Pharmacology Quiz on Antibiotics and Mechanisms
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Questions and Answers

What is the main mechanism of action of Metronidazole?

  • Inhibits protein synthesis
  • Formation of free radicals that damage DNA (correct)
  • Inhibits cell wall synthesis
  • Binds to ribosomal subunits

    • Which of the following side effects is commonly associated with Nitroimidazoles?

  • Nausea and vomiting
  • Metallic taste (correct)
  • Jaundice
  • Abdominal cramps

    • What is the primary clinical use of Nitrofurantoin?

  • Treatment of tuberculosis
  • Control of anaerobic infections
  • Management of urinary tract infections (correct)
  • Prevention of bacterial colitis

    • Which statement accurately describes the action of Polymyxin B?

    <p>Disrupts the cell membrane and causes leakage</p> Signup and view all the answers

    What type of infections are Nitrofurans primarily used to treat?

    <p>Urinary tract infections</p> Signup and view all the answers

    Which pharmacological class does the N-1-alkylated 3-carboxy-pyrid-4-one ring belong to?

    <p>Quinolones</p> Signup and view all the answers

    Which method is NOT part of the selection criteria for medicines according to the learning outcomes?

    <p>Delineation of allergic reactions</p> Signup and view all the answers

    Which antibiotic class is primarily used for the treatment of urinary tract infections (UTIs)?

    <p>Quinolones</p> Signup and view all the answers

    What is the primary action of sulfonamides in pharmacology?

    <p>Acting as antimetabolites</p> Signup and view all the answers

    Which of the following is a key pharmacokinetic property to recognize?

    <p>ADME</p> Signup and view all the answers

    Which of the following antibiotics is a beta-lactam?

    <p>Cephalosporin</p> Signup and view all the answers

    Which aspect is essential for understanding the mechanism of action of pharmacological entities?

    <p>Chemical structure</p> Signup and view all the answers

    Which class of antibiotics includes aminoglycosides?

    <p>Protein synthesis inhibitors</p> Signup and view all the answers

    What effect does a C5-amino substitution have on quinolones?

    <p>Decreases phototoxicity and increases activity</p> Signup and view all the answers

    Which of the following changes can increase the activity of quinolones?

    <p>Condensing the piperazine ring</p> Signup and view all the answers

    What is the principal mechanism of action for aminoacridines?

    <p>Direct interaction with bacterial DNA</p> Signup and view all the answers

    Why are aminoacridines not used for systemic bacterial infections?

    <p>They are toxic to host cells</p> Signup and view all the answers

    What effect does the addition of a methyl group on the piperazine ring of quinolones have?

    <p>Decreases GABA binding and CNS side effects</p> Signup and view all the answers

    What is the mechanism of action of rifamycins like rifampicin?

    <p>Non-covalent binding to DNA-dependent RNA polymerase</p> Signup and view all the answers

    Which structural feature is crucial for the activity of quinolones?

    <p>Presence of an aromatic ring</p> Signup and view all the answers

    What is the resulting effect of the structural modification involving a double bond in quinolones?

    <p>Improves pharmacokinetics and increases activity</p> Signup and view all the answers

    What is the primary mechanism of action of sulfonamides?

    <p>Inhibition of dihydropteroate synthetase</p> Signup and view all the answers

    Why are sulfonamides considered bacteriostatic?

    <p>They inhibit bacterial growth</p> Signup and view all the answers

    What is the consequence of humans not synthesizing folic acid?

    <p>They must obtain folic acid from their diet</p> Signup and view all the answers

    Which feature is crucial for the activity of sulfonamides?

    <p>p-amino group</p> Signup and view all the answers

    What is the role of trimethoprim when combined with sulfonamides?

    <p>It introduces synergism by inhibiting a different step</p> Signup and view all the answers

    What characteristic structure makes sulfonamides unique from other antibiotics?

