Antibiotics Flashcards
Timing of antibiotic surgical prophylaxis?
Ideally 30-60 min before surgical incision
Duration of antibiotic surgical prophylaxis? (5)
- Single dose just before procedure
- discontinue within 24 hours!
- if > 3h procedure, may need repeat intra-op doses
- re-administration indicated at intervals 1-2 times half life
- if insert prosthetic value, prophylaxis for 24 h (3 dose regimen)
Major pathogen, in wound infection after clean surgery?
S aureus
Major pathogen, in wound infection after surgery of colon, Gynae, Genito urinary procedures?
Gram negative bacteria
Which agent, in general, is preferred for surgical prophylaxis?
Cephalosporins
Which cephalosporin is preferred for s aureus surgical prophylaxis?
First generation eg cefazolin because more active, less expensive, narrow spectrum activity, moderately long serum half life 1,8h
Which cephalosporin is preferred for colorectal surgical prophylaxis?
Cefoxitin preferred: gram positive, negative and anaerobic cover (second gen)
Or
Cefazolin ( aerobes only)( first gen) plus metronidazole (anaerobe)
Name 4 aminoglycosides
- Gentamicin
- topramycin
- Amikacin
- streptomycin
Spectrum of aminoglycosides?
Gram negative aerobes, gram positive cocci and pseudomonas
Adverse effect aminoglycosides? (2)
• Ototoxic
• nephrotoxic
Also neuromuscular paralysis, skin rash with neomycin
Name a first generation quinolone and spectrum
Nalidixic acid
Narrow spec, urinary tract
What are quinolones used for?
- UTI
* prostatitis
Quinolones contraindication?
Pregnancy
Name 3 macrolides
•Erythromycin
• azithromycin
• clarithromycin
( ace)
Spectrum of macrolides?
Gram positive
Atypical: legionella, mycoplasma, mycobacteria, chlamydia, h influenza
First line treatment children for gas pharyngitis?
Penicillin V 50 mg/kg/day ÷ bid 10 days
Or
Amoxicillin 50 10 days
treatment children for gas pharyngitis if penicillin allergy?
Cephalexin 10 days 50 mg/kglday ÷ bid Or Clarithromycin 10 days 15 mg/kglday bid Or Azithromycin 12 mg/kglday 5 days
First line treatment gas pharyngitis adults?
Penicillin V 600 mg bid 10 days
treatment gas pharyngitis adults if penicillin allergy? (2)
Cefadroxil ( first gen ) or
Cephalexin ( first gen ) or
Clarithromycin (macrolide) or
Azithromycin (macrolide)
When should antibiotics be switched to different class?
Worsening or no improvement after 3-5 days
First line treatment acute bacterial rhinosinusitis? (3)
Amoxicillin clavulanate (augmentin)
500 mg /125 mg TDS or 875 mg /125 mg bid
If at risk for resistance, give 2 g bid po ie immunocompromised
Or doxycycline
Or respiratory fluoroquinolone: levofloxacin, moxifloxacin
if penicillin allergy
(Higher doses if failure)
First line treatment acute otitis media?
- Amoxicillin clavulanic acid 90 mg/kg/day ÷ bid
- or macrolides
- or clindamycin (anaerobes) if penicillin allergy.
Children <2 10 days, >2 5-7 days nb!
Empiric treatment conjunctivitis?
Erythromycin ointment
Or
Polymixin trimethoprim drops
Bacterial conjunctivitis treatment? (4)
Erythromycin ointment Or Polymyxin trimethoprim drops Or Fluoroquinolone drops (preferred if contact lenses) Or azithromycin drops
Treatment of severe blepharitis not responding to lid hygiene? (2)
Topical: erythromycin or bacitracin ointment
Oral: tetracycline
Treatment acute exacerbations blepharitis?
Topical glucocorticoids
Empiric treatment pyelonephritis?
Iv ceftriaxone 3rd gen because penetrate tissue and good spectrum - best.
Or
Piperacillin tazobactam
Or fluoroquinolone: ciprofloxacin, levafloxacin but avoid in pregnancy and children
Empiric treatment cystitis? (5)
Nitrofurantoin best: resistance uncommon, localised to urine, little systemic effect or Cefuroxime (2nd gen cephalo) or augmentin Or TMP/SMX if not resistant Or Fosfomycin: less efficacious, pseudomonas and acinnetobacter may be resistant
Which antibiotics are used for esbl producing organisms?
Carbapenems eg ertapenem
Treatment non severe community acquired pneumonia in young with no comorbidities
Amoxicillin (clavulanate) or ampicillin
Or macrolide / azalide if allergy
Treatment non severe community acquired pneumonia in elderly and or comorbid?
Amoxicillin clavulanate or
2nd gen cephalosporin if allergy eg cefoxitin
Treatment severe community acquired pneumonia (3)
Amoxicillin clavulanate or 2nd or 3rd gen cephalosporin if allergy
And
Macrolide/ azalide
What type of drugs have better ability to cross BBB (2)
- Lipid soluble eg quinolones, metronidazole
* low molecular weight
Which antibiotics are bactericidal? (3)
B lactams: • Cephalosporins .Penicillins • carbapenems • monobactams eg aztreonam • beta lactase inhibitors eg clavulanic acid
- metronidazole
- rifampicin
Which antibiotics are bacteriostatic? (3)
- Erythromycin
- sulphonamides
- tetracyclines
Penetration of aminoglycosides?
