QCM : Sulphonamides: History, Chemistry, and Clinical Use — 12 questions

Explication

Sulphonamides are primarily used to inhibit bacterial growth by interfering with bacterial synthesis pathways, specifically by blocking folic acid synthesis. This bacteriostatic mechanism prevents bacteria from multiplying, giving the immune system a better chance to eliminate the infection.

Explication

Understanding that sulphonamides are rapidly absorbed and undergo acetylation in the liver, with their metabolites less soluble in urine, helps clinicians adjust dosing in patients with renal impairment to prevent accumulation and crystalluria. Since metabolites are less soluble in acidic urine, monitoring urinary pH and kidney function is important to minimize side effects. The other options are incorrect because solubility is affected by urinary pH, not metabolism issues in all liver diseases, and higher doses are not necessary due to rapid absorption but need to be tailored to renal function.

Explication

The source describes sulphonamides as having a significant place in medical history as the first effective antimicrobial agents against bacterial infections, with early research involving the dye Prontosil red tested by Domagk. This historical context aligns with their discovery and establishment in the 1930s, making this the correct period. The other options are later periods that do not match the initial discovery and use described in the source.

Explication

The combination of cotrimoxazole inhibits bacterial folate synthesis by targeting two different enzymes—dihydropteroate synthase with sulfamethoxazole and dihydrofolate reductase with trimethoprim—leading to a synergistic bactericidal effect and broadening the spectrum of activity.

Explication

Sulphonamides inhibit bacterial folate synthesis by competitively binding to dihydropteroate synthase, an enzyme essential for the synthesis of dihydrofolic acid from PABA. This inhibition prevents bacteria from producing folic acid, which is necessary for DNA synthesis, thereby exerting their antibacterial effect.

Explication

Trimethoprim is classified as a diaminopyrimidine, a class of drugs that selectively inhibit bacterial dihydrofolate reductase, crucial for bacterial folate synthesis. It is part of the cotrimoxazole combination, which acts synergistically to inhibit bacterial growth.

Explication

Gerhard Domagk included Prontosil red in early research and observed its high efficacy against streptococcal infections, making him credited with the discovery of sulphonamides' antibacterial properties.

Explication

Sulphonamides are classified as a class of antimicrobial agents known for their ability to inhibit bacterial growth by interfering with bacterial synthesis pathways, specifically folic acid synthesis.

Explication

Sulphonamides primarily act as antibacterial agents by inhibiting bacterial folate synthesis, which is essential for bacterial growth. They do not have direct antifungal, anti-inflammatory, or immune-modulating purposes, making the inhibition of bacterial folate synthesis their main function.

Explication

Cotrimoxazole was established as a widely used antimicrobial in the 1960s, when the combination of sulfamethoxazole and trimethoprim was introduced to enhance antibacterial efficacy through synergistic action.

Explication

Sulfadiazine is recognized for its rapid absorption, whereas sulfamethoxazole has a slower absorption rate, as explicitly stated in the source. This difference influences their clinical applications, such as sulfadiazine's use in meningitis due to its quick CSF penetration.

Explication

Increased PABA production by bacteria outcompetes sulphonamides for the enzyme dihydropteroate synthase, directly reducing the drug's effectiveness. The other options are resistance mechanisms for different antibiotics or unrelated to sulphonamide action.