Silver sulfadiazine has a dual mechanism of action targeting both bacterial folate metabolism and DNA integrity. The sulfadiazine component acts as a competitive inhibitor of dihydropteroate synthase (DHPS), an enzyme involved in bacterial folate synthesis, thereby disrupting folate metabolism and inhibiting bacterial growth. The silver moiety, on the other hand, binds to bacterial DNA and disrupts its structure, preventing DNA replication. Silver ions also disrupt bacterial cell membranes, contributing to the antimicrobial effect. The combination of these two mechanisms results in broad-spectrum bactericidal activity. The compound acts on the bacterial cell membrane and cell wall, although the specific mechanism of action has not been fully determined.

In order to study bacterial infections in burns, silver sulfadiazine (AgSD) is used topically[2].
In vitro, silver sulfadiazine demonstrates broad-spectrum antimicrobial activity against a wide range of bacteria, including both Gram-positive (e.g., Staphylococcus aureus, Streptococcus species) and Gram-negative organisms (e.g., Pseudomonas aeruginosa, Escherichia coli). The compound is also effective against some yeasts and fungi. The minimum inhibitory concentrations (MICs) for silver sulfadiazine vary depending on the organism, with activity typically observed at concentrations ranging from 1 to 100 μg/mL. The compound shows concentration-dependent bactericidal activity, with higher concentrations achieving more rapid killing. Silver sulfadiazine is more effective against actively dividing bacteria than against stationary-phase organisms. In vitro studies have also demonstrated the compound's ability to prevent biofilm formation.

In vivo, silver sulfadiazine is used topically for the prevention and treatment of wound infections in burn patients. When applied to burn wounds, the compound reduces bacterial colonization and prevents the development of invasive wound infections. The silver sulfadiazine cream forms a protective barrier over the wound, maintaining a moist environment conducive to healing while providing sustained antimicrobial activity. Clinical studies have shown that silver sulfadiazine significantly reduces the incidence of wound infections in burn patients compared to placebo or other topical agents. The compound also promotes wound healing by reducing the inflammatory response and preventing infection-related tissue damage. Silver sulfadiazine is the standard of care for topical burn wound management.

In vitro assays for silver sulfadiazine typically involve determining its antimicrobial activity against various bacterial strains using broth dilution or agar diffusion methods. The minimum inhibitory concentration (MIC) is determined by culturing bacteria in the presence of serial dilutions of the compound and observing growth inhibition after 18-24 hours of incubation. The minimum bactericidal concentration (MBC) is determined by subculturing from wells showing no visible growth onto agar plates. Zone of inhibition assays are performed by placing compound-impregnated discs on agar plates seeded with bacteria and measuring the diameter of the inhibition zone. Activity against biofilms is assessed using crystal violet staining or viable cell counting. All assays include appropriate positive and negative controls.

In vitro cell-based assays for silver sulfadiazine are typically performed using keratinocytes or fibroblasts to assess the compound's effects on wound healing and cytotoxicity. Cells are treated with various concentrations of silver sulfadiazine (typically 1-100 μg/mL) for 24-72 hours. Cell viability is assessed using MTT or resazurin assays to determine the half-maximal cytotoxic concentration (CC50). Wound healing is assessed using scratch wound assays, where cell monolayers are scratched and the rate of wound closure is measured in the presence of the compound. Pro-inflammatory cytokine production (e.g., IL-6, TNF-α) is measured by ELISA to assess the compound's immunomodulatory effects. Silver sulfadiazine's effects on collagen synthesis and cell migration are also evaluated.

In vivo animal studies with silver sulfadiazine are conducted in rodent models of burn wounds or infected wounds. Full-thickness burn wounds are created on the backs of mice or rats and infected with bacterial pathogens (e.g., Pseudomonas aeruginosa, Staphylococcus aureus). Silver sulfadiazine cream is applied topically to the wounds, typically once or twice daily. Wound healing is monitored by measuring wound area over time using planimetry. Bacterial burden is assessed by quantitative cultures of wound tissue. Histological analysis is performed to evaluate re-epithelialization, granulation tissue formation, and inflammatory cell infiltration. Survival studies are conducted in severe infection models. Silver sulfadiazine-treated animals are compared to vehicle-treated and untreated controls.

