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Amoxicillin

Class: Aminopenicillins
Chemical Name: [2S-[2α,5α,6β(S*)]]-6-[[Amino(4-hydroxyphenyl)acetyl]amino]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid trihydrate
CAS Number: 61336-70-7

Medically reviewed by Drugs.com on Aug 24, 2021. Written by ASHP.

Introduction

Antibacterial; β-lactam antibiotic; aminopenicillin.

Uses for Amoxicillin

Otitis Media

Treatment of acute otitis media (AOM). AAP, AAFP, CDC, and others consider amoxicillin the drug of first choice for initial treatment of AOM, unless the infection is suspected of being caused by β-lactamase-producing bacteria resistant to the drug, in which case the fixed combination of amoxicillin and clavulanate is recommended for initial treatment. Those who fail to respond to amoxicillin should be retreated with amoxicillin and clavulanate.

Has been used for management of otitis media with effusion (OME). Anti-infectives not usually recommended; they provide only limited benefit in enhancing resolution of effusion and may promote resistance. AAP, AAFP, and others recommend watchful waiting for 3 months from date of effusion onset or diagnosis in those 2 months to 12 years of age who are not at risk for speech, language, or learning problems; some suggest a short course of anti-infectives may be considered for possible short-term benefits when parent and/or caregiver expresses a strong aversion to impending surgery. If anti-infectives are used, amoxicillin or the fixed combination of amoxicillin and clavulanate recommended.

Pharyngitis and Tonsillitis

Treatment of pharyngitis and tonsillitis caused by Streptococcus pyogenes (group A β-hemolytic streptococci; GAS) and prevention of initial attacks (primary prevention) of rheumatic fever.

AAP, IDSA, and AHA recommend a penicillin regimen (i.e., 10 days of oral penicillin V or oral amoxicillin or single dose of IM penicillin G benzathine) as treatment of choice for S. pyogenes pharyngitis and tonsillitis; other anti-infectives (narrow-spectrum oral cephalosporins, oral macrolides, oral clindamycin) recommended as alternatives in penicillin-allergic patients.

If signs and symptoms of pharyngitis recur shortly after initial treatment and presence of S. pyogenes documented, retreatment with original or alternative anti-infective recommended. Alternative regimens recommended for retreatment include a narrow-spectrum oral cephalosporin, oral clindamycin, oral fixed combination of amoxicillin and clavulanate, oral macrolide, or IM penicillin G benzathine.

Consider that multiple, recurrent episodes of symptomatic pharyngitis within a period of several months to years may indicate that patient is a long-term pharyngeal carrier of S. pyogenes experiencing repeated episodes of nonstreptococcal (e.g., viral) pharyngitis.

Treatment not usually recommended for asymptomatic chronic pharyngeal carriers of S. pyogenes. Eradication of the carrier state may be desirable in certain situations (e.g., community outbreak of acute rheumatic fever, acute poststreptococcal glomerulonephritis, or invasive S. pyogenes infections; outbreak of S. pyogenes pharyngitis in a closed or partially closed community; multiple episodes of documented symptomatic S. pyogenes pharyngitis occurring within a family for many weeks despite appropriate treatment; personal or family history of acute rheumatic fever). In such situations, recommended regimens include oral clindamycin, oral fixed combination of amoxicillin and clavulanate, or either IM penicillin G benzathine or oral penicillin V used in conjunction with oral rifampin.

Respiratory Tract Infections

Treatment of lower respiratory tract infections caused by susceptible Streptococcus (α- or β-hemolytic strains only), S. pneumoniae, Staphylococcus, or H. influenzae.

Skin and Skin Structure Infections

Treatment of skin and skin structure infections caused by susceptible Streptococcus (α- or β-hemolytic strains only), Staphylococcus, or Escherichia coli.

Urinary Tract Infections (UTIs)

Treatment of UTIs caused by susceptible Enterococcus faecalis, Escherichia coli, or Proteus mirabilis. A drug of choice for treatment of uncomplicated UTIs caused by E. faecalis; consider high incidence of amoxicillin-resistant E. coli and other Enterobacteriaceae.

