Sulfonamides and Antimetabolites Overview

Involves the liver converting a drug into inactive metabolites.

The elimination of drugs and their metabolites from the body, primarily through urine.

The process by which bacteria develop resistance to sulfonamide drugs.

Use of drugs directly on the skin or mucous membranes.

Use of drugs taken by mouth.

Use of drugs injected into a vein.

Sulfonamides are used to treat bacterial conjunctivitis, which is inflammation of the conjunctiva, the transparent membrane that lines the inside of the eyelid and covers the white part of the eye.

Sulfonamides are used to treat trachoma, a bacterial infection of the eye that can lead to blindness.

Antimetabolites are drugs that inhibit the synthesis of DNA, RNA, and proteins by interfering with the folate pathway, a crucial process for cell growth and function.

The folate pathway is a series of biochemical reactions that produce tetrahydrofolate (THF), a coenzyme vital for synthesizing purines, pyrimidines, and some amino acids. These molecules are essential building blocks for DNA, RNA, and proteins.

Sulfonamides are antimicrobial agents that act as competitive inhibitors of dihydropterotate synthetase, an enzyme involved in the folate pathway. This enzyme is responsible for converting PABA into dihydropteroate, a precursor to bacterial folic acid.

Sulfonamides are structurally similar to PABA, a key component of bacterial folic acid. This structural similarity allows them to bind to the active site of dihydropterotate synthetase, effectively blocking the enzyme's function.

By blocking dihydropterotate synthetase, sulfonamides prevent the synthesis of bacterial folic acid, which leads to a depletion of essential building blocks for DNA, RNA, and protein synthesis. This, in turn, inhibits bacterial growth.

Selective toxicity refers to the ability of a drug to target and kill specific pathogens without harming the host organism. Sulfonamides achieve this by specifically interfering with bacterial folic acid synthesis, while humans obtain this essential nutrient from their diet.

Trimethoprim is another antimetabolite that inhibits dihydrofolate reductase, an enzyme that converts dihydrofolate (DHF) to tetrahydrofolate (THF) in the folate pathway. By blocking this enzyme, trimethoprim further disrupts folate metabolism.

Trimethoprim has a much lower affinity for human dihydrofolate reductase compared to bacterial dihydrofolate reductase. This difference in affinity allows it to selectively target bacterial enzymes, minimizing the toxic effects on human cells.

Sulfonamides are a class of antibiotics that inhibit bacterial synthesis of folate. This inhibition is achieved through their structural similarity to PABA, a key component in folate production.

Most sulfonamides exhibit a broad spectrum of activity against bacterial species. They are effective against both Gram-positive and Gram-negative bacteria, including Chlamydia trachomatis, Nocardia, and certain protozoans.

Sulfonamides are not effective against all bacteria. They show poor activity against most anaerobes and have no effect on Rickettsiae species, which are actually stimulated by sulfonamides.

Sulfonamides are typically administered orally. However, they can also be given parenterally (injection), topically (applied to the skin), or as a suppository (inserted rectally).

Most sulfonamides are readily absorbed from the gastrointestinal tract (GI). Poorly absorbed sulfonamides are primarily used for treating infections within the GI tract.

Sulfonamides are widely distributed throughout the body fluids, including the cerebrospinal fluid (CSF).

The extent of protein binding varies significantly among different sulfonamides, ranging from 20% to over 90%.

Pharmacokinetic parameters, such as absorption, distribution, and elimination, are crucial factors determining the dosage and schedule of sulfonamides.

Sulfonamides are a class of antibiotics that work by inhibiting bacterial synthesis of folic acid, a vital nutrient for bacterial growth.

Sulfonamides are commonly used for patients with meningitis or those who cannot take medication orally.

Sulfonamides can cause side effects like fever, skin rashes, photosensitivity, and gastrointestinal problems.

Sulfonamides can crystallize in the urine, especially in acidic conditions, leading to kidney damage.

Sulfonamides can displace bilirubin from its binding sites on albumin, potentially causing brain damage in newborns.

Sulfonamides can cause various blood disorders like anemia, reduced white blood cell count, and low platelet count.

Frequent monitoring of blood cell counts is essential for patients taking sulfonamides.

Sulfonamides are prescribed with caution during pregnancy and breastfeeding due to potential risks to the fetus and infant.