PENBRITIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PENBRITIN (PENBRITIN).
Penicillin G inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidase activity and preventing peptidoglycan cross-linking, leading to cell lysis.
| Metabolism | Primarily renal excretion via tubular secretion; minimal hepatic metabolism. Approximately 60-90% excreted unchanged in urine within 24 hours. |
| Excretion | Renal: ~75-90% unchanged via glomerular filtration and tubular secretion. Biliary: ~10% in feces. Minor hepatic metabolism to penicilloic acid. |
| Half-life | 0.5-1 hour in normal renal function; extended to 2-6 hours in renal impairment. Hemodialysis shortens half-life. |
| Protein binding | ~20% bound to serum albumin. |
| Volume of Distribution | 0.2-0.3 L/kg; distributes into extracellular fluid including joint fluid, pleural fluid, and CSF only with inflamed meninges. |
| Bioavailability | Oral: 30-55% (food decreases absorption). IM: ~90%. IV: 100%. |
| Onset of Action | IV: immediate; IM: 15-30 minutes; Oral: 1-2 hours on empty stomach. |
| Duration of Action | 6-8 hours; prolonged in renal impairment. Twice-daily dosing used for severe infections. |
250-500 mg orally every 6 hours; 500 mg to 2 g intramuscularly or intravenously every 4-6 hours.
| Dosage form | CAPSULE |
| Renal impairment | CrCl 10-50 mL/min: give dose every 6-12 hours; CrCl <10 mL/min: give dose every 12-24 hours. |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment. Severe impairment (Child-Pugh C): consider dose reduction or interval prolongation, but specific guidelines lack evidence. |
| Pediatric use | Oral: 50-100 mg/kg/day divided every 6 hours; IM/IV: 100-200 mg/kg/day divided every 4-6 hours. Maximum dose 12 g/day. |
| Geriatric use | Consider renal function; use lower end of dosing interval (e.g., every 6 hours for mild impairment) and monitor for side effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PENBRITIN (PENBRITIN).
| Breastfeeding | Ampicillin is excreted into human milk in low concentrations. The milk-to-plasma ratio (M/P) is approximately 0.1 to 0.2. The amount ingested by the infant is less than 1% of the maternal therapeutic dose and is unlikely to cause adverse effects. However, potential for modifying infant gut flora or causing allergic sensitization exists. Use with caution in breastfeeding women, especially if the infant is allergic to penicillins or has gastrointestinal symptoms. |
| Teratogenic Risk | Penicillin antibiotics, including ampicillin (PENBRITIN), are generally considered low risk in pregnancy. Animal studies do not indicate direct or indirect harmful effects with respect to pregnancy, embryonal/fetal development, parturition, or postnatal development. However, there are no adequate and well-controlled studies in pregnant women. Use during pregnancy only if clearly needed. First trimester: No evidence of teratogenicity. Second and third trimesters: Considered safe; associated with decreased estrogen conjugation and increased clearance. |
■ FDA Black Box Warning
None.
| Serious Effects |
["History of severe immediate hypersensitivity to penicillins (e.g., anaphylaxis).","Hypersensitivity to cephalosporins (cross-sensitivity possible).","Not for treatment of severe pneumonia or empyema alone (use with other antibiotics if indicated)."]
| Precautions | ["Hypersensitivity: serious and occasionally fatal anaphylactic reactions; caution in penicillin allergy.","Neurotoxicity (seizures) with high doses or renal impairment.","Clostridioides difficile-associated diarrhea (CDAD).","Electrolyte disturbances: hypernatremia with large doses of potassium penicillin G.","Renal impairment: dose adjustment required due to reduced clearance.","Skin test for penicillin allergy recommended before parenteral therapy."] |
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| Fetal Monitoring | Monitor for signs of maternal hypersensitivity reactions (rash, urticaria, anaphylaxis). Monitor for signs of superinfection (e.g., oral thrush, diarrhea). In prolonged therapy, monitor renal and hepatic function. No specific fetal monitoring required; but assess fetal well-being if maternal adverse events occur. |
| Fertility Effects | Ampicillin does not have known direct effects on fertility. Animal studies have not shown impairment of fertility. No human data suggest adverse effects on gamete production or reproductive function. |