Gonorrhea

Previously used for treatment of acute uncomplicated gonorrhea (anogenital and urethral) caused by susceptible Neisseria gonorrhoeae. No longer recommended for gonorrhea by CDC or others (high incidence of penicillin-resistant strains of N. gonorrhoeae).

Typhoid Fever and other Salmonella Infections

Alternative for treatment of typhoid fever (enteric fever) caused by susceptible Salmonella typhi. Drugs of choice are fluoroquinolones and third generation cephalosporins (e.g., ceftriaxone, cefotaxime); consider that multidrug-resistant strains of S. typhi (strains resistant to ampicillin, amoxicillin, chloramphenicol, and/or co-trimoxazole) reported with increasing frequency.

Treatment of chronic carriers of S. typhi; drugs of choice are fluoroquinolones (e.g., ciprofloxacin), ampicillin, or amoxicillin (with probenecid).

Alternative for treatment of gastroenteritis caused by nontyphoidal Salmonella. Anti-infectives not indicated in otherwise healthy individuals with uncomplicated (noninvasive) gastroenteritis, but recommended if gastroenteritis is severe and in those at increased risk of invasive disease (e.g., <6 months or >50 years of age; hemoglobinopathies, severe atherosclerosis, valvular heart disease, prostheses, uremia, chronic GI disease, severe colitis; immunocompromised because of malignancy, immunosuppressive therapy, HIV infection). Drugs of choice are fluoroquinolones, third generation cephalosporins (cefotaxime, ceftriaxone), ampicillin, amoxicillin, co-trimoxazole, or chloramphenicol, depending on in vitro susceptibility.

Helicobacter pylori Infection and Duodenal Ulcer Disease

Treatment of Helicobacter pylori infection and duodenal ulcer disease (active or 1-year history of duodenal ulcer); eradication of H. pylori has been shown to reduce the risk of duodenal ulcer recurrence.

Used in a multidrug regimen that includes amoxicillin, clarithromycin, and either lansoprazole or omeprazole (triple therapy). Used with lansoprazole (dual therapy) in those allergic to or intolerant of clarithromycin or when clarithromycin resistance is suspected.

Lyme Disease

Treatment of early localized or early disseminated Lyme disease associated with erythema migrans, in the absence of neurologic involvement or third-degree AV heart block.

IDSA, AAP, and others consider amoxicillin a drug of choice for treatment of early localized or early disseminated Lyme disease when oral therapy is appropriate. May be used in those with mild Lyme carditis, Lyme arthritis (without associated neurologic disease), or isolated facial nerve palsy (without other neurologic involvement).

Amoxicillin is the preferred oral agent for treatment in pregnant women and children <8 years of age who should not receive doxycycline.

Chlamydial Infections

Treatment of uncomplicated urethritis and cervicitis caused by Chlamydia trachomatis in pregnant women. CDC recommends azithromycin as drug of choice and amoxicillin or erythromycin as alternatives for treatment of urogenital chlamydial infections in pregnant women.

Prevention of Bacterial Endocarditis

Prevention of α-hemolytic (viridans group) bacterial endocarditis in patients undergoing certain dental procedures (i.e., procedures that involve manipulation of gingival tissue or periapical region of teeth or perforation of oral mucosa) or certain invasive respiratory tract procedures (i.e., procedures involving incision or biopsy of respiratory mucosa) who have certain cardiac conditions that put them at highest risk of adverse outcomes from endocarditis. AHA recommends amoxicillin as drug of choice for such prophylaxis.

Anti-infective prophylaxis solely for prevention of bacterial endocarditis no longer recommended by AHA for patients undergoing GU or GI procedures.

Consult most recent AHA recommendations for information on which cardiac conditions are associated with highest risk of adverse outcomes from endocarditis and specific recommendations regarding use of prophylaxis to prevent endocarditis in these patients.

Prevention of S. pneumoniae Infections in Asplenic Individuals

Prevention of invasive S. pneumoniae infections in children with anatomic or functional asplenia (e.g., congenital, resulting from sickle cell disease or surgery) or children with malignant neoplasms or thalassemia.

Oral penicillin V usually drug of choice; some experts recommend amoxicillin.