    <p>Aromatic ring with a sulfonamide moiety</p> Signup and view all the answers

    What is an outcome of blocking the first step of folic acid synthesis?

    <p>Inhibition of thymidine and purine synthesis</p> Signup and view all the answers

    Why might resistance to sulfonamides develop slowly?

    <p>They inhibit multiple steps of metabolism</p> Signup and view all the answers

    What is the prototype drug used in the treatment of leprosy?

    <p>Dapsone</p> Signup and view all the answers

    Which enzyme is inhibited by Dapsone?

    <p>Dihydropteroate Synthase</p> Signup and view all the answers

    What characteristic of Dapsone contributes to its classification as a bacteriostatic agent?

    <p>It acts as a dihydropteroate synthetase inhibitor.</p> Signup and view all the answers

    Which of the following features is most likely to enhance the oral bioavailability of a β-lactam antibiotic?

    <p>Inclusion of a double ester prodrug form</p> Signup and view all the answers

    What modification would make a β-lactam antibiotic resistant to acid degradation?

    <p>Incorporating an isoxazole ring</p> Signup and view all the answers

    Which component of a β-lactam structure primarily facilitates its broad spectrum of activity?

    <p>The phenyl ring</p> Signup and view all the answers

    What is the main purpose of the prodrug Sultamcillin in relation to sulbactam?

    <p>To enhance β-lactamase resistance</p> Signup and view all the answers

    Which part of the β-lactam structure is NOT considered essential for function?

    <p>The sulfur atom</p> Signup and view all the answers

    Which sulfonamide is primarily used for the treatment of Toxoplasmosis?

    <p>Sulfadiazine</p> Signup and view all the answers

    What is the role of NaHCO3 when co-administered with sulfonamides?

    <p>Counteract acidity</p> Signup and view all the answers

    Which sulfonamide is utilized as a prodrug for the treatment of ulcerative colitis?

    <p>Sulfasalazine</p> Signup and view all the answers

    For which of the following infections is Sulfacetamide primarily used?

    <p>Conjunctivitis</p> Signup and view all the answers

    Which combination is used in the treatment of malaria?

    <p>Sulfadiazine + Pyrimethamine</p> Signup and view all the answers

    What differentiates Phthalyl Sulfathiazole from other sulfonamides?

    <p>It is non-absorbable and acts in the colon.</p> Signup and view all the answers

    What is the main mechanism of action of Trimethoprim?

    <p>Inhibits DNA synthesis</p> Signup and view all the answers

    What is a common use for Silver Sulfadiazine?

    <p>Topical treatment for burns</p> Signup and view all the answers

    Study Notes

    Antibiotics

    • Lecture 3: Inhibitors of Nucleic Acid Synthesis, Cell Membrane Disruptors, Antimetabolites
    • Course Outline:
      • LEC. I: Cell wall inhibitors
      • LEC. II: Protein synthesis inhibitors
      • LEC. III: DNA synthesis inhibitors, Antimetabolites, Cell membrane disruptors
    • Learning Outcomes (Los):
      • Categorize chemical structures into pharmacological classes and discuss potential activities.
      • Apply stereochemistry concepts to drug mechanisms.
      • Recognize pharmacokinetic (ADME) and pharmacodynamic properties of medicines.
      • Select appropriate synthesis, purification, and standardization methods.
      • Predict allergic reactions to drugs.
      • Understand and estimate pharmacokinetic interactions.
      • Understand drug interactions with food.
      • Estimate dosing intervals based on structure.
      • Understand mechanisms of action of various drug entities.

