Valganciclovir (Page 5 of 9)
12.3 PHARMACOKINETICS
Valganciclovir is a prodrug of ganciclovir. Valganciclovir C max and AUC are approximately 1% and 3% of those of ganciclovir, respectively.
Pharmacokinetics in Adults: The pharmacokinetics of ganciclovir after administration of valganciclovir tablets have been evaluated in HIV- and CMV-seropositive patients, patients with AIDS and CMV retinitis, and in solid organ transplant patients (Table 10).
PK Parameter | N | Value (Mean ± SD) |
AUC 0-24h (mcg∙h/mL) | 57 | 29.1 ± 9.7 |
C max (mcg/mL) | 58 | 5.61 ± 1.52 |
Absolute oral bioavailability (%) | 32 | 59.4 ± 6.1 |
Elimination half-life (hr) | 73 | 4.08 ± 0.76 |
Renal clearance (mL/min/kg) | 20 | 3.21 ± 0.75 |
The systemic ganciclovir exposures attained following administration of 900 mg valganciclovir tablets once daily were comparable across kidney, heart, and liver transplant recipients (Table 11).
Parameter | Value (Mean ± SD) | ||
Heart Transplant Recipients (N=17) | Liver Transplant Recipients (N=75) | Kidney Transplant Recipients* (N=68) | |
AUC 0-24h (mcg∙h/mL) | 40.2 ± 11.8 | 46.0 ± 16.1 | 48.2 ± 14.6 |
C max (mcg/mL) | 4.9 ± 1.1 | 5.4 ± 1.5 | 5.3 ± 1.5 |
Elimination half-life (hr) | 6.58 ± 1.50 | 6.18 ± 1.42 | 6.77 ± 1.25 |
The pharmacokinetic parameters of ganciclovir following 200 days of valganciclovir administration in high-risk kidney transplant patients were similar to those in solid organ transplant patients who received valganciclovir for 100 days.
Absorption, Distribution, Metabolism, and Excretion
The pharmacokinetic (PK) properties of valganciclovir are provided in Table 12.
| ||
Valganciclovir | Ganciclovir | |
Absorption | ||
T max (h) | 2.18 | |
Median (min-max)(fed conditions) | 1.7h to 3.0h | |
Food effect (high fat meal/fasting): PK parameter ratio and 90% confidence interval * | C max : 1.14 (0.95, 1.36) AUC: 1.30 (1.07, 1.51) * T max : ↔ | |
Distribution | ||
% Bound to human plasma (ex vivo) | Unknown | 1-2% over 0.5-51 mcg/mL |
Cerebrospinal fluid penetration | Unknown | Yes |
Metabolism | ||
Hydrolyzed by intestinal and liver esterases | No significant metabolism | |
Elimination | ||
Dose proportionality | AUC was dose proportional under fed conditions across a valganciclovir dose range of 450 to 2625 mg | |
Major route of elimination | Metabolism to ganciclovir | Glomerular filtration and active tubular secretion |
t ½ (h) | See Tables 10 and 11 | |
% Of dose excreted in urine | Unknown | |
% Of dose excreted in feces | Unknown |
Renal Impairment: The pharmacokinetics of ganciclovir from a single oral dose of 900 mg valganciclovir tablets were evaluated in 24 otherwise healthy individuals with renal impairment. Decreased renal function results in decreased clearance of ganciclovir and increased terminal half-life ( Table 13).
Estimated Creatinine Clearance* (mL/min) | N | Apparent Clearance (mL/min) Mean ± SD | AUC last (mcg∙h/mL) Mean ± SD | Half-life(hours) Mean ± SD |
51-70 | 6 | 249 ± 99 | 49.5 ± 22.4 | 4.85± 1.4 |
21-50 | 6 | 136 ± 64 | 91.9 ± 43.9 | 10.2 ± 4.4 |
11-20 | 6 | 45 ± 11 | 223 ± 46 | 21.8 ±5.2 |
≤ 10 | 6 | 12.8 ± 8 | 366 ± 66 | 67.5 ± 34 |
Hemodialysis reduces plasma concentrations of ganciclovir by about 50% following valganciclovir administration. Adult patients receiving hemodialysis (CrCl less than 10 mL/min) cannot use valganciclovir tablets because the daily dose of valganciclovir tablets required for these patients is less than 450 mg [ see Dosage and Administration (2.5) and Use in Specific Populations (8.6) ].
Pharmacokinetics in Pediatric Patients: The pharmacokinetics of ganciclovir were evaluated following the administration of valganciclovir in 63 pediatric solid organ transplant patients aged 4 months to 16 years and in 16 pediatric heart transplant patients less than 4 months of age. In these studies, patients received oral doses of valganciclovir (either valganciclovir for oral solution or tablets) to produce exposure equivalent to an adult 900 mg dose [ see Dosage and Administration (2.3), Adverse Reactions (6.1), Use in Specific Populations (8.4), and Clinical Studies (14.2) ].
In studies using the pediatric valganciclovir dosing algorithm, the pharmacokinetics of ganciclovir were similar across organ types and age ranges ( Table 14). Relative to adult transplant patients ( Table 11), AUC values in pediatric patients were somewhat increased, but were within the range considered safe and effective in adults.
| |||||
Organ | PK Parameter Mean (SD) | Age Group | |||
< 4 months | 4 months to ≤ 2 years | > 2 to < 12 years | ≥ 12 years | ||
Heart (N=26) | N | 14 * | 6 | 2 | 4 |
AUC 0-24h (mcg∙h/mL) | 66.3 (20.5) | 55.4 (22.8) | 59.6 (21.0) | 60.6 (25.0) | |
C max (mcg/mL) | 10.8 (3.30) | 8.2 (2.5) | 12.5 (1.2) | 9.5 (3.3) | |
t ½ (h) | 3.5 (0.87) | 3.8 (1.7) | 2.8 (0.9) | 4.9 (0.8) | |
Kidney (N=31) | N | NA | 2 | 10 | 19 |
AUC 0-24h (mcg∙h/mL) | 67.6 (13.0) | 55.9 (12.1) | 47.8 (12.4) | ||
C max (mcg/mL) | 10.4 (0.4) | 8.7 (2.1) | 7.7 (2.1) | ||
t ½ (h) | 4.5 (1.5) | 4.8 (1.0) | 6.0 (1.3) | ||
Liver (N=17) | N | NA | 9 | 6 | 2 |
AUC 0-24h (mcg∙h/mL) | 69.9 (37.0) | 59.4 (8.1) | 35.4 (2.8) | ||
C max (mcg/mL) | 11.9 (3.7) | 9.5 (2.3) | 5.5 (1.1) | ||
t ½ (h) | 2.8 (1.5) | 3.8 (0.7) | 4.4 (0.2) | ||
N=number of patients; NA=not applicable |
Pharmacokinetics in Geriatric Patients: The pharmacokinetic characteristics of valganciclovir in elderly patients have not been established.
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 valganciclovir [ 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.
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%) |
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%) |
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