Children at increased risk for pneumococcal infections should receive age-appropriate vaccination with pneumococcal 13-valent conjugate vaccine (PCV13) and pneumococcal 23-valent polysaccharide vaccine (PPSV23). Long-term anti-infective prophylaxis recommended for children with functional or anatomic asplenia regardless of vaccination status.

Anthrax

Alternative for postexposure prophylaxis of anthrax following exposure to Bacillus anthracis spores (inhalational anthrax). Ciprofloxacin or doxycycline are initial drugs of choice for prophylaxis following suspected or confirmed exposure to aerosolized anthrax spores, including exposures that occur in the context of biologic warfare or bioterrorism. If penicillin susceptibility confirmed, consideration can be given to changing prophylaxis to a penicillin (oral amoxicillin or penicillin V) in infants and children, pregnant or lactating women, or when drugs of choice not tolerated or not available; amoxicillin may be preferred, especially in infants and children.

Alternative for treatment of inhalational anthrax when a parenteral regimen not available (e.g., when there are supply or logistic problems in a mass-casualty setting).

Alternative for treatment of cutaneous anthrax caused by susceptible B. anthracis. If cutaneous anthrax occurs in the context of biologic warfare or bioterrorism, initial drugs of choice are ciprofloxacin or doxycycline. If penicillin susceptibility confirmed, consideration can be given to changing to a penicillin (oral amoxicillin or penicillin V) in infants and children, pregnant or lactating women, or when drugs of choice not tolerated or not available; amoxicillin may be preferred, especially in infants and children.

Amoxicillin Dosage and Administration

Administration

Oral Administration

Administer orally without regard to meals.

Following reconstitution, the required amount of oral suspension should be placed directly on the child’s tongue for swallowing. Alternatively, the required amount of suspension can be added to infant formula, milk, fruit juice, water, ginger ale, or cold drinks and these fluids taken immediately and completely consumed.

For most infections, continue therapy for at least 48–72 hours after patient becomes asymptomatic or evidence that the infection is eradicated is obtained. The drug should be given for at least 10 days for treatment of infections caused by S. pyogenes (group A β-hemolytic streptococci).

Reconstitution

Reconstitute oral suspension at the time of dispensing. Tap bottle to thoroughly loosen powder and then add the amount of water specified on the bottle in 2 portions; agitate vigorously after each addition.

Agitate suspension well prior to administration of each dose.

Dosage

Available as the trihydrate; dosage expressed in terms of anhydrous amoxicillin.

Pediatric Patients

General Pediatric Dosage
Oral

Neonates and infants ≤12 weeks (3 months) of age: Manufacturer states dosage up to 30 mg/kg daily can be given in divided doses every 12 hours.

Children ≥3 months of age weighing ≥40 kg: Manufacturer states use usual adult dosage.

Children beyond neonatal period with mild to moderate infections: AAP recommends 25–50 mg/kg daily given in 3 divided doses.

Children beyond neonatal period with severe infections: AAP states that 80–100 mg/kg daily given in 3 divided doses can be used for step-down therapy. For highly susceptible pathogens, 90 mg/kg daily given in 2 divided doses can be used.

Otitis Media
Treatment of Acute Otitis Media (AOM)
Oral

80–90 mg/kg daily given in 2 or 3 divided doses recommended by AAP, AAFP, CDC, and others.

Usual duration is 10 days; optimal duration uncertain. AAP recommends 10 days of treatment in those <2 years of age and in those with severe symptoms. For mild to moderate AOM in older children, AAP states 7- and 10-day regimens appear equally effective in those 2–5 years of age and a duration of 5–7 days may be adequate in those ≥6 years of age.

Pharyngitis and Tonsillitis
Oral

45 mg/kg daily in 2 divided doses or 40 mg/kg daily in 3 divided doses for 10 days recommended by manufacturer.

AHA and AAP recommend 50 mg/kg (up to 1 g) once daily for 10 days.

IDSA recommends 50 mg/kg (up to 1 g) once daily for 10 days or 25 mg/kg (up to 500 mg) twice daily for 10 days.

Ear, Nose, and Throat Infections
Oral

25 mg/kg daily in divided doses every 12 hours or 20 mg/kg daily in divided doses every 8 hours for mild to moderate infections.

45 mg/kg daily in divided doses every 12 hours or 40 mg/kg in divided doses every 8 hours for severe infections.

