus 1.5 mg/kg gentamicin IM or IV 30 min before procedure, followed by 1 g amoxicillin; for low-risk patients, 2 g 1 hr before procedure.
· H. pylori: 1 g bid with clarithromycin 500 mg bid and lansoprazole 30 mg bid for 14 days.
PEDIATRIC PATIENTS < 20 KG</SPAN>
· URIs, GU infections, skin, and soft-tissue infections: 20–40 mg/kg/day PO in divided doses q 8 hr.
· Post-exposure anthrax prophylaxis: 80 mg/kg/day PO divided into 3 doses.
· Lower respiratory infections: 40 mg/kg/day PO in divided doses q 8 hr.
· Prevention of SBE: Dental, oral, or upper respiratory procedures: 50 mg/kg 1 hr before procedure.
· GI or GU procedures: 50 mg/kg ampicillin plus 2 mg/kg gentamicin IM or IV 30 min before procedure followed by 25 mg/kg amoxicillin. For moderate-risk patients, 50 mg/kg PO 1 hr before procedure.

Pharmacokinetics
Route
Onset
Peak
Duration
Oral
Varies
1 hr
6–8 hr


Metabolism: T1/2: 1–1.4 hr
Distribution: Crosses placenta; passes into breast milk
Excretion: Unchanged in the urine

Adverse effects
· CNS: Lethargy, hallucinations, seizures
· GI: Glossitis, stomatitis, gastritis, sore mouth, furry tongue, black “hairy” tongue, nausea, vomiting, diarrhea, abdominal pain, bloody diarrhea, enterocolitis, pseudomembranous colitis, nonspecific hepatitis
· GU: Nephritis
· Hematologic: Anemia, thrombocytopenia, leukopenia, neutropenia, prolonged bleeding time
· Hypersensitivity: Rash, fever, wheezing, anaphylaxis
· Other: Superinfections--oral and rectal moniliasis, vaginitis

Interactions
Drug-drug
· Increased effect with probenecid
· Decreased effectiveness with tetracyclines, chloramphenicol
· Decreased efficacy of oral contraceptives
Drug-food
· Delayed or reduced GI absorption with food

Nursing considerations
Assessment
· History: Allergies to penicillins, cephalosporins, or other allergens; renal disorders; lactation
· Physical: Culture infected area; skin color, lesion; R, adventitious sounds; bowel sounds; CBC, liver and renal function tests, serum electrolytes, Hct, urinalysis

Interventions
· Culture infected area prior to treatment; reculture area if response is not as expected.
· Give in oral preparations only; absorption may be affected by presence of food; drug should be taken 1 hr before or 2 hr after meals.
· Continue therapy for at least 2 days after signs of infection have disappeared; continuation for 10 full days is recommended.
· Use corticosteroids, antihistamines for skin reactions.

Teaching points
· Take this drug around the clock. The drug should be taken on an empty stomach, 1 hr before or 2 hr after meals.
· Take the full course of therapy; do not stop because you feel better.
· This antibiotic is specific for this problem and should not be used to self-treat other infections.
· These side effects may occur: nausea, vomiting, GI upset (small frequent meals may help); diarrhea; sore mouth (frequent mouth care may help).
· Report unusual bleeding or bruising, sore throat, fever, rash, hives, severe diarrhea, difficulty breathing.

Adverse effects in Italic are most common; those in Bold are life-threatening.