10 Questions
What is the primary mechanism of action of trifluridine?
Inhibition of viral DNA synthesis
What is the significance of the trifluoromethyl group in trifluridine?
It replaces the iodine atom at the 5-position of the pyrimidine ring
What is the advantage of acyclovir over other antiviral agents?
Uninfected human cells are unaffected by the drug
What is the primary indication for the use of trifluridine?
Treatment of primary keratoconjunctivitis and recurrent epithelial keratitis caused by HSV types 1 and 2
What is unique about the group attached to the base in acyclovir?
It is similar to an open chain sugar
What is the primary function of idoxuridine in the viral DNA synthesis?
To facilitate the synthesis of DNA that contains the iodinated pyrimidine
What is the mechanism of action of cytarabine in blocking viral DNA replication?
By inhibiting the conversion of cytidine diphosphate into the deoxy derivative
Which of the following cells is NOT responsible for producing interferon-α?
Fibroblast
What is the primary use of cytarabine?
As an anticancer agent for Burkitt lymphoma and myeloid and lymphatic leukemias
What is the result of the transcription of iodinated DNA?
Miscoding errors in RNA and faulty protein synthesis
Study Notes
Interferon-α and β
- Produced by lymphocytes and macrophages (interferon-α) and fibroblast and epithelial cells (interferon-β)
Idoxuridine
- Mechanism of action involves phosphorylation at O-5 by viral thymidylate kinase to yield a monophosphate
- Undergoes biotransformation to a triphosphate, which inhibits viral DNA synthesis and facilitates faulty transcription
- Altered DNA leads to miscoding errors in RNA and faulty protein synthesis
Cytarabine
- A pyrimidine nucleoside drug related to idoxuridine
- Used primarily as an anticancer agent for Burkitt lymphoma and myeloid and lymphatic leukemias
- Blocks cellular utilization of deoxycytidine, inhibiting viral DNA replication
- Converted to monophosphates, diphosphates, and triphosphates, which block DNA polymerase and C-2 reductase
- Used topically to treat herpes zoster (shingles), herpetic keratitis, and viral infections that resist idoxuridine
- Toxicity affects bone marrow, GI tract, and kidneys
Trifluridine
- A fluorinated pyrimidine nucleoside with in vitro inhibitory activity against HSV-1, HSV-2, CMV, vaccinia, and some adenoviruses
- Possesses a trifluoromethyl group instead of an iodine atom at the 5-position of the pyrimidine ring
- Inhibits viral DNA synthesis by interfering with thymidylate synthetase and incorporating into viral and cellular DNA
- Approved in the United States for treating primary keratoconjunctivitis and recurrent epithelial keratitis caused by HSV types 1 and 2
- Topical trifluridine shows efficacy in acyclovir-resistant HSV cutaneous infections
- Solutions are heat-sensitive and require refrigeration
Acyclovir
- An acyclic nucleoside with antiviral activity against herpesviruses
- Most effective against HSV type 1, less effective against HSV type 2, and least effective against VZV
- Uninfected human cells are unaffected by the drug
- Inhibits viral DNA synthesis by inhibiting DNA polymerase and incorporating into viral DNA
This quiz covers the production and mechanism of action of antiviral agents, including interferon-α and idoxuridine, and their role in fighting viral infections.
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