Anti-infective Drugs

Question 1

what are some examples of penicillin beta lactams?

Answer 1

Flucloxacillin
Amoxicillin
Benzylpenicillin
Penicillin V

Question 2

what is the mechanism of action of penicillins?

Answer 2

Attaches to penicillin-binding-proteins on forming bacterial cell walls.
This inhibits the transpeptidase enzyme which cross-links the bacterial cell wall.
Failure to cross-link induces bacterial cell autolysis.

Amoxicillin provides some amount of gram-negative cover in addition to gram-positive drugs

Question 3

what are the indications for penicillins? - specifically flucloxacillin and amoxicillin?

Answer 3

Different penicillins have different indications as different spectrum of cover.

Flucloxacillin provides Staphylococcus aureus cover whereas Amoxicillin does not.

Flucloxacillin: Soft tissue infection; Staphylococcal endocarditis; Otitis externa

Amoxicillin: Non-severe community acquired pneumonia

Question 4

list some side effects of penicillins?

Answer 4

diarrhoea
vomiting
liver function impairment
hypersensitivity reactions

Question 5

what is important clinically regarding Pharmacokinetics/dynamics for penicillin?

Answer 5

good oral absorption

Flucloxacillin: Beta-lactamase stable/insensitive. (Beta-lactamase producing bacteria are vulnerable to it)

Amoxicillin: Beta-lactamase susceptible. (Beta-lactamase producing bacteria are resistant to it).

Question 6

what info should be given to a patient before commencing on a penicillin?

Answer 6

Return if symptoms persists after the course of antibiotics, may be infected with resistant organism.
Diarrhoea is a common side effect.
Report any incidence of a rash after use – risk of hypersensitivity reactions.

Question 7

how is resistance in bacteria that secrete beta lactamase overcome?

Answer 7

by a beta lactamase inhibitor given with the penicillin e.g. clavulanic acid along with amoxicillin - co-amoxiclav

Question 8

what are some examples of cephalosporin beta lactams?

Answer 8

ceftriaxone

cephalexin

Question 9

what is the MoA of cephalosporins?

Answer 9

Attaches to penicillin-binding-proteins on forming bacterial cell walls.
Inhibiting transpeptidase enzyme which cross-links the bacterial cell wall.
Failure to cross-link induces bacterial cell autolysis.
Less susceptible to beta-lactamases than penicillins.

Provides both gram-positive and gram-negative cover.

Question 10

What are the indications for cephalosporins?

Answer 10

Serious infection: septicaemia / pneumonia / meningitis

Question 11

list some side effects of cephalosporins

Answer 11

Hypersensitivity reactions
Antibiotic-associated C.Difficile diarrhoea
Liver function impairment

Question 12

what is important clinically regarding Pharmacokinetics/dynamics for cephalosporins?

Answer 12

renal excretion

longer half life - needs to be given once daily

Question 13

what info should be given to a patient before commencing on a cephalosporin?

Answer 13

diarrhoea is a common side effect

report incidence of a rash after use

Question 14

what is an example of a glycopeptide?

Answer 14

vancomycin

Question 15

what is the MoA of vancomycin?

Answer 15

bactericidal - inhibiting cell wall synthesis in gram positive bacteria

Question 16

what are the indications for vancomycin?

Answer 16

severe gram positive infections
MRSA
severe C. diff infection

Question 17

list some side effects of vancomycin:

Answer 17

• Fever
• Rash
• Local phlebitis at site of injection
• Nephrotoxicity
• Ototoxicity (Rare)
• Blood disorders, including neutropenia
• Anaphylactoid reaction “red-man syndrome” if infusion rate too fast

Question 18

what is important clinically regarding Pharmacokinetics/dynamics for glycopeptides?

Answer 18

can be given as continuous IV or pulsed infusion
long duration of action - can be given every 12 hours
therapeutic monitoring as narrow therapeutic window

Question 19

what info should be given to a patient before commencing on vancomycin?

Answer 19

Risk of kidney damage.
Patients should report any changes in hearing.
Regular blood tests required for monitoring.

Question 20

what is an example of an aminoglycoside?

Answer 20

gentamicin

Question 21

what is the MoA of gentamicin?

Answer 21

binds to 30s ribosomal subunit, inhibiting protein synthesis, inducing a prolonged post-antibiotic bacteriostatic effect
bactericidal on cell wall causes rapid killing early on
synergistic when used with other antibiotics

Question 22

what are the indications for gentamicin?

Answer 22

Severe gram-ve infections (e.g. biliary tract infection, pyelonephritis, hospital-acquired pneumonia).
Some severe gram+ve infections (e.g. soft tissue infection and endocarditis).

Question 23

list the side effects of aminoglycosides?

Answer 23

nephrotoxicity
ototoxicity
^related to prolonged exposure to high conc.

