Risk Summary
GBCAs cross the placenta and result in fetal exposure and gadolinium retention. The human data on the association between GBCAs and adverse fetal outcomes are limited and inconclusive (see Data). In animal reproduction studies, although teratogenicity was not observed, embryolethality was observed in monkeys, rabbits and rats receiving intravenous gadobutrol during organogenesis at doses 8 times and above the recommended human dose. Retardation of embryonal development was observed in rabbits and rats receiving intravenous gadobutrol during organogenesis at doses 8 and 12 times, respectively, the recommended human dose (see Data). Because of the potential risks of gadolinium to the fetus, use gadobutrol only if imaging is essential during pregnancy and cannot be delayed.
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and is 15% to 20%, respectively.
Data
Human Data.
Contrast enhancement is visualized in the placenta and fetal tissues after maternal GBCA administration.
Cohort studies and case reports on exposure to GBCAs during pregnancy have not reported a clear association between GBCAs and adverse effects in the exposed neonates. However, a retrospective cohort study, comparing pregnant women who had a GBCA MRI to pregnant women who did not have an MRI, reported a higher occurrence of stillbirths and neonatal deaths in the group receiving GBCA MRI. Limitations of this study include a lack of comparison with non-contrast MRI and lack of information about the maternal indication for MRI. Overall, these data preclude a reliable evaluation of the potential risk of adverse fetal outcomes with the use of GBCAs in pregnancy.
Animal Data
Gadolinium Retention
GBCAs administered to pregnant non-human primates (0.1 mmol/kg on gestational days 85 and 135) result in measurable gadolinium concentration in the offspring in bone, brain, skin, liver, kidney, and spleen for at least 7 months. GBCAs administered to pregnant mice (2 mmol/kg daily on gestational days 16 through 19) result in measurable gadolinium concentrations in the pups in bone, brain, kidney, liver, blood, muscle, and spleen at one month postnatal age.
Reproductive Toxicology
Embryolethality was observed when gadobutrol was administered intravenously to monkeys during organogenesis at doses 8 times the recommended single human dose (based on body surface area); gadobutrol was not maternally toxic or teratogenic at this dose. Embryolethality and retardation of embryonal development also occurred in pregnant rats receiving maternally toxic doses of gadobutrol (≥ 7.5 mmol/kg body weight; equivalent to 12 times the human dose based on body surface area) and in pregnant rabbits (≥ 2.5 mmol/kg body weight; equivalent to 8 times the recommended human dose based on body surface area). In rabbits, this finding occurred without evidence of pronounced maternal toxicity and with minimal placental transfer (0.01% of the administered dose detected in the fetuses).
Because pregnant animals received repeated daily doses of gadobutrol, their overall exposure was significantly higher than that achieved with the standard single dose administered to humans.
Risk Summary
There are no data on the presence of gadobutrol in human milk, the effects on the breastfed infant, or the effects on milk production. However, published lactation data on other GBCAs indicate that 0.01% to 0.04% of the maternal gadolinium dose is present in breast milk and there is limited GBCA gastrointestinal absorption in the breast-fed infant. Gadobutrol is present in rat milk (see Data). The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for gadobutrol and any potential adverse effects on the breastfed infant from gadobutrol or from the underlying maternal condition.
Data
In lactating rats receiving 0.5 mmol/kg of intravenous [153Gd]-gadobutrol, 0.01% of the total administered radioactivity was transferred to the pup via maternal milk within 3 hours after administration, and the gastrointestinal absorption is poor (approximately 5% of the dose orally administered was excreted in the urine).
