PRINCIPEN '500'
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PRINCIPEN '500' (PRINCIPEN '500').
Ampicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis and death.
| Metabolism | Ampicillin is metabolized primarily by hydrolysis to penicilloic acid; hepatic metabolism is minimal. |
| Excretion | Primarily renal (90% unchanged via glomerular filtration and tubular secretion); small amounts biliary/fecal (<5%). |
| Half-life | 0.5–1 hour; prolonged in renal impairment (up to 10 hours in anuria). |
| Protein binding | ~20% bound to serum albumin. |
| Volume of Distribution | 0.2–0.3 L/kg; limited to extracellular fluid. |
| Bioavailability | IM: 100% (complete); PO: 30–60% (acid-labile, variable). |
| Onset of Action | IM: 15–30 min; IV: immediate. |
| Duration of Action | 4–6 hours (short due to rapid renal elimination); requires frequent dosing. |
500 mg orally every 6 hours for 7-14 days for mild to moderate infections; for severe infections, 500 mg orally every 4 hours.
| Dosage form | CAPSULE |
| Renal impairment | For CrCl 30-50 mL/min: administer 500 mg every 8 hours; CrCl 10-30 mL/min: 500 mg every 12 hours; CrCl <10 mL/min: 500 mg every 24 hours. |
| Liver impairment | No specific adjustment required for hepatic impairment; caution in severe hepatic disease due to potential risk of crystalluria. |
| Pediatric use | For children >1 month: 12.5-25 mg/kg/dose orally every 6 hours; maximum 2 g/day. For neonates: 25 mg/kg/dose every 8 hours. |
| Geriatric use | Adjust based on renal function; monitor for crystalluria and superinfection; standard dosing if CrCl >50 mL/min. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PRINCIPEN '500' (PRINCIPEN '500').
| Breastfeeding | Ampicillin is excreted into breast milk in low concentrations (M/P ratio ~0.05–0.2). Compatible with breastfeeding; may cause diarrhea or rash in infant. Monitor for gastrointestinal effects or sensitization. |
| Teratogenic Risk | Pregnancy Category B. Animal studies have not demonstrated fetal risk, but no adequate human studies in pregnant women. Use only if clearly needed. No evidence of teratogenicity in first trimester; theoretical risk of diarrhea or rash in neonates if administered near term. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Hypersensitivity to ampicillin, penicillins, or any component of the formulation","Infections caused by beta-lactamase-producing organisms"]
| Precautions | ["Serious hypersensitivity reactions (anaphylaxis) may occur","Clostridium difficile-associated diarrhea (CDAD)","Seizures may occur in patients with renal impairment or high doses","Prolonged use may result in superinfection","Risk of bleeding abnormalities with high doses"] |
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| Fetal Monitoring |
| Monitor maternal renal function, complete blood count, and liver enzymes periodically. Observe for signs of hypersensitivity or superinfection in mother. Fetal monitoring not routinely required unless maternal infection poses risk. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies show no impairment of fertility. |