antibiotics Flashcards
amoxicillin
penicillin
mode of action of amoxicillin/penicillin?
inhibit enzymes repsonsible for cross linking peptidogylcans in cell wall
= weakens cell wall and causes cell swelling, lysis and death
amoxicillin increases activity against aerobic gram -ve bacteria = broad spectrum antibiotic
indications of amoxicillin
susceptible infections community acquired pneumonia exacerbation of COPD, bronchiectasis otitis media lyme disease dental abscess meningitis - listerial endocarditis H.pylori eradication acute diverticulitis UTI
contraindication for amoxicillin
penicillin allergy
side effects of amoxicillin
allergy - rash 7-10 days after first exposure
CNS toxicity with high dose where severe renal imapirment delays excretio
possible interactions of amoxicillin
reduces renal excretion of methotrexate so may precipitate overdose
cefalexin
cephalosporin
ceflexin/cephalosporin mode of action
weaken cell walls = bacterial cell lysis and death
more resistant to beta lactamase than penicillin
beta lactamase
enzymes produced by bacteria providing resistance against antibiotics
indications of ceflaxin/cephalosporin
oral cephalosporin = second and third line treatment options for UTI and respiratory tract infections
IV cephalosporins and carbapenems for very severe or complicated infections or antibiotic reistant organisms
broad spec so used for most indications
contrainidcations of cephalosporins
c.diff, those in hospital and elderly
history of penicillin, cephalosporin or carbapenem allergy espec. if anaphyactic repsonse
epilepsy = caution
dose reduction in renal impairment
side effects of cephalosporins
GI upset - nausea and diarrhoea
antibiotic associated colitis = Cdiff
allergy - hypersensitivity
CNS toxicity - seizures
interactions of cephalosporins
warfarin -can enhance anticoagulant effect by killing normal gut flora that synthesise vit K
increase nephrotoxicity of aminoglyosides
trimethoprim - how does it work
inhibits bacterial folate synthesis = slow bacterial growth
broad spectrum of action against gram +ve and -ve but activity reduced due to widespread resistance
indications of trimethoprim
first choice for uncomplicated UTIs - alternatives = nitrofurantoin and amoxicillin
co-trimoxazole (+sulfamethoxazole) used to treat and prevent pneumocytis penumonia with immunosuppresion
side effects of trimethoprim
GI upset and skin rash
hypersensitivity reactions
haematological disorders
hyperkalaemia
interactions of trimethoprim
use with potassium elevating drugs = hyperkalaemia
use with folate antagonists = adverse haematological effects
enhance anticoagulant effect of warfarin by killing gut flora that synthesise vit K
nitrofurantoin mode of action
metabolised by bacterial cells and its metabolites damage bacterias DNA and cause cell death = bacterialcidal effect
effective against gram -ve e coli and gram +ve staphylococcus saprophyticus common in UTIs
indications of nitrofuratoin
uncomplicated lower UTI - first line antibiotic
why is nitrofurantoin so good for UTIs
effective against commmon causative organisms
reaches therapeutic concentrations in urine thorugh renal excretion
bactericidal in acid environments such as urine
contraindications of nitrofurantoin
pregnancy or babies i< 3 months
renal impairment
side effects of nitrofurantoin
GI upset - nausea and diarrhoea
hypersensitivity reactions
chronic pulmonary reactions, hepatitis, peripheral neuropathy (prolonged administration)
haemolytic anaemia in neonates
doxycycline
tetracycline
doxycycline/tetracycline mode of action
inhibit bacterial protein synthesis
devleoped a while ago so there is resistance
indications for doxycycline/tetracycline
acne vulgaris
LRTI- exacerbations of COPD, pneumonia, atyical pneumonia
chlamydial infection inc pelvic inflammatory disease
other infections - typhoid, anthrax, malaria and lyme disease
contraindications of doxycycline/tetracycline
not prescribed during pregnancy, breastfeeding or children under 12 yo
avoid in renal impairment
side effects of doxycycline/tetracyclines
nausea, vomiting, diarrhoea
hypersensitivity reactions
oesophageal irritation, ulceration and dysphagia
photosensitivty and discolouration and or hypoplasia of tooth enamal in children
intracranial hypertension is rare = headache and visual disturbance
interactions of doxyxyline/tetracycline
not in 2hrs of calcium, antacids or iron (prevent antibiotic absorption)
enhance anticoagulant effect of warfarin
gentamicin
aminoglycosides
how do aminoglycosides/gentamicin work?
