Amoxicillin

Pronunciation: a-MOX-i-SIL-in
Class: Aminopenicillin, Helicobacter pylori agent

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Trade Names

Amoxicillin
- Capsules 250 mg (as trihydrate)
- Capsules 500 mg (as trihydrate)
- Tablets 500 mg (as trihydrate)
- Tablets, chewable 125 mg (as trihydrate)
- Tablets, chewable 200 mg (as trihydrate)
- Tablets, chewable 250 mg (as trihydrate)
- Tablets, chewable 400 mg (as trihydrate)
- Powder for oral suspension 125 mg per 5 mL (as trihydrate) when reconstituted
- Powder for oral suspension 200 mg per 5 mL (as trihydrate) when reconstituted
- Powder for oral suspension 250 mg per 5 mL (as trihydrate) when reconstituted
- Powder for oral suspension 400 mg per 5 mL (as trihydrate) when reconstituted

Amoxil
- Tablets 875 mg (as trihydrate)
- Capsules 500 mg (as trihydrate)
- Powder for oral suspension 125 mg per 5 mL (as trihydrate) when reconstituted

DisperMox
- Tablets for oral suspension 200 mg
- Tablets for oral suspension 400 mg

Moxatag
- Tablets, ER 775 mg

Trimox
- Capsules 500 mg (as trihydrate)
- Powder for oral suspension 125 mg per 5 mL (as trihydrate) when reconstituted

APO-Amoxi (Canada)
Gen-Amoxicillin (Canada)
Novamoxin (Canada)
Nu-Amoxi (Canada)

Pharmacology

Inhibits bacterial cell wall mucopeptide synthesis.

Pharmacokinetics

Absorption

Rapidly absorbed. T _max is 1 to 2 h; C _max is 3.5 mcg/mL (250 mg dose), 5 mcg/mL (500 mg dose), and approximately 13.8 mcg/mL (875 mg dose).

Extended-release

C _max is 6.6 mcg/mL; T _max is 3.1 h.

Distribution

Diffuses into most body tissues and fluids; penetration in CNS is poor unless meninges are inflamed. Approximately 20% protein bound.

Elimination

Half-life is 61.3 min; approximately 60% excreted in the urine within 6 to 8 h as unchanged drug.

Indications and Usage

Treatment of ear, nose, throat, GU, skin and skin structure, lower respiratory tract, and acute uncomplicated gonorrhea infections caused by susceptible strains of specific organisms. In combination with clarithromycin and/or lansoprazole for the eradication of H. pylori .

Moxatag

Treatment of tonsillitis and/or pharyngitis secondary to Streptococcus pyogenes .

Unlabeled Uses

Treatment of acute otitis media in children.

Contraindications

Hypersensitivity to penicillins, cephalosporins, or imipenem.

Dosage and Administration

Acute Uncomplicated Gonorrhea
Adults

PO 3 g as a single dose.

Prepubertal Children (2 yr of age and older)

PO Amoxicillin 50 mg/kg combined with probenecid 25 mg/kg as a single dose.

Ear, Nose, Throat, Skin and Skin Structure, GU Tract Infections
Adults and Children Weighing at least 40 kg Mild to moderate infections

PO 500 mg every 12 h or 250 mg every 8 h.

Severe infections

PO 875 mg every 12 h or 500 mg every 8 h.

Children (older than 3 mo of age and weighing less than 40 kg) Mild to moderate infections

PO 25 mg/kg/day in divided doses every 12 h or 20 mg/kg/day in divided doses every 8 h.

Severe infections

PO 45 mg/kg/day in divided doses every 12 h or 40 mg/kg/day in divided doses every 8 h.

H. Pylori Eradication
Adults Triple Therapy

PO Amoxicillin 1 g, clarithromycin 500 mg, and lansoprazole 30 mg all given twice daily (every 12 h) for 14 days.

Dual therapy

PO Amoxicillin 1 g and lansoprazole 30 mg each given 3 times daily (every 12 h) for 14 days.

Impaired Renal Function
Adults

PO Glomerular filtration rate (GFR) of 10 to 30 mL/min: Administer 500 or 250 mg every 12 h, depending on the severity of the infection.

GFR less than 10 mL/min

Administer 500 or 250 mg every 24 h, depending on the severity of the infection.

Hemodialysis patients

Administer 500 or 250 mg every 24 h, depending on the severity of the infection, plus an additional dose during and at the end of dialysis.

ER tablet

Not recommended in patients with CrCl less than 30 mL/min.

Lower Respiratory Tract Infections
Adults and Children Weighing at least 40 kg

PO 875 mg every 12 h or 500 mg every 8 h.

Children (older than 3 mo of age and weighing less than 40 kg)

PO 45 mg/kg/day in divided doses every 12 h or 40 mg/kg/day in divided doses every 8 h.

Tonsillitis, Pharyngitis
Adults and Children 12 yr and older

PO ER tablet: 775 mg once daily, within 1 h of finishing a meal, for 10 days.

