Antiviral Medications Flashcards
Acyclovir MOA (3):
- Acyclovir is phosphorylated to the inactive monophosphate form by a virus specific thymidine kinase and to the activated triphosphate form by cellular enzymes.
- Inhibits viral DNA polymerases and competes with deoxyguanosine triphosphate.
- Acts as a chain terminator.
Acyclovir pharmacokinetics (4):
- Renal adjustment required.
- Bioavailability 10 - 30%.
- Good CSF penetration (drug of choice for viral meningitis).
- Placenta and umbilical cord penetration.
Acyclovir ADRs (4):
- IV can cause phlebitis.
- Reversible renal toxicity due to crystalline nephropathy.
- GI: N/V/D.
- Hepatic.
Acyclovir clinical uses (5):
- Therapy started 48-72 hours of symptoms.
- Primary HSV-2: 10 days.
- Recurrent HSV-2: 5 days.
- IV for encephalitis (drug of choice).
- NOT for CMV.
Valacyclovir:
Prodrug of acyclovir.
Valacyclovir pharmacokinetics (2):
- 70% bioavailability.
- Converted to acyclovir by first pass metabolism and hydrolysis.
Valacyclovir ADRs (3):
High doses:
- Confusion, hallucinations.
- Nephrotoxicity.
- Thrombocytopenic syndromes.
Valacyclovir clinical uses (3):
- Herpes Zoster.
- Herpes Simplex.
- Recurrent HSV in HIV infected patients.
Valacyclovir advantage over acyclovir:
Less frequent dosing (BID vs TID-5x day).
Ganciclovir:
Acyclic nucleoside analogues of guanine similar to acyclovir.
Ganciclovir MOA:
Metabolized by thymidine kinase and other enzymes into triphosphate analog which inhibits DNA polymerase and incorporates into viral DNA.
Ganciclovir pharmacokinetics (4):
- Inhibition of CMV and EBV.
- HSV.
- VZV.
- Oral bioavailability 6-9%.
Ganciclovir ADRs (3):
- Bone marrow suppression.
- Neutropenia, thrombocytopenia and anemia.
- CNS.
- GI (N/V).
Ganciclovir clinical uses (4):
- CMV retinitis.
- CMV prophylaxis in transplant pts.
- IV: esophagitis, gastritis and colitis.
- Surgically implanted device for CMV retinitis in AIDS.
Valganciclovir:
Prodrug of ganciclovir.
Valganciclovir pharmacokinetics (2):
- Bioavailability ~ 60%.
- Renally excreted (adjustment required).
Valganciclovir clinical uses (2):
- CMV retinitis.
- CMV prophylaxis.
Penciclovir (3):
- Acyclic guanine nucleoside analog.
- Topical cream only.
- HSV-1 (cold sores).
Famciclovir (7):
- Prodrug of penciclovir.
- Bioavailability 65-77%.
- Renally excreted (adjustment required).
ADRs: - CNS.
- GI.
Uses: - Herpes zoster.
- HSV.
Cidofovir ADRs (4):
- Nephrotoxic (avoid SCr > 1.5 mg/dl).
- Neutropenia.
- Ocular hypotony.
- Metabolic acidosis.
Cidofovir clinical uses
- Administer with probenecid and normal saline (nephrotoxicity).
- Reserved for CMV retinitis in AIDS pts.
Foscarnet MOA:
Competes for pyrophosphate site in viral but not human DNA polymerase and reverse transcriptase.
Foscarnet ADRs (6):
- Nephrotoxic.
- Electrolyte disturbances.
- CNS (seizures, fever).
- Anemia/neutropenia.
- GI (N/V/D).
- EKG changes.
Foscarnet clinical uses (3):
- Second line agent.
- CMV retinitis in pts with AIDS.
- Acyclovir resistant mucocutaneous HSV in immunosuppressed.
