Amoxicillin trihydrate

amoxicillin trihydrate

(a mox i sill' in)

Amoxil, Amoxil Pediatric Drops, Apo-Amoxi (CAN), DisperMox, Novamoxin (CAN), Nu-Amoxi (CAN), Trimox

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, Escherichia coli, Proteus mirabilis, Neisseria gonorrhoeae, Streptococcus pneumoniae, Enterococcus faecalis, streptococci, non–penicillinase-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, 200, 250, 400 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; tablets for oral suspension—200, 400 mg

Available in oral preparations only.

Dosages

ADULTS AND PEDIATRIC PATIENTS > 40 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 in dental, oral, or upper respiratory procedures: 2 g 1 hr before procedure.

·        Prevention of SBE in 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 infections: 1 g bid with clarithromycin 500 mg bid and lansoprazole 30 mg bid for 14 days.

PEDIATRIC PATIENTS < 40 KG

·        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.

·        Prevention of SBE: Dental, oral, or upper respiratory procedures: 50 mg/kg 1 hr before procedure.

·        Prevention of SBE in 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.

PEDIATRIC PATIENTS < 12 WK

Up to 30 mg/kg daily in divided doses q 12 hr.

PEDIATRIC PATIENTS > 3 MO

·        Mild to moderate URIs, GU infections, and skin infections: 20 mg/kg daily in divided doses q 8 hr or 25 mg/kg in divided doses q 12 hr.

·        For lower respiratory infections, or severe URIs, GU, or skin infections: 40 mg/kg daily in divided doses q 8 hr or 45 mg/kg daily in divided doses q 12 hr.

Pharmacokinetics

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

Metabolism: T_1/2: 1–1.4 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Urine, unchanged

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 hormonal 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, LFTs, 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; amoxicillin is not affected by food.

·        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.

·        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.

·        You may experience these side effects: Nausea, vomiting, GI upset (eat frequent small meals); 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.