Switching to Oral Valganciclovir for CMV Retinitis
Yes, you can switch to oral valganciclovir 900 mg twice daily for both induction and maintenance therapy of CMV retinitis, as it provides ganciclovir exposure equivalent to IV ganciclovir 5 mg/kg twice daily. 1, 2, 3
Induction Therapy Protocol
Administer valganciclovir 900 mg orally twice daily for 14-21 days as induction therapy for CMV retinitis, which delivers systemic ganciclovir exposure comparable to IV ganciclovir 5 mg/kg twice daily 4, 1, 2, 3
The CDC explicitly recommends valganciclovir 900 mg twice daily for 14-21 days as an effective alternative to IV ganciclovir for induction in adults with CMV retinitis 4
Oral valganciclovir is preferred over IV ganciclovir for patients with peripheral lesions that are not immediately sight-threatening (not adjacent to optic nerve or fovea) due to ease of administration and avoidance of catheter-related complications 4
Maintenance Therapy Protocol
After completing induction, transition to valganciclovir 900 mg once daily for chronic suppressive therapy 4, 1, 2
Maintenance therapy must be continued lifelong until immune reconstitution occurs (CD4+ count >100-150 cells/µL sustained for 3-6 months on antiretroviral therapy) 1, 2
The once-daily maintenance regimen provides ganciclovir exposure equivalent to IV ganciclovir 5 mg/kg once daily 3, 5
When IV Therapy Remains Preferred
For sight-threatening lesions (adjacent to optic nerve or fovea), certain specialists prefer combination IV therapy with ganciclovir 5 mg/kg every 12 hours PLUS foscarnet 60 mg/kg every 8 hours for initial induction 4, 1
For CMV encephalitis or neurologic disease, IV combination therapy (ganciclovir plus foscarnet) is strongly preferred over oral monotherapy due to higher failure rates with single-agent treatment 1
Critical Monitoring Requirements
Monitor complete blood count twice weekly during induction and weekly during maintenance, as myelosuppression requiring dose reduction or interruption occurs in up to 40% of patients 1, 2
Monitor serum creatinine regularly and adjust dose based on creatinine clearance, as renal toxicity can occur 1, 2
Ophthalmologic examination with dilated indirect ophthalmoscopy is required at diagnosis, after completing induction, at 1 month, then monthly while on treatment 4, 2
Pharmacokinetic Justification
Valganciclovir 900 mg twice daily produces an AUC₂₄ comparable to IV ganciclovir 5 mg/kg twice daily, with the advantage of 10-fold higher bioavailability than oral ganciclovir capsules 5, 6
Peak ganciclovir concentrations occur 1.5-2 hours after valganciclovir administration when taken with food, and food increases ganciclovir AUC by 24-56% 5
Administer valganciclovir with food to maximize absorption 5
Common Pitfalls to Avoid
Do not shorten the induction period below 14 days, as this increases risk of early disease progression 1
Do not discontinue maintenance therapy even when retinitis appears stable, unless CD4+ count is sustained >100-150 cells/µL for 3-6 months with close ophthalmologic monitoring 1, 2
Do not use valganciclovir if severe gastrointestinal symptoms interfere with oral absorption—in this case, IV ganciclovir or foscarnet is required 4
Do not use valganciclovir in liver transplant patients due to higher rates of tissue-invasive CMV disease compared to IV ganciclovir 7, 3
Management of Treatment Failure
If retinitis progresses on maintenance therapy, reinitiate induction dosing with valganciclovir 900 mg twice daily for 14-21 days 2
Consider ganciclovir intraocular implant placement for patients who relapse on systemic therapy, as it provides superior intraocular drug levels 2
For ganciclovir-resistant CMV (IC₅₀ >3 µg/mL), switch to foscarnet or consider combination therapy 1