Unclassified and TB Antibiotics

Question 1

Metronidazole

Answer 1

In anaerobes, converted to free radicals by ferredoxin, binds to DNA and other macromolecules, bactericidal

What class of drugs are anaerobes innately resistant to?

(aminoglycosides, O2-dependent uptake)

Question 2

Uses for Metronidazole

Answer 2

Antiprotozoal: DOC for giardia, trichomonas, entamoeba

(“G.E.T. Met” for antiprotozoal infection)

Antibacterial: DOC in pseudomembranous colitis

(side effect seen in Clindamycin that can also be treated with Vancomycin)

Question 3

Side effects of metronidazole

Answer 3

Metallic taste and disulfiram-like effect (i.e., hangover)

Question 4

Antibiotics for H pylori GI ulcers

Answer 4

BMT regimen: bismuth, metronidazole, and tetracycline

OR clarithromycin, amoxicillin, and omeprazole

Question 5

Anti-TB drugs

Answer 5

RIPES

Combination drug therapy is the rule to delay or prevent the emergence of resistance

*On TESTS look for longest combination of drugs and pick that answer

Primary drugs = isoniazid (INH), rifampin, ethambutol, and pyrazinamide (+ streptomycin)

Question 6

MOA for Isoniazid (INH)

Answer 6

Inhibits mycolic acid synthesis (cell wall)

Prodrug

High level resistance = deletions in katG gene (encodes catalase needed for INH bioactivation)

Question 7

Side effects of isoniazid

Answer 7

Hepatitis (increased LFTs)

Peripheral Neuritis (use B6)

Sideroblastic Anemia (use B6)

SLE in slow acetylators (rare)

Question 8

Rifampin

Answer 8

Inhibits DNA-dependent RNA polymerase (inhibits transcription)

Question 9

side effects of rifampin

Answer 9

Hepatitis, Induction of P450, and Red-Orange metabolites

Think R: Rifampin inhibits RNA polymerase, Revs up P450, has Red-Orange Metabolites, and Rapid Resistance when used alone

Question 10

Ethambutol

Answer 10

Inhibits synthesis of arabinogalatan (cell-wall component)

important side effect = decreased red-green color discrimination

Question 11

Treatment of Mycobacterium avium-intracellulare (MAC)

Answer 11

Prophylaxis = azithromycin (1 x week) or clarithromycin (daily)

Treatment = clarithromycin + ethambutol + rifabutin

Question 12

What drug do you commonly give, along with INH, to prevent neuropathy and anemia?

Answer 12

Pyridoxine (aka Vitamin B6)

Question 13

Pyrazinamide

Answer 13

Inhibits mycolic acid production by blocking pyrazinamidase

Question 14

Side effects of Streptomycin

Answer 14

Remember that the side effects for all aminoglycosides are:

Nephrotoxicity

Ototoxicty

Neurotoxicity