Acyclovir
Rapid Review
- Mechanism of Action: Antiviral; inhibits DNA polymerase
- Indications: Commonly used to treat oral/genital herpes, varicella, zoster (shingles), and VZV encephalitis.
- Contraindications: allergy to class/drug
- Dosage: depends on condition; common dosage is 800mg PO 5x/day x 7 days.
- Half-life: 2.5 – 3.3 hours
- Adverse Reactions: Common side effects include N/V, headache, and rash. Serious reactions include hallucinations/psychosis
- Special Considerations: N/A
Pearls
- Acyclovir is renally cleared and can be particularly nephrotoxic if administered intravenously. Infusions should be run slowly over 1 hour.
- Acyclovir works best if administered early. It should only be started if within 24 hours of varicella rash or within 72 hours of herpes zoster (shingles) appearance.
Deep Dive
Rapid Review
Pearls
Oseltamivir
Rapid Review
- Mechanism of Action: Antiviral; competitively inhibits the influenza virus neuraminidase, preventing viral replication.
- Indications: Acute, uncomplicated influenza A or B
- Contraindications: Hypersensitivity
- Dosage: 75 mg PO BID x 5 days (adjust dose based on kidney function)
- Half-life: 1-3 hours
- Adverse Reactions: Nausea, vomiting, abdominal pain
- Special Considerations: Greatest benefit when taken within 48 hours of symptom onset
Pearls
- Oseltamivir has the greatest benefit when taken within 48 hours of symptom onset. However, at best, it usually only reduces duration of symptoms by 24 hours or less.
- Ironically, common side effects of oseltamivir include flu-like symptoms (malaise, nausea, vomiting, etc.). Given the side effect profile and limited benefit, this medication is likely best reserved for high-risk patients with significant underlying comorbidities.
Deep Dive
Remdesivir
Rapid Review
- Mechanism of Action: Antiviral; broad spectrum antiviral agent reduces virus production via disruption of viral RNA polymerase
- Indications: COVID-19
- Contraindications: Hypersensitivity, ALT levels > 5x upper limit of normal, severe renal or hepatic impairment
- Dosage: 200 mg IV loading dose, followed by 100 mg IV daily X 5-10 days
- Half-life: 1-1.3 hours
- Adverse Reactions: Nausea, increased ALT/AST, diarrhea, hypokalemia
Pearls
- Paxlovid (Ritonavir/nirmatrelvir) is currently the preferred antiviral for outpatient treatment of COVID-19. Remdesivir is a second line option, though it’s utility as an outpatient medication is limited by it’s solely intravenous formulation.
- Remdesivir is the preferred antiviral for patients hospitalized with COVID-19.
Deep Dive