A 32-year-old woman presents with recurrent herpes labialis occurring 3–4 times per year. Each episode lasts 7–10 days with vesicles on the lip margin and mild pain. She requests prophylaxis to reduce frequency and duration. What is the drug of choice for long-term suppressive therapy?

Explanation

## First-Line Suppressive Therapy for Recurrent HSV **Key Point:** Valacyclovir is the preferred agent for long-term suppression of recurrent herpes simplex because of superior oral bioavailability and convenient dosing (once or twice daily). ### Why Valacyclovir? **High-Yield:** Valacyclovir is the L-valyl ester prodrug of acyclovir. It achieves: - Higher serum acyclovir levels than oral acyclovir (3–5 fold higher) - Better oral absorption (54% vs 15–30% for acyclovir) - Convenient dosing: 500 mg once daily for suppression of recurrent HSV-1 - Reduced pill burden and improved compliance ### Suppressive Dosing Regimens | Drug | Dose | Frequency | Notes | | --- | --- | --- | --- | | Valacyclovir | 500 mg | Once daily | **First-line for suppression** | | Acyclovir | 400 mg | 2–3 times daily | More frequent dosing; lower bioavailability | | Famciclovir | 250 mg | Twice daily | Alternative; less commonly used for suppression | | Penciclovir | Topical only | 5 times daily | Topical agent; not systemic; for acute lesions only | **Clinical Pearl:** Suppressive therapy is indicated when: - ≥6 recurrences per year - Severe psychological impact - Immunocompromised state - Frequent transmission risk (e.g., discordant couples) ### Mechanism of Antivirals All acyclic nucleoside analogues (acyclovir, valacyclovir, famciclovir) work by: 1. Viral thymidine kinase phosphorylation (HSV-specific) 2. Inhibition of viral DNA polymerase 3. Chain termination of viral DNA synthesis **Key Point:** Valacyclovir's superior bioavailability makes it the preferred choice for both acute treatment and long-term suppression in immunocompetent patients with recurrent HSV. [cite:Harrison 21e Ch 187]