Penicillins

Question 1

Usual Amoxicillin dose?

Answer 1

500mg every 8 hours, or 1g twice a day

Question 2

Name 2 reasons to adjust the dose of amoxicillin

Answer 2

• in severe infections - 1g every 8 hours can be used
• in renal impairment need to reduce dose if CrCl is <30

Question 3

Most common ADRs of amoxicillin?

Answer 3

Diarrhoea, nausea, rash

Question 4

MOA of amoxicillin?

Answer 4

Forms a covalent bond with PBP, inactivating it. Prevents cell wall synthesis by preventing the cross linking of peptidoglycan chains

Question 5

Most common dose of Amoxicillin / clavulanate?

Answer 5

500 - 875mg every 12 hours for 5-10 days depending on infection

Clavulanic acid = 125mg

Question 6

MOA of clavulanic acid?

Answer 6

Inhibits B-lactamase - the enzyme responsible for breaking down B-lactams.

Question 7

Purpose of adding clavulanic acid to amoxicillin?

Answer 7

Extends its activity - includes more gram negative

Question 8

ADRs associated with clavulanic acid?

Answer 8

Cholestatic hepatitis

Question 9

Indication for flucloxacillin?

Answer 9

Staph, pneumonia, wounds, etc

Question 10

When should you reduce the dose of flucloxacilin?

Answer 10

When CrCl is less than 10

Question 11

Usual dose of flucloxacillin?

Answer 11

250-500mg every 6 hours. Max of 4g a day

Question 12

When to take flucloxacillin in relation to food?

Answer 12

Best absorbed on empty stomach. Half an hour before food or 2 hours after

Question 13

Indications of phenoxymethylpenicilin?

Answer 13

Tonsillitis, rheumatic fever, etc

Question 14

Dose of phenoxymethylpenicilin

Answer 14

250-500mg every 6 hours. Maximum 3g daily

When for tonsillitis to prevent rheumatic fever, 500mg bd for 10 days

Question 15

Which bacteria is metronidazole most effective against?

Answer 15

Anaerobic bacteria such as c. Diff

Question 16

Penicillins ADRs?

Answer 16

Pain at injection site, GIT affects, electrolyte disturbances, rash

Question 17

Main groups of bacteria that amoxicillin is effective against?

Answer 17

Gram positive and anaerobes

Question 18

Amoxicillin can be used for CAP. What is the most common causative organism

Answer 18

Streptococcus pneumoniae

Question 19

Monitoring required for penicillins?

Answer 19

Monitor hepatic and renal function if Tx duration is longer than 10 days

Question 20

Amox + clav can be used for HAP. What is the main causative organism

Answer 20

Gram negative - pseudomonas aeruginosa

Question 21

Max dose of Amox + Clav?

Answer 21

2g q6h for severe infections

Question 22

When should Amox+clav be taken with respect for food?

Answer 22

Take with food

Question 23

IV dosing of flucloxacillin?

Answer 23

1-2g every 6 hours, max = 12g (severe infections like staphylococcus pneumonia)

Question 24

Common causative organism for skin infections that flucloxacillin is used for?

Answer 24

Staphylococcus epidermidis

Question 25

Spectrum of flucloxacillin vs amoxicillin?

Answer 25

More narrow

Question 26

ADR unique to flucloxacillin?

Answer 26

Increase in liver enzymes and cholestatic hepatitis

Question 27

Main indication for phenoxymethylpenicilin?

Answer 27

Tonsillitis or pharyngitis caused by strep. Pyogenes

Question 28

Treatment for s. Pyogenes tonsillitis?

Answer 28

Phenoxymethylpenicilin 500mg bd for 10 days Dose of phenoxymethylpenicilin can be up to 500mg q6h (max 3G daily) 10 day Tx course is to eradicate s. pyrogenes and prevent development of acute rheumatic fever

Question 29

ADRs for phenoxymethylpenicilin?

Answer 29

Same as other penicillins

Question 30

When might antibiotics not be indicated for strep. Tonsillitis ?

Answer 30

When the case is mild and in a community with low risk of rheumatic fever. If risk is high, phenoxymethylpenicilin is used to prevent development of rheumatic fever

Question 31

Should phenoxymethylpenicilin be taken with or without food

Answer 31

Without

Question 32

First line treatment for sinusitis?

Answer 32

Symptomatic Tx If persisting for more than 7 days or if there is a fever, first line is amoxicillin (typical pathogen is s. Pneumonaie)

Question 33

Name 2 alternatives to phenoxymethylpenicilin for s. Pyogenes

Answer 33

Mild = cefalexin Severe= Azithromycin, clarithromycin

Question 34

Name 2 alternatives to amoxicillin for CAP

Answer 34

Doxycycline or clarithromycin

Question 35

Antibiotics useful for MRSA?

Answer 35

Resistant to all B-lactams except newest cephalosporins like ceftaroline Can use= vancomycin, doxycycline, trimethoprim / sulfamethoxazole

Question 36

Alternatives to flucloxacillin for staph?

Answer 36

Cefalexin or clindamycin or trimethoprim with sulfamethoxazole