Nucleoside Reverse Transcriptase Inhibitors

Question 1

Zidovudine
MOA

Answer 1

It is phosphorylated by host cell enzymes 3 times.
Inhibits the action of the reverse transcriptase of HIV viruses. This prevents the addition of nucleotides in DNA transcript which inhibits reverse transcription and thus viral DNA integration

Question 2

Zidovudine
Abs/Distrb/Elim

Answer 2

Given orally but can be given by i.v. infusion; the concentration in the CSF is 65% of the
blood level. The T0.5 of the false trisphosphate is 3h.

Question 3

Zidovudine
Clinical use

Answer 3

HIV infection (slows progress of disease not cure it)
Used in combination with other drugs to prevent resistance

Question 4

Zidovudine
Adverse effects

Answer 4

With long-term use: blood dyscrasias, GIT disturbances, myopathy, rashes, fever and a
ƒulike syndrome

Question 5

Acyclovir
MOA

Answer 5

Terminates viral DNA elongation by HSV-1 DNA polymerase due to absence of 3’-hydroxyl group on ACyclovir. Viral DNA polymerase is inactivated as a result and viral DNA can’t be replicated

Question 6

Acyclovir
Abs/Distbr/Elim

Answer 6

Given orally, i.v. (slowly) or topically; is degraded fairly rapidly within the host cell. CSF
concentration is ~50% of plasma level.

Question 7

Acyclovir
Clinical use

Answer 7

Herpes simplex infections (cold sores, mouth ulcers, etc)
Herpes zoster infections (shingles, chickenpox)

Question 8

Acyclovir
Adverse effects

Answer 8

nausea, headache; rarely encephalitis.