Penicillin (natural penicillin)
Gram-positive: non-beta-lactamase producing gram-positive cocci (including viridans streptococci, group A streptococci, Streptococcus pneumoniae, anaerobic Streptococcus), Enterococcus spp., non-penicillinase producing strains of Staphylococcus aureus, coagulase negative Staphylococcus aureus, Clostridium spp. (excluding C. difficile), Actinomyces spp.
Gram negative: Neisseria meningitides, non-penicillinase producing Neisseria gonorrheae, Pasteurella multocida
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.
Penicillins produce time-dependent killing
Hematologic: anemia, thrombocytopenia, neutropenia, agranulocytosis
Renal: nephrotoxicity, interstitial nephritis
Hepatic: transient increases in transaminases
Other: Jarisch-Herxheimer Reaction (fever, chills, sweating, tachycardia, hyperventilation, flushing, and myalgia)
Disease state based dosing:
Renal failure: Table 7
Contraindications: hypersensitivity to ampicillin or other penicillins
Chloramphenicol - decreased antibacterial effectiveness
Cholestyramine - decreased penicillin absorption
Contraceptives - decreased contraceptive effectiveness
Live Typhoid Vaccine - decreased immunological response to the typhoid vaccine
Probenecid - increased penicillin levels
Category B: No evidence of risk in humans but studies inadequate.
Therapeutic: Culture and sensitivities, signs and symptoms of infection
Toxic: Periodic CBC, urinalysis, BUN, SCr, AST and ALT, diarrhea, skin rash
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