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Amoxicillin (Amoxycillin)
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Pharmacology
Amoxicillin, a semisynthetic penicillin of the aminopenicillin group, is bactericidal against sensitive organisms. It acts through the inhibition of mucopeptide synthesis in the bacterial cell wall.
The spectrum of activity of amoxicillin includes H.influenzae, E.coli, P.mirabilis, Salmonella and some Shigella species as well as penicillin-sensitive gram-positive bacteria (see PenicillinG/PenicillinV, General Monograph). However, many Enterobacteriaceae, H.Influenzae, Salmonella and Shigella species are resistant to amoxicillin because these organisms produce b-lactamase. Amoxicillin has the same in vitro activity as ampicillin but has slightly better activity against E.faecalis, E.coli and Salmonella species. Combining amoxicillin with a b-lactamase inhibitor such as clavulanic acid effectively broadens its spectrum of activity to include many b-lactamase-producing strains of M. catarrhalis, E. coli, H. influenzae , Klebsiella and S. aureus.
Pharmacokinetics: Amoxicillin is rapidly absorbed after oral administration and is stable in the presence of gastric acid. Peak serum concentrations are usually attained within 1to 2hours following oral administration and are generally 2to 2.5times greater than those obtained with an equivalent dose of oral ampicillin. Amoxicillin diffuses readily into most body tissue and fluids, with the exception of the cerebrospinal fluid, although higher concentrations of the drug may be attained in patients with inflamed meninges. Amoxicillin is not highly protein bound. Its elimination half-life ranges from 0.7to 1.4hours in patients with normal renal function. Amoxicillin is partially metabolized to microbiologically inactive metabolites and then rapidly excreted in urine. Small amounts of the compounds are excreted in feces and bile.
Amoxicillin, a semisynthetic penicillin of the aminopenicillin group, is bactericidal against sensitive organisms. It acts through the inhibition of mucopeptide synthesis in the bacterial cell wall.
The spectrum of activity of amoxicillin includes H.influenzae, E.coli, P.mirabilis, Salmonella and some Shigella species as well as penicillin-sensitive gram-positive bacteria (see PenicillinG/PenicillinV, General Monograph). However, many Enterobacteriaceae, H.Influenzae, Salmonella and Shigella species are resistant to amoxicillin because these organisms produce b-lactamase. Amoxicillin has the same in vitro activity as ampicillin but has slightly better activity against E.faecalis, E.coli and Salmonella species. Combining amoxicillin with a b-lactamase inhibitor such as clavulanic acid effectively broadens its spectrum of activity to include many b-lactamase-producing strains of M. catarrhalis, E. coli, H. influenzae , Klebsiella and S. aureus.
Pharmacokinetics: Amoxicillin is rapidly absorbed after oral administration and is stable in the presence of gastric acid. Peak serum concentrations are usually attained within 1to 2hours following oral administration and are generally 2to 2.5times greater than those obtained with an equivalent dose of oral ampicillin. Amoxicillin diffuses readily into most body tissue and fluids, with the exception of the cerebrospinal fluid, although higher concentrations of the drug may be attained in patients with inflamed meninges. Amoxicillin is not highly protein bound. Its elimination half-life ranges from 0.7to 1.4hours in patients with normal renal function. Amoxicillin is partially metabolized to microbiologically inactive metabolites and then rapidly excreted in urine. Small amounts of the compounds are excreted in feces and bile.
Indications
Amoxicillin, A Semisynthetic Penicillin Of The Aminopenicillin Group, Is Bactericidal Against Sensitive Organisms. It Acts Through The Inhibition Of Mucopeptide Synthesis In The Bacterial Cell Wall.
The Spectrum Of Activity Of Amoxicillin Includes H.influenzae, E.coli, P.mirabilis, Salmonella And Some Shigella Species As Well As Penicillin-sensitive Gram-positive Bacteria (see PenicillinG/PenicillinV, General Monograph). However, Many Enterobacteriaceae, H.Influenzae, Salmonella And Shigella Species Are Resistant To Amoxicillin Because These Organisms Produce B-lactamase. Amoxicillin Has The Same In Vitro Activity As Ampicillin But Has Slightly Better Activity Against E.faecalis, E.coli And Salmonella Species. Combining Amoxicillin With A B-lactamase Inhibitor Such As Clavulanic Acid Effectively Broadens Its Spectrum Of Activity To Include Many B-lactamase-producing Strains Of M. Catarrhalis, E. Coli, H. Influenzae , Klebsiella And S. Aureus.
