Envarsus XR Dosing with Concurrent CellCept 500mg BID
When using Envarsus XR (extended-release tacrolimus) in combination with mycophenolate mofetil (CellCept) 500mg twice daily, start with 0.14 mg/kg once daily and adjust to maintain target tacrolimus trough levels of 6-11 ng/mL in the first month, then 4-11 ng/mL thereafter.
Initial Dosing Strategy
The FDA-approved starting dose for Envarsus XR in de novo transplant patients is 0.14 mg/kg once daily when combined with mycophenolate products and corticosteroids 1. This is approximately 30% lower than the dose needed for immediate-release tacrolimus (which starts at 0.2 mg/kg/day divided twice daily) due to the enhanced bioavailability of the extended-release formulation 2.
Target Trough Levels and Monitoring
- First 30 days post-transplant: Target tacrolimus trough 6-11 ng/mL
- After 30 days: Target tacrolimus trough 4-11 ng/mL 1
Monitor tacrolimus levels intensively in the first weeks (Days 2,3,4,7,10,14,21,30), then at regular intervals (Days 45,60,90,120,180,270,360) 1. Be aware that on Day 2, only 33% of patients achieved target range with the 0.17 mg/kg dose used in trials, while 39% were above range 1.
Mycophenolate Dosing Considerations
Your patient's CellCept dose of 500mg BID (1 gram total daily) is below the standard recommended dose. Clinical trials consistently used mycophenolate mofetil at 1 gram twice daily (2 grams total) in combination with tacrolimus 1, 3.
Key evidence:
- The combination of tacrolimus with MMF 2g/day showed only 8.6% acute rejection rates versus 32.2% with lower doses 3
- In long-term studies, the mean MMF dose decreased from 2g/day to approximately 1.5g/day by 6 months, primarily due to GI side effects 4, 3
- Guidelines support using antimetabolites like MMF in combination with CNIs to allow lower tacrolimus doses and reduce nephrotoxicity 5, 6
Critical Dosing Pitfalls
Do not assume bioequivalence: Envarsus XR is NOT bioequivalent to immediate-release tacrolimus. Converting from twice-daily tacrolimus requires a dose reduction, not a 1:1 conversion 2
First week monitoring is crucial: Mean tacrolimus trough concentrations with Envarsus XR tend to run above target range during the first week post-transplant 1. Dose adjustments should be made promptly to avoid toxicity.
Consider increasing the mycophenolate dose: If this is a transplant patient, 500mg BID may be subtherapeutic. The standard effective dose is 1g BID, which can be reduced later if GI side effects occur 3.
Drug Interaction Profile
The combination of tacrolimus and mycophenolate does not significantly alter tacrolimus pharmacokinetics 7. However, both drugs share some adverse effects (GI symptoms, leukopenia, infections), so monitoring for cumulative toxicity is important 1, 3.
Safety Monitoring
Common adverse reactions with this combination include:
- Diarrhea (31%), anemia (26%), UTI (25%), hypertension (23%), tremor (19%)
- New-onset diabetes after transplantation occurred in 21% at one year 1
- Infections are common (70% overall, with 26% serious infections) 1
The combination is generally well-tolerated, with similar safety profiles between Envarsus XR and immediate-release tacrolimus when used with mycophenolate 1.