antiviral

1. Virus
• Viruses are obligate intracellular parasites that
consist of either double- or single-stranded DNA
or RNA enclosed in a protein coat called a capsid.
Viral replication
• A virus cannot replicate on its own
• It must attach to and enter a host cell
• It then uses the host cell’s energy to synthesize
protein, DNA, and RNA
Viruses are difficult to kill because they live inside
the cells
• Any drug that kills a virus may also kill cells

3. Antiviral Drugs
Viruses controlled by current antiviral therapy
• Cytomegalovirus (CMV)
• Hepatitis viruses A, B, C (HAV, HBV, HCV)
• Herpes simplex viruses(HSV)
• Human immunodeficiency virus (HIV)
• Influenza viruses (the “flu”)
• Respiratory syncytial virus (RSV)

5. Anti-Viral Drugs
1.Anti-Herpes
virus
Acyclovir, Valacyclovir, Idoxuridine,
Famciclovir, Ganciclovir, Foscarnet
2.Anti-influenza
virus
Amantadine, Rimantadine, Oseltamivir,
Zanamivir
3.Anti-Hepatitis/
Non-selective
antiviral drugs
Ribavirin, Adefovir dipivoxil,
Interferon α

6. Anti-Retroviral Drugs
1.Nucleoside reverse
transcriptase inhibitors (NRTI)
Zidovudine, Didanosine,
Lamivudine, Stavudine, Abacavir
2.Non-Nucleoside reverse
transcriptase inhibitors (NNRTI)
Nevirapine, Efavirenz,Delavirdine
3.Protease Inhibitors (PI) Ritonavir, Indinavir, Nelfinavir,
Saquinavir,Amprenavir
4.Fusion inhibitor Enfuvirtide
5.CCR5 receptor inhibitor Maraviroc
6.Integrase inhibitor Raltegravir

7. Acyclovir & Valacyclovir
• Acyclovir is a deoxiguanosine analogue antiviral drug that
prevents DNA synthesis & viral replication.
Mechanism of Action
• It inhibits viral DNA polymerase and prevents incorporation of
natural deoxyguanosine triphosphate into viral DNA.
( Nucleic acid synthesis inhibitor)
Indication
• It is used mainly for the treatment of viral infections due to
Herpes Simplex Virus (types 1 and 2) and varicella-zoster virus
(herpes zoster and chickenpox).

8. Contraindication and Precaution
• pregnancy and hypersensitivity reaction
• Precaution should be taken by patients with renal problem,
neurological abnormalities with much hypoxia
Adverse Effects
• Skin irritation, skin dryness, burning sensation may occurs in
topical application
• Headache, diarrhea, nausea, and vomiting may result after oral
administration.
• Transient renal dysfunction may occur at high doses or in a
dehydrated patient receiving the drug intravenously.
Dose
• Acyclovir tablet is given orally as the dose of 200 to 400 mg four
to six times daily for 5 to 10 days.
• IV infusion is given as 5 to 10mg/kg/8 hourly.
• Cream of 5% is used for skin application
• 3% of eye ointment is used for eye application

9. Amantadine & Rimantadine
• Amantadine has antiviral effect on influenza type A virus.
Mechanism of Action
• Amantadine and Rimantadine inhibit an early step in viral
replication(uncoating of viral RNA of influenza A virus)
• The primary locus of action is the influenza A virus M2
protein, an integral membrane protein that functions as
an ion channel.
• It effectively blocks viral M2 ion channels, thus inhibiting
disassembly & ultimately inhibits viral replication.
Indication
• Used in the treatment of influenza virus, herpes zoster
and Parkinson’s disease.

10. Contraindication and Precaution
• Contraindicated in hypersensitivity, seizure
disorders, renal impairment, epilepsy and gastric
ulceration.
• Precaution should be taken by patients with
cardiovascular disease.
Adverse Effects
• GI disturbance, urinary retention, hallucinations,
seizures, anorexia and irritability.
Dose
• Adult: 100 mg daily for 5 days
• Child (10-15 yrs): 100 mg daily for 2-3 days.

