ST4 - Antibiotics Flashcards
What is the broad spectrum penicillin?
Co-amoxiclav
What is the broad spectrum cephalosporin?
Cefuroxime
How should penicillin G and V be administered?
G - IV V - Oral
Are beta-lactams safe in pregnancy?
Yes
In which patients are aminoglycosides (eg. gentamicin) at risk of causing toxicity?
Elderly, paediatric and neonatal patients, and those with kidney failure
For the antibiotic to be effective, what to factors come into play?
The BREAK POINT (chosen concentration (mg/L) of an antibiotic which defines whether a species of bacteria is susceptible or resistant to the antibiotic) must exceed the MINIMUM INHIBITORY CONCENTRATION (the lowest concentration of a chemical that prevents visible growth of a bacterium)
In which cases might prophylactic antimicrobial therapy be considered?
- Surgery - Prevention of IE - Post exposure prophylaxis eg. N. meningitidis
When prescribing IV antibiotics, how often should they be reviewed?
Every 48 hours
What are the indications for gentamicin?
Severe gram negative infections and bacterial endocarditis
What antibiotics are used for serious staph. aureus infections?
Flucloxacillin
What antibiotics are used for less serious staph. aureus infections?
Cephalosporins, clindamycin, erythromycin, lincomycin
What antibiotics are used for MRSA infections?
VANCOMYCIN If nosocomial infection: Rifampicin and fusidic acid
Which antibiotic targets the cell membrane, and what is it used for?
Colistin - used in infections with multi-resistant bacteria
Which antibiotics target the cell wall?
Beta lactams - penicillins, cephalosporins, carbapenems
How do beta lactams work?
BACTERICIDAL - Inhibit cell wall formation by preventing cross linking of peptoglycan
How are beta lactams excreted?
Renally - alter dose in renal impairment
Name 4 penicillins
Amoxicillin Penicillin V Flucloxacillin Piperacillin
What is the best antibiotic for a staph aureus skin/soft tissue infection?
Flucloxacillin - only covers gram positives
What antibiotic causes a widespread rash in glandular fever?
Amoxicillin
What is co-amoxiclav used for?
Gram positive, negative and anaerobic cover - good soft tissue penetration
What is amoxicillin used for?
Chest and ear infections Sometimes meningitis as it can cross the BBB
What is tazocin used for?
Gram positive, negative and anaerobic cover - used in red flag sepsis, very unwell patients due to broad cover. Doesn’t get into the CNS!
Name 3 cephalosporins
1st gen - cefalexin 2nd gen - cefuroxime 3rd gen - ceftriaxone The later the generation the better the GN cover but less GP cover
What is cefalexin used for?
UTIs
What is cefuroxime + metronidazole used for ?
Sepsis of unknown origin (IV)
What is ceftriazone used for?
Meningitis!! Can cross BBB
Name 2 carbapenems
Meropenem Ertapenem
When are carbapenems used?
Very broad GN, GP and anaerobic cover Multi-drug resistant infections, and penicillin allergy
What are the side effects of beta lactams?
Diarrhoea - could give C.diff! (the broader the cover, the higher the c diff risk) Deranged LFTs (coamoxiclav) Rash (amoxicillin)
Which antibiotics target the cytoplasm?
Metronidazole and daptomycin
What is metronidazole used for?
Bactericidal against anaerobes (clostridium) and protozoa
What does metronidazole react with?
Alcohol
What antibiotics target the ribosome?
Macrolides Clindamycin Aminoglycosides Tetracyclines Linezolid Chloramphenicol
Give 3 examples of macrolides
Clarithromycin, erythromycin and azithromycin
What are macrolides used for?
Pneumonia - to cover atypical organisms (give amox + clarithromycin)
What are the side effects of macrocodes?
Caution in renal and liver failure Prolong QT interval Increase warfarin/phenytoin levels (P450 inhibitors) GI upset Rash
What is clindamycin used for?
Toxic shock Nec fasc
What is doxycycline used for?
Travellers diarrhoea, chlamydia
When is doxycycline contraindicated?
Children under 12 Pregnancy Breastfeeding
Give an example of an aminoglycoside, and what is it used for?
Gentamicin Wide spectrum but poor - use in combo Use for IE
What are the side effects of gentamicin
Ototoxicity, renotoxic, myasthenia gravis reaction
Which antibiotics target the chromosome?
Quinolones Trimethoprim Nitrofurantoin
Give an example of a quinolone and its contraindications?
Ciprofloxacin Dont use in renal/hepatic failure, epilepsy, children or elderly (c diff risk)
What is trimethoprim used for and when is it contraindicated?
UTI Not in renal failure, antifolate drugs (methotrexate), pregnancy
When is nitrofurantoin used and when is it contraindicated?
UTI Not for pyelonephritis (conc not high enough), renal failure, infants, or pregnancy 3rd trimester (haemolysis risk)
Which antibiotics require therapeutic monitoring routinely?
- Gentamicin and vancomycin (IV) - narrow therapeutic index 2. Long term treatment 3. Renal impairment 4. Compliance issues
When should gentamicin and vancomycin levels be measured and what is the target?
Trough level ie. just before the next dose Gent - aim below 1 or 2mg Vanc - aim between 10-15mg
How should a patient with cellulitis be treated: a) hospital b) inpatient
a) IV flucloxacillin (+- ben pen) b) IV ceftriaxone Alternatives - clindamycin, daptomycin
What is the adverse effect associated with: a) clindamycin b) daptomycin
a) c. diff b) rhabdomyolysis
What is the most appropriate management of meningitis?
GP: IM ben pen Hospital: IV ceftriaxone (stat) Consider corticosteroids if bacterial IV fluids
How should household contacts of meningitis be treated prophylactically?
Rifampicin over 2 days Ciprofloxacin stat Ceftriaxone stat (in pregnancy)
What bacteria cause meningitis in: a) younger patients b) older patients and how does this alter management
a) N. meningitidis (5 days abx) b) strep pneumonia (10-14 days abx + steroids)
What is the most common pathogen in patients with IE? a) native valve b) prosthetic valve and how should each be treated?
a) Strep viridans - benpen + gentamicin b) staph aureus - fluclox + vancomycin
Should people get IE prophylaxis, and if so what should they get?
Only those with risk factors (heart disease) who are undergoing dental procedure or GI surgery Amoxicillin or clindamycin
What are the side effects of vancomycin?
Red man syndrome, ototoxicity, GI upset
