Sulfonamides, Quinolones and Urinary Antiseptics MCQs

Explanation: DNA gyrase is an essential bacterial enzyme responsible for introducing negative supercoils into DNA, which relieves the torsional strain generated ahead of the replication fork. Ciprofloxacin, a fluoroquinolone antibiotic, specifically inhibits DNA gyrase and topoisomerase IV. By inhibiting DNA gyrase, ciprofloxacin prevents proper DNA replication and transcription, ultimately leading to bacterial cell death.

The combination of clindamycin and primaquine is an alternative regimen in the treatment of pneumocystis, particularly mild to moderate disease. This regimen offers improved tolerance compared with high-dose trimethoprim-sulfamethoxazole or pentamidine, although its efficacy against severe pneumocystis pneumonia is not well studied. Reference: LANG' Basic & clinical pharmacology by Bertram G. Katzung, Susen B. Masters and Anthony J. Trevor 12 th edition. Chapter 52- Antiprotozoal Agents by Dr. Philip J. Rosenthal, MD. Page no. 924

DNA gyrase inhibitors REF: Goodman Gillman's 11th ed p. 722 The quinolone antibiotics target bacterial DNA gyrase and topoisomerase IV. For many gram positive bacteria, topoisomerase IV is the primary target. For many gram-negative bacteria, DNA gyrase is the primary quinolone target.

Ans. is `d' i.e., Sulfonamides o Sulfonamides affect intermediary metabolism by inhibiting folate synthase.

Levofloxacin It is the active levo(S) isomer of ofloxacin having improved activity against Strep. pneumoniae,tuberculosis and some other gram-positive and gram-negative bacteria. Anaerobes are moderately susceptible. Oral bioavailability of levofloxacin is nearly 100%; oral and i.v. doses are similar. It is mainly excreted unchanged, and a single daily dose is sufficient because of slower elimination and higher potency.

Ans. is 'd' i.e., More active at acidic pH Ciprofloxacin is the most potent first generation FQ. o Ciprofloxacin inhibit DNA gyrase and is contraindicated in pregnancy. It is less active at acidic pH.

Trimethoprim is the only weak base listed (fluoroquinolones and sulfonamides are acidic compounds), and its high lipid solubility at blood pH allows penetration of the drug into prostatic and vaginal fluid to reach levels similar to those in plasma. Leukopenia and thrombocytopenia may occur in folate deficiency when the drug is used alone or in combination with sulfamethoxazole. Fluoroquinolones and linezolid do not exacerbate symptoms of folic acid deficiency. Reference: Basic & Clinical Pharmacology, Fourteenth Edition By Bertram G. Katzung Pg no. 837

Ans. is 'b' i.e., Sulfadoxine Sulfadoxine and sulfamethopyrazine are long acting sulfonamides.