VERSAPEN-K
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VERSAPEN-K (VERSAPEN-K).
VERSAPEN-K (hetacillin potassium) is a prodrug that is hydrolyzed to ampicillin, which inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidase activity, and disrupting peptidoglycan cross-linking.
| Metabolism | Hetacillin is rapidly hydrolyzed in plasma and tissues to ampicillin and acetone. Ampicillin is primarily excreted unchanged in urine via renal tubular secretion and glomerular filtration. |
| Excretion | Renal: 60-80% unchanged via glomerular filtration and tubular secretion; biliary: 15-20% as active drug; fecal: <5%. |
| Half-life | 0.8-1.5 hours in adults with normal renal function (prolonged to 6-20 hours in severe renal impairment; dosing adjustment required when CrCl <30 mL/min). |
| Protein binding | 50-60% bound primarily to serum albumin. |
| Volume of Distribution | 0.3-0.5 L/kg; indicates distribution into extracellular fluid and limited tissue penetration, except in inflamed meninges. |
| Bioavailability | IM: 70-85%; PO: not available (parenteral only). |
| Onset of Action | IM: 30-60 minutes; IV: immediate (within minutes) after completion of infusion. |
| Duration of Action | 6-8 hours for susceptible organisms; requires frequent dosing due to short half-life. |
| Molecular Weight | 485.55 |
250-500 mg intramuscularly or intravenously every 6 hours for moderate infections; 1-2 g every 6 hours for severe infections.
| Dosage form | CAPSULE |
| Renal impairment | Creatinine clearance 30-50 mL/min: 250-500 mg every 8 hours; 10-29 mL/min: 250-500 mg every 12 hours; <10 mL/min: 250-500 mg every 24 hours. |
| Liver impairment | No specific guidelines; use with caution in severe hepatic impairment due to potential for prolonged half-life. |
| Pediatric use | Children >1 month: 50-100 mg/kg/day intramuscularly or intravenously divided every 6 hours; maximum 12 g/day. |
| Geriatric use | Age-related renal function decline requires dose adjustment based on creatinine clearance; monitor for ototoxicity and neurotoxicity. |
| 1st trimester | Versapen-K (hetacillin potassium) is a prodrug of ampicillin. Animal studies suggest no teratogenicity; however, human data are limited. Use only if clearly needed. |
| 2nd trimester | Generally considered safe; ampicillin is widely used in pregnancy. No known fetal risk. |
| 3rd trimester | Safe for use; may be used for group B streptococcus prophylaxis. Avoid in mothers with penicillin allergy. |
Clinical note
Comprehensive clinical and safety monograph for VERSAPEN-K (VERSAPEN-K).
| Placental transfer | Crosses placenta readily; achieves therapeutic levels in fetal serum and amniotic fluid. |
| Breastfeeding | Hetacillin is converted to ampicillin, which is excreted into breast milk in low concentrations. Not expected to cause adverse effects in the infant; however, caution with maternal penicillin allergy. |
■ FDA Black Box Warning
No FDA boxed warning exists for VERSAPEN-K.
| Serious Effects |
Hypersensitivity to penicillinsHistory of immediate allergic reactions (e.g., anaphylaxis) to beta-lactams
| Precautions | Serious and occasionally fatal hypersensitivity reactions (anaphylaxis) have been reported in patients on penicillin therapy., Clostridium difficile-associated diarrhea (CDAD) may occur., Prolonged use may result in overgrowth of nonsusceptible organisms., Use caution in patients with renal impairment (dose adjustment may be needed). |
| Food/Dietary | No specific food interactions; however, avoid alcohol during therapy to reduce side effect risk. |
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| Lactation Rating | L1 (Safe) |
| Teratogenic Risk | First trimester: No evidence of teratogenic effects in animal studies; limited human data. Second/third trimester: No known fetal harm; crosses placenta minimally. |
| Fetal Monitoring | Monitor maternal renal function (CrCl) and hepatic function; fetal ultrasound if used in late pregnancy for infection. |
| Fertility Effects | No known adverse effects on human fertility based on limited data. |
| Clinical Pearls |
| VERSAPEN-K (hetacillin potassium) is a prodrug of ampicillin. It is acid-labile and must be administered parenterally. Monitor for hypersensitivity reactions, especially in penicillin-allergic patients. Adjust dose in renal impairment (CrCl <30 mL/min). Not effective against beta-lactamase-producing organisms. Use with caution in neonates due to risk of kernicterus. |
| Patient Advice | This medication is given by injection only; do not attempt to take it orally. · Inform your healthcare provider if you are allergic to penicillins or cephalosporins. · Tell your doctor about all medications you are taking, especially methotrexate or warfarin. · Complete the full course of therapy even if you feel better. · Report any signs of allergic reaction: rash, itching, swelling, difficulty breathing. · Drink plenty of fluids unless advised otherwise by your doctor. |