Antibiotics Flashcards
which anti-biotics may cause c.diff? what other drug also increases the risk
Receipt of broad spectrum antibiotics* is often the cause and risk is increased with older age, frailty and use of proton pump inhibitors.
The ‘C’ antiobiotics are particularly associated with CDI:
Co-amoxiclav
Clarythromycin
Ciprofloxacin
Clindamycin
Cephalosporins
which are b lactam abx
Cephalosporins
Carbapenems
Benzylpenicillin
Penicillin V
Amoxicillin
Co-amoxiclav
Pipercillin and tazobactam
Flucloxacillin
Which abx inhibit protein synthesis?
Macrolides 50S
Aminoglycosides 30S
Lincosamides 50S
Tetracyclines 30S
5 points on M = 50S
3 points on A = 30S
Which antibiotics are P450 inducers?
Rifampicin
Griseofulvin
which abx are p450 inhibitors?
AODEVICES
A
O
D
Erythromycin (Macrolides)
V
Isoniazid
Ciprofloxacin and Chloramphenicol
E
Sulfonamides
+ Metronidazole
What does cell wall size of gram positive vs gram negative tell you about the action of b lactam antibiotics?
Gram positive abx have a much thicker cell wall. Gram negative bacteria are more protected by lipids etc added to their thin cell wall. B lactam antibiotics which inhibit cell wall synthesis are therefore more effective against gram positive bacteria
Side chains can be added which make penicillins more effective against gram negative bacteria eg amino group in amoxicillin.
mechanism of resistance MRSA
MRSA reduces penicillins binding affinity
what does MRSA mean
MRSA refers to staphylococcus aureus bacteria that have become resistant to beta-lactam antibiotics such as penicillins, cephalosporins and carbapenems.
How to treat MRSA?
options:
Doxycycline
Clindamycin
Vancomycin
Teicoplanin
Linezolid
what are ESBLs?
Extended Spectrum Beta Lactamase bacteria (ESBLs) are bacteria that have developed resistance to beta-lactam antibiotics. They produce beta lactamase enzymes that destroy the beta-lactam ring on the antibiotic. They can be resistant to a very broad range of antibiotics.
ESBLs tend to be e. coli or klebsiella and typically cause urinary tract infections but can also cause other infections such as pneumonia.
They are usually sensitive to carbapenems such as meropenem or imipenem.
name aminoglycosides
gentamicin, neomycin
what drugs increase risk of nephrotoxicity when co-prescribed aminoglycosides
ciclosporin, platinum chemo, cephalosporins and vancomycin
what drugs increase risk of ototoxicty aminoglycosides co-prescribed
diuretics, vancomycin
contraindications aminoglycosides
by inj: myasthenia gravis.
In ear: patent grommet, perforated tympanic membrane
spectrum of action aminoglycosides
gram negative aerobes, staphylococcus and mycobacteria
what drugs should you avoid with meropenem
valproate (reduces conc of valproate). Enhances anticoag of warfarin (INR increases),
name oral cephalosporin
cefalexin
name macrolides
clarithromycin, azithromycin, erythromycin
what macrolide, more likely to get adverse effects?
erythromycin
adverse effects macrolides
Irritant = N&V, abdo pain, diarrhoea, thrombophlebitis when IV.
antibiotic associated colitis and c.diff.
Liver abnormalities including cholestatic jaundice,
prolongation of QT,
ototox in high doses = tinnitus
caution macrolides
caution in patients taking drugs which prolong QT such as amiadarone, antipsychotics, quinine, quinolone abx, SSRIS.
Cuation in hepatic impairment as hepatic processed.
Caution in renal impairment (dose reduce).
May aggravate myasthenia gravis
what kind of bacteria does metronidazole work on
anaerobic
caution metronidazole
metabolised by cytochrome p450 so dose reduce in severe liver disease
pt communication metronidazole
alcohol- disulfiram like reaction. Don’t drink for the duration of treatment and for 48 horus after.
unique adverse effects nitrofurantoin
can turn urine dark yellow/brown.
chronic pulmonary reactions (including pneumonitis and fibrosis), hepatitis and peripheral neuropathy.
In neonates can cause haemolytic anaemia
contraindications nitrofurantoin
pregnant women near term,
babies under 3 months.
Contraindicated in renal impairment as it increases toxicity and reduces efficacy due to lower urinary drug concs.
what drug do penicillins reduce the renal excretion of and therefore increase risk of toxicity
reduces renal excretion of methotrexate, increasing risk of toxicity
what does using tazocin increase activity for
psedomonas
what adverse effects/interactions do you get specifically with broad spectrum penicillins
- risk of c.diff
- increases anticoag of warfarin as kills vit k producing flora
unique adverse effect fluclox
liver toxicity including cholestasis and hepatitis
name quinolones
ciprofloxacin, moxifloxacin, levofloxacin
what is the only oral abx with action against pseudomonas aerginosa
ciprofloxacin
unique adverse effects quinolones
lowering seizure threshold, hallucinations, inflammation and rupture of muscle tendons. Quinolones (particularly moxifloxacin) prolong the QT interval and therefore increase risk of arrhythmias.
caution in who - quinolones
ppl at risk of seizures, who are growing (risk of arthropathy) and risk factors for QT prolongation
co-prescription with what increases risk of tendon rupture quinolones
prednisolone
prescribe olone, not together!
co-prescription with what increases risk of seizures quinolones
NSAIDs
ciprofloxacin is a p450 ? impact?
Ciprofloxacin inhibits certain P450 enzymes increasing risk of toxicity with some drugs, notably theophylline
unique adverse effects tetracyclines
Oesophageal irritation, ulceration and dysphagia, photosensitivity, discoloration and/or hypoplasia of tooth enamel if prescribed for children. Intracranial hypertension is a rare adverse effect
contraindications tetracyclines
tetracyclines bind to teeth and bones during fetal development infants and childhood so
DO NOT prescribe during pregnancy, breastfeeding or for children under 12. Avoid in ppl with renal impairment
unique adverse effects anti-folates
haematological disorders such as megaloblastic anaemia, leukopenia and thrombocytopenia due to inhibition of folate synthesis.
Can cause hyperkalemia
interactions antifolates
use with potassium elevating drugs ef aldosterone antagonists, ACE inhibitorsm ARBs predisposes to hyperkalaemia.
Use with other folate antagonists eg methotrexate) and drugs that increase folate metabolism eg phenytoin, increases risk of haematological effects, t
rimethoprim can enhance the anticoagulant effect of warfarin by killing normal gut flora
indications vancomycin
treatment of gram positive infection e.g. endocarditis, where infection is severe and/or penicillins cannot be used due to resistance e.g. MRSA. Treatment of antibiotic-associated colitis caused by c.diff infection
unique adverse effects vancomycin
pain and inflammation of the vein (thrombophlebitis) at the infusion site,
if infused rapidly- anaphylactoid ‘red man syndrome’ - generalised erythema and may be associated with hypotension and bronchospasm. Anaphylactoid reactions are not true allergy - not antigen mediated.
However, true allergy can also occur.
IV can cause nephrotoxicity - including renal failure and interstitial nephritis,
ototoxicity with tinnitus and hearing loss
blood disorders including neutropenia and thrombocytopenia.
how to decrease adverse effects vancomycin
requires careful monitoring of plasma concentrations and dose adjustment to avoid toxicity.
side effect co-amoxiclav
cholestasis
which macrolide to prescribe pregnancy
Erythromycin
PrEgnancy
Clarithromycin is contraindicated in pregnancy unless there is no alternative and the benefits outweigh the risks.
