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 (B)</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 (B)</p> Signup and view all the answers

What is the most serious adverse effect associated with isoniazid?

<p>Hepatitis (C)</p> Signup and view all the answers

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

<p>Fluoroquinolone (C)</p> Signup and view all the answers

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

<p>Pyridoxine supplementation (A)</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 (A)</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 (C)</p> Signup and view all the answers

What is a characteristic of rifampin compared to isoniazid?

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

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

<p>Hypersensitivity reactions (C)</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 (A)</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 (B)</p> Signup and view all the answers

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

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

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

<p>9 months (A)</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 (C)</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 (B)</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 (D)</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 (A)</p> Signup and view all the answers

What type of microorganisms is rifampin bactericidal for?

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

What causes resistance to rifampin?

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

How does rifampin undergo elimination?

<p>Through enterohepatic recycling (B)</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 (C)</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 (D)</p> Signup and view all the answers

What is a common adverse effect of rifampin?

<p>Nausea (C)</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 (D)</p> Signup and view all the answers

What is a rare but serious adverse effect of rifampin?

<p>Hepatitis (A)</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 (D)</p> Signup and view all the answers

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

<p>Flu-like syndrome (D)</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 (B)</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 (D)</p> Signup and view all the answers

What is the primary route of excretion of isoniazid metabolites?

<p>Glomerular filtration and secretion (B)</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 (D)</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 (D)</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 (C)</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 (A)</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 (C)</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 (C)</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 (A)</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 (B)</p> Signup and view all the answers

What is a common adverse effect of rifabutin?

<p>All of the above (D)</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. (C)</p> Signup and view all the answers

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

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

What is a rare but serious adverse effect of rifampin?

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

Why should rifampin be used judiciously in certain patients?

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

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

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

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

<p>Ethionamide (A)</p> Signup and view all the answers

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

<p>Cycloserine (B)</p> Signup and view all the answers

What is a common adverse effect of Cycloserine?

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

Which of the following antibiotics inhibits protein synthesis?

<p>Capreomycin (C)</p> Signup and view all the answers

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

<p>Ethionamide (A)</p> Signup and view all the answers

Which of the following antibiotics works via folic acid inhibition?

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

What is a common adverse effect associated with pyrazinamide?

<p>Uric acid retention (D)</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 (C)</p> Signup and view all the answers

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

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

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

<p>Urinary excretion (B)</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 (A)</p> Signup and view all the answers

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