Pharmacokinetics: Amoxicillin Is Rapidly Absorbed After Oral Administration And Is Stable In The Presence Of Gastric Acid. Peak Serum Concentrations Are Usually Attained Within 1to 2hours Following Oral Administration And Are Generally 2to 2.5times Greater Than Those Obtained With An Equivalent Dose Of Oral Ampicillin. Amoxicillin Diffuses Readily Into Most Body Tissue And Fluids, With The Exception Of The Cerebrospinal Fluid, Although Higher Concentrations Of The Drug May Be Attained In Patients With Inflamed Meninges. Amoxicillin Is Not Highly Protein Bound. Its Elimination Half-life Ranges From 0.7to 1.4hours In Patients With Normal Renal Function. Amoxicillin Is Partially Metabolized To Microbiologically Inactive Metabolites And Then Rapidly Excreted In Urine. Small Amounts Of The Compounds Are Excreted In Feces And Bile.
Amoxicillin, A Semisynthetic Penicillin Of The Aminopenicillin Group, Is Bactericidal Against Sensitive Organisms. It Acts Through The Inhibition Of Mucopeptide Synthesis In The Bacterial Cell Wall.
The Spectrum Of Activity Of Amoxicillin Includes H.influenzae, E.coli, P.mirabilis, Salmonella And Some Shigella Species As Well As Penicillin-sensitive Gram-positive Bacteria (see PenicillinG/PenicillinV, General Monograph). However, Many Enterobacteriaceae, H.Influenzae, Salmonella And Shigella Species Are Resistant To Amoxicillin Because These Organisms Produce B-lactamase. Amoxicillin Has The Same In Vitro Activity As Ampicillin But Has Slightly Better Activity Against E.faecalis, E.coli And Salmonella Species. Combining Amoxicillin With A B-lactamase Inhibitor Such As Clavulanic Acid Effectively Broadens Its Spectrum Of Activity To Include Many B-lactamase-producing Strains Of M. Catarrhalis, E. Coli, H. Influenzae , Klebsiella And S. Aureus.
Pharmacokinetics: Amoxicillin Is Rapidly Absorbed After Oral Administration And Is Stable In The Presence Of Gastric Acid. Peak Serum Concentrations Are Usually Attained Within 1to 2hours Following Oral Administration And Are Generally 2to 2.5times Greater Than Those Obtained With An Equivalent Dose Of Oral Ampicillin. Amoxicillin Diffuses Readily Into Most Body Tissue And Fluids, With The Exception Of The Cerebrospinal Fluid, Although Higher Concentrations Of The Drug May Be Attained In Patients With Inflamed Meninges. Amoxicillin Is Not Highly Protein Bound. Its Elimination Half-life Ranges From 0.7to 1.4hours In Patients With Normal Renal Function. Amoxicillin Is Partially Metabolized To Microbiologically Inactive Metabolites And Then Rapidly Excreted In Urine. Small Amounts Of The Compounds Are Excreted In Feces And Bile.
Contraindications
History of allergic reaction to penicillins.
History of allergic reaction to penicillins.
Safety Information / Warning
Serious and occasionally fatal hypersensitivity reactions have been reported in patients on penicillin therapy. Although anaphylaxis is more frequent following parenteral therapy, it has occurred in patients taking oral penicillins. These reactions are more likely to occur in individuals with a history of sensitivity to multiple allergens.
Careful inquiry should be made concerning previous hypersensitivity reactions to penicillins, other b-lactam antibiotics or other allergens. The incidence of cross-sensitivity between penicillins and other b-lactam antibiotics such as cephalosporins or carbapenems is not precisely known. The possibility of cross-sensitivity must be considered in all patients reporting an allergic reaction to a b-lactam antibiotic.
If an allergic reaction occurs, discontinue amoxicillin and institute appropriate therapy. Serious anaphylactic reactions require immediate emergency treatment with epinephrine, oxygen, i.v. corticosteroids and airway management, including intubation, as indicated.