Absorption, Distribution and Excretion
Extremely poor skin penetration. Absorption problems only occur when used for large-area burns. Metabolism/Metabolites Sulfonamides undergo two degradation pathways: one is the N-acetylation pathway, which is genetically determined and saturable; the other is the cytochrome P450 pathway, which produces toxic hydroxylamine metabolites that require glutathione for detoxification. (A2885)
Silver sulfadiazine is applied topically and is minimally absorbed through intact skin. However, absorption can occur through burn wounds, especially with extensive application. Following absorption, silver binds to plasma proteins and is distributed to various tissues. The sulfadiazine component is metabolized in the liver and excreted in the urine. The silver component is primarily excreted in the feces via biliary elimination. The half-life of silver sulfadiazine in the body is not well-defined but is generally prolonged due to the slow release of silver ions. Systemic levels of silver and sulfadiazine are typically low with topical application. However, monitoring of serum silver levels may be recommended in patients with extensive burns or prolonged use.

Toxicity Summary
Studies using radioactive microparticle-based silver sulfadiazine, electron microscopy, and biochemical techniques have shown that the mechanism of action of silver sulfadiazine against bacteria differs from that of silver nitrate and sodium sulfadiazine. Silver sulfadiazine acts only on the cell membrane and cell wall, thereby producing a bactericidal effect. Its specific mechanism of action is not yet fully understood, but the effectiveness of silver sulfadiazine may stem from synergistic effects or the combined action of its components. Silver is a biocidal agent that can bind to a variety of targets. Silver ions can bind to nucleophilic amino acids, as well as thiol, amino, imidazole, phosphate, and carboxyl groups in proteins, leading to protein denaturation and enzyme inhibition. Silver can bind to cell surface membranes and proteins, causing membrane proton leakage and ultimately cell death. Sulfadiazine is a competitive inhibitor of bacterial para-aminobenzoic acid (PABA), a substrate of dihydropteroate synthase. This inhibitory response is essential for the synthesis of folic acid in these organisms.

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Toxicity Data
LD50: 10001 mg/kg (oral, rat)

Silver sulfadiazine is generally well-tolerated when applied topically. Common local adverse effects include burning sensation, pain, and itching at the application site. Allergic reactions to sulfonamides can occur, especially in patients with known sulfa allergies. Systemic toxicity is rare with topical use but can occur with extensive application, particularly in patients with large burn wounds. Silver toxicity (argyria) is a theoretical concern with prolonged use, characterized by grayish discoloration of the skin and mucous membranes. Sulfadiazine-related toxicity includes bone marrow suppression, renal toxicity, and hepatic dysfunction, though these are uncommon with topical use. The compound is contraindicated in pregnant women near term and in premature infants due to the risk of kernicterus.

[1]. Strydom SJ, et al. Poly(amidoamine) dendrimer-mediated synthesis and stabilization of silver sulfonamide nanoparticles with increased antibacterial activity. Nanomedicine. 2013;9(1):85-93.
[2]. Munhoz DR, et al. Alginate films functionalized with silver sulfadiazine-loaded [Mg-Al] layered double hydroxide as antimicrobial wound dressing. Int J Biol Macromol. 2019;141:504-510.

