13.1 Antimicrobials

Question 1

nitrofurantoin
-use
-how it works
-ADRs
-contraindications

Answer 1

-lower UTI, prophylaxis for recurrent

-affects protein synthesis, as active metabolites bind bacterial ribosomes

-brown/orange urine, peripheral neuropathy, pulmonary fibrosis

-renal impairment eGFR <45ml/min
3rd trimester- risk neonatal haemolysis

Question 2

trimethoprim
-use
-how it works
-ADRs
-contraindications

Answer 2

-lower UTI, prophylaxis, pyelonephritis, diverticulitis

-folate antagonist inhibits DHFR so tetrahydrofolate not made so don’t produce nucleic acids

-severe bone marrow suppression

-teratogenic in first trimester

Question 3

methotrexate
-use
-how it works
-ADRs
-contraindications

Answer 3

-RA

-folate antagonist inhibits DHFR so tetrahydrofolate not made so don’t produce nucleic acids

-severe bone marrow suppression, neutropenic sepsis

Question 4

why cant trimethoprim and methotrexate be used together?

Answer 4

same Moa so risk myelosuppression

Question 5

what AB class is gentamicin?

Answer 5

aminoglycoside

Question 6

gentamicin
-use
-how it works
-ADRs
-contraindications
*what to check

Answer 6

-sepsis, meningitis

-inhibits protein synthesis by binding 30s of ribosome

-decreased kidney function (nephrotoxic), ototoxic

-renal impairment (renal excreted)

*monitor serum conc due to narrow TI
check U&Es before and during
check auditory and vestibular function during

Question 7

symptoms of ototoxicity

Answer 7

tinnitus
hearing loss

Question 8

when to review ABx in inpaitients

Answer 8

-after senior review
-change in clinical condition
-daily, on ward round
-on receipt of investigation/culture results

Question 9

when to switch IV ABx to enteral

Answer 9

on overall clinical and patient improvement

Question 10

antibiotic for
1. acute sore throat
2. otitis media
3. acute COPD exacerbation
4. CAP
5. acute pyelonephritis

Answer 10

1. phenoxymethylpenicillin
2. amoxicillin
3. amoxicillin/doxycycline/clarithromycin
4. amoxicillin
   5.cefalexin/coamoxiclav/trimethorpim/ciprofloxacin

Question 11

can doxycyline be given iV?

Answer 11

no

Question 12

antibiotic for
6. human/animal bite
7. conjunctivitis
8. cellulitis
9. c diff

Answer 12

6. co amoxiclav
7. chloramphenicol
8. flucloxacillin
9. vancomycin

Question 13

why is it good to add clavulanic acid to amoxicillin?

Answer 13

beta lactase inhibitor so overcooks bacteria breaking down amoxicllin

Question 14

amoxicillin
-use
-how it works

Answer 14

-acute cholecystitis, otitis media, CAP, acute COPD exacerbation

-inhibits cell wall synthesis by blocking transpeptidase

Question 15

CAP antibiotic prescription if penicillin allergic

Answer 15

IV 500mg BD 5 days clarithromycin

Question 16

why is clarithromycin preferred to meropenem for CAP?

Answer 16

narrower, also meropenem has 10% risk of allergy if allergic to penicillins

Question 17

why should statins be withheld when taking clarithromycin?

Answer 17

inhibits CYP3A4 so would increase statin conc

Question 18

clarithromycin action

Answer 18

inhibits protein synthesis

Question 19

why is ceftriaxone so good?

Answer 19

broad
targets anaerobic bacteria
effective for gram positive and negative

Question 20

ceftriaxone class

Answer 20

beta lactam cephalosporin

Question 21

use of ceftriaxone

Answer 21

meningococcal septicaemia over 3 months old

Question 22

uses of acyclovir

Answer 22

varicella zoster
-chicken pox
-shingles

herpes simplex virus
-encephalitis (IV)
-genital herpes
-cold sores

Question 23

how does aciclovir work?

Answer 23

inhibits viral DNA polymerase and incorporates into replicating DNA to cause chain termination
=stops viral DNA replications