In vivo drug-drug interaction studies were not conducted with valganciclovir. However, because valganciclovir is rapidly and extensively converted to ganciclovir, drug-drug interactions associated with ganciclovir will be expected for VALCYTE. Drug-drug interaction studies with ganciclovir were conducted in patients with normal renal function. Following concomitant administration of VALCYTE and other renally excreted drugs, patients with impaired renal function may have increased concentrations of ganciclovir and the coadministered drug.
Therefore, these patients should be closely monitored for toxicity of ganciclovir and the coadministered drug. Established and other potentially significant drug interactions conducted with ganciclovir are listed in Table 9 . Table 9 Established and Other Potentially Significant Drug Interactions with Ganciclovir Name of the Concomitant Drug Change in the Concentration of Ganciclovir or Concomitant Drug Clinical Comment Imipenem-cilastatin Unknown Coadministration with imipenem-cilastatin is not recommended because generalized seizures have been reported in patients who received ganciclovir and imipenem-cilastatin.
Cyclosporine or amphotericin B Unknown Monitor renal function when VALCYTE is coadministered with cyclosporine or amphotericin B because of potential increase in serum creatinine [see Warnings and Precautions (5.2) ]. Mycophenolate mofetil (MMF) ↔ Ganciclovir (in patients with normal renal function) ↔ MMF (in patients with normal renal function) Based on increased risk, patients should be monitored for hematological and renal toxicity.
Other drugs associated with myelosuppression or nephrotoxicity (e.g., adriamycin, dapsone, doxorubicin, flucytosine, hydroxyurea, pentamidine, tacrolimus, trimethoprim/ sulfamethoxazole, vinblastine, vincristine, and zidovudine) Unknown Because of potential for higher toxicity, coadministration with VALCYTE should be considered only if the potential benefits are judged to outweigh the risks. Didanosine ↔ Ganciclovir ↑ Didanosine Patients should be closely monitored for didanosine toxicity (e.g., pancreatitis) Probenecid ↑ Ganciclovir VALCYTE dose may need to be reduced.
Monitor for evidence of ganciclovir toxicity. Imipenem-cilastatin: Seizures were reported in patients receiving ganciclovir and imipenem-cilastatin. Concomitant use is not recommended unless the potential benefits outweigh the risks. ( 7 ) Cyclosporine or amphotericin B: When coadministered with valganciclovir, the risk of nephrotoxicity may be increased. Monitor renal function. ( 5.2 , 7 ) Mycophenolate mofetil (MMF): When coadministered with valganciclovir, the risk of hematological and renal toxicity may be increased.
Monitor for ganciclovir and MMF toxicity. ( 7 ) Other drugs associated with myelosuppression or nephrotoxicity: Due to potential for increased toxicity, consider for concomitant use with valganciclovir only if the potential benefits are judged to outweigh the risks. ( 7 ) Didanosine: Ganciclovir coadministered with didanosine may increase didanosine levels. Monitor for didanosine toxicity (e.g., pancreatitis). ( 7 ) Probenecid: May increase ganciclovir levels.
Monitor for evidence of ganciclovir toxicity. ( 7 ) Drug Interactions: In vivo drug-drug interaction studies were not conducted with valganciclovir. However, because valganciclovir is rapidly and extensively converted to ganciclovir, interactions associated with ganciclovir will be expected for VALCYTE [see Drug Interactions (7) ]. Table 15 and Table 16 provide a listing of established drug interaction studies with ganciclovir.
Table 15 provides the effects of coadministered drug on ganciclovir plasma pharmacokinetic parameters, whereas Table 16 provides the effects of ganciclovir on plasma pharmacokinetic parameters of coadministered drug. Table 15 Results of Drug Interaction Studies with Ganciclovir: Effects of Coadministered Drug on Ganciclovir Pharmacokinetic Parameters Coadministered Drug Ganciclovir Dosage N Ganciclovir Pharmacokinetic (PK) Parameter Mycophenolate mofetil (MMF) 1.5 g single dose 5 mg/kg IV single dose 12 No effect on ganciclovir PK parameters observed (patients with normal renal function) Trimethoprim 200 mg once daily 1000 mg every 8 hours 12 No effect on ganciclovir PK parameters observed Didanosine 200 mg every 12 hours simultaneously administered with ganciclovir 5 mg/kg IV twice daily 11 No effect on ganciclovir PK parameters observed 5 mg/kg IV once daily 11 No effect on ganciclovir PK parameters observed Probenecid 500 mg every 6 hours 1000 mg every 8 hours 10 AUC ↑ 53 ± 91% (range: -14% to 299%) Ganciclovir renal clearance ↓ 22 ± 20% (range: -54% to -4%) Table 16 Results of Drug Interaction Studies with Ganciclovir: Effects of Ganciclovir on Pharmacokinetic Parameters of Coadministered Drug Coadministered Drug Ganciclovir Dosage N Coadministered Drug Pharmacokinetic (PK) Parameter Oral cyclosporine at therapeutic doses 5 mg/kg infused over 1 hour every 12 hours 93 In a retrospective analysis of liver allograft recipients, there was no evidence of an effect on cyclosporine whole blood concentrations.
Mycophenolate mofetil (MMF) 1.5 g single dose 5 mg/kg IV single dose 12 No PK interaction observed (patients with normal renal function) Trimethoprim 200 mg once daily 1000 mg every 8 hours 12 No effect on trimethoprim PK parameters observed Didanosine 200 mg every 12 hours 5 mg/kg IV twice daily 11 AUC 0-12 ↑70 ± 40% (range: 3% to 121%) C max ↑49 ± 48% (range: -28% to 125%) Didanosine 200 mg every 12 hours 5 mg/kg IV once daily 11 AUC 0-12 ↑50 ± 26% (range: 22% to 110%) C max ↑36 ± 36% (range: -27% to 94%)