Serious and occasionally fatal hypersensitivity reactions have been reported in patients on penicillin therapy. Although anaphylaxis is more frequent following parenteral therapy, it has occurred in patients taking oral penicillins. These reactions are more likely to occur in individuals with a history of sensitivity to multiple allergens.
Careful inquiry should be made concerning previous hypersensitivity reactions to penicillins, other b-lactam antibiotics or other allergens. The incidence of cross-sensitivity between penicillins and other b-lactam antibiotics such as cephalosporins or carbapenems is not precisely known. The possibility of cross-sensitivity must be considered in all patients reporting an allergic reaction to a b-lactam antibiotic.
If an allergic reaction occurs, discontinue amoxicillin and institute appropriate therapy. Serious anaphylactic reactions require immediate emergency treatment with epinephrine, oxygen, i.v. corticosteroids and airway management, including intubation, as indicated.
Precautions
The use of anti-infective agents sometimes leads to overgrowth of nonsusceptible organisms. Oral or vaginal candidiasis occasionally occurs amoxicillin therapy.
Because amoxicillin is excreted mostly by the kidney, dosage reduction is important in patients with a creatinine clearance less than 0.5mL/s. Dosage should be reduced in proportion to the degree of loss of renal function (see Dosage).
Amoxicillin should not be used if infectious mononucleosis is suspected, due to an increased incidence of maculopapular rash when it is used in this setting (see Adverse Effects).
Drug Interactions : Concurrent use of probenecid or other inhibitors of the renal acid secretory system decrease renal secretion of amoxicillin and increase and prolong blood amoxicillin concentrations. Allopurinol may increase the possibility of skin rash. Tetracyclines, chloramphenicol and other bacteriostatic drugs may interfere with the bactericidal effects of amoxicillin.
Whether amoxicillin decreases the effectiveness of oral contraceptives is controversial. Some clinicians recommend adding an alternative method of contraception for the duration of the cycle when amoxicillin is taken.
Pregnancy: Amoxicillin readily crosses the placenta and is generally considered to pose no significant teratogenic risk. Amoxicillin has been used to treat urinary tract and chlamydial infections during pregnancy with no evidence of adverse effects on the fetus.
Lactation: Amoxicillin appears in breast milk in low concentrations and is generally considered to be compatible with breast-feeding.
The use of anti-infective agents sometimes leads to overgrowth of nonsusceptible organisms. Oral or vaginal candidiasis occasionally occurs amoxicillin therapy.
Because amoxicillin is excreted mostly by the kidney, dosage reduction is important in patients with a creatinine clearance less than 0.5mL/s. Dosage should be reduced in proportion to the degree of loss of renal function (see Dosage).
Amoxicillin should not be used if infectious mononucleosis is suspected, due to an increased incidence of maculopapular rash when it is used in this setting (see Adverse Effects).
Drug Interactions : Concurrent use of probenecid or other inhibitors of the renal acid secretory system decrease renal secretion of amoxicillin and increase and prolong blood amoxicillin concentrations. Allopurinol may increase the possibility of skin rash. Tetracyclines, chloramphenicol and other bacteriostatic drugs may interfere with the bactericidal effects of amoxicillin.
Whether amoxicillin decreases the effectiveness of oral contraceptives is controversial. Some clinicians recommend adding an alternative method of contraception for the duration of the cycle when amoxicillin is taken.
Pregnancy: Amoxicillin readily crosses the placenta and is generally considered to pose no significant teratogenic risk. Amoxicillin has been used to treat urinary tract and chlamydial infections during pregnancy with no evidence of adverse effects on the fetus.
Lactation: Amoxicillin appears in breast milk in low concentrations and is generally considered to be compatible with breast-feeding.
Side Effects / Adverse Effects
Gastrointestinal: nausea, vomiting, diarrhea, anorexia, epigastric distress and gastritis. Black hairy tongue, glossitis and stomatitis have also been noted. Diarrhea is generally less frequent than with ampicillin. Antibiotic-associated pseudomembranous colitis has been reported. Severe abdominal pain and bloody diarrhea associated with acute, transient enterocolitis, but without evidence of pseudomembranous colitis, has also been reported.
Renal: Acute interstitial nephritis has been reported rarely.