    Mechanisms of Antibiotic Action

    • Inhibition of protein synthesis: Aminoglycosides, Tetracyclines, Chloramphenicol, Macrolides, Oxazolidinone
    • Inhibition of nucleic acid synthesis: Quinolones
    • Inhibition of cell wall synthesis: Beta-Lactams (Penicillin, Cephalosporin)
    • Disruption of cell membrane function: Polymyxins
    • Block pathways and inhibit metabolism: Folic acids inhibitors (Sulfonamides, Trimethoprim)

    Quinolones

    • Classification: 1st generation (Nalidixic acid), 2nd generation (Ciprofloxacin, Norfloxacin, Ofloxacin, Lomefloxacin), 3rd generation (Gatifloxacin, Moxifloxacin, Sparfloxacin, Levofloxacin), 4th generation (Trovafloxacin)
    • Mechanism of Action: Inhibit bacterial DNA gyrase (Topoisomerase II) and Topoisomerase IV enzymes, inhibiting DNA replication and transcription, leading to cell death.
    • Selectivity: Human topoisomerase II does not bind quinolones at therapeutic doses
    • Metabolism: Metabolized into 7-CH2OH metabolite (ACTIVE), 7-carboxylic metabolite (INACTIVE), 7-glucuronide metabolite (INACTIVE), undergo glucuronic acid conjugation.
    • Chemical Incompatibilities: Contraindicated with: co-administration of antacids, hematinics, and tonics. Should avoid consumption of dairy products soon after administration due to chelation with divalent/trivalent metals.

    Other Classes

    • Aminoacridines: Topical antibacterial for superficial wounds, toxic to host cells, mechanism is direct interaction with bacterial DNA (intercalation) disrupting DNA synthesis, bacteriostatic.
    • Rifamycins: Non-covalent binding to DNA-dependent RNA polymerase (DDRP), inhibiting the start of RNA synthesis, bacteriostatic, selective due to different peptide chain in mammalian RNA polymerase, rifampin (used once daily) and rifapentine (used twice weekly), orally active.
    • Nitroimidazoles: Drug enters cell→Reduction of nitro gp to nitroso gp by nitro reductase enzyme→Formation of free radicals→DNA fragmentation, Bactericidal, for amebiasis & anaerobic infections.
    • Polymyxins: Binds selectively to plasma membranes→Causes leakage of small molecules from the cell→Disrupt cell membrane→Cell death, Bactericidal.

    Antimetabolites

    • Sulfonamides: Structurally similar to PABA; compete as a substrate to inhibit synthesis of dihydrofolic acid(DHFA), Bacteriostatic, synergism with trimethoprim.

    • Side effects:

      • Sulpha allergy, fever with urticaria.
      • Stevens-Johnson Syndrome [severe skin eruption].
      • Hemolytic anemia.
      • Gastrointestinal distress.
      • Crystalluria

    • Synergism: combination with Trimethoprim

    • Mechanism of action: Inhibits DNA synthesis and cell growth and broadly the spectrum of bacterial infections.

      • Different classification based on duration of action:
        • Short-acting: Sulfisoxazole, Sulphamethazine, Sulfadiazine etc.
        • Intermediate-acting: Sulfamethoxazole, Cotrimoxazole combination etc.
        • Long-acting: Sulfadoxine
      • Synthesis: Synthesis of sulphonamides from 4-nitrobenzene-sulfonyl chloride.
      • Classification: Systemic, Intestinal, Topical

    • Structure-Activity Relationship considerations:

      • p-amino gp: Essential for activity; m/o-amino gp: inactive.
      • Alkyl gp: generally inactive .
      • Ring p-substitutions, Replacement with heterocyclic ring: inactivity

    • Sulfonamide Analogues: Amide group, Inactive form, can be used as prodrugs.

    • Structure-Activity Relationship for antibacterial drugs and various related mechanisms:

      • Relationship between chemical structure and activity, relevant functional groups or other structural changes affecting the activity of the drugs.

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    Antibiotics Lecture 3 ACU 2025 PDF

    Description

    Test your knowledge on various antibiotics and their mechanisms of action. This quiz covers important pharmacological concepts, including the use of Nitroimidazoles, Nitrofurans, and beta-lactam antibiotics. Assess your understanding of side effects, pharmacokinetic properties, and clinical applications in the field of pharmacology.

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