POLYCILLIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for POLYCILLIN (POLYCILLIN).
Polycillin (ampicillin) is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), disrupting peptidoglycan cross-linking, leading to cell lysis.
| Metabolism | Primarily hepatic metabolism via ester hydrolysis to active metabolite ampicillin; also undergoes renal tubular secretion. |
| Excretion | Renal excretion of unchanged drug accounts for 60-80% via glomerular filtration and tubular secretion; 20-40% is hepatically metabolized and eliminated in bile/feces. |
| Half-life | Terminal elimination half-life is 0.5-1 hour in adults with normal renal function; prolonged to 7-10 hours in anuria. |
| Protein binding | ~20% bound to serum albumin. |
| Volume of Distribution | 0.2-0.3 L/kg; approximates extracellular fluid volume, indicating limited tissue penetration. |
| Bioavailability | Oral: 30-50% (acid-labile); IM: ~100%. |
| Onset of Action | IM: 15-30 min; IV: immediate; oral: 30-60 min. |
| Duration of Action | 6-8 hours for IM/IV; 4-6 hours for oral; note: short elimination half-life requires frequent dosing. |
| Molecular Weight | 471.4 |
250-500 mg orally every 6 hours or 500 mg intravenously every 4-6 hours for moderate to severe infections.
| Dosage form | TABLET, CHEWABLE |
| Renal impairment | CrCl 30-50 mL/min: 500 mg every 8 hours; CrCl 10-29 mL/min: 500 mg every 12 hours; CrCl <10 mL/min: 500 mg every 24 hours. |
| Liver impairment | No dose adjustment required for Child-Pugh A or B. Child-Pugh C: use with caution, monitor for adverse effects. |
| Pediatric use | Children >1 month: 25-50 mg/kg/day orally divided every 6 hours; 100-200 mg/kg/day IV divided every 4-6 hours. Maximum dose: 12 g/day. |
| Geriatric use | No specific dose adjustment; use lower end of dosing range and monitor renal function due to age-related decline. |
| 1st trimester | Generally considered safe; no evidence of teratogenicity in animal studies or human data. |
| 2nd trimester | Safe for use; commonly prescribed for infections during pregnancy. |
| 3rd trimester | Safe; theoretical risk of neonatal diarrhea or candidiasis but rarely significant. |
Clinical note
Comprehensive clinical and safety monograph for POLYCILLIN (POLYCILLIN).
| Placental transfer | Crosses placenta in therapeutic concentrations; achieves fetal serum levels 10-50% of maternal levels. |
| Breastfeeding | Excreted in breast milk in low concentrations; generally considered compatible with breastfeeding due to negligible risk to infant. |
| Lactation Rating |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
Hypersensitivity to penicillinsHypersensitivity to cephalosporins (potential cross-reactivity)
| Precautions | Hypersensitivity reactions (anaphylaxis, rash) especially in penicillin-allergic patients, Pseudomembranous colitis due to Clostridium difficile, Neurotoxicity (seizures) with high doses or renal impairment, Superinfection with prolonged use |
| Food/Dietary | Avoid acidic juices or carbonated beverages within 1 hour of dosing. Food reduces absorption; take on an empty stomach. No known significant food-drug interactions. |
| Clinical Pearls |
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| L1 (Compatible) |
| Teratogenic Risk | Ampicillin is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, and there are no adequate well-controlled studies in pregnant women. Based on available data, ampicillin is considered low risk in all trimesters, but caution is advised. |
| Fetal Monitoring | Monitor for maternal allergic reactions (rash, anaphylaxis), gastrointestinal disturbances, and signs of superinfection. No specific fetal monitoring required, but assess for maternal adherence and therapeutic response during pregnancy. |
| Fertility Effects | No evidence of impaired fertility in animal studies. In humans, no adverse effects on fertility reported. |
| Polycillin (ampicillin) is a broad-spectrum aminopenicillin. Use with caution in patients with mononucleosis due to high risk of maculopapular rash. Does not cover beta-lactamase-producing organisms. Preferred over amoxicillin for listeriosis and enterococcal endocarditis (combined with gentamicin). Check renal function for dosing adjustments. |
| Patient Advice | Take exactly as prescribed, even if you feel better. · Complete the full course of therapy. · Take on an empty stomach (1 hour before or 2 hours after meals) for best absorption. · Report any rash, diarrhea, or difficulty breathing immediately. · Do not use outdated tetracycline or other antibiotics without consulting your doctor. |