SULFAMYLON
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SULFAMYLON (SULFAMYLON).
Sulfamylon (mafenide acetate) is a synthetic sulfonamide that exerts bacteriostatic activity against a wide range of Gram-negative and Gram-positive organisms. It acts by inhibiting the enzyme dihydropteroate synthase, which is involved in folate synthesis, thereby blocking bacterial DNA replication. Additionally, it may be bactericidal at high concentrations via inhibition of cell wall synthesis.
| Metabolism | Mafenide is rapidly absorbed through burn eschar and is metabolized in the liver to its inactive metabolite, p-carboxybenzenesulfonamide. It is primarily excreted renally. |
| Excretion | Primarily renal excretion as unchanged drug and its metabolite; approximately 87% of a dose is recovered in urine within 24 hours as sulfacetamide and its deacetylated metabolite, with about 10% as unchanged drug. Less than 2% is excreted in feces. |
| Half-life | The terminal elimination half-life is approximately 7-8 hours in patients with normal renal function. In renal impairment, half-life may be prolonged, requiring dosing adjustments. |
| Protein binding | Approximately 85-90% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution is not well defined due to topical use; systemic absorption is minimal. In limited studies, Vd is estimated at 0.3-0.5 L/kg, indicating distribution into extracellular fluid. |
| Bioavailability | Topical cream formulation results in negligible systemic bioavailability; less than 1% of the applied dose is absorbed through intact skin. Absorption may increase in burned or denuded skin, but systemic levels remain low. |
| Onset of Action | When applied topically as a cream, onset of action occurs within hours, with bactericidal activity present at the wound site. No systemic onset is relevant as the drug is not administered systemically. |
| Duration of Action | Dosing is every 6-12 hours for topical application; duration of action at wound site is approximately 12 hours, requiring reapplication to maintain antibacterial effect. |
| Molecular Weight | 246.28 g/mol (mafenide acetate) |
Topical: Apply a thin layer to the wound once or twice daily. Maximum coverage area should not exceed body surface area of 20%.
| Dosage form | CREAM |
| Renal impairment | No systemic absorption significant; no adjustment required. |
| Liver impairment | No systemic absorption significant; no adjustment required. |
| Pediatric use | Same as adult: topical application to burn wounds. Not recommended for use in premature infants or neonates due to risk of kernicterus. |
| Geriatric use | Same as adult dosing; caution with extensive application due to potential for systemic absorption in elderly with impaired renal function. |
| 1st trimester | Avoid due to potential for teratogenicity in animal studies; sulfonamides may cause kernicterus. |
| 2nd trimester | Use only if clearly needed; theoretical risk of kernicterus, but first-trimester concerns persist. |
| 3rd trimester | Avoid near term (after 36 weeks) due to risk of kernicterus in neonates; sulfonamides displace bilirubin from albumin. |
Clinical note
Comprehensive clinical and safety monograph for SULFAMYLON (SULFAMYLON).
| Placental transfer | Crosses placenta; sulfonamides reach fetal serum levels approximately 50-90% of maternal levels. |
| Breastfeeding | Excreted into breast milk in small amounts; concern for kernicterus in premature or hyperbilirubinemic infants. Use with caution, especially in infants with G6PD deficiency. |
■ FDA Black Box Warning
Sulfamylon cream has been associated with hemolytic anemia in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Use with caution in such patients and discontinue if signs of hemolysis occur.
| Serious Effects |
Hypersensitivity to sulfonamidesHistory of severe adverse reaction to sulfonamidesPorphyriaG6PD deficiency (relative, but consider absolute if severe)
| Precautions | Use with caution in patients with renal impairment, as accumulation may occur. Prolonged use may result in fungal superinfection. Apply only to burned areas; avoid contact with eyes and mucous membranes. Metabolic acidosis has been reported due to the carbonic anhydrase inhibitory effect of mafenide and its metabolite. |
| Food/Dietary | No known food interactions. Maintain adequate hydration to support renal function and acid-base balance. |
Loading safety data…
| Lactation Rating |
| L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category D. First trimester: Avoid due to potential teratogenicity, including cardiovascular and skeletal anomalies, based on animal studies; human data limited. Second and third trimesters: Use only if benefit outweighs risk; may cause hemolytic anemia, kernicterus in neonates if near term, and sulfonamide displacement of bilirubin from albumin increasing risk of neonatal hyperbilirubinemia. |
| Fetal Monitoring | Monitor maternal renal function, hepatic function, and CBC weekly; fetal ultrasound for anomalies if exposed in first trimester; assess newborn for jaundice, hemolytic anemia, and glucose-6-phosphate dehydrogenase deficiency. |
| Fertility Effects | No specific data on human fertility impairment. Animal studies at high doses have shown reversible testicular atrophy and impaired spermatogenesis; relevance to humans unknown. |
| Clinical Pearls | Sulfamylon (mafenide acetate) is a topical antimicrobial used for second- and third-degree burns. It penetrates eschar and is effective against Pseudomonas and certain gram-negative anaerobes. Application may cause intense pain (burning/stinging) for 20-30 minutes due to hypertonicity. Monitor for metabolic acidosis; mafenide is a carbonic anhydrase inhibitor and can cause bicarbonate wasting, especially in patients with renal impairment or extensive burns. Use with caution in sulfonamide allergy. |
| Patient Advice | Apply a thin layer to clean burn wounds once or twice daily; reapply if wiped off. · Expect a burning or stinging sensation for about 20-30 minutes after application. · Do not discontinue use without consulting your doctor, even if pain occurs. · Inform your doctor if you have kidney problems, asthma, or sulfa allergy. · Keep covered with dressing as directed; avoid sunlight on treated areas. |