Does not penetrate BBB but does placenta
Name 3 important pharmacodynamic and pharmacokinetic components of aminoglycosides (killing, effect, dosage)
- Concentration dependant killing
- PAE (post antibiotic effect)
- highly polar thus dosage based on lean body mass.
Moa aminoglycosides?
Inhibit ribosome s30 protein synthesis.
Concentration dependent killing (maximize exposure time)
Name the 3 types of beta lactams and examples of each.
- Penicillins: amoxicillin
- cephalosporins: cephtriaxone
- carbapenems: meropenem
Moa beta lactams? (3)
Inhibit cell wall synthesis
Time dependant killing (maximise exposure time)
Bactericidal
Name 3 broad classes penicillins with examples
Penicinillase-sensible
• natural, narrow spectrum penicillins: pen G , pen v (benzyl penicillins)
• broad spec aminopenicillins: ampicillin, amoxicillin
Penicinillase - resistant (.very narrow spec)
• nafcillin, oxacillin, dicloxacillin
Antipseudomonal extended spec
• carboxipenicillins: ticarcillin, carbenicillin
• ureidopenicillins: piperacillin, azlocillin, mezlocillin
Penicillins spectrum?
Gram positive. Primarily used for strep infections
Name 3 carbapenems
•Ertapenem
• meropenem
Imipenem with cylastatin (dihydropepidase inhibitor)
Which B lactam has broadest coverage?
Carbapenems: G positive, negative, anaerobes
Name 4 first generations cephalosporins
- Cefazolin
- cepalexin
- cephalothin
- cefadroxil
Name 4 second generations cephalosporins
- Cefoxitin!
- cefuroxime
- cefotetan
- cefador
Name 4 third generations cephalosporins
- Cefotaxime iv
- ceftriaxone! Iv
- cefpodoxime oral
- cefixime oral
Name fourth generations cephalosporins
Cefepime iv/im
What has developed resistance against third and fourth generation cephalosporins?
S pneumonia
Which cephalosporin may be considered for pseudomonas?
Fourth gen: cefepime
Penetration of cephalosporins?
Cross BBB
Vancomycin moa?
Interfere with cell wall synthesis
Time and concentration dependant killing
Name example glycopeptide
Vancomycin
Vancomycin spectrum?
Gram positive only
Name 2 uses for vancomycin
- MRSA iv
* c diff only if severe beta lactam resistance or hypersensitivity. Take orally.
Name an important pharmacokinetic factor of vancomycin
Not absorbed in git
Name 2 nb side effects vancomycin
• Flushing red man syndrome (rapid infusion cause histamine release)
• shock
Also fever, chills, phlebitis at iv side
Name a second generation quinolone and spectrum
Ciprofloxacin
Systemic aerobic gram negatives causing UTI
Bone infection
Name 2 third generation quinolone and spectrum
• Levofloxacin
• moxifloxacin
Gram negative UTI, gram positive resp infect, atypical mycoplasma pneumonia
Name a fourth generation quinolone and spectrum
Trovafloxacin
Gram negative UTI, positive respiratory, atypical mycoplasma pneum, and anaerobes
Quinolones moa? (3)
Interfere with DNA: bind to topoisomerase 2 (DNA gyrase)
Bactericidal
Time and concentration dependant killing
Name 3 contraindications quinolones
- Pregnancy
- Young
- athletes
- heart problems
Most common use for quinolones?
UTI
Name drug interactions with quinolones
Sucrulfate, antacid (al, mg) , diet supplements (fe, zn ), Ca = interfere with absorption
Name 2 adverse effects quinolones
• Connective tissue problems: great bv aneurysms, rupture tendons etc
. Prolong qt interval
Name 5 drug interactions with macrolides
- digoxin toxicity: destruction gut flora, p-gp inhibition intestines and kidney
- clozapine: inhibit cyp3a4 - seizures and disorientation
- Midazolam: inhibit cyp3a4 - increased hypnotic effect
- theophylline: inhibit cyp3a4 - tremors and tachycardia
- quinidine: inhibit cyp3a4 and p-gp inhibition - prolonged qt interval, ventricular dysrhythmia
Name 3 tetracyclines
• Doxycycline
• minocycline
. Demeclocycline
Name 3 adverse effects tetracyclines
- Deposition bones and teeth growing children
- vestibular problems
- photo toxic
- git
Which antibiotics have widespread resistance?
Tetracycline, especially to b lactam producing staph
Name an important pharmacokinetic property of tetracyclines
Forms unabsorbable chelates with Ca (don’t take with dairy), mg, Al (antacids), fe 2+, fe 3+
Best to take on empty stomach
Name 2 uses for tetracyclines
- Rocky Mountain spotted fever: rickettsia ricketsi
- STDs chlamydia
- malaria
Moa tetracyclines? (2)
Inhibit protein synthesis: ribosome s30
Bacteriostatic
Therapy of choice for salmonella?
Ceftriaxone or ciprofloxacin
Therapy of choice for neisseria meningitides?
Ceftriaxone
Which bugs are highly resistant to macrolides?
- S pneumonia
* hospital acquired staph
Which bug is highly resistant to third and fourth generation cephalosporins
S pneumonia
Which 2 bugs have high resistance to trimethorprim- sulfamethoxazole?
- s pneumonia
* H influenza