NSF Risk
No case of NSF associated with gadobutrol or any other GBCA has been identified in pediatric patients ages 6 years and younger. Pharmacokinetic studies suggest that clearance of gadobutrol is similar in pediatric patients and adults, including pediatric patients age younger than 2 years. No increased risk factor for NSF has been identified in juvenile animal studies of gadobutrol. Normal estimated GFR (eGFR) is around 30 mL/min/1.73m2 at birth and increases to mature levels around 1 year of age, reflecting growth in both glomerular function and relative body surface area. Clinical studies in pediatric patients younger than 1 year of age have been conducted in patients with the following minimum eGFR: 31 mL/min/1.73m2 (age 2 to 7 days), 38 mL/min/1.73m2 (age 8 to 28 days), 62 mL/min/1.73m2 (age 1 to 6 months), and 83 mL/min/1.73m2 (age 6 to 12 months).
Juvenile Animal Data
Single and repeat-dose toxicity studies in neonatal and juvenile rats did not reveal findings suggestive of a specific risk for use in pediatric patients including term neonates and infants.
Distribution
After intravenous administration, gadobutrol is rapidly distributed in the extracellular space. After a gadobutrol dose of 0.1 mmol/kg body weight, an average level of 0.59 mmol gadobutrol/L was measured in plasma 2 minutes after the injection and 0.3 mmol gadobutrol/L 60 minutes after the injection. Gadobutrol does not display any particular protein binding. Following GBCA administration, gadolinium is present for months or years in brain, bone, skin, and other organs [see Warnings and Precautions (5.3)].
Metabolism
Gadobutrol is not metabolized.
Elimination
Values for AUC, body weight normalized plasma clearance and half-life are given in Table 4, below.
Gadobutrol is excreted in an unchanged form via the kidneys. In healthy subjects, renal clearance of gadobutrol is 1.1 to 1.7 mL/(min∙kg) and thus comparable to the renal clearance of inulin, confirming that gadobutrol is eliminated by glomerular filtration.
Within two hours after intravenous administration more than 50% and within 12 hours more than 90% of the given dose is eliminated via the urine. Extra-renal elimination is negligible.
Specific Populations
Gender
Gender has no clinically relevant effect on the pharmacokinetics of gadobutrol.
Geriatric
A single intravenous dose of 0.1 mmol/kg gadobutrol was administered to 15 elderly and 16 non-elderly subjects. AUC was slightly higher and clearance slightly lower in elderly subjects as compared to non-elderly subjects [see Use in Specific Populations (8.5)].
Pediatric
The pharmacokinetics of gadobutrol were evaluated in two studies in a total of 130 patients age 2 to less than 18 years and in 43 patients less than 2 years of age (including term neonates). Patients received a single intravenous dose of 0.1 mmol/kg of gadobutrol. The pharmacokinetic profile of gadobutrol in pediatric patients is similar to that in adults, resulting in similar values for AUC, body weight normalized plasma clearance, as well as elimination half-life. Approximately 99% (median value) of the dose was recovered in urine within 6 hours (this information was derived from the 2 to less than 18 year old age group).
Table 4: Pharmacokinetics by Age Group (Median [Range])
| 0 to < 2 years N=43 | 2 to 6 years N=45 | 7 to 11 years N=39 | 12 to < 18 years N=46 | Adults N=93 |
| AUC (μmolxh/L)
| 781 [513, 1891]
| 846 [412, 1331]
| 1025 [623, 2285]
| 1237 [946, 2211]
| 1072 [667, 1992]
|
| CL (L/h/kg)
| 0.128 [0.053, 0.195]
| 0.119 [0.08, 0.215]
| 0.099 [0.043, 0.165]
| 0.081 [0.046, 0.103]
| 0.094 [0.051, 0.15]
|
| t1/2 (h)
| 2.91 [1.6, 12.4]
| 1.91 [1.04, 2.7]
| 1.66 [0.91, 2.71]
| 1.68 [1.31, 2.48]
| 1.8 [1.2, 6.55]
|
| C20 (μmol/L)
| 367 [280, 427]
| 421 [369, 673]
| 462 [392, 760]
| 511 [387, 1077]
| 441 [281, 829]
|
Renal Impairment
In patients with impaired renal function, the serum half-life of gadobutrol is prolonged and correlated with the reduction in creatinine clearance.
