CEPHAPIRIN SODIUM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CEPHAPIRIN SODIUM (CEPHAPIRIN SODIUM).
Cephapirin sodium is a first-generation cephalosporin antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), primarily PBP1 and PBP3, thereby inhibiting transpeptidation and disrupting peptidoglycan cross-linking, leading to cell lysis mediated by autolytic enzymes.
| Metabolism | Primarily hepatic deacetylation to desacetylcephapirin, which retains antibacterial activity; further metabolism is minimal. Renal excretion of unchanged drug and metabolites. |
| Excretion | Renal: 80-90% unchanged via glomerular filtration and tubular secretion; biliary/fecal: <5%. |
| Half-life | 0.5-1.0 hours; prolonged to 2-5 hours in renal impairment, requiring dose adjustment. |
| Protein binding | 40-50% bound to serum albumin. |
| Volume of Distribution | 0.13-0.32 L/kg; indicates distribution primarily into extracellular fluid. |
| Bioavailability | IM: 70-80% (variable due to injection site); oral: not absorbed. |
| Onset of Action | IM: 15-30 minutes; IV: immediate, within minutes. |
| Duration of Action | 6-8 hours for susceptible organisms; may require more frequent dosing in serious infections due to short half-life. |
500 mg to 1 g IM or IV every 6 hours.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 30-50 mL/min: 500 mg every 6-8 h; CrCl 15-29 mL/min: 500 mg every 12 h; CrCl <15 mL/min: 500 mg every 24 h; hemodialysis: 500 mg after each dialysis session. |
| Liver impairment | No dosage adjustment required for hepatic impairment; monitor liver function. |
| Pediatric use | Children: 10-20 mg/kg IV/IM every 6 hours; maximum 1 g per dose. |
| Geriatric use | Adjust based on renal function; no specific age-related dose adjustments, but monitor renal function and start at lower end of dosing range. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CEPHAPIRIN SODIUM (CEPHAPIRIN SODIUM).
| Breastfeeding | Cephapirin sodium is excreted into human breast milk in low concentrations. The milk-to-plasma (M/P) ratio is approximately 0.04–0.15. Estimated infant dose is less than 1% of the maternal therapeutic dose, considered compatible with breastfeeding. However, potential for alteration of infant gut flora and diarrhea exists. Use with caution in neonates with hyperbilirubinemia or glucose-6-phosphate dehydrogenase deficiency. |
| Teratogenic Risk | Cephapirin sodium is a first-generation cephalosporin classified as FDA Pregnancy Category B. Animal reproduction studies have not demonstrated fetal risk, but no adequate and well-controlled studies in pregnant women exist. It crosses the placenta minimally. First trimester: No known teratogenic effects. Second trimester: Low risk, similar to other cephalosporins. Third trimester: Generally considered safe; used for intrapartum prophylaxis for group B Streptococcus. Overall, the risk of major birth defects is not increased. |
■ FDA Black Box Warning
None
| Serious Effects |
Known hypersensitivity to cephapirin or any cephalosporin. Use in patients with immediate-type hypersensitivity reactions to penicillins is contraindicated due to risk of cross-allergenicity.
| Precautions | Serious and occasionally fatal hypersensitivity reactions (anaphylaxis) reported, especially in patients with penicillin allergy. Clostridium difficile-associated diarrhea (CDAD) may occur. Prolonged use may result in superinfection. Use with caution in patients with renal impairment, history of gastrointestinal disease (particularly colitis), and those with phenylketonuria (injectable formulation may contain phenylalanine). |
| Food/Dietary | No significant food interactions. Take with or without food. |
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| Fetal Monitoring | Monitor maternal renal function due to cephalosporin elimination; dose adjustment may be needed in severe renal impairment. Monitor for signs of hypersensitivity reactions, including rash, urticaria, anaphylaxis. In prolonged use, monitor for superinfection including Clostridioides difficile colitis. No specific fetal monitoring required; routine prenatal care suffices. |
| Fertility Effects | No known significant effects on human fertility. Animal studies have not shown impaired fertility at clinically relevant doses. However, like all antibiotics, it may alter gut microbiota which can indirectly affect fertility; no direct evidence of impact. |
| Clinical Pearls | Cephapirin is a first-generation cephalosporin with activity against gram-positive cocci except enterococci. It is used primarily for bovine mastitis; human use is rare. Avoid in patients with immediate-type hypersensitivity to penicillins due to cross-allergenicity. Renal dose adjustment required. |
| Patient Advice | Complete the full course of therapy even if symptoms improve. · Report any signs of allergic reaction (rash, hives, difficulty breathing) immediately. · This medication may cause diarrhea; contact your doctor if severe or persistent. · Store in a dry place away from light and moisture. |