11. Interferon α
• These are endogenous proteins, induced glycoproteins
that interfere with the ability of viruses to infect cell.
• Several alfa interferons are available: interferon alfa-
2a, interferon alfa-2b, alfa-n1, alfa-n3, alfacon-1, and
the pegylated interferons peginterferon alfa-2a and
peginterferon alfa-2b.
Mechanism of Action
• They induce host cell enzymes that inhibit viral RNA
translation and cause degradation of viral mRNA and
tRNA by binding to membrane receptors on cell
surface.
• It may also inhibit viral penetration, uncoating, mRNA
synthesis and translation, and virion assembly and
release.

12. Indication
• Interferon α are used in chronic hepatitis B and chronic
hepatitis C.
Contraindication and Precaution
• Contraindicated in patients with hepatic decompensation,
autoimmune hepatitis & depression.
Adverse Effects
• Irritability, conjuctivitis, rash, dry skin, arrythmia, sinusitis,
confusion, impaired concentration.
Dose
• Adult: 2.5 to 5 million units/m2
BD or TDS for 4-6 month.
• Child: not established.

13. Nucleoside Reverse Transcriptase Inhibitors (NRTIs)
In this class the following drugs are available:
• Zidovudine
• Didanosine
• Lamivudine
• Zalcitabine
• Stavudine
• Abacavir
Mechanism of Action of NRTIs
• NRTIs selectively inhibits viral reverse transcriptase.
• It blocks replication of the viral genome both by competitively
inhibiting incorporation of native nucleotides and by
terminating elongation of nascent proviral DNA.
Indications
• Component of HAART therapy

14. Non-Nucleoside Reverse Transcriptase
Inhibitors (NNRTIs)
• It includes:
• Nevirapine
• Delavirdine
• Efavirenz
Mechanism of Action of NNRTIs
• NNRTIs binds to site on viral reverse transcriptase,
different from NRTIs, resulting blockade of RNA
and DNA dependent DNA polymerase activity.
• They do not compete with nucleoside
triphosphates and do not require phosphorylation.
Indications
• Component of HAART therapy

15. Protease Inhibitors (PI)
• It includes:
• Indinavir
• Ritonavir
• Saquinavir
• Nelfinavir
• Amprenavir
Mechanism of Action
• These agents inhibit protease and prevent the
spread of infection.
• It inhibits last step of HIV replication.
Indication
• Component of HAART therapy

16. • HAART (Highly Active Anti-Retroviral Therapy)
• It includes combination of 3 drugs
2NRTI +1NNRTI
2NRTI +1PI
3NRTI
1NRTI + 1NNRTI + 1PI (Advance case)
When to start therapy
• Asymptomatic with CD4 <200/mm3
• CD4 count decline > 100/mm3
per year
• HIV RNA level >50,000 copies/ml

17. Zidovudine
• Zidovudine is a nucleoside reverse transcriptase inhibitor
structurally related to thymidine.
• It has activity against retroviruses including HIV and is used in
the management of HIV infection.
Mechanism of Action
• Zidovudine enters the cell via passive diffusion and it must be
converted to the triphosphate form by mammalian thymidine
kinase.
• After conversion to triphosphate form, it competitively inhibits
deoxythymidine triphosphate for the reverse transcriptase
enzyme and gets incorporated into viral DNA which cause viral
chain termination.
Indication
• It has greater activity against HIV-1, HIV-2 and human T Cell
lymphotropic viruses.
• Component of HAART therapy
• Post exposure prophylaxis & mother to offspring transmission

18. Contraindication and Precaution
• Contraindicated in patients with hyperensitivity.
• Precaution should be taken by patients with anaemia, renal and
hepatic impairment, low neutrophil or haemoglobin count.
Adverse Effects
• The commonest serious adverse effects are anaemia and
leucopenia, mainly neutropenia.
• Other reported adverse effects include asthenia(weakness), fever,
malaise (feeling discomfort), dizziness, headache, insomnia,
myalgia (muscle pain), myopathy (weakness of muscle), dyspnoea
(shortness of breath), cough, abdominal pain, anorexia, dyspepsia,
taste disturbance, diarrhoea, nausea, vomiting, and rashes.
Dose
• Adult: 600 mg daily in divided dose. IV infusion: 2 to 4 mg/mL over
1 hour
• Children: 360 to 480 mg/m2
daily in 3 or 4 divided doses. IV
infusion: 80 to 160 mg/m2
have been given every 6 hours.