OMNIPEN-N
Clinical safety rating: caution
Comprehensive clinical and safety monograph for OMNIPEN-N (OMNIPEN-N).
Omnipen-N (ampicillin sodium) is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), thereby interfering with transpeptidation and resulting in cell lysis.
| Metabolism | Ampicillin is primarily excreted unchanged by the kidneys via tubular secretion and glomerular filtration; minimal hepatic metabolism. |
| Excretion | Primarily renal (80-90% unchanged via tubular secretion); minor biliary/fecal (<10%). |
| Half-life | 30-60 minutes (normal renal function); prolonged to 7-10 hours in severe renal impairment (CrCl <10 mL/min). |
| Protein binding | Approximately 20-30% bound, primarily to serum albumin. |
| Volume of Distribution | 0.15-0.3 L/kg; reflects distribution primarily into extracellular fluid. |
| Bioavailability | Oral: 30-45% (incompletely absorbed, acid-labile); IM: ~100%. |
| Onset of Action | IV: Immediate; IM: 15-30 minutes; Oral: 60-90 minutes. |
| Duration of Action | IV/IM: 4-6 hours; Oral: 6-8 hours. Duration may be extended in renal impairment. |
| Molecular Weight | 349.41 |
250-500 mg orally every 6 hours for adults; for severe infections, up to 1 g every 6 hours.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl >50 mL/min: No adjustment. CrCl 10-50 mL/min: Administer every 8-12 hours. CrCl <10 mL/min: Administer every 12-18 hours. |
| Liver impairment | No specific adjustment recommended for hepatic impairment; monitor liver function. |
| Pediatric use | Children >1 month: 50-100 mg/kg/day divided every 6 hours; maximum 4 g/day. Neonates <1 month: 50 mg/kg/day divided every 12 hours. |
| Geriatric use | Use lower end of dosing range; monitor renal function and adjust based on creatinine clearance. |
| 1st trimester | Penicillin-class antibiotics are generally considered safe during pregnancy. Animal studies have not shown fetal risk, and there are no adequate well-controlled studies in pregnant women. Use only if clearly needed. |
| 2nd trimester | Penicillin-class antibiotics are generally considered safe. No known teratogenic effects. Use when clearly indicated. |
| 3rd trimester | Penicillin-class antibiotics are safe. Prolonged use may theoretically affect neonatal gut flora, but benefits outweigh risks. Use when necessary. |
Clinical note
Comprehensive clinical and safety monograph for OMNIPEN-N (OMNIPEN-N).
| Placental transfer | Ampicillin crosses the placenta readily, achieving fetal serum concentrations about 50-100% of maternal levels. It is considered safe for use during pregnancy. |
| Breastfeeding | Omnipen-N (ampicillin) is excreted into breast milk in low concentrations. It is generally considered compatible with breastfeeding as adverse effects in nursing infants are rare. Monitor infant for signs of gastrointestinal disturbance or rash. |
■ FDA Black Box Warning
No FDA black box warning is currently present for ampicillin, though serious and occasionally fatal hypersensitivity reactions (anaphylaxis) have been reported.
| Serious Effects |
Hypersensitivity to penicillinsHistory of allergic reaction to any beta-lactam antibiotic
| Precautions | Hypersensitivity reactions including anaphylaxis, Clostridioides difficile-associated diarrhea (CDAD), Superinfection with non-susceptible organisms, Renal impairment (dose adjustment required), Prolonged therapy may lead to neutropenia, thrombocytopenia, or other blood dyscrasias |
| Food/Dietary | No significant food interactions. However, absorption is unaffected by food when administered parenterally. Oral forms of ampicillin should be taken on an empty stomach for optimal absorption, but OMNIPEN-N is injectable only. |
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| Lactation Rating | L1 (Safe) |
| Teratogenic Risk | OMNIPEN-N (ampicillin/sulbactam) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal harm. No well-controlled human studies exist; however, ampicillin has been widely used in pregnancy with no documented teratogenicity. Sulbactam is not known to cause fetal harm. Theoretical risk of kernicterus in neonates if used near delivery due to bilirubin displacement by ampicillin. |
| Fetal Monitoring | Monitor for signs of maternal hypersensitivity reactions, including rash, urticaria, anaphylaxis. Monitor renal function, hepatic function, and CBC if prolonged therapy. Fetal monitoring not required routinely; consider fetal heart rate monitoring if maternal sepsis or significant adverse reaction occurs. |
| Fertility Effects | No known adverse effects on fertility in humans. Animal studies have not reported impairment of fertility. Antibiotic effects on gut flora may transiently alter menstrual regularity but no evidence of fertility impairment. |
| Clinical Pearls | OMNIPEN-N (ampicillin/sulbactam) is a beta-lactam/beta-lactamase inhibitor combination effective against beta-lactamase-producing strains of Staphylococcus aureus, Haemophilus influenzae, and Bacteroides fragilis. The sulbactam component irreversibly inhibits beta-lactamase enzymes, extending the spectrum of ampicillin. Administer intravenously or intramuscularly; do not mix with aminoglycosides in the same IV line due to inactivation. Monitor renal function and adjust dose in creatinine clearance <30 mL/min. Use with caution in patients with mononucleosis due to high risk of maculopapular rash. |
| Patient Advice | Take exactly as prescribed; do not skip doses or discontinue early even if feeling better. · Common side effects include diarrhea, nausea, vomiting, and injection site pain. · Notify your doctor if you develop severe diarrhea, skin rash, or difficulty breathing. · If you are on a low-sodium diet, note that the product contains sodium (2.5 mmol per gram of ampicillin/sulbactam). · Complete the full course of therapy to prevent bacterial resistance. |