antibiotics Flashcards
aminoglycosides imp points on concentrations
amikacin, gentamicin, teomycin, streptomycin, tobramycin
serum-aminoglycoside conc. measured in all pts receiving IV aminoglycosides
measure gentamicin conc. after 3/4 doses, then every 3 days and after a dose change
- measure 1 hour after dose (peak conc.) and just before next dose (trough)
peak conc. should be 5-10 mg/L
- in endocarditis 3-5 mg/L as co-prescribed with other antibiotics so want lower dose
trough conc. - <2mg/L
- endocarditis <1mg/L
aminoglycoside dose adjustments
trough too high - increase dose interval
- if every 8 hrs - change to every 12 hrs
peak too high - decrease dose
renal impairment:
- increase dose interval
severe renal impairment - decrease dose as well
aminoglycoside MHRA warning and interactions and imp points
avoid concomitant use with nephrotoxic drugs/drugs that cause renal impairment - NSAIDs, ACEi, metformin etc
MHRA warning - ototoxicity
interactions with ototoxicity:
- cisplatin
- loop diuretics (furosemide, bumetanide)
- vancomycin
- vinca alkaloids (vincristine, vinblastine)
contraindication - myasthenia gravis
pregnancy
- avoided due to auditory or vestibular nerve damage
- monitor serum conc if given
obese patients
- use IBW based on height to calculate dose
cephalosporins imp points
1st gen - fad fal frad
cefadroxil cefalexin cefradine
2nd gen - furry fox face
cefuroxime cefoxitin cefaclor
3rd and fifth gen are all IV except oral cefixime
pts with hypersensitivity to penicillin or other beta-lactams should not have cephalosporins due to cross-sensitivity
chloramphenicol
used for eye infections
avoid in pregnancy
- risk of neonatal grey baby syndrome in 3rd trimester
OTC - children > 2, prescription any age
clindamycin
associated with antibiotic-associated colitis - FATAL
- more common in elderly
- STOP and contact prescriber if severe, prolonged or bloody diarrhoea develops
if C diff suspected - STOP
- seek specialist advice
glycopeptide imp points
teicoplanin vancomycin
vancomycin - should only be given parenterally for systemic infection - reduced absorption with oral - broken down by stomach acid
avoid in pregnancy unless benefit outweighs risk
initial dose based on body weight - then dose adjust based on serum conc.
- trough conc. 15-20 mg/L
causes ototoxicity and nephrotoxicity
- similar to aminoglycosides
adverse effects:
- red man syndrome
- severe cutaneous reactions - SJS
- blood dyscrasias - agranulocytosis, neutropenia
- cardiogenic shock on rapid IV injection
avoid rapid infusion and rotate sites
linezolid imp points
important safety info:
risk of severe optic neuropathy:
- report visual impairment - blurred/altered
- monitor regularly if more than 28 days treatment
risk of blood disorders:
- monitor FBC weekly
- monitor regularly if treatment more than 10-14 days
interact with tyramine-rich foods:
- matured cheese
- fermented soy beans
- yeast
- marmite
- wines/beers
serotonin syndrome
- SSRIs, TCAs, MAO-i, lithium, sumatriptans
macrolides imp points
azithromycin (OD)
clarithromycin (BD)
erythromycin (QD)
caution - pt with myasthenia gravis
- erythro preferred in pregnancy (avoid clari in 1st trimester)
SE’s:
- hepatotoxicity
- ototoxicity
- GI - n&v, diarrhoea - TAKE WITH FOOD
- QT prolongation
interactions:
- macrolides are CYP inhibitor
statin - myopathy
warfarin - bleeding
- cause hypokalaemia
loop/thiazide diuretics, steroids, salbutamol, theophylline - increase risk of QT prolongation
amiodarone, methadone, SSRI, lithium, domperidone, quinolones
metronidazole imp points
side effect - taste disturbance
- metallic taste
- furred tongue
N&V - take med with or after food
DO NOT drink alcohol during treatment or 48hrs after treament
- disulfiram reaction (n&V, flushing)
nitrofurantoin imp points
renal impairment - avoid if eGFR < 45ml/min
pregnancy - avoid at term
urine yellow or brown - harmless
take med with or after food
MHRA - risk of pulmonary and hepatic events
penicillins imp points
narrow spectrum penicillins - beta lactamase sensitive - broken down by beta lactamase
- penicillin G - benzylpenicillin not gastric acid stable - PARENTERAL use only
- penicillin V - phenoxymethylpenicillin
