Pharmacology of the anti-virals and their use in ophthalmology. Mainly on their principals and mechanism of action. * This is short presentation as it was a small part of our medical retina team presentation where the topic was on CMV Retinitis.

2. Objectives
o Understand about each of the antiviral
o Understand the indications for their use
o Learn about the virus life cycle

3. Now, let’s learn
about the
virus life cycle

5. Ganciclovir
Synthetic guanosine analogue
First antiviral approved for CMV treatment

6. How does it work?

7. How come it doesn’t work in some
cases?
Mutations UL97 – encodes of CMV
phospotransferase
.

8. Which virus does it attack?

9. In what preparations do they
exist?
 Zirgan ointment 0.15% - ophthalmic gel
 Cytovene 500 mg

10. What are the effects of the
body on the drug?
 Absorption:
• Oral – very limited
• t ½ : 2-6 hours
 Distribution: All tissues
• Especially CSF and ocular tissue
 Excretion: 80-90% unchanged in urine

11. When do we use Ganciclovir?
1. Herpes Epithelial Keratitis
Ganciclovir Gel 0.15% (Zirgan)
2. CMV Retinitis
Initial: IV 5mg/kg BD for 14-21 days
Maintenance:
 IV 5mg/kg OD or
 IV 6 mg/kg OD for 5 days/week

12. What are the side effects?
 Bone marrow supression
 Neutropenia
 Granulocytopenia
 TOXICITY
 Potential carcinogen
 Teratogen
 Inhibits spermatogenesis

13. Valganciclovir
Prodrug of Ganciclovir
Taken orally
Changed to Ganciclovir by intestinal/hepatic esterase

14. In what preparations do they
exist?
 Valcyte Tablet 450 mg
 Valcyte Oral Solution 50 mg/mL

15. What are the effects of the
body on the drug?
 Absorption:
• Well-absorbed especially with fatty meals
 Distribution:
• Well distributed especially CSF and ocular tissues
 Metabolism:
• In liver & intestine  changed to Ganciclovir
 Excretion: 80-90% in urine

16. When do we use Valganciclovir?
CMV Retinitis
Initial: Oral 900 mg BD x 21 days
Maintenance:
 Oral 900 mg OD

17. Aciclovir
Most commonly used antiviral
Commonly used for HSV and Chickenpox

18. How does it work?

19. How come it doesn’t work in
some cases?
• Deficient viral thymidine-kinase
.
• Mutations to viral thymidine-kinase or DNA
polymerase

20. Which virus does it attack?
 Herpes-simplex 1
 Herpes-simplex 2
 Varicella-zoster virus
 Epstein-Barr virus
 Cytomegalovirus
Most activity

21. In what preparations do they
exist?
 Zovirax ointment 3%
 Tablet Aciclovir 200 mg / 400 mg

22. What are the effects of the
body on the drug?
 Absorption:
• Poor water-soluble
• Poor oral bioavailability
 Distribution: High distribution rate
• T ½: 3 hours
 Metabolism: Small amounts – liver
 Excretion: 62-90% unchanged in urine

24. When do we use Aciclovir?
Herpes-Zoster Ophthalmicus Herpex Simplex Blepharitis
Herpes keratitis

25. What are the side effects?
 Systemic
 Nausea, vomiting
 Encephalopathy  IV
 Local
 SPK
 Allergy