Week Six: Antifungals + Antivirals

Question 1

Fungal infections can be classified based on the site of infection, name some examples.

Answer 1

• Cutaneous (Skin, Hair and nails)
• Mucocutaneuos (Mucous membranes)
• Sytemic

Question 2

Name two oral fungal infections:

Answer 2

• Candida Albicans

- Angular Cheilitis

Question 3

What do antifungal medications do?

Answer 3

• Act against mycoses (fungal infections)
• May target fungal cell membrane - cell wall, DNA/RNA synthesis and cell division/replication
• Unlike bacteria, fungi are eukaryotes, so medication must kill the fungal organism without effecting the host.

Question 4

How do you classify antifungals?

Answer 4

There are many different classification systems, they are based on the site of action.

Question 5

What are sites of action for antifungals?

Answer 5

- Cell membrane:
Polyenes (used in dentistry)
Azoles (used in dentistry) 
Allylamines
- Cell wall
Glucan synthesis inhibitors
- DNA/RNA Synthesis
Antimetabolites

Question 6

What is the MOA for polyenes?

Answer 6

• Cytolytic

- Binds to ergosterol in the fungal cell membrane and formation of pores altering cell permeability and homeostasis

Question 7

What are considerations for polyenes?

Answer 7

• Toxic affects
• Stimulate host response causing a release of inflammatory mediators
• In higher concentrations can bind to cholesterol in host cell membrane

Question 8

Name examples of polyenes.

Answer 8

• Amphotericin
  A broad spectrum - mainly used systemically
• Nystatin
  Topical use only (too toxic for systemic use)

Question 9

What are key notes about polyenes amphotericin and nystatin?

Answer 9

Both are highly effective against candida species

Both are poorly absorbed through mucosa and GI to any significant levels

Few side effects of oral suspensions. Most common are mild GI symptoms.

Question 10

What is the MOA for azoles?

Answer 10

• Cytolytic
• Interrupt the synthesis of ergosterol in cell wall, resulting in increase of toxic intermediates, causing cell membrane permeability

Inhibits P450 cytochrome enzymes.

Question 11

What are considerations of azoles?

Answer 11

• Drug interactions

- Carbamazepine and warfarin - potentially increasing the effect of these drugs.

Question 12

Name some azoles that are used topically and treat thrush, ringworm/tinea and skin rash

Answer 12

Bifonazole
Clotrimazole
Econazole
Ketoconazole
Miconazole

Question 13

What are some adverse affects of azoles?

Answer 13

• Hepatotoxicity and hypoadrenalism
• Potential effect for drug interactions
• May impact INR ‘international normalized ratio’ even in topical suspension.

Question 14

What should patients be counselled on?

Answer 14

Patients using topical antifungal agents should be counselled to continue treatment for seven days after symptoms have disappeared, to prevent germination of the remaining spores that are present.

Question 15

What are some oral viral infections?

Answer 15

Active herpes simplex

Varicella-zoster

Question 16

What do antiviral medications do?

Answer 16

Inhibit viral replication
Can be classified on where the act on virus to inhibit cell replication
Most common types are molecules that mimic the structure of a nucleoside.

Question 17

What are some antiviral medications?

Answer 17

• Guanine Analogues

- Thymidine Analogues

Question 18

What is guanine Analogues classified for?

Answer 18

• Aciclovir, famciclovir and valaciclovir
• Aciclovir is used topically, either alone or in
combination with topical for the treatment of
cutaneous herpes simplex virus infection
• Contraindicated in pregnancy

Question 19

What are thymidine analogues classified for?

Answer 19

• Used topically in the treatment of cutaneous herpes simplex virus infection