Gadolinium Clearance in the First 5 Weeks After Repeated Intravenous Administration of Gadoteridol, Gadoterate Meglumine, and Gadobutrol to rats.

BACKGROUND: Studies of gadolinium (Gd) clearance from animals in the first weeks after administration of gadolinium-based contrast agents (GBCAs) have previously looked at solitary timepoints only. However, this does not give information on differences between GBCAs and between organs in terms of Gd elimination kinetics. PURPOSE: To compare Gd levels in rat cerebellum, cerebrum, skin, and blood at 1, 2, 3, and 5 weeks after repeated administration of macrocyclic GBCAs. STUDY TYPE: Prospective. ANIMAL MODEL: One hundred eighty male Sprague-Dawley rats randomized to three groups (n = 60/group), received intravenous administrations of gadoteridol, gadoterate meglumine, or gadobutrol (0.6 mmol/kg for each) four times/week for 5 consecutive weeks. Rats were sacrificed after washout periods of 1, 2, 3, or 5 weeks. FIELD STRENGTH/SEQUENCE: Not applicable. ASSESSMENT: Cerebellum, cerebrum, skin, and blood were harvested for Gd determination by inductively coupled plasma-mass spectrometry (15 animals/group/all timepoints). STATISTICAL TESTS: Anova and Dunnett's test (data with homogeneous variances and normal distribution). Kruskal-Wallis and Wilcoxon's rank sum tests (data showing nonhomogeneous variances or a non-normal distribution, significance levels: P < 0.05, P < 0.01, and P < 0.001). RESULTS: Gd levels in cerebellum, cerebrum, and skin were significantly lower after gadoteridol than after gadoterate and gadobutrol at all timepoints. Mean cerebellum Gd concentrations after gadoteridol, gadoterate, and gadobutrol decreased from 0.693, 0.878, and 1.011 nmol Gd/g at 1 week to 0.144, 0.282, and 0.297 nmol Gd/g at 5 weeks after injection. Similar findings were noted for cerebrum and skin. Conversely, significantly higher Gd levels were noted in blood after gadoteridol compared to gadobutrol at 1, 2, and 3 weeks and compared to gadoterate at all timepoints. DATA CONCLUSION: Gadoteridol is eliminated more rapidly from rat cerebellum, cerebrum, and skin compared to gadoterate and gadobutrol in the first 5 weeks after administration, resulting in lower levels of retained Gd in these tissues. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 5.

Specificities of the Skin Morphology in Juvenile Minipigs.

The Göttingen minipig is recognized by the scientific community and by health authorities as the animal model of choice to evaluate dermally applied drugs under development. Young adults of approximately 4 months of age are most generally chosen to participate in dermal pharmacology and toxicology studies, and recently, minipigs have been proved to be also suitable for juvenile studies. A complete anatomical cartography of the skin morphology of juvenile male and female minipigs from postnatal day 1 (PND1) to twelve weeks of age was performed measuring the thickness of skin layers for each anatomical location and time point. Overall, the neonatal skin of minipigs (PND1 and PND8) shows prominent cellularity, similar to that seen in human neonates, and the morphology of the skin of older animals is considered similar to that of young adult minipigs. Epidermal thickness varies only minimally over the period; whereas, the dermal and more markedly, the subcutaneous thicknesses increase over time.

Non-clinical assessment of safety and gadolinium deposition after cumulative administration of gadobenate dimeglumine (MultiHance®) to neonatal and juvenile rats.

To determine the impact of single and cumulative doses of MultiHance on toxicity, pharmacokinetics, tissue gadolinium presence, behavior and neurological function in juvenile rats. Juvenile male and female rats received either physiological saline or MultiHance at 0.6, 1.25 or 2.5 mmol/kg bodyweight. Animals received either single or six consecutive MultiHance administrations and were sacrificed the day after the last administration or after a 60-day treatment-free period. Animals were assessed for behavior, cognitive function, grip strength, gait, pupillary reflex, and auditory reflex, as well as for physical development, sexual maturation and histopathology. Gadolinium presence in brain, femur, kidneys, liver and skin was determined using inductively coupled plasma-mass spectrometry (ICP-MS). No effects of MultiHance on behavior, cognitive function or any other parameter were noted, even for the highest administered cumulative dose (15 mmol/kg). Gadolinium presence was variable across tissues and decreased during the 60-day treatment-free period. The highest levels were noted in the femur and the lowest levels in the brain. Gadolinium presence in juvenile rat brain following single or repeated MultiHance administrations was minimal and non-impactful.

"All pigs are equal" Does the background data from juvenile Göttingen minipigs support this?

For pediatric indications requiring juvenile toxicity testing, the rat is the preferred species. However, for some drugs it might not be an appropriate model or regulatory agencies may also request a non-rodent species. Due to the relatively recent use of Göttingen minipigs, little background data are available. This shortage of historical data can raise concerns with respect to interpretation, thus potentially discouraging investigators. This article presents background data from 82 piglets collected at different ages. The data described show the normal variations and changes which are important in the interpretations of these studies. Age-related changes were observed for several cardiac and clinical pathology parameters and in the haematopoietic tissues. Therefore, all pigs were not considered equal. It can be concluded that these data can be used as guidance, to support the concurrent study control data but cannot completely replace them.