Antibiotics - Pt2 Flashcards
What are some groups of antibiotics which target protein synthesis?
Aminoglycosides, tetracyclines, macrolides, lincosamides, oxazolidinones and chloramphenicol
What are some types of aminoglycosides?
Gentamicin, streptomycin, kanamycin and neomycin
What is the mechanism of action of aminoglycosides?
Binds 30S subunit of rRNA complex
Bacteriostatic
Irreversible binding of 30S subunit
Depolarises cell membrane - binds anionic cell membrane component which gives reduced membrane integrity
When is streptomycin used?
TB
Given by IV
When is kanamycin used?
Gentamicin - sepsis - IV and topical
Tobramycin - sepsis and CF - IV and inhaled
Amikacin - sepsis, TB, CF and nocardia - IV
Plazomicin - sepsis
What is neomycin used for?
Intraluminal treatment
Giardia, amoebiasis, cryptosporidium and topical treatment leishmania
PO or topical route
Describe nephrotoxicity of aminoglycosides
RF - age, cirrhosis, prolonged use and other nephrotoxins
Commoner after 7 day use
Reversible
Site is renal cortex
Describe ototoxicity/ vestibulotoxicity by aminoglycosides
Mitochondrial toxicity - hair cell death
Dose independent and often irreversible
Deafness - high frequency initially and worse with furosemide
Describe neuromuscular blockade by aminoglycosides
Blocks presynaptic ACh release/ postsynaptic receptors
Caution when concomitantly with neuromuscular blockade drugs
Describe tetracyclines
Broad spectrum bacteriostatic antibiotics
Differ in pharmacological properties rather than spectrum of cover
High bioavailability - given orally
Inhibits bacterial protein synthesis - reversible binding to 30S subunit
What are the types of tetracyclines?
Tetracycline, doxycycline and tigecycline
Describe doxycycline spectrum and usage
SSTI, CAP and atypical, Genito-urinary infection, rickettsia, malaria prophylaxis and treatment and bone + joint
What are the tetracycline side effects?
Photosensitivity and gastritis - oesophageal ulcer
Why are tetracyclines not used for children and pregnancy?
Crosses placenta - maternal hepatotoxicity, foetal tooth discoloration and delay of long bones
High conc. in breast milk
Children under 8 - cause permanent tooth staining
What are types of macrolides?
Erythromycin
Clarithromycin
Azithromycin
What is erythromycin used for?
Skin and soft tissue infections (SSTI)
Community acquired pneumonia
What is clarithromycin used for?
Skin and soft tissue infections
Community acquired pneumonia
Atypical pneumonia - listeria, mycoplasma and psticossis
H. pylori
Toxoplasma gondii
What is azithromycin used for?
Typhoid fever - salmonella typhi and paratyphi
STI - gonorrhoea and chlamydia
What are the side effects of macrolides?
Jaundice, ototoxicity, prolonged QT syndrome and GI disturbance
Are macrolides used when pregnant or breastfeeding?
Erythromycin - not known to be harmful and only small amounts in breastmilk
Clarithromycin - avoid unless positives outweigh and present in breastmilk
Azithromycin - only use if alternative is mot available and present in breastmilk
Describe metronidazole
Inhibition of DNA synthesis
Anaerobic organisms
Pro drug and activated intracellularly in anaerobic conditions
Widespread throughout all tissues
Metallic taste reported
Don’t take with alcohol
What antibiotics can inhibit folic acid synthesis and what are the side effects?
Trimethoprim and co-trimoxazole
Side effects - renal impairment and bone marrow suppression
When is trimethoprim used?
UTIs
When is co-trimoxazole used?
Pneumocystis jiroveci pneumonia
Toxoplasmosis
Multidrug resistant organisms - mycobacterium species and stenotrophomonas
How is susceptibility or resistance measured?
Disc diffusion (zone of inhibition seen on disc) and gradient strips
What are some mechanisms of resistance?
Efflux pumps, decreased uptake, target alterations, alternative enzymes and inactivating enzymes
What are some considerations for prescribing?
Formulation, source of infection, patient allergies, patient medications and likely organisms
