Absorption, Distribution and Excretion
Rapidly absorbed.
Sulfamethizole is readily absorbed form the GI tract. Following oral administration of a single 2-g dose of sulfamethizole in a limited number of patients, blood concentrations of approximately 30 ug/mL were attained within 1 hour. Peak blood concentrations of about 60 ug/mL were reached within 2 hours followed by a gradual decrease to 6.6 ug/mL within eight hours and to 5 ug/mL within 12 hours. Approximately 2-11% of sulfamethizole present in the blood is in the N4-acetylated form.
Sulfamethizole is distributed into most body tissues but does not appear to diffuse into the CSF of patients with normal meninges. Sulfamethizole is approximately 90% bound to plasma proteins. Since the drug is rapidly eliminated in urine, the manufacturer states that accumulation of sulfamethizole in tissues outside the urinary tract is minimal
Sulfamethizole...is a rapidly eliminated sulfonamide; concentrations of drug in blood are thus low after administration of conventional doses.
Approximately 80% of an administered dose is recoverable within eight hours; approximately 98% is cleared in 15 to 24 hours. Sulfamethizole is cleared by the kidney at a rate only 10 to 20% lower than that of creatinine.
For more Absorption, Distribution and Excretion (Complete) data for SULFAMETHIZOLE (21 total), please visit the HSDB record page.

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Metabolism / Metabolites
Hepatic.
Approximately 95% of a given dose of sulfamethizole is not metabolized; less than 5% is acetylated. As a consequence, almost all of a given dose of sulfamethizole is present in its active form in the body.
Renal clearance values of metabolite N4-acetylsulfonamides are 6-20 times higher than their parent compd. Sulfamethizole is acetylated very little.
Although the liver is the major site of metabolism, sulfonamides may also be metabolized in other body tissues. Most sulfonamides are metabolized mainly by N4-acetylation. The degree of acetylation, which is a function of time, varies from less than 5% for sulfamethizole to up to 40% for sulfadiazine. The N4-acetyl metabolites, which do not possess antibacterial activity, have greater affinity for plasma albumin than does the nonacetylated drug and are usually less soluble than the parent sulfonamide, particularly in acidic urine. Like acetyl derivatives, glucuronide derivatives do not possess antibacterial activity; however, glucuronide derivatives are water soluble, appear to resemble the nonacetylated sulfonamide in plasma binding capacity, and have not been associated with adverse effects. /Sulfonamides/

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Biological Half-Life
3-8 hours
Sulfonamides are generally classified as short-acting, intermediate-acting, or long-acting depending on the rate at which they are absorbed and eliminated. Sulfamethizole, sulfasalazine, and sulfisoxazole are generally considered to be short-acting sulfonamides and reportedly have plasma half-lives of about 4-8 hours. Sulfadiazine and sulfapyridine are generally considered to be intermediate-acting sulfonamides and reportedly have plasma half-lives of about 7-17 hours. /Sulfonamides/

Protein Binding
98-99%

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Interactions
These medications /coumarin- or indandione-derivative anticoagulants; hydantoin anticonvulsants or oral antidiabetic agents/ may be displaced from protein binding sites and/or their metabolism may be inhibited by some sulfonamides, resulting in increased or prolonged effects and/or toxicity; dosage adjustments may be necessary during and after sulfonamide therapy. /Sulfonamides/
Concurrent use of bone marrow depressants with sulfonamides may increase the leukopenic and/or thrombocytopenic effects; if concurrent use is required, close observation for myelotoxic effects should be considered. /Sulfonamides/
Concurrent long-term use of sulfonamides /with estrogen-containing, oral contraceptives/ may result in increased incidence of breakthrough bleeding and pregnancy. /Sulfonamides/
Concurrent use /of cyclosporine/ with sulfonamides may increase the metabolism of cyclosporine, resulting in decreased plasma concentration and potential transplant rejection, and additive nephrotoxicity; plasma cyclosporine concentrations and renal function should be monitored. /Sulfonamides/
For more Interactions (Complete) data for SULFAMETHIZOLE (12 total), please visit the HSDB record page.

