Can Acyclovir Be Started After One Week of Shingles?
Yes, an 80-year-old man with a one-week-old herpes zoster rash that has not yet fully crusted should be started on oral acyclovir, with careful attention to renal dosing adjustments given his age-related risk of impaired kidney function. 1, 2
Treatment Rationale Beyond the 72-Hour Window
While antiviral therapy is most effective when initiated within 72 hours of rash onset, the key clinical endpoint for treatment is complete crusting of all lesions, not an arbitrary time from symptom onset. 1, 2 The American Academy of Dermatology and Infectious Diseases Society of America recommend continuing antiviral therapy until all lesions have scabbed, and treatment should be initiated if lesions remain active beyond 7 days. 1
Special Considerations for This Patient
Elderly patients (≥80 years) are at particularly high risk for postherpetic neuralgia and disseminated disease, making antiviral treatment beneficial even when started late. 1, 2
The presence of uncrusted lesions at one week indicates ongoing viral replication, which warrants antiviral intervention regardless of timing. 1
Immunocompromised patients should receive antiviral therapy regardless of timing due to higher risk for disseminated infection. 3 While this patient's immune status is not specified, advanced age (80 years) often correlates with some degree of immunosenescence.
Recommended Treatment Regimen
First-Line Oral Therapy
Oral acyclovir 800 mg five times daily should be continued until all lesions have completely scabbed, not for a fixed 7-day duration. 1, 2 This typically requires 7–10 days of therapy, but may need extension if new lesions continue to form. 2
Alternative agents with better bioavailability and more convenient dosing include: 1, 2
- Valacyclovir 1000 mg three times daily
- Famciclovir 500 mg three times daily
These alternatives offer superior pain reduction outcomes compared to acyclovir, though all three are therapeutically equivalent for viral suppression. 2, 4
Critical Renal Dosing Adjustments
Baseline renal function must be assessed before initiating therapy, as acyclovir is renally excreted and can cause crystalluria and obstructive nephropathy in up to 20% of patients, particularly after 4 days of therapy. 5, 2
Dose reductions based on creatinine clearance are mandatory to prevent neurotoxicity and nephrotoxicity in elderly patients. 1, 2 For example, famciclovir dosing should be adjusted from 500 mg every 8 hours (CrCl ≥60 mL/min) down to 250 mg every 24 hours (CrCl <20 mL/min). 1
Maintain adequate hydration throughout treatment to reduce crystalluria risk. 1
When to Escalate to Intravenous Therapy
Switch to intravenous acyclovir 10 mg/kg every 8 hours if any of the following are present: 1, 2
- Disseminated disease (≥3 dermatomes, visceral involvement, hemorrhagic lesions)
- Facial or ophthalmic involvement with risk of cranial nerve complications
- CNS complications (encephalitis, meningitis, Guillain-Barré syndrome)
- Severe immunosuppression
- Inability to absorb oral medication
- Lesions fail to improve within 7–10 days of oral therapy (suspect acyclovir resistance) 1, 2
Monitoring and Treatment Failure
If lesions have not begun to resolve within 7–10 days of appropriate antiviral therapy, suspect acyclovir resistance and obtain viral culture with susceptibility testing. 1, 2 Resistance occurs in <0.5% of immunocompetent patients but up to 7% of immunocompromised patients. 2
For confirmed acyclovir-resistant VZV, switch to foscarnet 40 mg/kg IV every 8 hours until clinical resolution. 1, 2
Adjunctive Pain Management
Gabapentin is first-line therapy for acute zoster-associated neuropathic pain, titrated up to 2400 mg per day in divided doses. 1, 2 Approximately 80% of patients experience somnolence, which should be discussed during counseling. 1
Over-the-counter analgesics (acetaminophen or ibuprofen) and application of ice or cold packs provide additional relief during the acute phase. 1, 2
Common Pitfalls to Avoid
Do not discontinue antiviral therapy at exactly 7 days if lesions have not fully scabbed; continue until complete crusting. 1, 2
Do not use short-course (1–3 day) antiviral regimens designed for genital herpes (e.g., 400 mg TDS); they are inadequate for VZV infection. 1, 2
Do not rely on topical antivirals, which are substantially less effective than systemic therapy. 1, 2
Do not apply topical corticosteroids to active lesions, as this increases dissemination risk. 2
Post-Recovery Vaccination
After complete recovery, the recombinant zoster vaccine (Shingrix) is strongly recommended for all adults ≥50 years, providing >90% efficacy in preventing future episodes. 1, 2 The two-dose series should be administered regardless of prior herpes zoster episodes. 1
Infection Control
The patient remains contagious until all lesions have crusted; during this period he should avoid contact with susceptible persons (those who have not had chickenpox or vaccination), keep lesions covered, and maintain physical separation of at least 6 feet from others. 1, 2