Pharmacology of Antiviral Drugs explains mechanisms and actions of drugs that inhibit viral replication and treat viral infections.
Definition of Pharmacology of Antiviral Drugs
- Antiviral drugs are used to treat viral infections by targeting specific steps in the viral life cycle, such as:
- Preventing viral entry
- Inhibiting replication
- Blocking release or maturation of new viral particles
- Viruses replicate inside host cells, so antiviral drugs must selectively target viral enzymes or replication steps to avoid harming host cells.
Major Classes of Antiviral Drugs
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Anti-Herpes Virus Drugs
- Examples: Acyclovir, Valacyclovir
- Mechanism: Inhibit viral DNA polymerase (require activation by viral thymidine kinase)
- Use: Herpes simplex (HSV), Varicella zoster (VZV)
- Adverse Effects: Nephrotoxicity (crystalluria)
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Anti-Influenza Drugs
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Neuraminidase Inhibitors
- Examples: Oseltamivir, Zanamivir
- Mechanism: Inhibit neuraminidase → block viral release
- Use: Influenza A & B
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M2 Inhibitors (historical use only)
- Examples: Amantadine, Rimantadine (active only vs. Influenza A)
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Anti-HIV Drugs (Antiretrovirals)
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Nucleoside Reverse Transcriptase Inhibitors (NRTIs)
- Examples: Zidovudine, Lamivudine
- Mechanism: Inhibit reverse transcriptase by incorporation into viral DNA
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Non-Nucleoside RTIs (NNRTIs)
- Examples: Nevirapine, Efavirenz
- Mechanism: Directly inhibit reverse transcriptase
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Protease Inhibitors
- Examples: Ritonavir, Lopinavir
- Mechanism: Inhibit viral protease → block maturation
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Integrase Inhibitors
- Examples: Raltegravir
- Mechanism: Prevent integration of viral DNA into host genome
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Entry/Fusion Inhibitors
- Examples: Enfuvirtide, Maraviroc
- Note:
- HAART (Highly Active Antiretroviral Therapy): Combination therapy using ≥3 antiretroviral drugs from different classes
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Anti-Hepatitis Drugs
- Hepatitis B: Tenofovir, Entecavir
- Hepatitis C: Sofosbuvir (RNA polymerase inhibitor), Ledipasvir (NS5A inhibitor)
Pharmacokinetics of Antiviral Drugs
| Aspect | Key Points |
| Absorption | Varies by route (oral, IV, topical); affected by food & pH |
| Distribution | May penetrate CNS, lungs, liver depending on drug |
| Metabolism | Often hepatic via CYP enzymes; interactions possible |
| Elimination | Renal, biliary, or fecal; dosing depends on organ function |
| Drug Interactions | Common, especially with CYP450 inhibitors/inducers |
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