PENICILLIN G POTASSIUM IN PLASTIC CONTAINER
Clinical safety rating: safe
Probenecid may decrease excretion Serious and occasionally fatal hypersensitivity reactions have been reported.
Penicillin G is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidation and activating autolytic enzymes.
| Metabolism | Penicillin G is primarily metabolized by hydrolysis to penicilloic acid, which is inactive. It is also metabolized via renal tubular secretion and glomerular filtration. |
| Excretion | Renal: 60–90% unchanged via tubular secretion and glomerular filtration. Biliary/fecal: <10%. |
| Half-life | 0.5–1 hour (normal renal function). Prolonged in renal impairment (up to 7–10 hours in anuria). |
| Protein binding | Approximately 60% bound to serum albumin. |
| Volume of Distribution | 0.3–0.5 L/kg; limited distribution, primarily extracellular fluid. |
| Bioavailability | IM: 60–80% due to partial degradation at injection site. Oral: Not applicable (acid-labile, not orally administered). |
| Onset of Action | IV: Immediate (minutes). IM: 15–30 minutes. |
| Duration of Action | IV: 4–6 hours (rapidly cleared). IM: 6–8 hours due to slower absorption. |
2-4 million units IV every 4 hours for moderate to severe infections; up to 24 million units/day for serious infections (meningitis, endocarditis).
| Dosage form | INJECTABLE |
| Renal impairment | CrCl >50 mL/min: no adjustment; CrCl 10-50 mL/min: administer every 6-8 hours; CrCl <10 mL/min: administer every 8-12 hours. |
| Liver impairment | No dose adjustment required for hepatic impairment. |
| Pediatric use | Neonates: <7 days, 50,000 units/kg/dose IV every 12 hours; 7-28 days, 75,000 units/kg/dose IV every 8 hours. Infants and children: 100,000-250,000 units/kg/day IV divided every 4-6 hours; maximum 24 million units/day. For meningitis: 250,000-400,000 units/kg/day IV divided every 4-6 hours. |
| Geriatric use | Adjust dose based on renal function; consider lower initial doses due to age-related decline in GFR; monitor for electrolyte disturbances (hyperkalemia) and neurotoxicity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Probenecid may decrease excretion Serious and occasionally fatal hypersensitivity reactions have been reported.
| FDA category | Human |
| Breastfeeding | Penicillin G is excreted into breast milk in low concentrations (M/P ratio approximately 0.1 to 0.2). Considered compatible with breastfeeding; risk to nursing infant is minimal. |
| Teratogenic Risk | Penicillin G potassium is generally considered safe during pregnancy. No teratogenic effects have been reported in human studies across all trimesters. However, as with all medications, use only if clearly needed. |
■ FDA Black Box Warning
WARNING: SERIOUS HYPERSENSITIVITY REACTIONS, INCLUDING ANAPHYLAXIS, HAVE BEEN REPORTED IN PATIENTS ON PENICILLIN THERAPY. BEFORE INITIATING THERAPY, CAREFUL INQUIRY SHOULD BE MADE CONCERNING PREVIOUS HYPERSENSITIVITY REACTIONS TO PENICILLINS, CEPHALOSPORINS, OR OTHER ALLERGENS. IF AN ALLERGIC REACTION OCCURS, DISCONTINUE PENICILLIN G AND INSTITUTE APPROPRIATE THERAPY.
| Common Effects | Diarrhea |
| Serious Effects |
["History of hypersensitivity to any penicillin","Previous anaphylactic reaction to beta-lactam antibiotics"]
| Precautions | ["Hypersensitivity reactions including anaphylaxis","Clostridium difficile-associated diarrhea","Electrolyte disturbances (hyperkalemia with potassium salt)","Neurologic adverse effects (seizures) with high doses or renal impairment","Thrombophlebitis at injection site","Use with caution in patients with renal impairment or history of allergies"] |
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| Fetal Monitoring | Monitor maternal vital signs and for signs of hypersensitivity reactions. Fetal monitoring not routinely required unless maternal condition warrants. |
| Fertility Effects | No known adverse effects on fertility in animal or human studies. |