- Have similar activity
- Major differences in side effects, half lives (frequency of dosage), admin method
- Obtained from streptomyces erythreus
- Binds to 50s ribosomal DNA - bacteriostatic/cidal depending on dosage and susceptibility
- Activity
- G+ve stuff - pneumococci, strep, staph, corynebacterium
- atypicals - chlamydia, mycoplasma, legionella, helicobacter, listeria
- mycobacteria
- Plasmid encoded
- Cross-resistance complete btw all macrolides
- Stimulates gut motility - used in post operative gut surgery to promote gastric emptying - only for erythromycin NOT other macrolides
- Due to this SE - we don't use them a lot routinely
- Liver toxic
- Inhibit cP450
- increased activity with g+ve (Horvath)
- advantage over erythromycin - lower GIT SE, better gut absorption - hence used in eradication of H. pylori
- Difference from above - penetrates tissue extremely well - [tissue] > [serum] - hence slowly released from tissue = longer T1/2 of 3 days
- hence once daily dosing
- 1g = 7 day of doxycycline
- semisynthetic macrolide
- 3-keto group added
- eg: telithromycin
Lincomycin - no longer used due to toxicity
Clindamycin
- like erythromycin in activity - binds 50s ribosomal subunit - reduce toxin production - hence used in necrotising fasciitis (reduces exotoxin produced by Strep)
- covers g+ve (strep, staph, pneumococci) and anaerobes
- doesn't cover: enterococci, g-ve aerobic, clostridium
- bacteriostatic --> hence if someone has staph bacteremia --> treat with fluclox first to kill, then use clindamycin orally --> if not use clindamycin + other agents eg rifampicin (never use this alone)
- has excellent oral bioavailability (one of those to use orally unless mechanical reason, like ciprofloxacin)
- clinical uses
- has the best oral bioavailability for staph (1st clindamycin, 2nd fluclox, 3rd augmentin, last keflex)
- severe anaerobic infection (bacteroides)
- diarrhoea - major SE leading to disuse
- colitis - usually pseudomembranous
Linezolid
- g+ve: staph, strep, enterococci, listeria, corynebacteria
- binds to 23S ribosomal RNA of 50S subunit - unique to linezolid - hence there's no cross resistance
- problem: hematologic toxic - low PLT most common (3%), neutropaenia
- use: VRE
No comments:
Post a Comment