After intravenous injection of 0.1 mmol gadobutrol/kg body weight, the elimination half-life was 5.8 ± 2.4 hours in mild to moderately impaired patients (80 > CLCR > 30 mL/min) and 17.6 ± 6.2 hours in severely impaired patients not on dialysis (CLCR< 30 mL/min). The mean AUC of gadobutrol in patients with normal renal function was 1.1 ± 0.1 mmol∙h/L, compared to 4 ± 1.8 mmol∙h/L in patients with mild to moderate renal impairment and 11.5 ± 4.3 mmol∙h/L in patients with severe renal impairment.
Complete recovery in the urine was seen in patients with mild or moderate renal impairment within 72 hours. In patients with severely impaired renal function about 80% of the administered dose was recovered in the urine within 5 days. For patients receiving hemodialysis, physicians may consider the prompt initiation of hemodialysis following the administration of gadobutrol in order to enhance the contrast agent's elimination. Sixty-eight percent (68%) of gadobutrol is removed from the body after the first dialysis, 94% after the second dialysis, and 98% after the third dialysis session. [See Warnings and Precautions (5.1) and Use in Specific Populations (8.6).]
Pediatric Patients
Two studies in 44 pediatric patients age younger than 2 years and 135 pediatric patients age 2 to less than 18 years with CNS and non-CNS lesions supported extrapolation of adult CNS efficacy findings. For example, comparing pre vs paired pre- and post-contrast images, investigators selected the best of four descriptors under the heading, “Visualization of lesion-internal morphology (lesion characterization) or homogeneity of vessel enhancement” for 27/44 (62% = pre) vs 43/44 (98% = paired) MR images from patients age 0 to less than 2 years and 106/135 (78% = pre) vs 108/135 (80% = paired) MR images from patients age 2 to less than 18 years.
Measurement Variability
For both MRA and CTA, readers varied in the quantity of narrowing they assigned to the same arterial segments. Table 11 shows the percentage of patients in whom the measurement range was 30% or greater for the left or right internal carotid and proximal renal artery segments. There were approximately four measurements per patient segment, one from the site and three from the central readers. Measurement variability was high for both CTA and MRA, but numerically lower for gadobutrol compared to non-contrast ToF MRA.
Table 11: Percent of Patients with Range ≥ 30%, ≥ 50%, ≥ 70% for Measurement of Stenoses and Normal Vessel Diameters
| Internal Carotid | Proximal Main Renal |
| N | ≥
30% | ≥
50% | ≥
70% | N | ≥
30% | ≥
50% | ≥
70% |
| CTA
| 456
| 40
| 11
| 4
| 292
| 59
| 33
| 9
|
| ToF MRA
| 443
| 55
| 22
| 9
| 270
| 44
| 22
| 9
|
| Gadobutrol MRA
| 454
| 47
| 13
| 4
| 286
| 34
| 14
| 4
|
Visualization of Accessory Renal Arteries for Surgical Planning and Renal Donor Evaluation (Study D only)
Of 1752 main arteries visualized by the central CTA readers, 266 (15%) were also associated with positive visualization of at least one accessory (duplicate) artery. With the central MRA readers, the comparable rates were 232 of 1752 (13%) for gadobutrol MRA compared to 53 of 1752 (3%) for ToF MRA.
Left Mainstem Stenosis (LMS)
The studies did not include sufficient numbers of subjects to characterize the performance of gadobutrol CMRI for detection of LMS, a subgroup at high risk from false negative reads. In Studies E and F, only three subjects had isolated LMS stenosis >50%. In two of the three cases, the CMRI was interpreted as normal by at least two of the three readers (false negative). Sixteen subjects had LMS stenosis >50% (including subjects with isolated LMS stenosis and subjects with LMS stenosis in addition to stenoses elsewhere). In five of these sixteen cases, the CMR was interpreted as normal by at least two of the three readers (false negative).