Respiratory Tract Infections
Oral

45 mg/kg daily in divided doses every 12 hours or 40 mg/kg daily in divided doses every 8 hours for mild, moderate, or severe lower respiratory tract infections.

Skin and Skin Structure Infections
Oral

25 mg/kg daily in divided doses every 12 hours or 20 mg/kg daily in divided doses every 8 hours for mild to moderate infections.

45 mg/kg daily in divided doses every 12 hours or 40 mg/kg daily in divided doses every 8 hours for severe infections or those caused by less susceptible bacteria.

Urinary Tract Infections (UTIs)
Oral

25 mg/kg daily in divided doses every 12 hours or 20 mg/kg daily in divided doses every 8 hours for mild to moderate infections.

45 mg/kg daily in divided doses every 12 hours or 40 mg/kg daily in divided doses every 8 hours for severe infections or those caused by less susceptible bacteria.

Gonorrhea
Oral

Prepubertal children ≥2 years of age: 50 mg/kg as a single dose given with a single dose of probenecid (25 mg/kg) recommended by manufacturer.

No longer recommended for gonorrhea by CDC or other experts.

Lyme Disease†
Oral

25–50 mg/kg daily (up to 2 g daily) in 2–3 divided doses for 14–21 days for treatment of early localized or early disseminated Lyme disease.

50 mg/kg daily in 3 divided doses for 14–28 days for mild Lyme carditis or for 28 days for Lyme arthritis (without associated neurologic disease).

Prevention of Bacterial Endocarditis†
Patients Undergoing Certain Dental or Respiratory Tract Procedures†
Oral

50 mg/kg given as a single dose 30–60 minutes prior to the procedure.

Prevention of S. pneumoniae Infections in Asplenic Individuals†
Oral

20 mg/kg daily in children with anatomic or functional asplenia.

In infants with sickle cell anemia, initiate prophylaxis as soon as diagnosis is established (preferably by 2 months of age); continue until approximately 5 years of age. Appropriate duration in children with asplenia from other causes unknown; some experts recommend that asplenic children at high risk receive prophylaxis throughout childhood and into adulthood.

Anthrax†
Postexposure Prophylaxis of Anthrax†
Oral

Full-term neonates ≤4 weeks of age: AAP recommends 75 mg/kg daily given in divided doses every 8 hours.

Preterm neonates (gestational age 32–37 weeks): AAP recommends 50 mg/kg daily given in divided doses every 12 hours in those ≤1 week of age and 75 mg/kg daily given in divided doses every 8 hours in those 1–4 weeks of age.

Infants and children ≥1 month of age: AAP recommends 75 mg/kg daily (up to 1 g daily) given in divided doses every 8 hours.

Children: Some experts recommend 80 mg/kg daily given in divided doses every 8 hours in those weighing <20 kg and 500 mg every 8 hours in those weighing ≥20 kg.

Use only if penicillin-susceptible B. anthracis involved.

Total duration of anti-infective prophylaxis should be ≥60 days.

Treatment of Inhalational Anthrax†
Oral

Full-term neonates ≤4 weeks of age for follow-up after initial parenteral regimen: AAP recommends 75 mg/kg daily given in divided doses every 8 hours in conjunction with other anti-infectives.

Preterm neonates (gestational age 32–37 weeks) for follow-up after initial parenteral regimen: AAP recommends 50 mg/kg daily given in divided doses every 12 hours in those ≤1 week of age and 75 mg/kg daily given in divided doses every 8 hours in those 1–4 weeks of age in conjunction with other anti-infectives.

Infants and children ≥1 month of age for follow-up after initial parenteral regimen: 75 mg/kg daily (up to 1 g daily) given in divided doses every 8 hours in conjunction with other anti-infectives.

Children with inhalational anthrax in mass casualty setting when parenteral anti-infectives not available: Some experts recommend 80 mg/kg daily given in divided doses every 8 hours in those weighing <20 kg and 500 mg every 8 hours in those weighing ≥20 kg.

Recommended dosages are for infections that occur in the context of biologic warfare or bioterrorism and when meningitis can be ruled out.

Use only if infection known to be caused by penicillin-susceptible B. anthracis.

