Antibiotics

Question 1

Name 5 clinical indications for antimicrobials to be prescribed

Answer 1

1. Periapical or periodontal disease
2. Cellulitis
3. Sinusitis
4. Oral candidiasis
5. Angular cheilitis

Question 2

What is the major issue with antibiotics?

Answer 2

Antimicrobial resistance

Question 3

What is the most commonly prescribed type of antibiotic?

Answer 3

Penicillins

Question 4

Name 3 main types of antimicrobials

Answer 4

1. Antibiotics
2. Antifungals
3. Antivirals

Question 5

Name 3 β-lactam drugs which are penicillin based

Answer 5

1. Amoxicillin
2. Penicillin V
3. Flucloxacillin

Question 6

What are 3 possible targets for chemotherapeutic agents?

Answer 6

1. Cell wall
2. Processes of protein synthesis
3. Toxicity limited to low oxygen environments

Question 7

What are the 2 monomers which build a bacterial cell wall?

Answer 7

1. N-acetylglucosamine (NAG)

2. N-acetylmuramic acid (NAMA)

Question 8

What is the significance of the enzyme which binds strands of monomers together to form a bacterial cell wall?

Answer 8

Transpeptidase is the protein which penicillin binds to

Question 9

Name 2 groups of drugs which are cell wall active agents

Answer 9

1. β-lactams

2. Glycopeptides

Question 10

Name 4 types of β-lactam drugs

Answer 10

1. Penicillins
2. Cephalosporins
3. Monobactams
4. Carbapenems

Question 11

Name 2 glycopeptide antibiotic drugs

Answer 11

1. Vancomycin

2. Teicoplanin

Question 12

Describe the structural properties of penicillin as a drug

Answer 12

• β-lactam ring found in all penicillin drugs
• Ring binds with enzyme and prevents cross linking of chains of the cell wall
• Side chains contribute to variety of drugs
• Penicillin based drugs will all have similar effects due to the β-lactam ring

Question 13

Describe the ADME of penicillins

Answer 13

• Variable stability to gastric acids so variable oral bioavailability
• 50% protein bound and low concentration in serous fluids
• Variable half life
• Entirely excreted renally

Question 14

Name 4 adverse effects of penicillin

Answer 14

1. GI upset
2. Candidiasis
3. Non IgE mediated rashes
4. Reproducibility of reaction amongst other penicillins

Question 15

Describe a true allergic reaction to penicillin

Answer 15

IgE mediated hypersensitivity causing angio-oedema, anaphylaxis, urticarial rash. There is immediate onset and cross reactivity amongst all penicillins

Question 16

What are 3 ways an antibiotic can become resistant to penicillin?

Answer 16

1. Altered target site for the antimicrobial
2. Alteration of the uptake or output of antimicrobial agents
3. Enzymatic degradation of antimicrobial agents

Question 17

Why may β-lactam drugs be combined with β-lactamase inhibitors?

Answer 17

β-lactamase inhibitors limit the action of β-lactamase enzymes so increase activity of an antibiotic

Question 18

What is the main penicillin combined with β-lactamase inhibitor drug prescribed?

Answer 18

Co-Amoxiclav (amoxicillin/clavulanate)

Question 19

Name a tetracycline drug

Answer 19

Doxycycline

Question 20

What 4 reasons would doxycycline be used?

Answer 20

1. Periodontitis
2. Refractory or severe forms of oral infections
3. Sinusitis in the case of penicillin allergy
4. Rinsed for aphthous ulcers

Question 21

Describe the ADMA of tetracyclines

Answer 21

• Oral drugs
• Rapidly absorbed but residual in gut
• Reduced absorption with metallic ions
• Widely distributed into tissues
• Doxycycline mainly biliary excretion (can be renal and gut)

Question 22

Why is there reduced absorption if tetracyclines are taken with metallic ions?

