Antibiotics - don't do these.. use "fever" below, which has ABx in Flashcards
MOA of macrolide? (2)
> Bind to 50s ribosome sub-unit and inhibit protein synthesis (block translocation)
BACTERIOSTATIC
Which bacteria are macrolides active against? (7)
Gram +ve e.g. staph, strep
Some gram -ve including: > H flu (not erythro) > N meningitidis > Legionella > Mycoplasma > N gonorrhoea
What clinical uses do macrolides have? (4)
> Skin infections
Respiratory infections including pneumonia, legionella, mycoplasma, H flu, chlamydia
STDs (chlamydia, gonorrhoea)
Any strep / staph infections
Common side effects of macrolides? (5)
> N&V
Diarrhoea (erythro ++)
Prolonged QT interval -> arrythmias
Liver dysfunction -> cholestatic jaundice
Increased risk of statin-induced myopathy
Cautions with macrolides? (2)
> Patients with risk of QT prolongation e.g. electrolyte disturbances, other medications that prolong QT
Patients with MG (may aggravate)
Patients taking warfarin, theophylline, statins (CYP metabolised drugs)
Which macrolide causes diarrhoea most commonly and why?
> Erythromycin
> Due to pro-motility effect
When would a macrolide be used in a non-infection setting, why, and which one?
> Erythromycin
Pro-motility
Gastroparesis
Which antibiotics must caution be taken with warfarin and why? What other drugs should be monitored?
> Macrolides
Quinolones
INHIBITION of hepatic CYP450 enzymes
Theophylline, statins
> Also Rifampicin but thats the other way, it INDUCES hepatic CYP450 enzymes
What is the dosing regime and routes available for azithromycin?
> OD
> PO only
What is the dosing regime and routes available for erythromycin?
> QDS or BD
> PO or IV
What is the dosing regime and routes available for clarithromycin?
> BD (modified release = OD)
> PO or IV
What are the names of the macrolides, and their routes?
> Erythromycin PO/IV
Clarithromycin PO/IV
Azithromycin IV
What are the names of the aminoglycosides? (5)
> Gentamicin > Tobramycin > Amikacin > Streptomycin > Neomycin
What is the MOA of aminoglycosides?
> Enter bacterial cells via oxygen-dependent transport system
Bind to 30s sub-unit of ribosome to inhibit protein synthesis
Spectrum of aminoglycosides? (1+5+3)
> Aerobes only as they require oxygen-dependent transport system
> Gram -ve aerobic rods
e.g. E coli, pseudomonas, klebsiella, proteus, enterobacter
> Gram +ve aerobes e.g. staph, strep, mycobacteria
Routes of administration of aminoglycosides? (3 main points)
> Poor oral absorption (highly polar), low lipid diffusion and poor penetration across body membranes so PO not available
> IV or IM injection
> Tobramycin = inhaler/neb
Clinical uses of aminoglycosides?
Gentamicin is the aminoglycoside of choice in the UK usually. It’s used in serious infections.
Usually given in combination therapy.
> Endocarditis (gent) > Bacteraemia / sepsis > TB (streptomycin) > S aureus food poisoning > CF (tobra)
What other antibiotics are aminoglycosides usually administered with and why?
Penicillin or a macrolide because they increase the activity of the aminoglycoside and reduce its toxicity
How are aminoglycosides excreted?
Renal (urine)
Adverse effects of aminoglycosides?
There are many:
> Nephrotoxicity can lead to renal failure
Ototoxicity due to damage of VIIIth cranial nerve causing irreversible deafness and vestibular damage
NMJ breakdown
Headache, fever, dizziness
Why are the aminoglycosides considered more dangerous than many other ABx?
Narrow therapeutic window and serious side effects
Contraindications for aminoglycoside use?
> Myasthenia gravis
Cautions for aminoglycosides?
> Elderly: vulnerable to nephrotoxicity and ototoxicity
> Regular monitoring of serum levels (high peak = lower dose, high trough = longer interval)
Oral absorption, lipid diffusion and membrane penetration of aminoglycosides?
> Poor oral absorption
Low lipid diffusion
Poor penetration
Therefore no PO formulations available