Hematologic: Anemia, thrombocytopenia, thrombocytopenic purpura, eosinophilia, leukopenia, neutropenia and agranulocytosis have been reported during therapy with amoxicillin. These reactions are usually reversible on discontinuation of therapy.
Hypersensitivity: A morbilliform, erythematous, urticarial rash, similar to those reported with other penicillins, may occur. In addition, aminopenicillins may cause an erythematous, maculopapular rash which may or may not be immunologically mediated. The overall incidence of rash in patients taking amoxicillin is 1.4 to 10%, with greater than 65% being of the maculopapular type.
Hepatic: Moderate rise in serum aspartate transferase (AST), alkaline phosphatase and lactic dehydrogenase has been noted, but the significance of these findings is unknown.
Gastrointestinal: nausea, vomiting, diarrhea, anorexia, epigastric distress and gastritis. Black hairy tongue, glossitis and stomatitis have also been noted. Diarrhea is generally less frequent than with ampicillin. Antibiotic-associated pseudomembranous colitis has been reported. Severe abdominal pain and bloody diarrhea associated with acute, transient enterocolitis, but without evidence of pseudomembranous colitis, has also been reported.
Renal: Acute interstitial nephritis has been reported rarely.
Hematologic: Anemia, thrombocytopenia, thrombocytopenic purpura, eosinophilia, leukopenia, neutropenia and agranulocytosis have been reported during therapy with amoxicillin. These reactions are usually reversible on discontinuation of therapy.
Hypersensitivity: A morbilliform, erythematous, urticarial rash, similar to those reported with other penicillins, may occur. In addition, aminopenicillins may cause an erythematous, maculopapular rash which may or may not be immunologically mediated. The overall incidence of rash in patients taking amoxicillin is 1.4 to 10%, with greater than 65% being of the maculopapular type.
Hepatic: Moderate rise in serum aspartate transferase (AST), alkaline phosphatase and lactic dehydrogenase has been noted, but the significance of these findings is unknown.
Overdose
Symptoms: Serious toxicity is unlikely following large doses of amoxicillin. Acute ingestion of large doses of amoxicillin may cause nausea, vomiting, diarrhea and abdominal pain. Acute oliguric renal failure and hematuria may occur following large doses.
Treatment: Activated charcoal is recommended only for very large recent ingestions. For amoxicillin ingestions of less than 250mg/kg, treatment is not usually required in patients with normal renal function. Monitor fluid and electrolyte status and renal function in patients with severe vomiting and/or diarrhea. Hemodialysis may be useful following severe overdose with renal impairment.
Symptoms: Serious toxicity is unlikely following large doses of amoxicillin. Acute ingestion of large doses of amoxicillin may cause nausea, vomiting, diarrhea and abdominal pain. Acute oliguric renal failure and hematuria may occur following large doses.
Treatment: Activated charcoal is recommended only for very large recent ingestions. For amoxicillin ingestions of less than 250mg/kg, treatment is not usually required in patients with normal renal function. Monitor fluid and electrolyte status and renal function in patients with severe vomiting and/or diarrhea. Hemodialysis may be useful following severe overdose with renal impairment.
Recommended Dosage
Amoxicillin is given orally and because it is stable in the presence of gastric acid, it may be given without regard to meals. The duration of therapy depends on the type and severity of the infection, and can vary from 7 to 10days to several weeks.
For upper respiratory tract infections, including otitis media, due to susceptible strains of streptococci, nonpenicillinase producing staphylococci or H.influenzae , genitourinary tract infections caused by susceptible strains of E.coli, P.mirabilis or E.faecalis , or skin and soft tissue infections involving susceptible streptococci, nonpenicillinase-producing staphylococci, or E.coli : Adults and children >20kg: 250mg every 8hours. Children <20kg: 20mg/kg/day in divided doses every 8hours, not to exceed the recommended adult dose.
For severe infections or those caused by less susceptible organisms: 500mg every 8hours for adults and children >20kg; 40mg/kg/day in divided doses every 8hours for children <20kg, not to exceed the recommended adult dosage.
For lower respiratory tract infections due to streptococci, nonpenicillinase-producing staphylococci or H.influenzae : Adults and children >20kg: 500mg every 8hours. Children <20kg: 40mg/kg/day in divided doses every 8hours, not to exceed the recommended adult dosage.
