60 Questions
What is the primary goal of multidrug therapy in tuberculosis treatment?
To suppress resistant organisms
What is the typical duration of the intensive phase of standard short-course chemotherapy for tuberculosis?
2 months
When is it advisable to use rifabutin or rifapentine instead of rifampin?
Under certain circumstances
What is the purpose of continuing therapy for a longer period after initial improvement?
To eradicate persistent organisms and prevent relapse
What is the typical duration of the continuation phase of standard short-course chemotherapy for tuberculosis?
4 months
What is the most serious adverse effect associated with isoniazid?
Hepatitis
What is a common component of second-line regimens for MDR-TB?
Fluoroquinolone
What can be used to prevent peripheral neuropathy caused by isoniazid?
Pyridoxine supplementation
What is a risk factor for the incidence of hepatitis caused by isoniazid?
Age greater than 35 years old
What is a potential interaction between isoniazid and other medications?
Isoniazid potentiates the adverse effects of carbamazepine and phenytoin
What is a characteristic of rifampin compared to isoniazid?
Rifampin has broader antimicrobial activity than isoniazid
What is a common adverse effect of rifampin and other rifamycins?
Hypersensitivity reactions
What is the difference in treatment duration between drug-susceptible TB and multidrug-resistant TB (MDR-TB)?
1.5 years vs 2 years
What can happen to resistant organisms under selective pressure from inadequate treatment?
They emerge as the dominant population
What is the minimum duration of treatment for active TB disease?
6 months
What is the treatment duration for Latent TB Infections (LTBI) with isoniazid (INH) monotherapy?
9 months
Why are second-line drugs used in TB treatment?
Because they are used for patients who cannot tolerate first-line drugs or have resistant TB
What is the reason for the rapid development of resistance in TB patients given only streptomycin?
Because monotherapy with streptomycin leads to rapid development of resistance
Why is rifampin never given as a single agent in the treatment of active tuberculosis?
Because resistant strains rapidly emerge during monotherapy
What is the mechanism of action of rifampin?
Blocking RNA transcription by interacting with the β subunit of mycobacterial DNA-dependent RNA polymerase
What type of microorganisms is rifampin bactericidal for?
Both intracellular and extracellular mycobacteria
What causes resistance to rifampin?
Mutations in the bacterial DNA-dependent RNA polymerase gene
How does rifampin undergo elimination?
Through enterohepatic recycling
What is a potential consequence of rifampin's effect on hepatic cytochrome P450 enzymes?
Increased risk of drug interactions
What is the main route of elimination of rifampin and its metabolites?
Primarily through the bile and into the feces
What is a common adverse effect of rifampin?
Nausea
Why should patients be warned about taking rifampin?
Because it can cause urine and tears to turn orange-red
What is a rare but serious adverse effect of rifampin?
Hepatitis
What happens to the elimination half-life of rifampin over the first 1-2 weeks of dosing?
It decreases
What is a potential problem associated with intermittent dosing of rifampin?
Flu-like syndrome
What is the primary mechanism of resistance to isoniazid?
Chromosomal mutations, including mutation or deletion of KatG
What is the effect of food, particularly high-fat meals, on isoniazid absorption?
It impairs the absorption of isoniazid
What is the primary route of excretion of isoniazid metabolites?
Glomerular filtration and secretion
What is the difference in serum half-life between fast and slow acetylators of isoniazid?
90 minutes vs. 3-4 hours
What is the consequence of overexpression of the target enzyme InhA in relation to isoniazid?
Resistance to isoniazid
What is the concentration of isoniazid in cerebrospinal fluid (CSF) compared to serum?
Similar to serum concentrations
Rifampin induces which type of enzymes, leading to decreased half-lives of co-administered drugs?
Both phase I cytochrome P450 enzymes and phase II enzymes
Why is rifabutin preferred over rifampin for TB patients coinfected with HIV?
Rifabutin is a less potent inducer of cytochrome P450 enzymes
What is a characteristic of rifapentine compared to rifampin?
Rifapentine has a longer half-life than rifampin
What is the mechanism of action of pyrazinamide?
Unclear, but it is used in combination with isoniazid, rifampin, and ethambutol
What is a potential consequence of rifampin's effect on hepatic cytochrome P450 enzymes?
Increased dosages of co-administered drugs
What is a common adverse effect of rifabutin?
All of the above
What is the effect of autoinduction on rifampin's elimination half-life?
It shortens over the first 1 to 2 weeks of dosing.
What percentage of rifampin and its metabolites is cleared in the urine?
A small percentage.
Why should patients be warned about taking rifampin?
Because urine and tears may turn orange-red in color.
What is a rare but serious adverse effect of rifampin?
Death due to liver failure.
Why should rifampin be used judiciously in certain patients?
Because of the risk of hepatic dysfunction.
What can occur with intermittent dosing of rifampin, especially with higher doses?
A flu-like syndrome.
Which of the following antibiotics is a structural analog of isoniazid?
Ethionamide
Which of the following antibiotics is primarily excreted unchanged in urine?
Cycloserine
What is a common adverse effect of Cycloserine?
CNS disturbances
Which of the following antibiotics inhibits protein synthesis?
Capreomycin
Which of the following antibiotics is widely distributed throughout the body, including the CSF?
Ethionamide
Which of the following antibiotics works via folic acid inhibition?
Para-aminosalicylic acid
What is the primary mechanism of action of pyrazinamide against tuberculosis bacilli?
Being enzymatically hydrolyzed to pyrazinoic acid
What is a common adverse effect associated with pyrazinamide?
Uric acid retention
What is the primary reason for discontinuing pyrazinamide after 2 months of treatment?
Because most of the clinical benefit occurs early in treatment
What is the specific target of ethambutol in the mycobacterial cell wall?
Arabinosyl transferase
What is the primary route of elimination of ethambutol and its metabolites?
Urinary excretion
Why may ethambutol be discontinued during treatment?
If the isolate is determined to be susceptible to isoniazid, rifampin, and pyrazinamide
This quiz covers the chemotherapy of tuberculosis, including the mechanism of action of Isoniazid and how resistance to it develops. Learn about the mutations that lead to resistance and the cross-resistance with other drugs.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
