CONTEPO
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CONTEPO (CONTEPO).
Fosfomycin inhibits bacterial cell wall synthesis by inactivating the enzyme UDP-N-acetylglucosamine-3-enolpyruvyltransferase (MurA), which catalyzes the formation of N-acetylmuramic acid, a critical component of the bacterial cell wall. It is bactericidal against a broad range of Gram-positive and Gram-negative bacteria.
| Metabolism | Fosfomycin is not metabolized hepatically; it is primarily eliminated unchanged by the kidneys via glomerular filtration and tubular secretion. Minor hepatic metabolism may occur. |
| Excretion | Primarily renal (approximately 80% as unchanged drug via glomerular filtration and tubular secretion); biliary/fecal excretion accounts for <15%. |
| Half-life | 6.9 hours (terminal elimination half-life); prolonged in renal impairment (up to 24 hours in severe impairment), necessitating dose adjustment for CrCl <50 mL/min. |
| Protein binding | Approximately 20% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | 0.30–0.35 L/kg (suggesting distribution primarily into extracellular fluid; does not readily penetrate CSF or intracellular compartments). |
| Bioavailability | Intravenous: 100% (administered only as IV infusion; no oral formulation). |
| Onset of Action | Intravenous: bactericidal effect begins within 1–2 hours after infusion start; clinical response typically observed within 24–48 hours. |
| Duration of Action | Duration of bactericidal activity corresponds to dosing interval (q8h); pharmacodynamic effect persists for 8–12 hours post-dose based on time above MIC. |
CONTEPO (fosfomycin tromethamine for injection) is typically administered as 4 grams intravenously every 8 hours.
| Dosage form | POWDER |
| Renal impairment | For CrCl 30-59 mL/min: 4 grams IV every 12 hours; for CrCl 15-29 mL/min: 4 grams IV every 24 hours; for CrCl <15 mL/min or hemodialysis: 4 grams IV every 48 hours after dialysis. |
| Liver impairment | No dose adjustment required for hepatic impairment. |
| Pediatric use | Safety and efficacy in pediatric patients have not been established; no approved dosing. |
| Geriatric use | Elderly patients often have reduced renal function; dose adjustment based on CrCl is recommended. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CONTEPO (CONTEPO).
| Breastfeeding | Fosfomycin is excreted in human milk. The M/P ratio is not established. Caution should be exercised when administered to a nursing woman; consider the developmental and health benefits of breastfeeding along with the mother's clinical need. |
| Teratogenic Risk | CONTEPO (fosfomycin tromethamine) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal harm, but there are no adequate and well-controlled studies in pregnant women. Risk cannot be excluded. First trimester: theoretical risk based on animal data; second and third trimesters: no evidence of teratogenicity. |
■ FDA Black Box Warning
Hypersensitivity reactions (including anaphylaxis) have been reported; discontinue therapy if severe allergic reaction occurs.
| Serious Effects |
["Hypersensitivity to fosfomycin or any component of the formulation","Severe renal impairment (CrCl < 30 mL/min) for intravenous formulation"]
| Precautions | ["Hypersensitivity reactions including anaphylaxis","Clostridioides difficile-associated diarrhea","Development of drug-resistant bacteria","Use in patients with renal impairment requires dose adjustment","Contains sodium; caution in patients on sodium restriction"] |
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| Fetal Monitoring | Monitor maternal renal function and for signs of hypersensitivity. Fetal monitoring is not specifically required, but standard prenatal care should continue. |
| Fertility Effects | There are no adequate data on effects of fosfomycin on human fertility. Animal studies have not shown impaired fertility at clinically relevant doses. |