General Advice

In neonates and infants 12 wk of age and younger, the recommended maximum dosage is 30 mg/kg/day divided every 12 h.
After reconstitution, the required amount of suspension should be placed directly on the child's tongue for swallowing. Alternatively, add required amount of suspension to formula, milk, fruit juice, water, ginger ale, or cold drink.
Except for gonorrhea, treatment should be continued for a minimum of 48 to 72 h after the patient becomes asymptomatic or evidence of bacterial eradication has been obtained.
At least 10 days of treatment for any infection caused by S. pyogenes is recommended to prevent acute rheumatic fever.

Storage/Stability

Store 250 and 500 mg capsules and 125 and 250 mg unreconstituted powder at or below 68°F.

Store 200 and 400 mg unreconstituted powder, 200 and 400 mg chewable tablets, and 500 and 875 mg tablets at or below 77°F. Dispense in a tight container. Any unused portion of the reconstituted suspension must be discarded after 14 days. Refrigeration is preferable but not required.

Store ER tablets at 77°F; excursions are permitted between 59° and 86°F.

Drug Interactions

Chloramphenicol, macrolide antibiotics (eg, erythromycin), sulfonamides

May impair bactericidal effects of amoxicillin.

Contraceptives, oral

May reduce efficacy of oral contraceptives.

Methotrexate

Methotrexate plasma levels may be elevated, increasing the risk of toxicity.

Probenecid

Renal tubular secretion of amoxicillin may be reduced, resulting in increased and prolonged amoxicillin blood levels.

Tetracyclines

May impair bactericidal effects of amoxicillin.

Laboratory Test Interactions

May cause false-positive urine glucose test results with Benedict solution, Fehling solution, or Clinitest tablets (enzyme-based tests [eg, Clinistix , Tes-Tape ] are recommended); false-positive direct Coombs test result in certain patient groups; false-positive protein reactions with sulfosalicylic acid and boiling test, acetic acid test, biuret reaction and nitric acid test (bromphenol blue test, Multistix , is recommended).

Adverse Reactions

CNS

Headache (1%); agitation; anxiety; behavioral changes; confusion; convulsions; dizziness; hyperactivity; insomnia.

Dermatologic

Acute generalized exanthematous pustulosis; erythema multiforme; erythematous maculopapular rashes; exfoliative dermatitis; mucocutaneous candidiasis; Stevens-Johnson syndrome; toxic epidermal necrolysis; urticaria.

GI

Diarrhea (2%); nausea (1%); black, hairy tongue; hemorrhagic pseudomembranous colitis; tooth discoloration; vomiting.

Genitourinary

Vulvovaginal mycotic infection (2%); crystalluria.

Hematologic-Lymphatic

Agranulocytosis; anemia; eosinophilia; hemolytic anemia; leukopenia; thrombocytopenia; thrombocytopenic purpura.

Hepatic

Acute cytolytic hepatitis; cholestatic jaundice; hepatic cholestasis; increased ALT and AST.

Hypersensitivity

Anaphylaxis; hypersensitivity vasculitis.

Miscellaneous

Serum sickness–like reactions.

Precautions

Monitor

Periodically assess renal, hepatic, and hematopoietic function during prolonged therapy. Patients diagnosed with gonorrhea should have a serologic test for syphilis at the time of treatment and a follow-up serologic test after 3 mo. In the treatment of UTI, frequent bacteriological and clinical appraisals are necessary.

Pregnancy

Category B .

Lactation

Excreted in breast milk.

Children

Moxatag

Safety and efficacy not established in children younger 12 yr of age.

Elderly

Differences in response between elderly patients (65 yr of age and older) and younger patients have not been identified.

Hypersensitivity

Serious and occasionally fatal hypersensitivity (eg, anaphylactic) reactions may occur. Use with caution in cephalosporin-sensitive patients because of possible cross-allergenicity.

Renal Function

Moxatag

Dosage reduction may be necessary. Administration is not recommended in patients with severe renal function impairment (CrCl less than 30 mL/min) or patients on hemodialysis.

Superinfection

May result in overgrowth of nonsusceptible bacterial or fungal organisms.

Phenylketonurics

DisperMox tablets for suspension and Amoxil 200 and 400 mg chewable tablets contain phenylalanine.

Pseudomembranous colitis

Consider possibility in patients with diarrhea.

Streptococcal infections

Minimum 10 days required for effective treatment.

Overdosage

Symptoms

Crystalluria, interstitial nephritis.

Patient Information

Instruct patient to time doses evenly over a 24-h period.
Inform patient that capsules, chewable tablets, and oral suspension may be given without regard to meals.
Take Moxatag with food.
Instruct patient to increase fluid intake to 2,000 to 3,000 mL/day unless contraindicated.
Advise patient to discard oral liquid preparations that are more than 14 days old.
If therapy is changed because of allergic reaction, explain significance of penicillin allergy and inform patient of potential sensitivity to cephalosporins.
Instruct patient to report the following symptoms to health care provider: difficulty breathing, rash.