inhibit protein synthesis = bactericidal
indications of aminoglycosides/gentamicin
severe infections, particularly caused by gram -ve aerobes
severe sepsis inc where source is unidentified
pyelonephritis and complicated UTI
biliary and other intra-abdo spesis
endocarditis
contraindications of aminoglycosides/gentamicin
monitoring plasma drug concentrations to prevent renal, cochlear and vesitublar damage particularly in neonates and elderly
side effects of aminoglycosides/gentamicin
reversible nephrotoxicity and irrecersible toxicity = reduced urine output and raised creatinine and urea
interactions of aminoglycosides/gentamicin
ototoxicity more likely if aminoglycosides co prescribed with loop diuretics or vancomycin
nephrotoxicity is more likely if aminoglycosides are co prescribed with ciclosporin, chemo, cephalosporins or vancomycin
erythromycin
macrolides
how does erythromycin/macrolides work?
macrolides inhibit bacterial protein synthesis
indications of erythromycin/macrolides
treatment of respiratory and skin soft tissue infections when penicillin is contraindicated by allergy
severe pneumonia added to penicillin to cover atypical organisms
eradication of H.pylori in combo w PPI and amoxicillin or metronidazole
contraindications of erythromycin/macrolides
history of macrolide hypersensitivity
side effects of erythromycin/macrolides
irritant, causing nausea, vomiting and abdo pain and diarrhoea when taken orally
thrombophlebitis when given IV
allergy, antibiotic associated colitis, lvier abnormalities, arrhythmias and toxicity at higher doses
possible interactions of erythromycin/macrolides
inhibits cytochrome P450 enzymes, so increases plasma conc and adverse effects with drugs metabolised by P450 enzymes
- warfarin (increased bleeding risk) and statins (increased risk of myopathy)
ciprofloxacin
quinolones
how does ciprofloxacin/quinolones work?
inhibit DNA synthesis in bacteria and hence kill
particularly against aerobic gram -ve
indications of ciprofloxacin
second or third line treatment due to potential for rapid emergence of resistance associated with cdiff infection
UTI, severe GI infection, psudomonas aeruginosa
contraindications of ciprofloxacin
quinolones used with caution in ppl at particular risk of adverse effects - inc risk of seizures, growing and risk factors for QT prolongation (cardiac disease or electorlyte disturbance)
side effects of ciprofloxacin
GI upset
hypersensitivity reactions
class specific adverse reactions inc neurological effects , inflammation and rupture of muscle tendons
prolong QT interval and increase risk of arrhythmias
promote Cdiff colitits
interactions of ciprofloxacin
calcium and antacids reduce absipriton of quinolones
inhibits cytochrome P450 enzymes, so increase risk of toxicity in some drugs e.g. theophylline
metronidazole
anaerobic antimicrobial
how does metronidazole work?
reduces DNA synthesis, cuasing DNA degradation and cell death in anaerobic bacteria
indications of metronidazole
antibiotic associated colitis caused by Cdiff (gram +ve anaerobe)
oral infections or aspiration pneumonia caused by gram +ve anaerobes
surgical and gynaecological infections caused by gram -ve anaerobes from colon
contraindications of metronidazole
metaoblised by cytochrome P450 enzymes - dose reduced in those w severe liver disease
alcohol - can cause disulfiram like reaction - flushing, headache, nausea and vomiting
side effects of metronidazole
GI upset - nausea and vomiting
hypersensitivity reactions
neurological adverse effects inc peripheral and optic neuropathy, seizures and encephalopathy in prolonged courses
interactions of metronidazole
inhibitory effect on cytochrome P450 enzymes
- risk of bleeding with warfarin
- risk of toxicity in phenytoin
- increased risk fo toxicity with lithium
- phenytoin and rifampicin cna causes decreases antimicrobial efficacy
vancomycin
glycopeptide
how does vancomyci/glycopeptides work?
inhibits cell wall synthesis in gram +ve bacteria
resistance repeatedly reported
indications of vancomycin/glycopeptides
treatment of gram +ve infections e.g. endocarditis, where severe infection and penicillins cannot be used due to resistance
treatment of antibiotic associated colitis by CDiff (second line to metronidazole)
surgical prophylaxis when high chance of MRSA
contraindications of vancomycin/glycopeptides
careful monitoring of plasma drug conc and dose adjustment to avoid toxicity
dose reduction when renal impairment and elderly
side effects of vancomycin/glycopeptides
thrombophlebitis at infusion site
anaphylaxis - red man syndrome = generalised erythema and hypotension and bronchospasm
IV can lead to nephrotoxicity, ototoxicity and blood disorders
interactions of vancomycin/glycopeptides
increases risk of toxicity and or nephrotoxicity when prescribed with aminoglycosides, loop diuretics or ciclosporin (immunosuppresent)
