Sulfonamide (medicine)

Sulfonamides

Name	Structure
* Mafenide
* Prontosil
* Sulfabenzamide
* Sulfacetamide
* Sulfachlorpyridazine
* Sulfacytine
* Sulfadiazine
* Sulfadimethoxine
* Sulfadimidine
* Sulfadoxine
* Sulfafurazole
* Sulfaguanidine
* Sulfamazone
* Sulfamerazine
* Sulfamethizole
* Sulfametomidine
* Sulfametoxydiazine
* Sulfametrole
* Sulfanilamide
* Sulfanitran
* Sulfaperin
* Sulfaphenazole
* Sulfathiazole
* Sulfathiourea
* Sulfisomidine
* Sulfoxone
* Terephtyl

Sulfonamides, commonly referred to as sulfa drugs or sulpha drugs, are a group of synthetic pharmaceuticals distinguished by the presence of a sulfonamide functional group. Their broad utility in pharmacology, spanning from antibacterial to various non-antibacterial uses, marks their pivotal role in the development of modern therapeutics.

Chemical Structure

The quintessential element of sulfonamides is the Sulfonamide functional group, symbolized as -SO2NH2 in chemical language. This group's inclusion in the drug's molecular structure is essential for its diverse therapeutic actions, enabling its ability to mimic and interfere with substances naturally utilized by bacteria.

Antibacterial Sulfonamides

Historically, the first sulfonamides brought into medical practice acted as antibacterial agents. These drugs are nonantibiotic antimicrobials, which means they combat bacterial proliferation not by killing the bacteria directly but by impeding the synthesis of folic acid within the bacterial cell. Since folic acid is vital for bacterial DNA replication, its disruption halts the growth and multiplication of the bacteria, thus rendering them ineffective.

Non-Antibacterial Sulfonamides

The scope of sulfonamides extends beyond antibacterial action. Some derivatives, such as Sultiame, lack antibacterial capabilities but are crucial in other medical contexts, particularly as anticonvulsants for seizure control.

Modern Drug Groups

The subsequent evolution in sulfonamide research has ushered in new categories of drugs with varying applications. Among these are Sulfonylureas, which stimulate insulin release in the treatment of type 2 diabetes, and Thiazide diuretics, which are integral to hypertension management protocols due to their effects on renal function and fluid balance.

Function of Sulfonamides

Sulfonamides, a class of drugs with broad clinical applications, primarily function as dihydropteroate synthase inhibitors in bacteria. This enzyme is crucial for folate synthesis, which is essential for bacterial growth and multiplication. By acting as competitive inhibitors, sulfonamides prevent the bacteria from producing folate, thus exhibiting a bacteriostatic effect that inhibits bacterial proliferation without directly killing the organisms. In contrast, humans obtain folate, also known as vitamin B9, through their diet and are not affected by this mechanism.

Structural Similarity and Inhibitory Action

The structural similarity between sulfanilamide, a sulfonamide, and p-aminobenzoic acid (PABA) underlies the inhibitory action of sulfa drugs on bacterial tetrahydrofolate synthesis, which is vital for their nucleic acid synthesis.

Clinical Uses Beyond Antibacterial Properties

Beyond their role as antibacterial agents, sulfonamides possess a variety of other medicinal properties. They are utilized in the treatment of allergies and coughs and exhibit antifungal and antimalarial activities. The sulfonamide group is also a component in non-antimicrobial medications, including:

• Thiazide diuretics such as hydrochlorothiazide, metolazone, and indapamide;
• Loop diuretics like furosemide, bumetanide, and torsemide;
• Acetazolamide, used primarily as a diuretic and in the treatment of glaucoma;
• Sulfonylureas, a class of medications used to manage type 2 diabetes, including glipizide and glyburide;
• Certain COX-2 inhibitors, for example, celecoxib, which are used for their anti-inflammatory properties.

Additionally, Sulfasalazine is a sulfonamide with dual functionality; it acts as an antibiotic and is also employed in managing inflammatory bowel disease, including conditions such as ulcerative colitis and Crohn's disease.

Use and Side Effects

Sulfonamides are prescribed for an array of bacterial infections, from respiratory tract infections to urinary tract infections, and even skin infections. Adverse reactions to sulfonamides may manifest as skin rashes, hypersensitivity reactions, and, though infrequently, serious conditions like Stevens-Johnson Syndrome.

Despite the proliferation of advanced, targeted antibiotics, sulfonamides remain a staple in the medical field due to their wide-ranging efficacy against various pathogens and cost-effectiveness, especially in resource-limited settings.

List of sulfonamide antibiotics

• Elixir sulfanilamide
• Mafenide
• Phthalylsulfathiazole
• Prontosil
• Silver sulfadiazine
• Succinylsulfathiazole
• Sulfabenzamide
• Sulfacetamide
• Sulfachlorpyridazine
• Sulfacytine
• Sulfadiazine
• Sulfadicramide
• Sulfadimethoxine
• Sulfadimidine
• Sulfadoxine
• Sulfafurazole
• Sulfaguanidine
• Sulfalene
• Sulfamazone
• Sulfamerazine
• Sulfamethizole
• Sulfamethoxazole
• Sulfamethoxypyridazine
• Sulfametomidine
• Sulfametoxydiazine
• Sulfametrole
• Sulfamoxole
• Sulfanilamide
• Sulfanitran
• Sulfaperin
• Sulfaphenazole
• Sulfapyridine
• Sulfaquinoxaline
• Sulfathiazole
• Sulfathiourea
• Sulfatolamide
• Sulfisomidine
• Sulfoxone
• Terephtyl

See Also

• Antibiotics
• Antimicrobial resistance
• Drug design

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