UNIPEN IN PLASTIC CONTAINER
Clinical safety rating: caution
Comprehensive clinical and safety monograph for UNIPEN IN PLASTIC CONTAINER (UNIPEN IN PLASTIC CONTAINER).
Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidase activity and peptidoglycan cross-linking.
| Metabolism | Primarily hepatic metabolism via hydrolysis to penicilloic acid; minor renal elimination of unchanged drug. |
| Excretion | Renal: 60-90% unchanged via glomerular filtration and tubular secretion; biliary/fecal: minor, <10% |
| Half-life | 0.5-1 hour (normal renal function); prolonged to 2-5 hours in renal impairment |
| Protein binding | 40-60% primarily to albumin |
| Volume of Distribution | 0.3-0.5 L/kg, indicating limited tissue penetration |
| Bioavailability | IM: 60-100% (variable); oral: not available |
| Onset of Action | IV: immediate; IM: 10-20 minutes |
| Duration of Action | 4-6 hours (dose-dependent); clinical note: frequent dosing required due to short half-life |
| Molecular Weight | 436.5 |
250-500 mg intravenously or intramuscularly every 4-6 hours. Maximum dose 12 g per day.
| Dosage form | INJECTABLE |
| Renal impairment | Adults with GFR 10-50 mL/min: 250-500 mg every 6-8 hours. GFR <10 mL/min: 250-500 mg every 8-12 hours. |
| Liver impairment | No dose adjustment required for hepatic impairment. |
| Pediatric use | Children >20 kg: 12.5-25 mg/kg intravenously or intramuscularly every 4-6 hours. Maximum dose 12 g per day. Infants <7 days: 25 mg/kg every 8-12 hours. |
| Geriatric use | Dose selection should be cautious, starting at the lower end of the dosing range, due to decreased renal function and increased risk of adverse effects. |
| 1st trimester | Animal studies have not shown teratogenicity; however, adequate human studies in the first trimester are lacking. Use only if clearly needed. |
| 2nd trimester | Penicillins are generally considered safe during the second trimester; no known fetal harm. |
| 3rd trimester | Safe; no known adverse effects on the fetus or newborn. |
Clinical note
Comprehensive clinical and safety monograph for UNIPEN IN PLASTIC CONTAINER (UNIPEN IN PLASTIC CONTAINER).
| Placental transfer | Placental transfer occurs; fetal concentrations are low relative to maternal serum. |
| Breastfeeding | Nafcillin is excreted into breast milk in trace amounts, unlikely to cause adverse effects in the infant. Considered compatible with breastfeeding. |
| Lactation Rating |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to nafcillin, any penicillin, or cephalosporins (cross-hypersensitivity)
| Precautions | Severe hypersensitivity reactions (anaphylaxis) reported; monitor renal function in high-dose therapy; use caution in patients with cephalosporin allergy; Clostridioides difficile-associated diarrhea. |
| Food/Dietary | No significant food interactions. However, take on an empty stomach (1 hour before or 2 hours after meals) for oral nafcillin to enhance absorption. For IV formulation, no dietary restrictions. |
| Clinical Pearls |
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| L1 (Safest) |
| Teratogenic Risk | First trimester: Penicillins cross the placenta but no increased risk of major malformations based on large cohort studies. Second and third trimesters: No known fetal toxicity; risk of neonatal diarrhea or candidiasis with high maternal doses. |
| Fetal Monitoring | Monitor maternal renal function, signs of hypersensitivity, and superinfection. Fetal monitoring indicated in high-risk pregnancies; no specific fetal monitoring required. |
| Fertility Effects | No known adverse effects on human fertility based on available data. |
| Unipen (nafcillin) is a penicillinase-resistant penicillin used for methicillin-susceptible Staphylococcus aureus (MSSA) infections. Obtain drug levels in renal insufficiency as accumulation may occur. Administer IV slowly over 30–60 minutes to avoid phlebitis. Monitor for hepatotoxicity, especially with prolonged use. Incompatible with aminoglycosides in solution. |
| Patient Advice | Take this medication exactly as prescribed, even if you feel better. · Notify your doctor immediately if you experience skin rash, hives, or difficulty breathing. · Complete the full course of therapy to prevent antibiotic resistance. · Avoid alcohol while on this medication to reduce risk of liver injury. · Inform your doctor if you have kidney disease, as dose adjustment may be needed. |