The pharmacokinetics of total gadolinium assessed up to 48 hours following an intravenously administered 0.1 mmol/kg dose of DOTAREM in healthy adult subjects demonstrated a mean elimination half-life (reported as mean ± SD) of about 1.4 ± 0.2 hr and 2.0 ± 0.7 hr in female and male subjects, respectively. Similar pharmacokinetic profile and elimination half-life values were observed after intravenous injection of 0.1 mmol/kg of DOTAREM followed 20 minutes later by a second injection of 0.2 mmol/kg (1.7 ± 0.3 hr and 1.9 ± 0.2 hr in female and male subjects, respectively).
Distribution
The volume of distribution at steady state of total gadolinium in healthy subjects is 179 ± 26 and 211 ± 35 mL/kg in female and male subjects respectively, roughly equivalent to that of extracellular water.
Gadoterate does not undergo protein binding in vitro. The extent of blood cell partitioning of gadoterate is not known.
Metabolism
Gadoterate is not known to be metabolized.
Elimination
Following a 0.1 mmol/kg dose of DOTAREM, total gadolinium is excreted primarily in the urine with 72.9 ± 17.0 % and 85.4 ± 9.7 % (mean ± SD) eliminated within 48 hours, in female and male subjects, respectively. Similar values were achieved after a cumulative dose of 0.3 mmol/kg (0.1 + 0.2 mmol/kg, 20 minutes later), with 85.5 ± 13.2 % and 92.0 ± 12.0 % recovered in urine within 48 hrs in female and male subjects respectively.
In healthy subjects, the renal and total clearance rates of total gadolinium are comparable (1.27 ± 0.32 and 1.74 ± 0.12 mL/min/kg in females; and 1.40 ± 0.31 and 1.64 ± 0.35 mL/min/kg in males, respectively) indicating that the drug is primarily cleared through the kidneys. Within the studied dose range (0.1 to 0.3 mmol/kg), the kinetics of total gadolinium appear to be linear.
Special Populations
Renal Impairment
A single intravenous dose of 0.1 mmol/kg of DOTAREM was administered to 8 patients (5 men and 3 women) with impaired renal function (mean serum creatinine of 498 ± 98 µmol/L in the 10-30 mL/min creatinine clearance group and 192 ± 62 µmol/L in the 30-60 mL/min creatinine clearance group). Renal impairment delayed the elimination of total gadolinium. Total clearance decreased as a function of the degree of renal impairment. The distribution volume was unaffected by the severity of renal impairment (Table 5). No changes in renal function test parameters were observed after DOTAREM injection. The mean cumulative urinary excretion of total gadolinium was approximately 76.9 ± 4.5% in 48 hrs in patients with moderate renal impairment, 68.4 ± 3.5% in 72 hrs in patients with severe renal impairment and 93.3 ± 4.7% in 24 hrs for subjects with normal renal function.
Table 5: Pharmacokinetic Profile of Total Gadolinium in Normal and Renally Impaired PatientsPopulation | Elimination Half-life (hr) | Plasma Clearance (L/h/kg) | Distribution Volume (L/kg) |
Healthy volunteers | 1.6 ± 0.2 | 0.10 ± 0.01 | 0.246 ± 0.03 |
Patients with moderate renal impairment | 5.1 ± 1.0 | 0.036 ± 0.007 | 0.236 ± 0.01 |
Patients with severe renal impairment | 13.9 ± 1.2 | 0.012 ± 0.001 | 0.234 ± 0.01 |
Gadoterate was shown to be dialyzable after an IV injection of DOTAREM in 10 patients with end-stage renal failure who required hemodialysis treatment. Gd serum concentration decreased over time by 88%, 93% and 97% at 0.5 hr, 1.5 hr, and 4 hrs after start of dialysis, respectively. A second and third hemodialysis session further removed Gd. After the third dialysis, Gd serum concentration decreased by 99.7%.
Pediatric population
The pharmacokinetics of gadoterate in pediatric patients receiving DOTAREM aged birth (term neonates) to 23 months, was investigated in an open label, multicenter study, using a population pharmacokinetics approach. A total of 45 subjects (22 males, 23 females) received a single intravenous dose of DOTAREM 0.1 mmol/kg (0.2 mL/kg). The age ranged from less than one week to 23.8 months (mean 9.9 months) and body weight ranged from 3 to 15 kg (mean 8.1 kg). Individual level of renal maturity in the study population, as expressed by eGFR ranged between 52 and 281 mL/min/1.73 m2 and 11 patients had an eGFR below 100 mL/min/1.73 m2 (range 52 to 95 mL/min/1.73 m2).
Gadoterate concentrations obtained up to 8 hours after DOTAREM administration were best fitted using a biphasic model with linear elimination from the intravascular space. The mean clearance adjusted to body weight was estimated at 0.16 ± 0.07 L/h/kg and increased with eGFR. The estimated mean elimination half-life was 1.47 ± 0.45 hr.
The body weight adjusted clearance of gadoterate after single intravenous injection of 0.1 mmol/kg of DOTAREM in pediatric subjects aged less than 2 years was similar to that observed in healthy adults.