Antibiotics

Question 1

what drug class does amoxicillin belong to?

Answer 1

penecilliin

Question 2

How does amoxicillin work?

Answer 2

inhibits enzymes responsible for cross-linking PEPTIDOGLYCANS in bacterial cell walls.

causes cell wall to weaken, swell, lysis and death.

Question 3

What structure do penicillins contain which is responsible for its antimicrobial activity?

Answer 3

B lactam ring

Question 4

what are penicillin indicated for?

Answer 4

pneumonia
UTI (escherichia coli)
HAI or Intra-abdominal sepsis (i.e. co-amoxiclav)
as part of combo treatment for H.Pylori assoc PUD

Question 5

give an example of a gram +ve and gram -ve pathogen responsible for causing pneumonia

Answer 5

streptococcus pneumonia (g +ve) 
haemophilus influenzae (g-ve)

Question 6

what are the contraindications for penicillins

Answer 6

penicillin allergy
pts at risk of C difficile infection
severe renal impairment

Question 7

what are the side effects of penicillin?

Answer 7

GI upset
antibiotic associated colitis
allergic reaction - presenting as skin rash

Question 8

what are the possible drug interactions for penecillins?

Answer 8

increase toxicity of methotrexate and warfarin

Question 9

what drug class does cephradine belong to?

Answer 9

cephalosporins

Question 10

what structure is responsible for the antimicrobial activity of cephalosporins such as cephradine?

Answer 10

B lactam ring

Question 11

what is the mechanism of action for cephalosporins?

Answer 11

inhibitis enzymes responsible for cross linking peptidoglycans in bacterial cell wall

weakens cell, cell swelling, lysis, death

Question 12

what spectrum do cephalosporins have?

Answer 12

broad spectrum

Question 13

what are cephalosproins indicated for?

Answer 13

oral - 2nd and 3rd line for UTI and Respiratory tract infections

IV- reserved for very severe/complicated antibiotic resistant organisms

Question 14

what are the contraindications for cephalosporins?

Answer 14

risk of c.difficile infection
elderly
allergy/anaphylactic reaction to penicillin, cephalosporin
caution in epilepsy
dose reduction needed in renal impairement

Question 15

what are the side effects of cephalosporins?

Answer 15

GI upset 
antibiotic associated colitis 
hypersensitivity 
CNS toxicity - seizures 
cross reactivity may occur in pts with penecillin allergies because of similar structure

Question 16

what are the possible drug interactions with cephalosporins?

Answer 16

enhances anticoagulant effect of WARFARIN

increases nephrotoxicity of aminoglycosides

Question 17

how are penicillins and cephalosporins eliminated?

Answer 17

renal

Question 18

how does trimethoprim work?

Answer 18

inhibits bacterial folate synthesis - bacteriostatic

however its clinical utility is reduced due to widespread bacterial resistance

Question 19

what spectrum does trimethoprim have?

Answer 19

broad spectrum

Question 20

what is trimethoprim indicated for?

Answer 20

1st line - UTI

Question 21

what are the contraindications for trimethoprim?

Answer 21

1st trimester of pregnancy
pts with folate deficiency
renal impairement - needs dose reduction

Question 22

who are susceptible to adverse reactions of trimethoprim?

Answer 22

neonates
elderly
pts with HIV

Question 23

what are the side effects of trimethoprim?

Answer 23

GI upset
skin rash
hypersensitivity 
hematological disorders (e.g megaloblastic anaemia, thrombocytopenia - due to its effect on folate)
hyperkalaemia

Question 24

what are the possible interactions for trimethoprim?

Answer 24

use with K+ elevating drugs risks hyperkalaemia - i.e. aldosterone antagonists, ACE-I, ARBs

use with other folate antagonists (methotrexate) and drugs that increase folate metabolism (phenytoin) increases risk of heamatological effects

Question 25

how is trimethoprim eliminated?

Answer 25

renal! its excreted unchanged making it really good for UTIs

Question 26

what is the mechanism of action for nitrofurantoin?

