Valacyclovir Dosing and Safety with Rinvoq in Herpes Simplex Dermatitis
Yes, valacyclovir can be used safely in patients taking Rinvoq (upadacitinib) for eczema, but heightened vigilance is required due to the increased baseline risk of herpes infections with JAK inhibitors.
Valacyclovir Dosing for Herpes Simplex Dermatitis
For herpes simplex infections in the setting of atopic dermatitis (eczema herpeticum), use valacyclovir 500 mg to 1000 mg twice daily, with treatment duration of 5-10 days depending on severity. 1
Standard Dosing Regimens:
- Mild to moderate herpes simplex dermatitis: Valacyclovir 500 mg twice daily for 5-7 days 1
- Eczema herpeticum (disseminated HSV in eczema): Valacyclovir 1000 mg twice daily for 7-10 days, or consider IV acyclovir if patient is ill or febrile 2, 3, 4
- Severe or widespread disease: IV acyclovir is preferred over oral therapy 2, 3
Key Treatment Principles:
- Initiate antiviral therapy immediately upon clinical suspicion without waiting for laboratory confirmation, as early treatment correlates with better outcomes and shorter disease duration 3, 4
- Oral acyclovir 200 mg five times daily for 5 days is an alternative if valacyclovir is unavailable 5
- Oral valacyclovir has been successfully used even in pediatric patients as young as 9 months 6
Safety Considerations with Rinvoq (Upadacitinib)
The combination is safe to use, but patients on Rinvoq have an inherently elevated risk of herpes infections that requires monitoring.
Herpes Infection Risk on Rinvoq:
- Eczema herpeticum occurs in 1.6-2.6% of patients on Rinvoq compared to 1.6% on placebo during the first 16 weeks of treatment 7
- Over 12 months, eczema herpeticum incidence remains stable at 1.5-1.6 per 100 patient-years with Rinvoq 7
- Most eczema herpeticum events (79%) are mild to moderate and affect ≤2% body surface area 7
- Serious eczema herpeticum occurred exclusively in patients with poor disease control (vIGA-AD score ≥3) 7
Clinical Monitoring:
- Continue Rinvoq during herpes simplex treatment unless the infection is severe or widespread 7
- Monitor for signs of bacterial superinfection (purulent exudate, pustules, systemic fever) which would require adding antibiotics 1, 4
- Add flucloxacillin if bacterial superinfection is clinically evident, as Staphylococcus aureus commonly co-infects eczema herpeticum 2, 3, 4
When to Consider Stopping Rinvoq:
- Severe eczema herpeticum affecting >50% body surface area 7
- Systemic symptoms with hemodynamic instability requiring hospitalization 3
- Recurrent eczema herpeticum despite adequate antiviral prophylaxis 8
Important Clinical Pitfalls
Do not delay antiviral therapy to obtain viral cultures or wait for laboratory confirmation, as eczema herpeticum can progress rapidly and early treatment is critical for outcomes 3, 4
Do not routinely add antibiotics unless there is clear clinical evidence of bacterial superinfection (purulent discharge, pustules, or systemic signs of bacterial infection) 1, 4
Do not use systemic corticosteroids during active herpes infection, as this can worsen viral dissemination 1
Recognize that herpes simplex in AD patients on JAK inhibitors may present atypically, with one case report documenting recurrent ocular herpes simplex infections on upadacitinib 8
Adjunctive Symptomatic Management
- Sedating antihistamines at night (e.g., hydroxyzine, chlorphenamine 4-12 mg) provide the most effective itch relief during eczema herpeticum 2
- Cooling antipruritic lotions (calamine, 1% menthol in aqueous cream) can provide additional symptomatic relief 2
- Continue appropriate topical corticosteroids for underlying eczema once antiviral therapy is initiated 1, 4
Drug Interaction Considerations
There are no significant pharmacokinetic interactions between valacyclovir and upadacitinib, as valacyclovir is renally eliminated and upadacitinib is metabolized via CYP3A4 7
Monitor renal function if using valacyclovir in patients with pre-existing renal impairment, as dose adjustment may be needed 1