8.4 Flashcards
What is the mechanism of rifamycins?
Targets RNA polymerase (which is used in transcription) to prevent DNA –> mRNA
How do bugs develop resistance to rifamycins?
Mutation, common
How are rifampin used?
TB, sometimes as an add-on coverage targeting biofilms
Prophylactically against Neiserria meningitis, and H. flu
What are some examples of rifampins? Consequences?
Rifampin- PO, IV induce P450
Rifabutin- PO less P450
Rifapentine- PO, q week for TB
Rifamaxin- PO, for traveller’s diarrhea
What are the toxicities of rifampin?
N/V/D
Hepatitis
Rashes
Orange/red urine/tears
What is the spectrum of rifampin?
My New Strange Friend Mycobacterium- TB, avian, leprae Neisseria meningitis Staph H. Flu
What is the mechanism of aminoglycosides?
AG (+) bings to membrane (-) and makes a transient hole.
Binds to 30s causing mis read
Do ahminoglycosides cover aerobes or anaerobes?
Aerobes- the transporter that brings them in requires O2
What is the spectrum for ahminoglycosides?
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
How do bugs become resistant to aminoglycosides?
More efflux pumps
Ribosomal mutation
** Resistance is not class-wide
How are aminoglycosides usually used?
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
What is streptomycin used for?
IV, oldest, second line for TB
What is gentamicin used for?
IV, most commonly use
What is tobramycin used for?
IV, cross resistant with gentamicin; No activity against enterococcus
What is amikacin used for?
Reserved for resistant cases after tobra/gent therapy failed
No enterococcus coverage
What is neomycin used for?
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
What are the toxicities of aminoglycosides?
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
What is the mechanism of macrocodes and ketolides?
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
How do bugs gain resistance to macrolides/ketolides?
Prevent penetration – bulky size Efflux Enz-mediated ribosome site alteration Mutation of ribosome binding site Resistance is a class effect
What is the spectrum of macrolides/ketolides?
G(+): Strep, Staph,
G(-): Neisseria, H. Flu, Bordetella pertussis,
Atypical: Chlamydia, Mycoplasma, Legionella, Rickettsia, Mycobacterium, Spirochetes (i.e. Treponema, Borrelia)
Which macrocodes/ketolides are PO and IV?
Erythromycin
Azithromycin
What does erythromycin PO treat?
Intestinal amebiasis, syphillis, gastropheresis
What G- exception does erythromycin have?
No H. flu
What does the Z-pack treat?
Pharyngitis, Community Acquired PNA, COPD, Chlamydia
What is the difference between PO and IV azithromycin?
better penetration with IV
What is Clarithromycin (Biaxin) used for?
CAP, MAC proph, and H pilori
CAP = pna
What is telithromycin used for?
Community-aquired PNA inpatient