Total duration of anti-infective treatment should be 60 days.

Treatment of Cutaneous Anthrax†
Oral

Full-term neonates ≤4 weeks of age with cutaneous anthrax without systemic involvement: AAP recommends 75 mg/kg daily given in divided doses every 8 hours.

Preterm neonates (gestational age 32–37 weeks) with cutaneous anthrax without systemic involvement: AAP recommends 50 mg/kg daily given in divided doses every 12 hours in those ≤1 week of age and 75 mg/kg daily given in divided doses every 8 hours in those 1–4 weeks of age.

Infants and children ≥1 month of age with cutaneous anthrax without systemic involvement: AAP recommends 75 mg/kg daily (up to 1 g daily) given in divided doses every 8 hours.

Children: Some experts recommend 80 mg/kg daily (up to 1.5 g daily) given in divided doses every 8 hours.

Recommended dosages are for infections that occur in the context of biologic warfare or bioterrorism.

Use only if infection known to be caused by penicillin-susceptible B. anthracis.

Although 7–10 days may be adequate if cutaneous anthrax occurred as the result of natural or endemic exposure to anthrax, CDC, AAP, and others recommend 60 days of anti-infective treatment if cutaneous anthrax occurred as the result of exposure to aerosolized anthrax spores (e.g., in context of biologic warfare or bioterrorism).

Adults

Pharyngitis and Tonsillitis
Oral

AHA recommends 50 mg/kg (up to 1 g) once daily for 10 days.

IDSA recommends 50 mg/kg (up to 1 g) once daily for 10 days or 25 mg/kg (up to 500 mg) twice daily for 10 days.

Ear, Nose, and Throat Infections
Oral

500 mg every 12 hours or 250 mg every 8 hours for mild to moderate infections.

875 mg every 12 hours or 500 mg every 8 hours for severe infections or those caused by less susceptible bacteria.

Respiratory Tract Infections
Oral

875 mg every 12 hours or 500 mg every 8 hours for mild, moderate, or severe lower respiratory tract infections.

Skin and Skin Structure Infections
Oral

500 mg every 12 hours or 250 mg every 8 hours for mild to moderate infections.

875 mg every 12 hours or 500 mg every 8 hours for severe infections or those caused by less susceptible bacteria.

Urinary Tract Infections (UTIs)
Oral

500 mg every 12 hours or 250 mg every 8 hours for mild to moderate infections.

875 mg every 12 hours or 500 mg every 8 hours for severe infections or those caused by less susceptible bacteria.

Gonorrhea
Oral

3 g as a single dose recommended by manufacturer.

No longer recommended for gonorrhea by CDC or other experts.

Typhoid Fever†
Oral

100 mg/kg daily or 1–1.5 g every 6 hours for 14 days.

Helicobacter pylori Infection and Duodenal Ulcer Disease
Oral

1 g 2 times daily for 10 or 14 days given in conjunction with clarithromycin and either lansoprazole or omeprazole (triple therapy).

1 g 3 times daily for 14 days given in conjunction with lansoprazole (dual therapy).

Lyme Disease†
Oral

500 mg 3 times daily for 14–21 days for treatment of early localized or early disseminated Lyme disease.

500 mg 3 times daily for 14–28 days for mild Lyme carditis or for 28 days for Lyme arthritis (without associated neurologic disease).

Chlamydial Infections†
Oral

500 mg 3 times daily for 7 days for treatment of chlamydial infections in pregnant women.

Prevention of Bacterial Endocarditis†
Patients Undergoing Certain Dental or Respiratory Tract Procedures†
Oral

2 g as a single dose given 30–60 minutes prior to the procedure.

Anthrax†
Postexposure Prophylaxis of Anthrax†
Oral

500 mg every 8 hours has been recommended.

1 g every 8 hours recommended by CDC for adults (including pregnant and postpartum women) if exposure occurred in the context of biologic warfare or bioterrorism.

Use only if penicillin-susceptible B. anthracis involved.

Total duration of anti-infective prophylaxis should be ≥60 days.

Treatment of Inhalational Anthrax†
Oral

Inhalational anthrax in mass casualty setting when parenteral anti-infectives not available: 500 mg every 8 hours for 60 days.