Silver sulfadiazine (1+) is a silver salt belonging to the sulfonamide class of compounds and is also a pyrimidine drug. It possesses antibacterial and antimicrobial activity. It contains a sulfadiazine group. Silver sulfadiazine is a sulfonamide derivative topical antibacterial agent, primarily used for second- and third-degree burns. Silver sulfadiazine is a sulfonamide antibacterial agent. Silver sulfadiazine is a sulfonamide topical medication with antibacterial and antifungal activity. The mechanism of action of silver sulfadiazine may be the combined effect of silver and sulfadiazine. When this drug interacts with body fluids containing sodium chloride, silver ions are slowly and continuously released into the wound area. Ionized silver atoms catalyze the formation of disulfide bonds, leading to changes in protein structure and inactivation of thiol-containing enzymes; silver ions may also intercalate into DNA, thereby interfering with bacterial replication and transcription. As a competitive inhibitor of para-aminobenzoic acid (PABA), sulfadiazine inhibits bacterial dihydropteroate synthase, thereby disrupting folic acid metabolism and ultimately affecting DNA synthesis. Silver sulfadiazine is only present in individuals who have used or ingested the drug. It is a sulfonamide derivative topical antibacterial agent primarily used to treat second- and third-degree burns. [Wikipedia] Studies using radioactive microparticle-based silver sulfadiazine, electron microscopy, and biochemical techniques have shown that the mechanism of action of silver sulfadiazine against bacteria differs from that of silver nitrate and sodium sulfadiazine. Silver sulfadiazine acts only on the cell membrane and cell wall, thereby producing a bactericidal effect. Its specific mechanism of action is not yet determined, but the effectiveness of silver sulfadiazine may stem from synergistic effects or the combined action of its components. Silver is a bactericide that can bind to a variety of targets. Silver ions can bind to nucleophilic amino acids, as well as thiol, amino, imidazole, phosphate, and carboxyl groups in proteins, leading to protein denaturation and inhibiting enzyme activity. Silver can bind to cell membranes and proteins, causing membrane proton leakage and ultimately cell death. Sulfadiazine is a competitive inhibitor of bacterial para-aminobenzoic acid (PABA), a substrate of dihydropteroic acid synthase. This inhibitory response is crucial for the synthesis of folic acid by these microorganisms.
A topical antibacterial agent used for burn treatment.
See also: sulfadiazine (active moiety); silver ions (active moiety); enrofloxacin; silver sulfadiazine (component).
Indications
For the prevention and treatment of wound infections in patients with second- and third-degree burns.
Mechanism of Action
Studies using radioactive microparticle-based silver sulfadiazine, electron microscopy, and biochemical techniques have shown that the mechanism of action of silver sulfadiazine against bacteria differs from that of silver nitrate and sodium sulfadiazine. Silver sulfadiazine acts only on the cell membrane and cell wall, thereby producing a bactericidal effect. Its specific mechanism of action is not yet clear, but the effectiveness of silver sulfadiazine may stem from synergistic effects or the combined action of its components. Silver is a biocidal agent that can bind to a variety of targets. Silver ions can bind to nucleophilic amino acids, as well as thiol, amino, imidazole, phosphate, and carboxyl groups in proteins, leading to protein denaturation and inhibition of enzyme activity. Silver ions can also bind to cell membranes and proteins, causing membrane proton leakage and ultimately leading to cell death. Sulfadiazine is a competitive inhibitor of bacterial para-aminobenzoic acid (PABA), a substrate of dihydropteroate synthase. This inhibition is crucial for folic acid synthesis in these organisms.

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Pharmacodynamics
Silver sulfadiazine has broad-spectrum antibacterial activity. It is bactericidal against a variety of Gram-negative and Gram-positive bacteria, and is also effective against yeast. Silver sulfadiazine is not a carbonic anhydrase inhibitor, therefore it may be suitable in situations where carbonic anhydrase inhibitors are contraindicated.
Silver sulfadiazine was first introduced in the 1960s and has become the standard topical antimicrobial agent for burn wound management. The drug is approved by the FDA and other regulatory agencies worldwide for the prevention and treatment of wound infections in burn patients. It is available as a 1% topical cream (e.g., Silvadene, Flamazine, Thermazene). The compound's broad-spectrum antimicrobial activity, low systemic toxicity, and favorable wound-healing properties have made it a mainstay in burn care. However, concerns about emerging resistance and the availability of alternative agents (e.g., silver dressings, mupirocin) have led to evolving practice patterns. Silver sulfadiazine remains an important topical antimicrobial for burn wound management and is listed on the WHO Model List of Essential Medicines.

C10H9AGN4O2S

357.14

355.949

22199-08-2

441244

White to off-white solid powder

1.496g/cm3

512.6ºC at 760 mmHg

285 °C (dec.)(lit.)

263.8ºC

1.28E-10mmHg at 25°C

3.114

1

6

3

18

327

0

O=S([N-]C1=NC=CC=N1)(C2=CC=C(N)C=C2)=O.[Ag+]

UEJSSZHHYBHCEL-UHFFFAOYSA-N

InChI=1S/C10H9N4O2S.Ag/c11-8-2-4-9(5-3-8)17(15,16)14-10-12-6-1-7-13-10;/h1-7H,11H2;/q-1;+1

silver;(4-aminophenyl)sulfonyl-pyrimidin-2-ylazanide

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : < 0.1 mg/mL
DMSO : < 1 mg/mL

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)