Antimycobacterial Drugs
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Questions and Answers

What is the primary goal of multidrug therapy in tuberculosis treatment?

  • To replace rifampin with rifabutin
  • To reduce the incidence of toxicity
  • To shorten the treatment duration
  • To suppress resistant organisms (correct)

    • What is the typical duration of the intensive phase of standard short-course chemotherapy for tuberculosis?

  • 2 months (correct)
  • 4 months
  • 1 month
  • 6 months

    • When is it advisable to use rifabutin or rifapentine instead of rifampin?

  • In cases of standard tuberculosis
  • Under certain circumstances (correct)
  • In combination with isoniazid
  • In cases of MDR-TB

    • What is the purpose of continuing therapy for a longer period after initial improvement?

    <p>To eradicate persistent organisms and prevent relapse</p> Signup and view all the answers

    What is the typical duration of the continuation phase of standard short-course chemotherapy for tuberculosis?

    <p>4 months</p> Signup and view all the answers

    What is the most serious adverse effect associated with isoniazid?

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

    What is a common component of second-line regimens for MDR-TB?

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

    What can be used to prevent peripheral neuropathy caused by isoniazid?

    <p>Pyridoxine supplementation</p> Signup and view all the answers

    What is a risk factor for the incidence of hepatitis caused by isoniazid?

    <p>Age greater than 35 years old</p> Signup and view all the answers

    What is a potential interaction between isoniazid and other medications?

    <p>Isoniazid potentiates the adverse effects of carbamazepine and phenytoin</p> Signup and view all the answers

    What is a characteristic of rifampin compared to isoniazid?

    <p>Rifampin has broader antimicrobial activity than isoniazid</p> Signup and view all the answers

    What is a common adverse effect of rifampin and other rifamycins?

    <p>Hypersensitivity reactions</p> Signup and view all the answers

    What is the difference in treatment duration between drug-susceptible TB and multidrug-resistant TB (MDR-TB)?

    <p>1.5 years vs 2 years</p> Signup and view all the answers

    What can happen to resistant organisms under selective pressure from inadequate treatment?

    <p>They emerge as the dominant population</p> Signup and view all the answers

    What is the minimum duration of treatment for active TB disease?

    <p>6 months</p> Signup and view all the answers

    What is the treatment duration for Latent TB Infections (LTBI) with isoniazid (INH) monotherapy?

    <p>9 months</p> Signup and view all the answers

    Why are second-line drugs used in TB treatment?

    <p>Because they are used for patients who cannot tolerate first-line drugs or have resistant TB</p> Signup and view all the answers

    What is the reason for the rapid development of resistance in TB patients given only streptomycin?

    <p>Because monotherapy with streptomycin leads to rapid development of resistance</p> Signup and view all the answers

    Why is rifampin never given as a single agent in the treatment of active tuberculosis?

    <p>Because resistant strains rapidly emerge during monotherapy</p> Signup and view all the answers

    What is the mechanism of action of rifampin?

    <p>Blocking RNA transcription by interacting with the β subunit of mycobacterial DNA-dependent RNA polymerase</p> Signup and view all the answers

    What type of microorganisms is rifampin bactericidal for?

    <p>Both intracellular and extracellular mycobacteria</p> Signup and view all the answers

    What causes resistance to rifampin?

    <p>Mutations in the bacterial DNA-dependent RNA polymerase gene</p> Signup and view all the answers

    How does rifampin undergo elimination?

    <p>Through enterohepatic recycling</p> Signup and view all the answers

    What is a potential consequence of rifampin's effect on hepatic cytochrome P450 enzymes?

    <p>Increased risk of drug interactions</p> Signup and view all the answers

    What is the main route of elimination of rifampin and its metabolites?

    <p>Primarily through the bile and into the feces</p> Signup and view all the answers

    What is a common adverse effect of rifampin?

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

    Why should patients be warned about taking rifampin?

    <p>Because it can cause urine and tears to turn orange-red</p> Signup and view all the answers

    What is a rare but serious adverse effect of rifampin?

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

    What happens to the elimination half-life of rifampin over the first 1-2 weeks of dosing?

    <p>It decreases</p> Signup and view all the answers

    What is a potential problem associated with intermittent dosing of rifampin?