Treatment of Cutaneous Anthrax†
Oral

500 mg every 8 hours has been recommended.

1 g every 8 hours recommended by CDC for adults (including pregnant and postpartum women) for cutaneous anthrax without systemic involvement if infection occurred in the context of biologic warfare or bioterrorism.

Use only if infection known to be caused by penicillin-susceptible B. anthracis.

Although 7–10 days may be adequate if cutaneous anthrax occurred as the result of natural or endemic exposure to anthrax, CDC and others recommend 60 days of anti-infective treatment if cutaneous anthrax occurred as the result of exposure to aerosolized anthrax spores (e.g., in context of biologic warfare or bioterrorism).

Prescribing Limits

Pediatric Patients

Neonates and Infants ≤12 weeks (3 Months) of Age
Oral

Maximum 30 mg/kg daily in divided doses every 12 hours.

Special Populations

Renal Impairment

Dosage adjustment necessary in severe renal impairment.

Do not use 875-mg tablets in those with severe renal impairment and GFR <30 mL/minute.

Dosage recommendations not available for pediatric patients with renal impairment.

Dosage for Adults with Renal Impairment

GFR (mL/min)

Daily Dosage

10–30

250 or 500 mg every 12 hours depending on infection severity

<10

250 or 500 mg every 24 hours depending on infection severity

Hemodialysis Patients

250 or 500 mg every 24 hours depending on infection severity; with an additional dose both during and at the end of dialysis

Cautions for Amoxicillin

Contraindications

  • Known hypersensitivity to any penicillin.

Warnings/Precautions

Warnings

Superinfection/Clostridium difficile-associated Colitis

Possible emergence and overgrowth of nonsusceptible bacteria or fungi. Discontinue and institute appropriate therapy if superinfection occurs.

Treatment with anti-infectives may permit overgrowth of clostridia. Consider Clostridium difficile-associated diarrhea and colitis (antibiotic-associated pseudomembranous colitis) if diarrhea develops and manage accordingly.

Some mild cases of C. difficile-associated diarrhea and colitis may respond to discontinuance alone. Manage moderate to severe cases with fluid, electrolyte, and protein supplementation; appropriate anti-infective therapy (e.g., oral metronidazole or vancomycin) recommended if colitis is severe.

Sensitivity Reactions

Hypersensitivity Reactions

Serious and occasionally fatal hypersensitivity reactions, including anaphylaxis, reported with penicillins.

Prior to initiation of therapy, make careful inquiry regarding previous hypersensitivity reactions to penicillins, cephalosporins, or other drugs. Partial cross-allergenicity occurs among penicillins and other β-lactam antibiotics including cephalosporins and cephamycins.

If a severe hypersensitivity reaction occurs, discontinue immediately and institute appropriate therapy as indicated (e.g., epinephrine, corticosteroids, maintenance of an adequate airway and oxygen).

General Precautions

Selection and Use of Anti-infectives

To reduce development of drug-resistant bacteria and maintain effectiveness of amoxicillin and other antibacterials, use only for treatment or prevention of infections proven or strongly suspected to be caused by susceptible bacteria.

When selecting or modifying anti-infective therapy, use results of culture and in vitro susceptibility testing. In the absence of such data, consider local epidemiology and susceptibility patterns when selecting anti-infectives for empiric therapy.

Hepatic Effects

Moderate increases in serum AST and/or ALT reported.

Hepatic dysfunction, including cholestatic jaundice, hepatic cholestasis, and acute cytolytic hepatitis reported.

Assess hepatic function periodically during prolonged therapy.

Renal Effects

Assess renal function periodically during prolonged therapy.

Hematologic Effects

Adverse hematologic effects (e.g., anemia, hemolytic anemia, leukopenia, agranulocytosis, thrombocytopenia, thrombocytopenic purpura) reported with penicillins. Usually reversible when drug discontinued; may be a hypersensitivity reaction.

Assess hematologic function periodically during prolonged therapy.

Mononucleosis

Possible increased risk of rash in patients with mononucleosis; use in these patients not recommended.

Phenylketonuria

200- and 400-mg chewable tablets contain aspartame (NutraSweet), which is metabolized in the GI tract to provide 1.82 or 3.64 mg of phenylalanine, respectively.