Answer 22

Tetracycline will bind with calcium (etc) and reduce the amount of drug which can move into the blood stream

Question 23

What is the mode of action of tetracyclines?

Answer 23

Biding to the 30S subunit, preventing entry of amino acetyl tRNA complexes

Question 24

Describe 4 adverse effects of tetracyclines

Answer 24

1. Staining of teeth (developing teeth)
2. GI disturbance
3. Candidiasis
4. Photosensitivity

Question 25

Name 2 macrolide drugs which are prescribed as classic alternatives to penicillin

Answer 25

1. Erythromycin | 2. Clarithromycin

Question 26

Describe the ADME of macrolides

Answer 26

- Absorption is generally good - Wide distribution and tissue concentrations - Half life much longer in clarithromycin than erythromycin - Broken down in body but a small amount excreted unchanged in urine

Question 27

Why is clarithromycin absorption generally better than erythromycin?

Answer 27

It is given as an estolate salt

Question 28

What is the mode of action of macrolides?

Answer 28

Binds to 50S subunit, preventing translocation of the next amino acid onto the nascent peptide chain

Question 29

What are 3 adverse effects of macrolides?

Answer 29

1. GI upset 2. Acts as hepatic enzyme inhibitor, so can potentiate effects of other drugs e.g. warfarin 3. Rare causes of cholestatic hepatitis

Question 30

To what group of drugs does clindamycin belong?

Answer 30

Lincosamide group

Question 31

Name 3 situations where clindamycin may be used

Answer 31

1. Recommended for endocarditis prophylaxis if penicillin allergic 2. Ludwig's angina 3. Cellulitis

Question 32

Describe ADME of clindamycin

Answer 32

- High bioavailability, with almost complete absorption - Widely distributed including into bone and joints - Metabolized by liver and excreted in bile and urine - Small amount excreted unchanged in urine

Question 33

What is the mode of action of clindamycin?

Answer 33

Binds to 50S subunit, preventing translocation of the next amino acid onto the nascent peptide chain

Question 34

Name 4 adverse affects of clindamycin

Answer 34

- Diarrhoea - Pseudomembranous colitis - Nausea - Rare cases of exfoliative dermatitis

Question 35

Why can diarrhoea be a side effect of taking clindamycin?

Answer 35

Action on anaerobic bacteria

Question 36

What type of drug can limit toxicity to low oxygen environments?

Answer 36

Nitroimidazoles

Question 37

What is the name of the primary nitroimidazole prescribed in dentistry?

Answer 37

Metronidazole

Question 38

What 4 things may metronidazole be used for?

Answer 38

1. Pericoronitis 2. ANUG 3. Periodontitis 4. Periapical disease

Question 39

Describe the ADME of metronidazole

Answer 39

- Well absorbed and high oral bioavailability - Distributed widely including into tissue spaces and abscess cavities - Metabolized by liver - Large quantity is secreted into the colon following upper GI absorption

Question 40

What is the mode of action of metronidazole?

Answer 40

It is a pro-drug so in low oxygen conditions gets reduced to a metabolite toxic to DNA, causing inhibition of DNA synthesis and strand breakdown

Question 41

What are 4 adverse effects of metronidazole?

Answer 41

- GI upset - Nausea - Disulfiram like effect (inhibits alcohol metabolism) - Inhibits hepatic metabolism of warfarin

Question 42

Name 4 general adverse effects from antimicrobials

Answer 42

1. Stevens-Johnson syndrome 2. Intrinsic staining 3. Oral candidiasis 4. Taste disturbance

Question 43

What 3 groups of antimicrobials are likely to cause Stevens-Johnson syndrome?

Answer 43

1. Antibacterial agents 2. Antiretroviral agents 3. Sulphonamide agents

Question 44

What type of antibiotic is likely to cause intrinsic staining?

Answer 44

Tetracyclines

Question 45

What 2 antibiotics are likely to cause taste disturbances?

Answer 45

1. Metronidazole | 2. Clarithromycin