Antibiotic Classes Flashcards
Mechanism of antibiotic resistance?
– Prevent access to bug (Pseudomonas sp)
– Bug produces destructive enzyme (penicillins, cephalosporins)
– Bug changes drug binding site (penicillins)
– Drug pumped out of bug (tetracyclines)
– Bug creates bypass pathways to overcome loss of function (sulphonamides)
Mechanisms of beta lactam resistance
beta- lacatamase
modification of penicillin binding protein
no access to PBP
Efflux pump
safety issues with penecillins
allergy
hepatotoxicity
renal clearance ↓ by probenecid
oral contraceptive failure
half life of penicillins?
30-75 mins (with normal kidney clearance)
What are the classifications of penicillins?
Narrow spectrum
Narrow spectrum with anti-staph action
moderate spectrum
broad spectrum
broad spectrum with anti pseduomonas
Narrow spectrum penicillins
penicillin G/ Benzyle penicillin
Penicillin V/ phenoxymethyl penicillin
benzathine penicillin
procaine penicillin
What are narrow spectrum penicillins used for?
pneumococcus
meningococcus
streptococcus
syphilis
actinomycosis
listeria
What route can narrow spectrum penicillins be given?
IM or IV generally
(not acid stable, degraded in stomach)
Penicillin V can be given orally, except with food
Narrow spectrum anti-staph penicillin?
flucloxacillin (cloxacillin, dicloxacillin, methicillin)
What route can narrow spectrum with anti-staph property penicillins be given?
oral or IV
safety issues with narrow spectrum with anti-staph property penicillins
specific risk of cholestatic jaundice
moderate spectrum penicillins?
amoxycillin (ampicillin)
routes of moderate spectrum penicillins?
oral or IV
Common uses of moderate spectrum penicillins?
bacterial URTIs
bacterial bronchitis
UTIs (not best choice given patchy coverage)
How does spectrum of moderate spectrum penicillins differ compared to narrow spectrum?
less gram +ve coverage, but more gram -ve
safety issues with moderate spectrum penicillins
high risk or rash when given during some viral infections such as glandular fever
(does not contraindicate all future penicillin)
Broad spectrum antibiotics
β-lactam plus β-lactamase inhibitor
- amoxycillin + clavulanate
- tazocin
What are the broad spectrum with anti Pseudomonas activity penicillins?
carbenicillin, piperacillin, ticercillin (+/- clavulanate)
How does spectrum of cephalosporins compare to penicillins?
broader spectrum than penicillins but probably less
effective than penicillin for sensitive organisms
Safety issues with cephalosporins?
risk of allergy in severe penicillin-allergic patients
causes OCP failure
1st gen cephalosporins?
cefazolin
cephalexin
3rd gen cephalosporins
cefotaxamine, ceftriaxone, ceftazidime
which cephalosporins can be given PO?
cephalexin
some 2nd gens (cefaclor, cefuroxime)
Side effects of cephalosporins?
diarrhoea, rash, electrolytedisturbance, fever, neutropaenia, hepatic toxicity
Common uses of cephalosporins?
• skin and soft tissue including staph - 1st gen
• gonorrhoea (due to penicillin resistance) - 3rd gen
• empirical meningitis - 3rd gen
• serious enteric infections - 3rd gen
• 4th gen – empirical treatment of nosocomial infections
Aminoglycasides
gentamycin, streptomycin, Tobramycin
route of aminoglycasides
IM/ IV – not bioavailable orally but well absorbed from wounds / irrigation
elimination of aminoglycasides
100% renally eliminated – need to adjust dose in renal impairment
safety issues with amino glycasides
nephrotoxicity
(reversible)
ototoxicity - deafness or balance
(usually irreversible)
use of aminoglycasides
Serious Gm-ve infections
– Pyelonephritis
– Sepsis
– Synergistic with penicillin for bacterial endocarditis
route for metronidazole?
IV or PO
metronidazole drug interactions?
alcohol (decreased acetaldehyde function)
warfarin
side effects of metronidazole
many
• nausea, vomiting, constipation, diarrhoea
• dizziness, headache
• bitter metallic taste
macrolides
erythromycin,
clarithromycin,
azithromycin,
roxithromycin
Adverse effects of macrolides?
• motilin agonist → high rate of GI upset; dose dependent
• cholestatichepatitis
• drug metabolising enzyme inhibitor
quinolones
ciprofloxacin, moxifloxacin, norfloxacin, ofloxacin (eye drops only)
spectrum of quinolones
broad Gm-ve coverage including Pseudomonas, variable Gm+ve coverage
use for quinolones
• urinary tract infection
• enteric infections including typhoid, shigella,
travellers’s diarrhoea
• bronchitis, pneumonia, cystic fibrosis
• osteomyelitis
AE of quinolones
– GI,
– hallucination, delirium, seizures
– photosensitive rash
– tendon rupture
– long QT (moxifloxacin)
lincosamides
clindamycin
lincomycin
elimination of lincosamides
mostly through the liver
adverse effects lincosamides
And example of lincosamide
very severe diarrhoea (can be c diff)
allergy/ rash
Clindamycin
elimination of vancomycin
renally
adverse effects of vancomycin
nephrotoxic
ototoxic
anaphylaxis
red man syndrome
tetracyclines
tetracycline, minocycline, doxycycline
uses of tetracyclines
limited due to wide spread resistance
• rickettsia, mycoplasma, trachoma, Lyme disease
• community acquired pneumonia,
• pelvic inflammatory disease
• acne
adverse effects of tetracyclines
teeth discolouration (don’t give to kids)
OCP failure
GIT
Skin
Fungal overgrowth
empiric treatment for mild HAP (ETG)
augmentin duo
empiric treatment for moderate HAP (ETG)
3rd gen cephalosporin
(ceftriaxone or cefotaxamine)
empiric treatment for severe HAP (ETG)
tazocin
empiric treatment for mild CAP (ETG)
amoxycillin or doxycyline PO
empiric treatment for moderate CAP (ETG)
Benzylpenicillin IV + doxycycline PO
empirical treatment for severe CAP (ETG)
3rd gen cephalosporin
(ceftriaxone or cefotaxamine)
+
azithromycin
empiric treatment for meningitis?
benzylpenicillin or ceftriaxone
empirical treatment for COPD exacerbation?
amoxycillin or doxycycline
empirical treatment for acute gastroenteritis?
ciprofloxacin or norfloxacin
empirical treatment for mild acute pyelonephritis?
augmentin duo or copra of Ax
Then target
empirical treatment for severe acute pyelonephritis?
gentamycin + amoxy/ampicillin
empirical treatment for acute cystitis?
1st line - trimetheprim (unless preggers)
2nd line - cephalexin
empirical treatment for cellulitis (with systemic symptoms)
flucloxacillin (If SA suspected - purulence, skin wound)
if SA not suspected - benzylpenicillin