Answer 26

metabolised by bacterial cells to give active metabolite. this damages bacterial DNA it is bacteroicidal

Question 27

what organisms if nirtofurantoin commonoly used against?

Answer 27

gram -ve = escheria coli | gram +ve. staphylococcus saprophyticus

Question 28

what is nitrofurantoin indicated for?

Answer 28

uncomplicated lower UTI

Question 29

what are the contraindications for nitrofurantoin?

Answer 29

pregnant women toward term babies in first 3 months of life renal impairment long term use - caution required

Question 30

what are the side effects of nitrofurantoin?

Answer 30

GI upset hypersensitivity can turn urine dark yellow/brown haemolytic anemia in neonates

Question 31

how is trimethoprim and nirtofurantoin excreted?

Answer 31

renal

Question 32

what is the mechanism of action for tetracyclines such as doxcycline?

Answer 32

bacteriastatic | inhibits bacterial protein synthesis by binding to ribsomal 30s subunit in bacteria.

Question 33

what drug class does doxycycline belong to and what spectrum does this class have?

Answer 33

tetracyclines | broad spectrum

Question 34

what is tetracycline (such as doxycycline) commonly indicated for?

Answer 34

acne vulgaris LRTI - infective exacerbation COPD, typical and atypical pneumonia pelvic inflammatory disease

Question 35

what are the contraindications of tetracyclines?

Answer 35

pregnancy breastfeeding children =12 yrs renal impairment

Question 36

what are the side effects of tetracyclines?

Answer 36

GI upset hypersensitivity oesophageal irritation, ulceration, dysphagia photosensitivity discolouration and/or hypoplasia of tooth enamel

Question 37

what are the possible drug interactions of tetracyclines?

Answer 37

enhances anticoagulatory effect of WARFARIN | dont use within 2 hrs of giving calcium, iron or antacids as this will prevent its absorption

Question 38

how are tetracyclines excreted?

Answer 38

renal and biliary (urine and faeces)

Question 39

what drug class does gentamicin belong to?

Answer 39

aminoglycoside

Question 40

what is the mechanism of action of aminoglycosides such as gentamicin?

Answer 40

bacteriacidal | inhibits bacterial protein syntheis by irreversibly binding to ribosomal 30s subunit

Question 41

which bacterial organsisms do aminoglycosides (i.e.gentamicin) work against?

Answer 41

gram -ve aerobic bacteria = staphylococci and mycobacteria

Question 42

what are aminoglycosides (gentamicin) indicated for?

Answer 42

severe sepsis (biliary and intra-abdo sepsis) complicated LUTI pyelonephritis endocarditis

Question 43

what are the contraindications for aminoglycosides (gentamicin)?

Answer 43

neonates elderly renal impairment myasthenia gravis

Question 44

what are the side effects of aminoglycosides (gentamicin)?

Answer 44

irreversible ototoxicity | reversible nephrotoxicity

Question 45

what are the possible interactions with aminoglycosies (gentamicin)?

Answer 45

use with loop diuretics or nacomycin increases ototoxicity risk use with ciclosporins, vancomycin, cephalosporins, plaitnum and chemotherapy increases nephrotoxicity risk

Question 46

how is gentamicin or any aminoglycoside excreted?

Answer 46

renal

Question 47

what are common nephrotoxic drugs?

Answer 47

LIGANDS! ``` lithium, loop diuretics iodine gentamicin ACE-I, ARBs NSAIDs digoxin steroids ``` ``` opiods beta blockers (water soluble) - atenolol amphotericin ciclosporin tacrolimus ```

Question 48

which drug class does erythromycin belong to?

Answer 48

macrolides

Question 49

what is the mechanism of action for macrolides (such as erythromycin)

Answer 49

bacteriostatic inhibtis bacterial protein synthesis binds to ribosomal 50s subunit

Question 50

what are macrolides indicated for?

Answer 50

respiratory and skin and soft tissue infections alternative to penicillin if CI severe pneumonia -combo with penecillin - to cover atypical organisms H. Pylori - in combo with PPi and amoxicillin or metronidazole