40 Questions
What is isoniazid effective against?
Both rapidly growing bacilli and intracellular organisms
What is the main reason for resistance to isoniazid?
Chromosomal mutations
Why is absorption of isoniazid impaired?
When taken with food, particularly high-fat meals
What is the mechanism of inactivation of isoniazid in the body?
N-acetylation and hydrolysis
What is the difference between fast and slow acetylators of isoniazid?
Fast acetylators have a shorter half-life
What is the primary route of excretion of isoniazid?
Glomerular filtration and secretion
What is the enzyme required for the activation of pyrazinamide?
Pyrazinamidase
What is the reason for usually discontinuing pyrazinamide after 2 months of a 6-month regimen?
Because most of the clinical benefit occurs early in treatment
What is the primary organ responsible for the excretion of ethambutol and its metabolites?
Kidneys
Why is ethambutol used in combination with other antitubercular drugs?
Pending culture and susceptibility data
Why is rifampin not 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?
It interacts with the β subunit of mycobacterial DNA-dependent RNA polymerase
What is the common side effect of pyrazinamide?
Uric acid retention
What is the limitation of ethambutol in the treatment of tuberculous meningitis?
Penetration into the CNS is variable
Which of the following is rifampin effective against?
Both gram-positive and gram-negative organisms
What is the cause of resistance to rifampin?
Mutations in the bacterial DNA-dependent RNA polymerase gene
What is the effect of rifampin on hepatic cytochrome P450 enzymes?
It induces their activity
What is the fate of rifampin after oral administration?
It is distributed to all body fluids and organs and undergoes enterohepatic recycling
Which mechanism of action does para-aminosalicylic acid work through?
Inhibition of folic acid
What is the primary concern when using capreomycin for the treatment of MDR-TB?
Nephrotoxicity and ototoxicity
Which drug is primarily excreted unchanged in the urine?
Cycloserine
What is the primary effect of cycloserine on the bacterial cell wall?
Disruption of D-alanine incorporation
Which of the following drugs is a structural analog of isoniazid?
Ethionamide
Which of the following drugs is not typically used for the treatment of MDR-TB?
Isoniazid
What is the primary mechanism of action of dapsone in inhibiting bacteria?
Inhibiting dihydropteroate synthase in the folate synthesis pathway
Why should rifampin be avoided when taking the agent mentioned?
Because it is a strong CYP3A4 inducer
What is the primary site of concentration of dapsone in the body?
Skin
What is a common adverse reaction of dapsone, especially in patients with glucose-6-phosphate dehydrogenase deficiency?
Hemolysis
What is the primary route of elimination of dapsone and its metabolites?
Urine
What is another disease that dapsone is used to treat, besides leprosy?
Pneumonia caused by Pneumocystis jirovecii
What is the primary organ responsible for the metabolism of ethionamide?
Liver
What is the primary mechanism of action of bedaquiline?
Inhibiting the ATP synthase
What is a common adverse effect of ethionamide?
Nausea and vomiting
Which of the following fluoroquinolones is effective against multidrug-resistant tuberculosis?
Moxifloxacin
What is the primary reason for preferring azithromycin over clarithromycin in certain patients?
Azithromycin is less likely to interact with other drugs
What is the boxed warning associated with bedaquiline?
QT prolongation
Which of the following macrolides is a substrate and inhibitor of cytochrome P450 enzymes?
Clarithromycin
What is the primary route of administration of bedaquiline?
Oral
Which of the following is a common laboratory abnormality associated with bedaquiline therapy?
Elevated liver enzymes
What is the primary indication for bedaquiline?
Treatment of MDR-TB
Learn about the mechanisms of resistance to Isoniazid, a drug used to treat tuberculosis. Understand how chromosomal mutations, including KatG and InhA, lead to resistance and how cross-resistance occurs with ethionamide. Test your knowledge of tuberculosis chemotherapy.
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