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Non-Human Toxicity Values
LD50 Rat oral 3500 mg/kg

Sulfamethizole is a white powder. (NTP, 1992)
Sulfamethizole is a sulfonamide consisting of a 1,3,4-thiadiazole nucleus with a methyl substituent at C-5 and a 4-aminobenzenesulfonamido group at C-2. It has a role as an antimicrobial agent, an EC 2.5.1.15 (dihydropteroate synthase) inhibitor, an antiinfective agent and a drug allergen. It is a sulfonamide, a member of thiadiazoles and a sulfonamide antibiotic.
A sulfathiazole antibacterial agent.
Sulfamethizole has been reported in Apis cerana with data available.
Sulfamethizole is a broad-spectrum sulfanilamide and a synthetic analog of para-aminobenzoic acid (PABA) with antibacterial property. Sulfamethizole competes with PABA for the bacterial enzyme dihydropteroate synthase, thereby preventing the incorporation of PABA into dihydrofolic acid, the immediate precursor of folic acid. This leads to an inhibition of bacterial folic acid synthesis and de novo synthesis of purines and pyrimidines, ultimately resulting in cell growth arrest and cell death.
A sulfathiazole antibacterial agent.
See also: Methenamine Mandelate; Sulfamethizole (component of).

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Drug Indication
For the treatment of urinary tract infection

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Mechanism of Action
Sulfamethizole is a competitive inhibitor of bacterial enzyme dihydropteroate synthetase. The normal para-aminobenzoic acid (PABA) substrate is prevented from binding. The inhibited reaction is necessary in these organisms for the synthesis of folic acid.
Sulfonamides are usually bacteriostatic in action. Sulfonamides interfere with the utilization of p-aminobenzoic acid (PABA) in the biosynthesis of tetrahydrofolic acid (the reduced form of folic acid) cofactors in susceptible bacteria. Sulfonamides are structural analogs of PABA and appear to interfere with PABA utilization by competitively inhibiting the enzyme dihydropteroate synthase, which catalyzes the formation of dihydropteroic acid (a precursor of tetrahydrofolic acid) from PABA and pteridine; however, other mechanism(s) affecting the biosynthetic pathway also may be involved. Compounds such as pyrimethamine and trimethoprim, which block later stages in the synthesis of folic acid, act synergistically with sulfonamides. Only microorganisms that synthesize their own folic acid are inhibited by sulfonamides; animal cells and bacteria which are capable of utilizing folic acid precursors or preformed folic acid are not affected by these drugs. The antibacterial activity of the sulfonamides is reportedly decreased in the presence of blood or purulent body exudates. /Sulfonamides/
The sulfonamides are structural analogs of para-aminobenzoic acid (PABA) and competitively inhibit an enzymatic step (dihydropterate synthetase) during which PABA is incorporated into the synthesis of dihydrofolic acid (folic acid). Because dihydrofolate synthesis is reduced, the levels of tetrahydrofolate (folinic acid) formed from dihydrofolate diminish. Tetrahydrofolate is an essential component of the coenzymes responsible for single carbon metabolism in cells. Acting as antimetabolites to PABA, sulfonamides eventually block, in a complex fashion, several enzymes. These enzymes include those needed for the biogenesis of purine bases; for the transfer of desoxyuridine to thymidine; and for the biosynthesis of methionine, glycine, and formylmethionyl-transfer-RNA. This results in suppression of protein synthesis, impairment of metabolic processes, and inhibition of growth and multiplication of those organisms that cannot use preformed folate. The effect is bacteriostatic, although a bactericidal action is evident at the high concentrations that may be found in urine.

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Therapeutic Uses
Anti-Infective Agents /SRP: Antibacterial/
Sulfamethizole is indicated in the treatment of urinary tract infections (primarily pyelonephritis, pyelitis, and cystitis) in the absence of obstructive uropathy or foreign bodies, when these infections are caused by susceptible strains of the following organisms: Escherichia coli, Klebsiella-Enterobacter, Staphylococcus aureus, Proteus mirabilis, and Proteus vulgaris. /Included in US product label/
Sulfonamides are indicated in the treatment of chancroid caused by Hemophilus ducreyi. However, other agents such as erythromycin and ceftriaxone, are considered to be first line agents. /Sulfonamides; Included in US product labeling/
Sulfonamides are indicated in the treatment of endocervical and urethral infections caused by Chlamydia trachomatis. However, other agents, such as doxycycline and azithromycin, are considered to be first line agents. /Sulfonamides; Included in US product labeling/
For more Therapeutic Uses (Complete) data for SULFAMETHIZOLE (17 total), please visit the HSDB record page.

