Lincosamides - Clindamycin Overview
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Questions and Answers

What is the primary mechanism by which anti-HSV drugs inhibit viral replication?

  • Competing with nucleotides on the DNA polymerase substrate site (correct)
  • Inhibition of viral protein synthesis
  • Blocking viral entry into the host cell
  • Interference with host cell RNA polymerase
  • Which of the following is not a requirement for the activation of anti-HSV drugs?

  • Presence of specific host cell enzymes (correct)
  • Conversion into nucleoside triphosphates
  • Phosphorylation by viral enzymes
  • Analogues of deoxyribonucleosidetriphosphates
  • Which condition requires incision and drainage as a primary treatment?

  • Redness/heat
  • Abscess (correct)
  • Oedema
  • Draining sinus tract
  • What is a common characteristic of drugs like Acyclovir and Valacyclovir?

    <p>They are nucleoside analogues that require viral phosphorylation for activation</p> Signup and view all the answers

    Which of the following statements about purulence is true?

    <p>It is resolved by drainage of pus or debridement</p> Signup and view all the answers

    What is the primary mechanism by which AmpB induces cell death in fungal cells?

    <p>Sequestering ergosterol in the cell membrane</p> Signup and view all the answers

    Which of the following is a significant adverse effect associated with Amphotericin B?

    <p>Renal tubular acidosis</p> Signup and view all the answers

    Why must Amphotericin B be formulated with artificial lipids for administration?

    <p>To form liposomal preparations</p> Signup and view all the answers

    What type of reaction can occur shortly after the intravenous administration of Amphotericin B?

    <p>Severe systemic reaction</p> Signup and view all the answers

    Which of the following statements about Griseofulvin is true?

    <p>It inhibits microtubule assembly to block mitosis.</p> Signup and view all the answers

    What is the primary mechanism of action of azole antifungals?

    <p>Blocking demethylation of lanosterol to ergosterol</p> Signup and view all the answers

    Which azole has the greatest potential to inhibit the CYP450 3A4 isoenzyme?

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

    Which of the following drugs falls under the echinocandin class?

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

    What is a common side effect of echinocandins?

    <p>Phlebitis at the infusion site</p> Signup and view all the answers

    Why should azole antifungals be avoided in pregnancy?

    <p>They are teratogenic and pose risks to the fetus</p> Signup and view all the answers

    What is the mechanism of action of clindamycin?

    <p>Bind to 50S subunit inhibiting protein synthesis</p> Signup and view all the answers

    Which of the following is a significant side effect associated with clindamycin use?

    <p>Antibiotic-associated colitis</p> Signup and view all the answers

    What type of bacteria is clindamycin effective against?

    <p>Gram-positive aerobic and anaerobic bacteria</p> Signup and view all the answers

    Which of the following antibiotics are aminoglycosides?

    <p>Gentamicin and neomycin</p> Signup and view all the answers

    What is a primary characteristic of aminoglycosides in terms of their killing action?

    <p>Concentration-dependent killing</p> Signup and view all the answers

    What is a consequence of aminoglycosides’ poor tissue penetration?

    <p>They should not be used for infections outside the urinary tract</p> Signup and view all the answers

    Why is dosage adjustment necessary in renal failure for aminoglycosides?

    <p>Excretion is directly proportional to creatinine clearance</p> Signup and view all the answers

    Which of the following statements about clindamycin resistance is true?

    <p>Intrinsic resistance to Gram-negative bacteria</p> Signup and view all the answers

    What is the preferred route of administration for drugs that can cause a histamine-like reaction when infused rapidly?

    <p>Slow IV infusion</p> Signup and view all the answers

    Which medication is specifically indicated for patients with invasive candidiasis?

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

    In cases of mild oropharyngeal candidiasis, which treatment is preferred?

    <p>Topical therapy</p> Signup and view all the answers

    What should be done for a patient with severe oropharyngeal candidiasis?

    <p>Oral azoles like fluconazole</p> Signup and view all the answers

    Why are oral azoles contraindicated during the first trimester of pregnancy?

