POLYCILLIN-PRB
Clinical safety rating: caution
Comprehensive clinical and safety monograph for POLYCILLIN-PRB (POLYCILLIN-PRB).
POLYCILLIN-PRB combines ampicillin and probenecid. Ampicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs). Probenecid inhibits renal tubular secretion of ampicillin, increasing its plasma concentration.
| Metabolism | Ampicillin is partially metabolized by hydrolysis, but mainly excreted unchanged; probenecid is metabolized primarily via glucuronidation and oxidation. |
| Excretion | Renal: 60-80% unchanged via glomerular filtration and tubular secretion; Biliary/fecal: 20-40% as metabolites and unchanged drug. |
| Half-life | Terminal elimination half-life: 1-1.5 hours in patients with normal renal function; prolonged to 7-10 hours in anuria. |
| Protein binding | 55-60% bound primarily to serum albumin. |
| Volume of Distribution | 0.3-0.4 L/kg; indicates distribution into extracellular fluid. |
| Bioavailability | Oral: 30-50% (acid-labile, food reduces absorption); Intramuscular: 70-85% (procaine delays absorption). |
| Onset of Action | Oral: 30-60 minutes; Intramuscular: 15-30 minutes. |
| Duration of Action | Oral: 6-8 hours; Intramuscular: 12-24 hours due to procaine component. |
250-500 mg orally every 6 hours or 500 mg-1 g intramuscularly every 6-8 hours.
| Dosage form | FOR SUSPENSION |
| Renal impairment | CrCl 10-50 mL/min: every 8-12 hours; CrCl <10 mL/min: every 12-18 hours; hemodialysis: dose after dialysis. |
| Liver impairment | No adjustment required for mild to moderate hepatic impairment. Severe impairment: use with caution; no specific guidelines. |
| Pediatric use | Children >1 month: 12.5-25 mg/kg orally every 6 hours; 25-50 mg/kg/day IM in divided doses every 6-8 hours. Maximum 2 g/day. |
| Geriatric use | Initiate at lower end of dosing range; monitor renal function; adjust based on CrCl. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for POLYCILLIN-PRB (POLYCILLIN-PRB).
| Breastfeeding | Penicillins are excreted into breast milk in low concentrations; M/P ratio approximately 0.2. Considered compatible with breastfeeding but monitor for infant diarrhea, rash, or sensitization. |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies. Limited human data; fetal risk cannot be ruled out. Use only if clearly needed. |
| Fetal Monitoring |
■ FDA Black Box Warning
None identified.
| Serious Effects |
["Hypersensitivity to ampicillin, probenecid, or any beta-lactam antibiotic","Concomitant use with methotrexate","Severe renal impairment (CrCl <30 mL/min) with probenecid"]
| Precautions | ["Severe hypersensitivity reactions (anaphylaxis)","Clostridioides difficile-associated diarrhea","Renal impairment (dose adjustment required)","Prolonged use may lead to superinfection"] |
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| Monitor maternal renal function, hematologic parameters (CBC with differential) during prolonged therapy. Assess for signs of hypersensitivity or superinfection. Fetal monitoring as clinically indicated. |
| Fertility Effects | No known adverse effects on fertility in animal studies. No human data available; unlikely to impair fertility at therapeutic doses. |