Viruses are small infectious agents that are incapable of reproduction outside host cells. They use the host cell's energy to synthesize proteins, DNA, and RNA. Antiviral drugs target different stages of the viral replication cycle to inhibit viral growth. Common antiviral medications include acyclovir, ganciclovir, foscarnet, and interferons. These drugs work by inhibiting viral DNA or RNA polymerase enzymes. Side effects can include nausea, vomiting, diarrhea, and organ toxicity. Antiviral therapy aims to kill viruses without harming the host cell.

1. ANTIVIRAL DRUGS
Assigned by
Dr. Sanna
Presented by
Sohail, Shakeela, Sundus, Bakht Munir

2. Objectives
• Definition of virus
• Structure of virus
• Mechanism of virus replication
• Antiviral therapy
• Viral infections
• Types of viruses
• Antiviral drugs

3. Virus
• Small infective agents
• Size = 20-30nm
• Incapable of reproduction outside the host cell
• Uses the host cell’s energy for synthesis of protein, DNA & RNA

4. Structure of
Virus

5. Viral
Replication

6. Antiviral Therapy
• Difficult to kill viruses
• Because they live inside the cell
• Killing the virus through drugs may kill the cell

7. Viral Infections
• IMMUNE SYSTEM
• Competent immune system kills the viruses
• Best response to viral infections
• Well functioning system effectively eliminates viral products in cell

8. Continued..
• Immuno-compromised patients have frequent viral infections
For example:
 Cancer patients leukemia or lymphoma
 Transplant patients immunosuppressant therapy
 AIDS patients weak immune system

10. DNA VIRUSES
• Poxviruses e.g. smallpox
• Herpesviruses e.g. chickenpox, shingles, cold sores,
glandular fever.
• Adenoviruses e.g. sore throat, conjunctivitis
• Papillomaviruses e.g. warts

11. RNA VIRUSES
• Orthomyxoviruses (influenza),
• Paramyxoviruses (measles, mumps, respiratory tract
infections)
• Rubella virus (German measles)
• Rhabdoviruses (rabies)
• Picornaviruses (colds, meningitis, poliomyelitis)
• Retroviruses (acquired immunodeficiency syndrome
[AIDS], T-cell leukemia)
• Arenaviruses (meningitis, Lassa fever)
• Hepadnaviruses (serum hepatitis)
• Arboviruses (arthropod-borne encephalitis and various
febrile illnesses, e.g. yellow fever).

13. AGENTS TO TREAT HERPES SIMPLEX VIRUS (HSV) &
VARICELLA-ZOSTER VIRUS (VZV) INFECTIONS
• Herpes Simplex Virus causes sores around mouth, lips (Cold sores)
and genital organs and rectum.
• Vericella Zoster virus causes chicken pox in children and adults.
• Acyclovir
• Valacyclovir
• Famciclovir
• Penciclovir
• Docosanol
• Trifluridine

14. Acyclovir
For treatment of:
• Herpes simplex virus infections
• Vericella zoster virus infections
• MECHANISM OF ACTION:
• Active form of Acyclovir metabolite inhibits viral DNA
synthesis, thus results in spreading and growth of virus.

15. Mechanism
of Action

16. Continued..
INDICATIONS
• Herpes simplex infections (cold sores)
• Vericella zoster virus infections (Chicken pox)
• Epstein Barr virus (EBV) infections.
SIDE EFFECTS
• Nausea, vomiting and diarrhea.
• Headache
• Swelling in hands and foot
• Loss of hair.

17. AGENTS TO TREAT CYTOMEGALOVIRUS (CMV)
INFECTIONS
• CMV infections include retinitis, colitis, esophagitis, central nervous
system disease, and pneumonitis.
• Ganciclovir
• Valganciclovir
• Foscarnet
• Cidofovir

18. FOSCARNET
Used for treatment of:
• Herpes simplex
• CMV infections
• Alternate therapy for HIV patients.
MECHANISM OF ACTION
Foscarnet inhibits viral DNA synthesis by inhibiting DNA polymerase
enzyme, resulting in inhibition of growth of virus in host body.

19. Mechanism
of Action

20. Continued..
INDICATIONS
• Herpes simplex viruses infections
• Drug resistant CMV infections
• Other viral infections in AIDS patients.
SIDE EFFECTS
• Nephrotoxicity
• Electrolyte imbalance
• Seizures and headache
• Anaemia

21. ANTIRETROVIRAL AGENTS
.
• Abacavir
• Didanosine
• Emtricitabine
• Lamivudine
• Stavudine
• Tenofovir
• Zalcitabine
• Zidovudine
.
• Delavirdine
• Efavirenz
• Amprenavir
• Atazanavir
• Fosamprenavir
• Indinavir
• Ritonavir
• Saquinavir
• Enfuvirtide

22. ANTIHEPATITIS AGENTS:
• Interferon alpha
• Lamivudine
• Adefovir dipivoxil
• Entecavir
• Ribavirin

23. ANTI-INFLUENZA AGENTS
• Amantadine
• Rimantadine
• Zinamivir
• Oseltamivir

24. INTERFERONS
Interferon Alpha,
produced by virus
infected leukocytes.
Interferon Beta,
produced by virus
infected epithelial cells.
Interferon Gamma,
produced by immune
system cells in response
to antigen stimulation of
lymphocytes.

25. Interferon
Released by host cell
In response to intracellular pathogen
To alert the neighboring cells against pathogen
Leads to close of cellular protein synthesis

26. Mechanism
of Action

27. Continued..
CLINICAL USES:
• Acute and chronic Hepatitis B and C.
• Different types of cancer including Basal cell carcinoma (skin cancer),
hairy cell leukemia, chronic myloid leukemia.
• Multiple sclerosis
SIDE EFFECTS:
• Fever, malaise (general feeling of discomfort), fatigue, muscle pains.
• High levels of interferons can cause kidney, liver, bone marrow and
heart toxicity.

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