Question 24

what is important clinically regarding Pharmacokinetics/dynamics for aminoglycosides?

Answer 24

Give high initial dose to take advantage of rapid killing
Leave long dosing interval to minimise toxicity
Measure trough level to ensure gentamicin is not accumulating before giving more doses.
Try to limit use to approximately 3 days to minimise risk of side-effects.

Question 25

what info should be given to a patient before commencing on gentamicin?

Answer 25

patient should report any change in hearing

risk of kidney damage so need to monitor drug levels and renal function

Question 26

what is an example of a quinolone?

Answer 26

ciproflaxin

Question 27

what is the MoA of a quinolone?

Answer 27

interferes with bacterial DNA replication and repair

broad spec bactericidal antibiotics, provides gram +ve and -ve cover

Question 28

what are the indications for ciprofloxacin?

Answer 28

Gram negative bacterial infection
Respiratory tract infection
Upper urinary tract infection
Peritoneal infection
Gonorrhoea
Prostatitis

Question 29

what are some of the side effects of quinolones?

Answer 29

GI toxicity
QT wave prolongation
Clostridium difficile infection
Tendonitis (this is extremely rare a type B adverse drug reaction)

Question 30

what info should be given to the patient before commencing on ciprofloxacin

Answer 30

risk of diarrhoea after use

Question 31

what are some examples of macrolides?

Answer 31

clarithromycin

erythromycin

Question 32

what is the MoA of macrolides?

Answer 32

binds to 50s ribosomal subunit

inhibits bacterial protein synthesis

Question 33

what are the indications for macrolides?

Answer 33

Atypical organisms causing pneumonia/Severe CAP
Severe campylobacter infection
Mild/mod skin and soft-tissue infection
Otitis media
Lyme disease
Helicobacter pylori eradication therapy

Question 34

list the side effects of macrolides?

Answer 34

diarrhoea
vomiting
QT wave prolongation
ototoxicity with long-term use

Question 35

what is important clinically regarding Pharmacokinetics/dynamics for macrolides?

Answer 35

Uses hepatic enzyme Cytochrome P450 pathway

Can interact with all drugs using this pathway, especially Simvastatin, Atorvastatin and Warfarin.

Question 36

what info should be given to the patient before commencing on macrolides?

Answer 36

Risk of Diarrhoea
Senses of smell and taste may be disturbed during therapy.
Tooth and tongue discoloration may occur during therapy.

Question 37

what is an example of an inhibitor of folate synthesis?

Answer 37

trimethoprim

Question 38

what is the mechanism of action of inhibitors of folate synthesis?

Answer 38

inhibits folate metabolism pathway and leads to impaired nucleotide synthesis
therefore interferes with bacterial DNA replication

Question 39

what are the indications for inhibitors of folate synthesis?

Answer 39

First line antibiotic in uncomplicated UTI.
Acute / chronic bronchitis
Pneumocystis pneumonia (PCP)
Good range of action against gram -ve and gram +ve bacteria. And some MRSA cover.

Question 40

list the side effects of inhibitors of folate synthesis

Answer 40

Elevated serum creatinine
Hyperkalaemia
Depressed haematopoiesis
Rash and GI disturbance both relatively common

Question 41

what is important clinically regarding Pharmacokinetics/dynamics for trimethoprim?

Answer 41

• Penetrates well into the prostate, suitable for men with uncomplicated UTI
• Avoid in the 1st trimester
• Resistant organisms are a major problem in clinical use.
• Hyperkalaemia is more common in patients with impaired renal function.

Question 42

what info should be given to the patient before commencing on trimethoprim?

Answer 42

Blood tests required in those at risk of hyperkalaemia.
Return to the doctor if symptoms do not clear after trimethoprim course, resistance does occur.
Rash and GI disturbances are common adverse reactions.

Question 43

what is an example of an anti-viral?

Answer 43

aciclovir

Question 44

what is the MoA of aciclovir?

Answer 44

A guanosine derivative, converted to triphosphate by infected host cells.
Aciclovir triphosphate then inhibits DNA polymerase, terminating the nucleotide chain and inhibiting viral DNA replication.

Question 45

what are the indications for anti-virals?

Answer 45

herpes simplex infection

varicella zoster infection

Question 46

what are the side effects of aciclovir?

Answer 46

nausea
vomiting
local inflammation at infusion site (IV)

Question 47

what is important clinically regarding Pharmacokinetics/dynamics for aciclovir?

Answer 47

Can be oral, IV or topical.
Penetrates well into the CSF with CSF concentrations being 50% concentration of that of plasma.
Excreted by the kidneys so dose adjustment is needed in renal impairment.

Question 48

what info needs to be given to the patient before commencing on aciclovir?

Answer 48

multiple/repeat doses may be required in immunosuppressed patients