Antibiotic Therapy

Front 1

What are the different kinds of antibiotics and their mechanisms of action?

Back 1

Front 2

How can antibiotics be classified?

Back 2

Front 3

What is the spectrum of activity for penicillin? (PO)

Back 3

Penicillin G:

- mainly gram +ve: MSSA, strep, enterococci, pneumococci, clostridium

- also some gram -ve: Neisseria

- Spirochetes

Extended spectrum penicillins (Amoxicillin, Piperacillin)

- gram +ve and more gram -ve than penicillin G

* Augmentin (clavulanic acid + amoxicillin)

- gram +ve: staph, strep, enterococcus

- gram -ve: E.coli, Moraxella, Klebsiella, H. inf, some enterobacter species

* Piptazo (tazobactam + piperacillin)

- as per augmentin, plus increased gram -ve coverage (Pseudomonas)

Front 4

What is the SE of penicillin?

Back 4

neurotoxicity (when levels are high in renal disease):

- convulsions, confusion, hallucinations

Front 5

What is the spectrum of activity for cephalosporins? (IV/IM)

Back 5

1st gen (cefalexin, cefazolin):

- gram +ve, with some gram -ve activity (E.coli, Klebsiella, proteus)

- substitute for penicillin G

2nd gen (cefuroxime, cefaclor):

- greater activity against gram -ve (also cover enterobacter, H.inf)

3rd gen (ceftriaxone, ceftazidime, cefotaxime)

- gram +ve and gram -ve

- increased activity against enterobacteriaceae and pseudomonas aeruginosa

- decreased activity against MSSA

4th gen:

- similar spectrum to 3rd gen, but increased stability

Front 6

What is one important benefit of cephalosporins?

Back 6

3rd gen cephalosporins can penetrate CSF

Front 7

what are linezolid, dalfopristine, quinupristin used in?

Back 7

for treatment resistant gram +ve bacteria:

- MRSA

- VRE

*** be careful in patients who are taking SSRI (may lead to serotonin syndrome)

Front 8

What is meropenem reserved for?

Back 8

broad spectrum antibiotic which covers gram +ve, gram -ve and anaerobics

empirical monotherapy for serious infections

Front 9

What is the spectrum of activity for tetracyclines?

(doxycycline, tetracycline, minocycline, demeclocycline, chloramphenicol)

Back 9

Broad spectrum:

gram +ve and gram -ve and others (chlamydia, clostridium, spirochetes, mycoplasma)

Front 10

What are the precautions when taking tetracyclines?

Back 10

1. Good oral bioavailability, but should not take with milk (calcium), antacids (magnesium, aluminium) or iron tablets --> will cause chelation

2. It crosses placenta and is excreted in milk --> avoid in pregnancy and breast-feeding mothers

3. Warn patients about GI discomfort, and consider prescribing it with omeprazole

Front 11

What are the side effects of tetracyclines?

Back 11

- liver toxicity

- renal toxicity

- vestibular reactions

- AAPMC, CDAD

- tetracyclines deposits in any calcium rich structures (bone, teeth) --> lead to dysplasia and discoloration

- avoid in children below 8, and pregnant women

Front 12

What is tigecycline useful for?

Back 12

complicated soft tissue and skin infection, and complicated intra-abdominal infections

Front 13

What is the spectrum of activity for aminoglycosides?

(only IV form available)

(streptomycin, gentamicin, amikacin, neomycin)

Back 13

- similar to macrolides

- useful especially for covering multi-drug resistant gram negative aerobic organisms, including pseudomonas

- usually used in combination with a beta-lactam for synergistic effects

- amikacin is stronger than gentamicin

Front 14

What are the precautions when taking aminoglycosides?

Back 14

1. Avoid in those with eGFR below 30, be cautious in those with eGFR above 30

2. Be cautious in prescribing it to elderly, due to ototoxicity

3. Avoid in those patients who was just administered with neuromuscular blocking agents (post-anaesthesia), as it blocks calcium uptake which is required for acetylcholine release at pre-synaptic terminal --> respiratory muscle paralysis

4. aminoglycosides have post-antibiotic effect, which may be beneficial

Front 15

What are the side effects of aminoglycosides?

Back 15

- ototoxicity

- nephrotoxicity

- hypersensitivity

- neuromuscular blockage

Front 16

What is the spectrum of activity for macrolides?

(erythromycin, clarithromycin, azithromycin)

Back 16

erythromycin:

- similar activity to penicillin G

- also covers chlamydia

clarithromycin:

- similar to erythromycin, but has a broader spectrum and covers: chlamydia, legionella, mycobacterium, moraxella, H.pylori, toxoplasma

azithromycin:

- less active to strep and staph

- more active to h.inf, legionella, moraxella

Front 17

What are the precautions to take when taking macrolides?

Back 17

1. Food may impair absorption of some macrolides --> take before meal

2. can be given orally or intravenously, but may cause thrombophlebitis when given IV

3. hepatic enzyme inhibitors (thus will increase levels of warfarin, theophylline)

4. increases bioavailability of digoxin

5. Be cautious when giving erythromycin, because it can lead to prolonged QTc

6. Warn patients about GI discomfort, and consider prescribing it with omeprazole

7. macrolides have post-antibiotic effect, which may be beneficial

Front 18

What are the side effects of macrolides?

Back 18

** azithromycin have no effects on hepatic enzymes

** erythromycin can also cause prolonged QT interval

Front 19

What is the spectrum of activity of clindamycin?

What is it useful for?

Back 19

1. same activity as erythromycin

2. clindamycin penetrates well into bone and abscess. can also be used for MRSA and bacteroides fragilis (trauma associated bacteria)

Front 20

What is the spectrum of activity for quinolones?

(ciprofloxacin, levofloxacin, ofloxacin)

Back 20

ciprofloxacin and ofloxacin:

- better potency and greater efficacy against resistant organisms

- good for gram negative cocci and bacilli, mycobacteria, mycoplasma, rickettsia

(generally for anthrax, gastrointestinal and urinary tract infections)

levofloxacin (AKA respiratory quinolone)

- good for gram positive: typical, atypical and anaerobic pathogens

(note that ciprofloxacin is weak against strep pneumonia, do it's not first line)

Front 21

What are the precautions to take when taking quinolones?

Back 21

1. avoid in children because of potential damage to cartilage, causing athralgia

2. may lead to prolonged QTc, so avoid in arrhythmia

3. should not take with milk (calcium), antacids (magnesium, aluminium) or iron tablets --> will cause chelation

4. Warn patient about GI side effects, consider giving omeprazole

5. Avoid in pregnancy and breast feeding mothers??

Front 22

What are the side effects of quinolones?

Back 22

- CNS effects include: headache, dizziness, insomnia, seizures

- Also causes QTc prolongation

- Avoid use with NSAIDs (quinolone induced seizures)

Front 23

What is the spectrum of activity for co-trimoxazole?

Back 23

** note that it readily enters CSF

Front 24

What are the side effects?

Back 24

** avoid in G6PD as it will cause acute hemolysis

** can consider giving folic acid supplementation to prevent myelosuppression

** can cause liver toxicity too

Front 25

What is metronidazole useful for?

Back 25

anaerobic organisms