Oral suspensions do not contain aspartame and can be used in individuals with phenylketonuria (i.e., homozygous genetic deficiency of phenylalanine hydroxylase) and other individuals who must restrict their intake of phenylalanine.

Use of Fixed Combination

When used in fixed combination with other agents, consider the cautions, precautions, and contraindications associated with the concomitant agents.

Specific Populations

Pregnancy

Category B.

Recommended as an alternative for various indications in pregnant women (e.g., treatment of chlamydial infections, treatment of Lyme disease, postexposure prophylaxis or treatment of anthrax).

Lactation

Distributed into milk; use with caution.

Use in a breast-feeding woman may result in sensitization of infants.

Recommended as an alternative for postexposure prophylaxis or treatment of anthrax in women who are breast-feeding.

Pediatric Use

Renal clearance of amoxicillin may be delayed in neonates and young infants because of incompletely developed renal function.

Neonates and infants ≤12 weeks (3 months) of age should receive no more than 30 mg/kg daily given in divided doses every 12 hours.

Tooth discoloration (brown, yellow, gray) reported rarely, most frequently in pediatric patients. Brushing or dental cleaning reduces or eliminates discoloration in most cases.

Geriatric Use

Renal clearance may be decreased.

Hepatic Impairment

Assess hepatic function periodically during prolonged therapy.

Renal Impairment

Assess renal function periodically during prolonged therapy.

Dosage adjustments necessary in severe renal impairment.

Common Adverse Effects

Adverse GI effects (e.g., nausea, vomiting, diarrhea), hypersensitivity reactions (e.g., rash).

Interactions for Amoxicillin

Specific Drugs and Laboratory Tests

Drug

Interaction

Comments

Allopurinol

Possible increased incidence of rash; reported with ampicillin but no data regarding amoxicillin

Unclear whether potentiation of rash is caused by allopurinol or hyperuricemia present in these patients

Chloramphenicol

In vitro evidence of antagonism

Clinical importance unclear

Clavulanic acid

In vitro and in vivo synergistic bactericidal effect

Used to therapeutic advantage in infections caused by β-lactamase-producing bacteria; commercially available in fixed combination with clavulanate potassium

Macrolides

In vitro evidence of antagonism

Clinical importance unclear

Methotrexate

Possible decreased renal clearance of methotrexate; possible increased methotrexate concentrations and hematologic and GI toxicity

Monitor closely if used concomitantly

Probenecid

Decreased renal tubular secretion of amoxicillin; increased and prolonged amoxicillin concentrations may occur

Sulfonamides

In vitro evidence of antagonism

Clinical importance unclear

Tests for glucose

Possible false-positive reactions in urine glucose tests using Clinitest, Benedict’s solution, or Fehling’s solution; reported with ampicillin but no data regarding amoxicillin

Use glucose tests based on enzymatic glucose oxidase reactions (e.g., Clinistix, Tes-Tape)

Tetracyclines

In vitro evidence of antagonism

Clinical importance unclear

Amoxicillin Pharmacokinetics

Absorption

Bioavailability

74–92% of an oral dose absorbed from GI tract.

Peak serum concentrations usually attained within 1–2 hours.

A 400-mg chewable tablet is bioequivalent to 5 mL of the oral suspension containing 400 mg/5 mL.

Food

Food has minimal or no effect on bioavailability of oral amoxicillin.

Special Populations

Oral absorption delayed in neonates compared with older children and adults; peak concentrations attained within 3–4.5 hours in neonates.

Distribution

Extent

Readily distributed into most tissues and fluids following oral administration, including lungs, bronchial secretions, maxillary sinus secretions, bile, pleural fluid, sputum, and middle ear fluid.

Only low concentrations attained in CSF.

Crosses the placenta and is distributed into human milk.

Plasma Protein Binding

17–20%.

Elimination

Metabolism

Probably metabolized to some extent in the liver.

Elimination Route

Eliminated principally in urine by both glomerular filtration and tubular secretion.

Approximately 50–80% of amoxicillin dose excreted unchanged in urine.

Half-life

1–1.4 hours.

Special Populations

Serum concentrations increased and half-life prolonged in patients with renal impairment.