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Drug Warnings
The number of conditions for which the sulfonamides are therapeutically useful and constitute drugs of first choice has been reduced sharply by the development of more effective antimicrobial agents and by the gradual increase in the resistance of a number of bacterial species to this class of drugs. /Sulfonamides/
Many of the adverse effects that have been attributed to the sulfonamides appear to be hypersensitivity reactions. The incidence of hypersensitivity reactions appears to increase with increased sulfonamide dosage. Although cross-sensitization has been reported to occur between the various anti-infective sulfonamides, some diuretics such as acetazolamide and the thiazides, some goitrogens, and sulfonylurea antidiabetic agents, the association between hypersensitivity to sulfonamide anti-infectives and subsequent sensitivity reactions to non-anti-infective sulfonamides (e.g., thiazides, sulfonylurea antidiabetic agents, furosemide, dapsone, probenecid) appears to result from a predisposition to allergic reactions in general rather than to cross-sensitivity to the sulfa moiety per se. /Sulfonamides/
Various dermatologic reactions, including rash, pruritus, urticaria, erythema nodosum, erythema multiforme (Stevens-Johnson syndrome), Lyell's syndrome (may be associated with corneal damage), Behcet's syndrome, toxic epidermal necrolysis, and exfoliative dermatitis, have been reported in patients receiving sulfonamides. Because photosensitivity may also occur, patients should be cautioned against exposure to UV light or prolonged exposure to sunlight. A relatively high proportion of fatalities has occurred as a result of the Stevens-Johnson syndrome, especially in children. Although long-acting sulfonamides (which are no longer commercially available) have been associated most often with the Stevens-Johnson syndrome, other sulfonamides also have been reported to cause this reaction. The physician should be alert to the signs, including high fever, severe headache, stomatitis, conjunctivitis, rhinitis, urethritis, and balanitis, which may precede the onset of the cutaneous lesions of the Stevens-Johnson syndrome. If a rash develops during therapy, the sulfonamide should be discontinued at once. In rare instances, a skin rash may precede a more serious reaction such as Stevens-Johnson syndrome, toxic epidermal necrolysis, hepatic necrosis, and/or serious blood disorders. /Sulfonamides/
Fever, which may develop 7-10 days after the initial sulfonamide dose, is a common adverse effect of sulfonamide therapy. Serum sickness syndrome or serum sickness-like reactions (e.g., fever, chills, rigors, flushing, joint pain, urticarial eruptions, conjunctivitis, bronchospasm, leukopenia), have been reported; rarely, anaphylactoid reactions and anaphylaxis may occur. Lupus erythematosus-like syndrome, disseminated lupus erythematosus, angioedema, vasculitis, vascular lesions including periarteritis nodosa and arteritis, cough, shortness of breath, chills, pulmonary infiltrates, pneumonitis (which may be associated with eosinophilia), fibrosing alveolitis, pleuritis, pericarditis with or without tamponade, allergic myocarditis, hepatitis, hepatic necrosis with or without immune complexes, parapsoriasis varioliformis acuta, alopecia, conjunctival and scleral injection, periorbital edema, and arthralgia have also been reported. /Sulfonamides/
For more Drug Warnings (Complete) data for SULFAMETHIZOLE (27 total), please visit the HSDB record page.

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Pharmacodynamics
Sulfamethizole is a sulfonamide antibiotic. The sulfonamides are synthetic bacteriostatic antibiotics with a wide spectrum against most gram-positive and many gram-negative organisms. However, many strains of an individual species may be resistant. Sulfonamides inhibit multiplication of bacteria by acting as competitive inhibitors of p-aminobenzoic acid in the folic acid metabolism cycle. Bacterial sensitivity is the same for the various sulfonamides, and resistance to one sulfonamide indicates resistance to all. Most sulfonamides are readily absorbed orally. However, parenteral administration is difficult, since the soluble sulfonamide salts are highly alkaline and irritating to the tissues. The sulfonamides are widely distributed throughout all tissues. High levels are achieved in pleural, peritoneal, synovial, and ocular fluids. Although these drugs are no longer used to treat meningitis, CSF levels are high in meningeal infections. Their antibacterial action is inhibited by pus.

C9H12N4O2S2

272.341

270.024

144-82-1

Sulfamethizole-d4;Sulfamethizole-d4-1;2470130-12-0

5328

Crystals from water
Colorless crystal

1.6±0.1 g/cm3

504.9±52.0 °C at 760 mmHg

210 °C

259.1±30.7 °C

0.0±1.3 mmHg at 25°C

1.687

0.51

2

7

3

17

349

0

S(C1C([H])=C([H])C(=C([H])C=1[H])N([H])[H])(N([H])C1=NN=C(C([H])([H])[H])S1)(=O)=O

VACCAVUAMIDAGB-UHFFFAOYSA-N

InChI=1S/C9H10N4O2S2/c1-6-11-12-9(16-6)13-17(14,15)8-4-2-7(10)3-5-8/h2-5H,10H2,1H3,(H,12,13)

4-amino-N-(5-methyl-1,3,4-thiadiazol-2-yl)benzenesulfonamide

RP-2145; RP2145; RP 2145

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

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

DMSO : ≥ 100 mg/mL (~369.92 mM)
H2O : ~0.67 mg/mL (~2.48 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (9.25 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (9.25 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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