    <p>Flu-like syndrome</p> Signup and view all the answers

    What is the primary mechanism of resistance to isoniazid?

    <p>Chromosomal mutations, including mutation or deletion of KatG</p> Signup and view all the answers

    What is the effect of food, particularly high-fat meals, on isoniazid absorption?

    <p>It impairs the absorption of isoniazid</p> Signup and view all the answers

    What is the primary route of excretion of isoniazid metabolites?

    <p>Glomerular filtration and secretion</p> Signup and view all the answers

    What is the difference in serum half-life between fast and slow acetylators of isoniazid?

    <p>90 minutes vs. 3-4 hours</p> Signup and view all the answers

    What is the consequence of overexpression of the target enzyme InhA in relation to isoniazid?

    <p>Resistance to isoniazid</p> Signup and view all the answers

    What is the concentration of isoniazid in cerebrospinal fluid (CSF) compared to serum?

    <p>Similar to serum concentrations</p> Signup and view all the answers

    Rifampin induces which type of enzymes, leading to decreased half-lives of co-administered drugs?

    <p>Both phase I cytochrome P450 enzymes and phase II enzymes</p> Signup and view all the answers

    Why is rifabutin preferred over rifampin for TB patients coinfected with HIV?

    <p>Rifabutin is a less potent inducer of cytochrome P450 enzymes</p> Signup and view all the answers

    What is a characteristic of rifapentine compared to rifampin?

    <p>Rifapentine has a longer half-life than rifampin</p> Signup and view all the answers

    What is the mechanism of action of pyrazinamide?

    <p>Unclear, but it is used in combination with isoniazid, rifampin, and ethambutol</p> Signup and view all the answers

    What is a potential consequence of rifampin's effect on hepatic cytochrome P450 enzymes?

    <p>Increased dosages of co-administered drugs</p> Signup and view all the answers

    What is a common adverse effect of rifabutin?

    <p>All of the above</p> Signup and view all the answers

    What is the effect of autoinduction on rifampin's elimination half-life?

    <p>It shortens over the first 1 to 2 weeks of dosing.</p> Signup and view all the answers

    What percentage of rifampin and its metabolites is cleared in the urine?

    <p>A small percentage.</p> Signup and view all the answers

    Why should patients be warned about taking rifampin?

    <p>Because urine and tears may turn orange-red in color.</p> Signup and view all the answers

    What is a rare but serious adverse effect of rifampin?

    <p>Death due to liver failure.</p> Signup and view all the answers

    Why should rifampin be used judiciously in certain patients?

    <p>Because of the risk of hepatic dysfunction.</p> Signup and view all the answers

    What can occur with intermittent dosing of rifampin, especially with higher doses?

    <p>A flu-like syndrome.</p> Signup and view all the answers

    Which of the following antibiotics is a structural analog of isoniazid?

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

    Which of the following antibiotics is primarily excreted unchanged in urine?

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

    What is a common adverse effect of Cycloserine?

    <p>CNS disturbances</p> Signup and view all the answers

    Which of the following antibiotics inhibits protein synthesis?

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

    Which of the following antibiotics is widely distributed throughout the body, including the CSF?

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

    Which of the following antibiotics works via folic acid inhibition?

    <p>Para-aminosalicylic acid</p> Signup and view all the answers

    What is the primary mechanism of action of pyrazinamide against tuberculosis bacilli?

    <p>Being enzymatically hydrolyzed to pyrazinoic acid</p> Signup and view all the answers

    What is a common adverse effect associated with pyrazinamide?

    <p>Uric acid retention</p> Signup and view all the answers

    What is the primary reason for discontinuing pyrazinamide after 2 months of treatment?

    <p>Because most of the clinical benefit occurs early in treatment</p> Signup and view all the answers

    What is the specific target of ethambutol in the mycobacterial cell wall?

    <p>Arabinosyl transferase</p> Signup and view all the answers

    What is the primary route of elimination of ethambutol and its metabolites?

    <p>Urinary excretion</p> Signup and view all the answers

    Why may ethambutol be discontinued during treatment?

    <p>If the isolate is determined to be susceptible to isoniazid, rifampin, and pyrazinamide</p> Signup and view all the answers

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