Renal clearance may be delayed in neonates and young infants because of incompletely developed renal function.

Stability

Storage

Oral

Capsules

≤20°C.

For Suspension

250 mg/5 mL: ≤20°C. Following reconstitution, refrigerate (preferable but not required) and discard after 14 days.

200 or 400 mg/5 mL: ≤25°C. Following reconstitution, refrigerate (preferable but not required) and discard after 14 days.

Tablets

200- and 400-mg chewable tablets and 500- or 875-mg film-coated tablets: ≤25°C.

Actions and Spectrum

  • A β-lactam antibacterial classified as an aminopenicillin. The p-hydroxyl analog of ampicillin.

  • Usually bactericidal.

  • Gram-positive aerobes: Active in vitro and in clinical infections against Staphylococcus (β-lactamase-negative strains only), Streptococcus pneumoniae, other Streptococcus (α- and β-hemolytic strains only), and Enterococcus faecalis.

  • Gram-negative aerobes: Active in vitro and in clinical infections against H. influenzae, N. gonorrhoeae, E. coli, Corynebacterium diphtheriae, Listeria monocytogenes, Proteus mirabilis, Salmonella, and Shigella.

  • Other organisms: Active in vitro and in clinical infections caused by H. pylori. Also active against Borrelia burgdorferi.

  • Generally has same spectrum and level of activity as ampicillin, but more active than ampicillin against enterococci and Salmonella and less active against Shigella and Enterobacter.

  • Resistance reported in gram-positive and gram-negative bacteria that produce β-lactamases, including β-lactamase-producing S. aureus and E. faecalis.

  • Complete cross-resistance generally occurs between amoxicillin and ampicillin.

Advice to Patients

  • Advise patients that antibacterials (including amoxicillin) should only be used to treat bacterial infections and not used to treat viral infections (e.g., the common cold).

  • Importance of completing the entire prescribed course of treatment, even if feeling better after a few days.

  • Advise patients that skipping doses or not completing the full course of therapy may decrease effectiveness and increase the likelihood that bacteria will develop resistance and will not be treatable with amoxicillin or other antibacterials in the future.

  • Advise individuals with phenylketonuria and other individuals who must restrict their intake of phenylalanine that 200- and 400-mg chewable tablets contain aspartame (NutraSweet), which is metabolized in the GI tract to phenylalanine.

  • Importance of discontinuing therapy and informing clinician if an allergic reaction occurs.

  • Importance of informing clinician of existing or contemplated concomitant therapy, including prescription and OTC drugs.

  • Importance of women informing clinicians if they are or plan to become pregnant or to breast-feed.

  • Importance of advising patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Amoxicillin (Trihydrate)

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Capsules

250 mg (of amoxicillin)*

Amoxicillin Capsules

500 mg (of amoxicillin)*

Amoxicillin Capsules

For suspension

125 mg (of amoxicillin) per 5 mL*

Amoxicillin for Suspension

200 mg (of amoxicillin) per 5 mL*

Amoxicillin for Suspension

250 mg (of amoxicillin) per 5 mL*

Amoxicillin for Suspension

50 mg (of amoxicillin) per mL*

Amoxicillin for Suspension

400 mg (of amoxicillin) per 5 mL*

Amoxicillin for Suspension

Tablets, chewable

125 mg (of amoxicillin)*

Amoxicillin Chewable Tablets

250 mg (of amoxicillin)*

Amoxicillin Chewable Tablets

Tablets, film-coated

500 mg (of amoxicillin)*

Amoxicillin Tablets

875 mg (of amoxicillin)*

Amoxicillin Tablets

Amoxicillin (Trihydrate) Combinations

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Kit

4 Capsules, Amoxicillin (trihydrate) 500 mg (of amoxicillin)

2 Capsules, delayed-release (containing enteric-coated granules) Lansoprazole 30 mg (Prevacid)

2 Tablets, film-coated, Clarithromycin 500 mg (Biaxin) Filmtab (with povidone and propylene glycol)

Prevpac

Takeda

AHFS DI Essentials™. © Copyright 2022, Selected Revisions September 3, 2018. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

† Use is not currently included in the labeling approved by the US Food and Drug Administration.

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