C15+16 Flashcards
Macrolides
3
- Clarithromycin
- Azithromycin
- Roxithromycin
Ketolides
Telithromycin
Macrolides MOA
- bacterioSTATIC inhibitors of protein synth. (50s)
- block transpeptidation
macrolide structure?
- cyclic lactone ring with sugars attatched
Clarithromycin Pharmacokinetics
- administration : oral !
- Bioavailability: good oral bioavailability
- distribution: most body tissues
- metabolism: hepatic
- elimination: urinary excretion
Azithromycin pharmacokinetics
- absorption: impeded by food (not good oral availability)
- administration: I.V
- distribution: levels in tissues & phagocytes > plasma
- clearance: Hepatic
Antimicrobial activity of Azithromycin and Clarithromycin
- CAP
- Corynebacteria
- Chlamydial infection
- Pertussis
(CCCP) - G+ cocci,
- some G- organisms
G+ resistance mechanisms?
- efflux pump
- production of a methylase –> adds a methyl to the ribosomal binding site
what is special indications of Azithromycin?
given IV
- effective in gonorrhea (alternative to ceftriaxone)
- effective in syphilis (alternative to penicillin G)
Macrolides clinical uses?
- CAP (Chlamydophila pneumoniae, Legionella pneumophila, M. pneumoniae)
- cornyebacteria
- chlamydia
- pertussis
- G+ cocci (except PRSP)
special clinical uses of Azithromycin?
[ H&M ;) ]
- H influenzae
- Neisseria
- Moraxella catarrhalis
also:
UGIs by: C.Trachomatis
(long 1/2 life –> single dose is given)
also:
CAP (4-d course)
special clinical uses of Clarithromycin
- Prophylaxis treatment of Mycobacterium avium complex
- component of drug regimens for ulcers (by H pylori)
Macrolides Toxicity in general?
- G.I. irritation (motolin rec. Stim)
- Hepatic dysfunction
- QT prolongation
- CYP450 inhibition (NOT azithromycin)
- skin rashes
- eosinophilia
Clarithromycin toxicity?
- inhibits several cyt.P450 –> increase the plasma levels of other drugs
(ex. anticoagulants, carbamazepine, digoxin, theophylline)
Azithromycin Toxicity?
- drug interactions are uncommon (does not inhibit hepatic cyt.P450)
about Telithromycin?
ketolide structurally related to macrolides
Telithromycin MOA and spectrum
similar to Macrolides but narrower spectrum\
bind 50s subunit > inhibit protein syn
bacterioSTATIC
why we use Telithromycin?
- some macrolide-resistant strains are susceptible to Telithro
- because it binds more tightly to ribosomes and is a TOO LARGE substrate for efflux pumps
Telithromycin clinical uses?
- used in CAP (including MDRs)
Telithromycin pharmacokinetix
oral!
eliminated in the bile and the urine
Telithromycin Toxicity?
- hepatic dysfunction
- QTc interval prolongation
- inhibitor of the CYP3A4
Clindamycin MOA
- binds 50S ribosome> inhibits bacterial protein synth.
- block transpeptidation
bacteriostatic
Resistance to Clindamycin ?
- binding site methylation on 50S
- enzymatic inactivation
- Clinda has poor penetration through the outer membrane of G- Aerobes!
Clindamycin Pharmacokinetix
oral, IV
- distribution: Good tissue penetration after oral abs
- clearance: hepatic
- Elimination: biliary & renal excretion (both intact drug + metabolites)
Clindamycin uses?
- skin, soft tissue infections
- ANaerobic infection (ex. Bacteroides -severe-)
- backup against G+ cocci (ex. MRSA)
- prophylaxis of endocarditis in valvular disease (allergix to penicillin)
- against P.jirovecii
Clindamycin Toxicity?
- G.I. upset
- C.difficile colitis
- skin rashes
- NEUTROpenia
- hepatic dysfunction
Streptogramins?
Quinupristin-dalfopristin
bactericidal!!
Quinupristin-dalfopristin MOA?
- Bactericidal
- 50S ribosomal subunit –> constricting the exit channel on the ribosome –> nascent polypeptides are extruded.
- tRNA synthetase activity is inhibited –> decrease in free tRNA within the cell
Quinupristin-dalfopristin activity?
- staphylococci
* VRE. faecium
Quinupristin-dalfopristin Spectrum?
- PRSP
- MRSA
- VRSA
- VRE.Faecium
Quinupristin-dalfopristin administration?
I.V.
Quinupristin-dalfopristin Toxicity?
- pain
- infusion related arthralgia-myalgia syndrome
inhibitors of CYP3A4 –> increase plasma levels of drugs
(cyclosporine, diazepam, NNRTI, warfarin)
Oxazolidinones?
Linezolid
Linezolid MOA?
- bacterioSTATIC
- 50S –> Block tRNA-ribosome-mRNA ternary complex formation –> inhibit initiation
Linezolid Spectrum?
- against drug-resistant G+ cocci, including strains resistant to penicillins
- MRSA (skin &soft tissue infections)
- PRSP
- vancomycin (eg, VRE)
- against L. monocytogenes and corynebacteria
indications kinda similar to streptogramins (quinapristin/dalfopristin )
can linezolid be resisted?
RARE
Linezolid formulation?
both Oral and I.V
Linezolid Pharmacokinetix?
-oral, I.V
- metabolism: hepatic
- elimination half-life: 4–6 h
Linezolid Toxicity?
- dose-related ANEMIA
- optic Neuropathy
- in immunocompromised:
Thrombocytopenia * Neutropenia