Amoxicillin

 

Antibiotic Class:

Penicillin (aminopenicillin)

Antimicrobial Spectrum:

Gram-positive:  Streptococcus spp., Enterococcus spp., Listeria monocytogenes

Gram-negative:  H. influenzae, E. coli, Proteus mirabilis, Salmonella spp., Shigella spp.

Mechanism of Action:

Exerts bactericidal activity via inhibition of bacterial cell wall synthesis by binding one or more of the penicillin binding proteins (PBPs). Exerts bacterial autolytic effect by inhibition of certain PBPs related to the activation of a bacterial autolytic process.

Pharmacodynamics:

Penicillins produce time-dependent killing

Pharmacokinetics:

Cmax: 7.5mcg/ml; Oral bioavailability: 80%; Half-life: 1-1.3h; Table 6  

Adverse Effects:

Hematologic: 

anemia, thrombocytopenia, neutropenia, agranulocytosis

CNS: 

seizures

Renal: 

nephrotoxicity, interstitial nephritis

Hepatic: 

transient increases in transaminases

Other: 

Jarisch-Herxheimer Reaction (fever, chills, sweating, tachycardia, hyperventilation, flushing, and myalgia)

Dosage:

Adult:

500mg po q12h or 250-500mg po q8h or 875mg po q12h

Pediatric:   > 1 month and < 20 kg: 20-40 mg/kg/day in 3 divided doses

                 > 20 kg: usual adult dose 

Disease state based dosing:

Renal failure:  CrCL 10-50 mL/min: Consider extending dosing interval to q12h.

                     CrCL < 10 mL/min: Extend dosing interval to q12-24h.

Contraindications/Warnings/Precautions:

Contraindications: 

Anaphylaxis amoxicillin or other penicillins

Precautions: 

Drug Interactions:

Acenocoumarin increased risk of bleeding; Allopurinol higher probablility of amoxicillin rash; Contraceptives - decreased contraceptive effectiveness; Live Typhoid Vaccine - decreased immunological response to the typhoid vaccine; Methotrexate methotrexate toxicity; Probenecid - increased amoxicillin levels; Warfarin increased risk of bleeding

Pregnancy:

Category B: No evidence of risk in humans but studies inadequate.

Monitoring Requirements:

Therapeutic:  Culture and sensitivities, signs and symptoms of infection

Toxic:  Periodic CBC, urinalysis, BUN, Creatinine, AST and ALT, diarrhea, skin rash

Brand names/Manufacturer:

Available by many names and manufacturers (click here)