Micro - Antimicrobials (Antimycobacterial drugs) Flashcards
Pg. 187-188 in First Aid 2014 Sections include: -Antimycobacterial drugs -Isoniazid (INH) -Rifamycins -Pyrazinamide -Ethambutol
What drug is used as prophylaxis for M. tuberculosis?
Isoniazid
What 4 drugs are used as treatments for M. tuberculosis?
(1) Rifampin (2) Isoniazid (3) Pyrazinamide (4) Ethambutol; Think: “RIPE for treatment”
What are 2 drugs used as prophylaxis for M. avium-intracellulare?
(1) Azithromycin (2) Rifabutin
What is the treatment for M. avium-intracellulare? Include possible options.
Azithromycin or clarithromycin + ethambutol. Can add rifabutin or ciprofloxacin.
What is the prophylaxis for M. leprae?
N/A :-) Trick question!
What is the treatment for M. leprae tuberculoid versus lepromatous form?
Long-term treatment with dapsone and rifampin for tuberculoid form. Add clofazimine for lepromatous form.
How does M. avium-intracellulare compare to M. tuberculosis in terms of resistance?
More drug resistant than M. tuberculosis.
What is the mechanism for Isoniazid (INH)? What is needed for INH to become active?
Decrease synthesis of mycolic acids; Bacterial catalase-peroxidase (encoded by KatG) needed to convert INH to active metabolite
What is the clinical use for Isoniazid (INH)?
Mycobacterium tuberculosis
What is the only agent used as solo prophylaxis against TB?
Isoniazid (INH)
How do the INH half-lives differ?
Different INH half-lives in fast vs. slow acetylators.
What are 2 toxicities associated with INH?
(1) Neurotoxicity (2) Hepatotoxicity; Think: “INH Injures Neurons and Hepatocytes”
What can prevent neurotoxicity due to Isoniazid (INH)? With what other condition can it help?
Pyridoxine (vitamin B6) can prevent neurotoxicity, lupus.
What are 2 examples of Rifamycins?
(1) Rifampin (2) Rifabutin
What is the mechanism of Rifamycins?
Inhibits DNA-dependent RNA polymerase
What is the clinical use of Rifamycins?
Mycobacterium tuberculosis; delays resistance to dapsone when used for leprosy. Used for meningococcal prophylaxis and chemoprophylaxis in contacts of children with Haemophilus influenzae type B.
What are 2 potentially hazardous toxicities of rifamycins? What is a nonhazardous side effect of rifamycin?
Minor hepatotoxicity and drug interactions (increased P-450); Orange body fluids (nonhazardous effects)
Which rifamycin is favored in patients with HIV infection, and why?
Rifabutin favored over Rifampin in patients with HIV infection due to less cytochrome P-450 stimulation; Think: “RifAMPin RAMPs up cytochrome P-450, BUT rifaBUTin does not.”
What are 4 R’s to associate with Rifampin?
Rifampin’s 4 R’s: (1) RNA polymerase inhibitor (2) Ramps up microsomal cytochrome P-450 (3) Red/orange body fluids (4) Rapid resistance if used alone
What is the mechanism of pyrazinamide?
Mechanism uncertain. Thought to acidify intracellular environment via conversion to pyrazinoic acid.
In what context is pyrazinamide effective, and what is its relevance to TB?
Effective in acidic pH of phagolysosomes, where TB engulfed by macrophages is found.
What is the clinical use for pyrazinamide?
Mycobacterium tuberculosis
What are 2 toxicities associated with Pyrazinamide?
(1) Hyperuricemia (2) Hepatotoxicity
What is the mechanism of Ethambutol?
Decreases carbohydrate polymerization of mycobacterium cell wall by blocking arabinosyltransferase
What is the clinical use for Ethambutol?
Mycobacterium tuberculosis
What toxicity is associated with Ethambutol?
Optic neuropathy (red-green color blindness).
What are 4 antimycobacterial drugs?
(1) Isoniazid (INH) (2) Rifamycins (3) Pyrazinamide (4) Ethambutol