    <p>They are teratogenic</p> Signup and view all the answers

    When would oral fluconazole be an appropriate option for treating oropharyngeal candidiasis?

    <p>If the patient cannot use topical therapies</p> Signup and view all the answers

    Which medication options are considered effective for initial therapy in oropharyngeal candidiasis?

    <p>Clotrimazole and miconazole</p> Signup and view all the answers

    Which of the following is NOT a characteristic of fluconazole as a treatment for severe disease?

    <p>High side effect profile</p> Signup and view all the answers

    Study Notes

    Lincosamides - Clindamycin

    • Inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit.
    • Exhibits bacteriostatic activity against Gram-positive aerobic and anaerobic bacteria.
    • Resistance mechanisms include intrinsic resistance in Gram-negative bacteria and cross-resistance with macrolides.
    • Pharmacokinetics: Distributed widely in tissues, including bones and abscesses, but poorly penetrates the central nervous system (CNS).
    • Side effects include nausea, diarrhea, rash, contact dermatitis, impaired liver function, and neutropenia.
    • C. difficile can cause antibiotic-associated colitis, necessitating treatment with metronidazole or vancomycin.

    Aminoglycosides

    • Bactericidal antibiotics affecting the 30S ribosomal subunit.
    • Key agents: Streptomycin, neomycin, kanamycin, amikacin, gentamicin, tobramycin, sisomicin, netlicin.
    • Mechanism of action involves inhibiting protein synthesis via interference with ribosomal function.
    • Demonstrates concentration-dependent killing with significant post-antibiotic effects; more effective with single large doses versus multiple smaller doses.
    • Pharmacokinetics: High concentration in renal cortex; poor tissue penetration; primarily excreted by the kidneys, needing dosage adjustment in renal failure.

    Antivirals - Mechanism of Action for HSV

    • Primarily inhibit DNA polymerase through two mechanisms:
      • A: Compete with nucleotides on the substrate site—nucleoside analogues (e.g., acyclovir, valacyclovir).
      • B: Require viral enzymes for phosphorylation to activate, preventing viral DNA synthesis selectively.
    • Other drug actions include disruption of fungal RNA/DNA synthesis via metabolites and inhibition of mitotic cell division (e.g., griseofulvin).
    • Amphotericin B binds to ergosterol in fungal cell membranes, leading to cell death, either fungicidal or fungistatic depending on concentration and organism.

    Amphotericin B

    • Administered via slow intravenous infusion due to low water solubility; requires lipid formulation to reduce toxicity.
    • Known for a low therapeutic index with side effects including fever, chills, headaches, vomiting, and renal impairment.
    • Can cause renal tubular acidosis and requires potassium supplementation due to magnesium wasting.

    Azoles

    • Work by inhibiting the fungal cytochrome P450 enzyme (14-α demethylase), disrupting ergosterol production and affecting fungal membrane structure.
    • Contraindicated in pregnancy due to teratogenic effects; should avoid in the first trimester.
    • All azoles can cause QT prolongation; some notable ones include ketoconazole, itraconazole, voriconazole, and fluconazole.

    Echinocandins

    • Agents: Caspofungin, micafungin, anidulafungin, which inhibit β(1,3)-D-glucan synthesis in fungal cell walls.
    • Effective against Aspergillus and most resistant Candida species.
    • Common side effects include fever, rash, nausea, and phlebitis; avoid rapid infusion to prevent histamine-like reactions.

    Oropharyngeal Candidiasis - Initial Therapy

    • Mild cases benefit from topical therapies such as clotrimazole troches or miconazole buccal tablets, which are more effective than nystatin.
    • Fluconazole is favored for severe cases due to ease of administration and favorable side effect profile.
    • Pregnant women should use topical therapies (e.g., clotrimazole, miconazole), avoiding oral azoles in the first trimester due to teratogenicity risks.

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    Description

    This quiz covers the mechanism of action of Clindamycin, a type of lincosamide, and its effects on bacterial protein synthesis. It includes information on its spectrum of activity against gram-positive bacteria, resistance mechanisms, and pharmacokinetics. Test your knowledge on this important antibiotic and its clinical implications.

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