Amoxicillin is not recommended as first- or second-line therapy for gonococcal or chlamydial infections, but can be used to treat chlamydial cervicitis, as an alternative to erythromycin, in pregnancy. The dose in this setting is 500mg 3times daily for 10 days. A test to confirm the infection was cured is recommended 3weeks after treatment.
For prophylaxis of bacterial endocarditis in selected patients: Adults: 2g 1hour before the procedure. Children: 50mg/kg 1hour before the procedure, to a maximum of 2g. For more information, see Endocarditis Prophylaxis in the Clin-Info section.
In chronic urinary tract infections, frequent bacteriologic and clinical evaluations are necessary. Do not use doses smaller than those recommended above for the treatment of genitourinary tract infections. In persistent infections, therapy may be required for several weeks, sometimes at higher doses than recommended above. Concurrent bacteriologic sensitivity monitoring is recommended. It may be necessary to continue clinical and/or bacteriologic follow up for several months after cessation of therapy.
For treatment of H.pylori infection in adults with associated peptic ulcer disease, the dose of amoxicillin is 1g twice daily for 7 days in conjunction with clarithromycin and either ranitidine plus bismuth or a proton pump inhibitor.
Dosage in Renal Failure: ClCr0.83to 0.17mL/s: Increase dosing interval from 8hours to 12hours; ClCr<0.17mL/s: increase dosing interval to 12to 24hours.
Hemodialysis: 250to 500mg orally every 24hours. An additional 250mg may be given after each dialysis period.
Amoxicillin is given orally and because it is stable in the presence of gastric acid, it may be given without regard to meals. The duration of therapy depends on the type and severity of the infection, and can vary from 7 to 10days to several weeks.
For upper respiratory tract infections, including otitis media, due to susceptible strains of streptococci, nonpenicillinase producing staphylococci or H.influenzae , genitourinary tract infections caused by susceptible strains of E.coli, P.mirabilis or E.faecalis , or skin and soft tissue infections involving susceptible streptococci, nonpenicillinase-producing staphylococci, or E.coli : Adults and children >20kg: 250mg every 8hours. Children <20kg: 20mg/kg/day in divided doses every 8hours, not to exceed the recommended adult dose.
For severe infections or those caused by less susceptible organisms: 500mg every 8hours for adults and children >20kg; 40mg/kg/day in divided doses every 8hours for children <20kg, not to exceed the recommended adult dosage.
For lower respiratory tract infections due to streptococci, nonpenicillinase-producing staphylococci or H.influenzae : Adults and children >20kg: 500mg every 8hours. Children <20kg: 40mg/kg/day in divided doses every 8hours, not to exceed the recommended adult dosage.
Amoxicillin is not recommended as first- or second-line therapy for gonococcal or chlamydial infections, but can be used to treat chlamydial cervicitis, as an alternative to erythromycin, in pregnancy. The dose in this setting is 500mg 3times daily for 10 days. A test to confirm the infection was cured is recommended 3weeks after treatment.
For prophylaxis of bacterial endocarditis in selected patients: Adults: 2g 1hour before the procedure. Children: 50mg/kg 1hour before the procedure, to a maximum of 2g. For more information, see Endocarditis Prophylaxis in the Clin-Info section.
In chronic urinary tract infections, frequent bacteriologic and clinical evaluations are necessary. Do not use doses smaller than those recommended above for the treatment of genitourinary tract infections. In persistent infections, therapy may be required for several weeks, sometimes at higher doses than recommended above. Concurrent bacteriologic sensitivity monitoring is recommended. It may be necessary to continue clinical and/or bacteriologic follow up for several months after cessation of therapy.
For treatment of H.pylori infection in adults with associated peptic ulcer disease, the dose of amoxicillin is 1g twice daily for 7 days in conjunction with clarithromycin and either ranitidine plus bismuth or a proton pump inhibitor.
Dosage in Renal Failure: ClCr0.83to 0.17mL/s: Increase dosing interval from 8hours to 12hours; ClCr<0.17mL/s: increase dosing interval to 12to 24hours.
Hemodialysis: 250to 500mg orally every 24hours. An additional 250mg may be given after each dialysis period.
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