gastric acid stable - oral use
broad spectrum penicillin - beta lactamase sensitive
- ampicillin
- amoxicillin
- amox + clavulanic acid = co-amoxiclav (beta lactamse resistant)
diarrhoea most common with broad spectrum - can cause antibiotic associated colitis
maculopapular rash - occurs in people with glandular fever - caution broad spectrum in sore throat
penicillinase-resistant penicillins (flucloxacillin)
- take on empty stomach 1 hr before or 2 hr after
- cholestatic jaundice and hepatitis may occur rarely upto 2 months after treatment stopped
antipseudomonal penicillins:
- piperacillin only available in combination with beta lactamase inhibitor tazobactam
- ticarcillin available in combo with beta lactamase inhibitor clavulanic acid
DO NOT GIVE PENICILLIN INTRATHECALLY - can cause encephalopathy - fatal
quinolones imp points
ciprofloxacin levofloxacin
- lower seizure threshold - avoid in epilepsy
- psychiatric disorders
- tendon disorders
- hypersensitivity reactions
reduce UV and sunlight exposure + may impair driving ability
MHRA info:
- tendinitis - more common in over 60 year old, if suspected - STOP and seek attention
- small risk of aortic aneurysm - seek attention if sudden onset severe abdominal chest or back pain
- small risk of heart valve regurgitation - seek attention if SOB, new heart palpitations
- risk of suicidal thoughts and behaviour
quinolones only prescribed when other common antibiotics are inappropriate
caution - QT prolongation, myasthenia gravis, arthropathy in children, perforated tympanic membrane (when used by ear)
INTERACTIONS:
avoid dairy and fortified mineral products - reduce absorption
drugs that cause QT prolongation
reduce seizure threshold - quinolones + NSAIDs
tetracyclines imp points
doxycyline lymecycline minocycline oxytetracycline tetracycline tigecycline
label: do not take milk, indigestion remedies or meds containing iron or zinc 2 hrs before or after this med
can have with milk:
Does Like Milk
- doxycycline
- lymecycline
- minocycline
benign intercranial hypertension
- stop and report on headache + visual disturbances
lupus-erythematosus-like syndrome and irreversible pigmentation
- highest risk in minocycline
teeth discolouration and bone deposit
- do not give in children < 12 or pregnant women
counselling points:
hepatotoxic - avoid in liver failure
can cause photosensitivity - avoid sunlight or sun lamps
can cause dysphagia - tabs should be swallowed whole with water whilst sitting/standing
caution in myasthenia gravis
trimethoprim imp points
causes blood dyscrasias
- look out for fever, sore throat, rash, mouth ulcers, bleeding/bruising
trimethoprim - antifolate
- teratogenic in 1st trimester - avoid in pregnancy
- interaction with other antifolates - phenytoin, methotrexate
can cause hyperkalaemia
caution in renal impairment
when used alone - bacteriostatic
when combined with sulfonamides - bactericidal
narrow vs broad spectrum antibiotics
narrow:
P - penicillins (pen G + pen V)
G - glycopeptides
T - trimethoprim
L - linezolid
C - clindamycin
broad:
C - chloramphenicol
A - aminoglycosides
P - penicillins (ampi/amox)
T - tetracyclines
N - nitrofurantoin
M - macrolides
C - cephalosporins
Q - quinolones
anaerobic - metronidazole
bacteriostatic vs bactericidal antibiotic
bacteriostatic - prevents bacterial growth:
- chloramphenicol
- linezolid
- macrolides
- tetracycline
- clindamycin
bactericidal - kills bacteria:
- penicillins
- cephalosporins
- aminoglycosides
- glycopeptides
- metronidazole
- nitrofurantoin
- trimethoprim
- quinolones
antibiotic administration directions
with or after food
- metronidazole
- nitrourantoin
- clarithromycin MR
- pivmecillinam
take on empty stomach - 30/60 mins before or 2 hours after food
- flucloxacillin
- phenoxymethylpenicillin
- azithromycin caps (not tabs/liquid)
- tetracycline/oxytetracycline
which antibiotics should be taken in caution with myasthenia gravis?
quinolones
macrolides
aminoglycosides
tetracyclines
nephrotoxic antibiotics and hepatotoxic antibiotics
nephrotoxic:
nitrofurantoin
aminoglycosides
glycopeptides
hepatotoxic:
macrolides
flucloxacillin
co-amoxiclav
rifampicin + isoniazid + pyrazinamide (3/4 TB meds)
