Antimetabolites - Antifungal class

Question 1

What drugs fall into this class?

Answer 1

Flucytosine (5-FC)

Question 2

Flucytosine was originally founded as what area in practice instead of an antifungal?

Answer 2

Oncology

Question 3

What is 5-FC primarily indicated for?

Answer 3

Cryptococcal disease combined with amphotericin B

Question 4

What is the MOA of 5-FC?

Answer 4

It’s an antimetabolite that interferes with DNA synthesis by entering fungal cell and become converted to fluorouracil to compete with uracil leading to interference with fungal RNA and protein synthesis

Question 5

5-FC has a good spectrum over which fungals?

Answer 5

In combination with amphotericin B:

• Cryptococcal neoformans
• Most species of Candida

Question 6

What adverse events can occur with the use of 5-FC?

Answer 6

• Bone marrow suppression
• GI disturbances
• CNS effects

Question 7

Why does bone marrow suppression happen?

Answer 7

High doses for a prolonged period

Question 8

What types of CNS effects can happen when taking 5-FC?

Answer 8

• HA
• Hallucinations
• Ataxia
• Confusion

Question 9

Are drug concentrations for 5-FC available?

Answer 9

Yes

Question 10

When should 5-FC peak concentration be checked?

Answer 10

2 hours after a dose is given

Question 11

(T/F) - Drug concentrations for 5-FC are sent out to a lab

Answer 11

TRUE

Question 12

(T/F) - Rely on concentrations alone to monitor toxicity

Answer 12

FALSE - Do not rely on concentrations alone; hematologic values are more important than drug levels

Question 13

5-FC can interact with which drugs?

Answer 13

• Amphotericin B (increase 5-FC levels)

Question 14

Does 5-FC need any adjustments done in patients who have insufficient organs?

Answer 14

Yes - renal insufficient patients

Question 15

What should be avoided when using 5-FC?

Answer 15

Avoid using the “5-FC” abbreviation in practice due to potential confusion to 5-FU