Lec 04 Antivirals

Question 1

The following are characteristics of viruses EXCEPT

A. small acellular infective agents
B. made of DNA, RNA, or both
C. has no metabolic machinery of its own
D. obligate intracellular parasites
E. NOTA

Answer 1

B.

Viruses are made of DNA or RNA, but not both.

Question 2

T/F

Most viruses have corresponding anti-viral agents.

Answer 2

F

Question 3

Enumerate complications of chickenpox.

Answer 3

viral pneumonia
superimposed bacterial infection
congenital limb anomalies

Question 4

Name the oral prodrug of the following antivirals.

acyclovir
penciclovir
ganciclovir

Answer 4

acyclovir - valacyclovir
penciclovir - famciclovir
ganciclovir - valganciclovir

Question 5

The following are true of acyclovir EXCEPT

A. It is an acyclic guanosine derivative.
B. It is phorsphorylated first by viral thymidine kinase.
C. The active form is a biphosphate.
D. The active form is a DNA chain terminator.
E. NOTA

Answer 5

C.

The active form is a triphosphate. It is phosphorylated first by viral thymidine kinase followed by two round of phosphorylation by cellular enzymes.

Question 6

T/F

Acyclovir has high activity for cytomegalovirus.

Answer 6

F

Question 7

Intravenous acyclovir is indicated in the following conditions EXCEPT

A. encephalitis
B. severe hepatitis
C. acute retinal necrosis syndrome
D. pediatric varicella lesions
E. NOTA

Answer 7

D. pediatric varicella lesions

Acyclovir is usually not needed in children with varicella lesions since they are usually mild.

Question 8

The following conditions lead to acyclovir resistance EXCEPT

A. absent production of viral thymidine kinase
B. partial decrease in production of viral thymidine kinase
C. altered viral thymidine kinase
D. altered viral DNA polymerase
E. NOTA

Answer 8

E. NOTA

Question 9

True of valacyclovir EXCEPT

A. It is an L-valyl ester of acyclovir.
B. It has oral and IV preparations.
C. It results in serum levels same with oral acyclovir.
D. It is excreted renally.
E. It has approximately the same half-life with acyclovir.

Answer 9

B. & C.

Valacyclovir is prepared in oral form only. Oral administration results in serum levels 3-5 times higher than oral acyclovir. This is because valacyclovir has higher bioavailability and is rapidly converted to acyclovir through first-pass metabolism.

Question 10

Enumerate adverse drug reactions of acyclovir and valacyclovir.

Answer 10

nausea and vomiting
diarrhea
thrombophlebitis (IV)
renal dysfunction
hematologic abnormalities

Question 11

This treatment is indicated for immunocompromised patients with mucocutaneous HSV lesions.

Answer 11

intravenous acyclovir

Question 12

True of ganciclovir EXCEPT.

A. It competes with guanosine triphosphate for incorporation.
B. It is a DNA chain terminator.
C. It is phosphorylated by viral phosphotransferase.
D. It has greater activity against CMV than acyclovir.
E. NOTA

Answer 12

B.

Ganciclovir is only a suppressor of viral DNA polymerase but not a DNA chain terminator.

Question 13

Give indications for ganciclovir and valganciclovir use.

Answer 13

CMV retinitis and congenital CMV

Question 14

T/F

Valganciclovir is a mixture of two diastereomers.

Answer 14

T

Valganciclovir also has higher bioavailability than ganciclovir.

Question 15

Enumerate the three steps of viral entry into host cell.

Answer 15

1. Attachment
2. Co-receptor Binding
3. Fusion

Question 16

Identify the following. Give an answer per letter.

A. This enzyme converts viral RNA into DNA.
B. This enzyme incorporates viral DNA into host DNA.
C. This enzyme hydrolyzes viral proteins into smaller units to become functional.
D. These drugs act on A.
E. These drugs act on C.

Answer 16

A. reverse transcriptase
B. integrase
C. protease
D. NRTI / NNRTI
E. protease inhibitors

Question 17

These type of viral inhibitors are not available in the Philippines.

Answer 17

entry and fusion inhibitors

Question 18

Enumerate the adverse effects of non-nucleoside reverse transcriptase inhibitors (NRTIs)

Answer 18

lactic acidosis
hepatic steatosis
dyslipidemia

Question 19

This is the prototype NRTI drug.

Answer 19

zidovudine (ZDV) / azidothymidine (AZT)

Question 20

These two NRTIs are commonly recommended as they are well tolerated.

Answer 20

lamivudine (3TC)

tenofovir (TDF)

Question 21

Enumerate the contraindications for zidovudine.

Answer 21

concurrent stavudine

concurrent myelosuppressive agents (gaciclovir, ribavirin)

Question 22

True of non-nucleoside reverse transcriptase inhibitors (NNRTIs) EXCEPT

A. It is a noncompetitive inhibitor of reverse transcriptase.
B. It is metabolized by CYP3A4 and has many drug interactions.
C. It should not be administered with concurrent NRTIs.
D. Nevirapine (NVP) is the most recommended NNRTI.
E. NOTA

Answer 22

C.

NNRTIs may be administered concurrently with NRTIs since they have different mechanisms of action.

Question 23

True of nevirapine EXCEPT.

A. It has poor bioavailability.
B. It is teratogenic.
C. It is given as fixed dose.
D. It can be used as prophylaxis.
E. NOTA

Answer 23

A.

NVP has good bioavailability (90%)

Question 24

T/F

Protease inhibitors are also CYP3A4 inhibitors.

Answer 24

T

Question 25

T/F

Protease inhibitors has limited CNS penetration.

Answer 25

T

Question 26

Why is the combination of protease inhibitors lopinavir and ritonavir recommended?

Answer 26

The resultant drug-drug interactions increase the serum levels of both drugs.

Question 27

Enumerate adverse effects of lopinavir/ritonavir combination.

Answer 27

diarrhea
abdominal pain
nausea
hypertriglyceridemia
headache
increased liver enzymes

Question 28

This if the first integrase inhibitor to receive FDA approval.

Answer 28

raltegravir

Question 29

What is the mechanism of action of enfurvitide?

Answer 29

It is a fusion inhibitor which blocks the conformational change of GP41 that is necessary for the fusion of virions with the host cell.

Question 30

This test should be used to determine if the effectiveness of CCR5 inhibitor can be confounded by the co-receptor CXCR4.

Answer 30

trofile assay