8.4

Question 1

What is the mechanism of rifamycins?

Answer 1

Targets RNA polymerase (which is used in transcription) to prevent DNA –> mRNA

Question 2

How do bugs develop resistance to rifamycins?

Answer 2

Mutation, common

Question 3

How are rifampin used?

Answer 3

TB, sometimes as an add-on coverage targeting biofilms

Prophylactically against Neiserria meningitis, and H. flu

Question 4

What are some examples of rifampins? Consequences?

Answer 4

Rifampin- PO, IV induce P450
Rifabutin- PO less P450
Rifapentine- PO, q week for TB
Rifamaxin- PO, for traveller’s diarrhea

Question 5

What are the toxicities of rifampin?

Answer 5

N/V/D
Hepatitis
Rashes
Orange/red urine/tears

Question 6

What is the spectrum of rifampin?

Answer 6

My New Strange Friend
Mycobacterium- TB, avian, leprae
Neisseria meningitis
Staph
H. Flu

Question 7

What is the mechanism of aminoglycosides?

Answer 7

AG (+) bings to membrane (-) and makes a transient hole.

Binds to 30s causing mis read

Question 8

Do ahminoglycosides cover aerobes or anaerobes?

Answer 8

Aerobes- the transporter that brings them in requires O2

Question 9

What is the spectrum for ahminoglycosides?

Answer 9

Anaerobic G-
Enterobacteriacea, Pseudomonas, Mycobacterium tuberculosis, or mycobacterium Avium Complex (MAC)

No activity against G+ alone, can use synergistically with other drugs, eg with vanc for endocarditits

Question 10

How do bugs become resistant to aminoglycosides?

Answer 10

More efflux pumps
Ribosomal mutation
** Resistance is not class-wide

Question 11

How are aminoglycosides usually used?

Answer 11

Usually used together with other cell wall acting abx for synergy (i.e. PCN and Vancomycin)
Uptake of AG enhanced by cell wall acting abxs
Use for G+ enterococci even the bacteria is moderately resistant to AG

Question 12

What is streptomycin used for?

Answer 12

IV, oldest, second line for TB

Question 13

What is gentamicin used for?

Answer 13

IV, most commonly use

Question 14

What is tobramycin used for?

Answer 14

IV, cross resistant with gentamicin; No activity against enterococcus

Question 15

What is amikacin used for?

Answer 15

Reserved for resistant cases after tobra/gent therapy failed

No enterococcus coverage

Question 16

What is neomycin used for?

Answer 16

topical cream, ointment, eye drops – not for systemic use due to toxicity
PO – bowel prep – 1gm Q1h x4, 1gm Q4h x 4
Hepatic encephalopathy – (reducing NH3+ level) – 1-3gm Q6h x 5-6days

Question 17

What are the toxicities of aminoglycosides?

Answer 17

Risk factors: elderly and combining with other renal toxic drugs
Ototoxicity – (up to 50% with risk factors)
Auditory impairment – irreversible hearing loss
Vestibular toxicity – disturbances in balance (esp. Streptomycin)
Nephrotoxicity – penetrate proximal renal tubule cells (up to 5-10%)
Usually reversible – return to baseline after drug is d/c’ed
Usually after 4-5 days of therapy

Question 18

What is the mechanism of macrocodes and ketolides?

Answer 18

The macrolides bind reversibly to the 50S subunit inhibit peptidyltransferase prevent forming peptide bonds between the amino acids.

=Target 50s, when binds prevents elongation of protein, stopping protein production

Question 19

How do bugs gain resistance to macrolides/ketolides?

Answer 19

Prevent penetration – bulky size
Efflux
Enz-mediated ribosome site alteration
Mutation of ribosome binding site
Resistance is a class effect

Question 20

What is the spectrum of macrolides/ketolides?

Answer 20

G(+): Strep, Staph,
G(-): Neisseria, H. Flu, Bordetella pertussis,
Atypical: Chlamydia, Mycoplasma, Legionella, Rickettsia, Mycobacterium, Spirochetes (i.e. Treponema, Borrelia)

Question 21

Which macrocodes/ketolides are PO and IV?

Answer 21

Erythromycin

Azithromycin

Question 22

What does erythromycin PO treat?

Answer 22

Intestinal amebiasis, syphillis, gastropheresis

Question 23

What G- exception does erythromycin have?

Answer 23

No H. flu

Question 24

What does the Z-pack treat?

Answer 24

Pharyngitis, Community Acquired PNA, COPD, Chlamydia

Question 25

What is the difference between PO and IV azithromycin?

Answer 25

better penetration with IV

Question 26

What is Clarithromycin (Biaxin) used for?

Answer 26

CAP, MAC proph, and H pilori

CAP = pna

Question 27

What is telithromycin used for?

Answer 27

Community-aquired PNA inpatient