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. |
| Molecular Weight | 349.4 |
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 | Penicillin antibiotics are generally considered safe during pregnancy; animal studies have not shown fetal harm. However, use only if clearly needed. |
| 2nd trimester | Safe for use; no evidence of teratogenicity or fetal harm in human studies. |
| 3rd trimester | Safe for use; no known risks to the fetus or neonate. |
Clinical note
Comprehensive clinical and safety monograph for PENBRITIN (PENBRITIN).
| Placental transfer | Penicillins cross the placenta to a limited extent; therapeutic concentrations are achieved in fetal tissues. |
| Breastfeeding | Penbritin is excreted into breast milk in low concentrations. It is generally considered compatible with breastfeeding; however, it may cause diarrhea or allergic reactions in the infant. Monitor the infant for potential effects. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to penicillinsHistory of severe allergic reaction (e.g., anaphylaxis) to any beta-lactam antibiotic
| 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. |
| Food/Dietary | Food significantly decreases ampicillin absorption. Avoid taking with meals. No known specific food interactions. |
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| Lactation Rating |
| L1 - Compatible |
| 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. |
| 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. |
| Clinical Pearls | Penbritin (ampicillin) is a bactericidal aminopenicillin that inhibits cell wall synthesis. It has activity against Gram-positive cocci (except penicillinase-producing staphylococci) and some Gram-negative bacilli (e.g., E. coli, Proteus mirabilis, H. influenzae). It is susceptible to beta-lactamases; consider combination with sulbactam if resistance suspected. Excreted renally; dose adjustment needed for CrCl <30 mL/min. Administer on an empty stomach (1 hour before or 2 hours after meals) for maximal absorption. Monitor for rash, especially in patients with mononucleosis (90% incidence). |
| Patient Advice | Take ampicillin on an empty stomach with a full glass of water 1 hour before or 2 hours after meals. · Complete the entire prescribed course even if you feel better. · Notify your doctor if you develop a skin rash, diarrhea, or unusual bleeding. · Avoid alcohol while taking this medication. · Penicillin allergies can be serious; seek emergency care if you experience difficulty breathing or swelling of the face/throat. |