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OptiMARK

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OptiMARK

CLINICAL PHARMACOLOGY

Mechanism Of Action

Gadoversetamide is a paramagnetic agent that develops a magnetic moment when placed in a magnetic field. The relatively large magnetic moment can enhance the relaxation rates of water protons in its vicinity, leading to an increase in signal intensity (brightness) of tissues.

Pharmacodynamics

In MRI, visualization of normal and pathological brain, spinal and hepatic tissue depends in part on variations in the radiofrequency signal intensity that occurs with: 1) changes in proton density; 2) alterations of the spin-lattice or longitudinal relaxation time (T1); and 3) variation of the spin-spin or transverse relaxation time (T2). When placed in a magnetic field, gadoversetamide decreases T1 and T2 relaxation times in tissues where it accumulates. At the recommended dose, the effect is primarily on T1 relaxation time, and produces an increase in signal intensity (brightness).

Pharmacokinetics

The pharmacokinetics of intravenously administered gadoversetamide in normal subjects conforms to a two-compartment open-model with mean distribution and elimination half-lives (reported as mean ± SD) of about 13.3 ± 6.8 and 103.6 ± 19.5 minutes.

Distribution

Gadoversetamide does not undergo protein binding in vitro. In pregnant and lactating rats which received 153Gd-labeled gadoversetamide, radioactivity was detected in the placenta, fetus, and maternal milk. The volume of distribution at steady state of gadoversetamide in normal subjects is 162 ± 25 mL/kg, roughly equivalent to that of extracellular water.

Gadoversetamide does not cross the intact blood-brain barrier, and, therefore, does not accumulate in the normal brain or in lesions that may have a normal blood-brain barrier. However, disruption of the blood-brain barrier or abnormal vascularity allows accumulation of gadoversetamide in the extravascular spaces of lesions. The pharmacokinetic parameters of gadoversetamide in various lesions are not known.

Metabolism

Gadoversetamide is not metabolized.

Elimination Gadoversetamide (0.1 mmol/kg) is eliminated primarily in the urine with 95.5 ± 17.4% (mean ± SD) of the administered dose eliminated by 24 hours. Animal data demonstrated that insignificant levels of 153Gd-labeled gadoversetamide are eliminated via the feces. In experimentally induced anephria in the rat, hepatobiliary excretion did not significantly compensate for the absence of urinary elimination. The renal and plasma clearance rates of gadoversetamide in normal subjects are similar (69 ± 15.4 and 72 ± 16.3 mL/hr/kg, respectively) indicating that the drug is cleared through the kidneys via glomerular filtration. Within the studied dose range (0.1 to 0.7 mmol/kg), the kinetics of gadoversetamide appear to be linear. Gadoversetamide is removed from the body by hemodialysis. Approximately 98% of the administered dose (0.1 mmol/kg) was cleared from the circulation over the three dialysis sessions that occurred 2 hours, 48 hours, and 120 hours after injection. After each of three dialysis sessions, respectively, 70%, 93%, and 98% of the administered dose was cleared from the plasma. The mean dialysis clearance of gadoversetamide was 93.2 ± 17.1 mL/min, or 48% of the creatinine clearance (194 ± 18.6 mL/min), using a high flux PMMA membrane.

Clinical Studies

OptiMARK was evaluated in 4 controlled clinical trials (two liver and two CNS studies). Out of 461 patients who received OptiMARK, there were 252 men and 209 women with a mean age of 49 years (range 12 to 82 years); 83% were Caucasian, 9% Black, 3% Asian, and 5% other racial or ethnic groups. The trials were designed to compare combined non-contrast and OptiMARK 0.1 mmol/kg contrast MR images to non-contrast MR images, based on pre-specified imaging characteristics (endpoints).

In the two CNS studies, MR images were analyzed from 262 patients who were highly suspect for CNS disorders and received OptiMARK. Pre-contrast and pre-plus-post-contrast (combined) images were independently evaluated by three blinded readers (each reader examined approximately 1/3 of the images). The images were evaluated by the blinded readers for the following endpoints using a scale from 1 to 10: the level of conspicuity of all lesions, the ability to delineate lesion borders from parenchyma/structures, the number of lesions, and the confidence in the number of lesions. As shown in Table 5, the first row of each endpoint group represents the difference in the mean score of the combined pre-and post-contrast MRI from the mean score of the pre-contrast MRI alone. Also, the table shows the number of patients whose paired MRI images were better, worse or the same as the pre-contrast MRI. Results from the contrast image alone were not evaluated. In Table 5 for these endpoints, when read in combination with the non-contrast images, OptiMARK provided a statistically significant improvement over baseline. In addition to these measures, the images were evaluated for the blinded reader's confidence in the diagnosis. Although improvement over baseline was noted, the diagnosis was not rigorously confirmed.

Table 5 :Results of MRI Central Nervous System Studies with 0.1 mmol/kg OptiMARK

Endpoints Study A Study B
OptiMARK
N = 132†
OptiMARK
N = 129
Conspicuity: Difference of Meansa 0.39* 0.66*
  Worse 24 (18%) 24 (19%)
  Same 69 (52%) 52 (40%)
  Better 39 (30%) 53 (41%)
Border Delineation: Difference of Means 0.70* 0.86*
  Worse 23 (17%) 25 (19%)
  Same 55 (42%) 51 (40%)
  Better 54 (41%) 53 (41%)
Number of Lesions: Difference of Means
  Pre 1.8 3.0
  Pairb 2.0◊ 3.3*
  Worse 9 (7%) 16 (12%)
  Same 101 (77%) 86 (67%)
  Better 22 (16%) 27 (21%)
Confidence in Number of Lesions: Difference of Means 0.11* 0.56*
  Worse 19 (14%) 18 (14%)
  Same 86 (65%) 60 (47%)
  Better 27 (20%) 51 (40%)
a Difference of means = (Side-by-side pre-and post-OptiMARK mean) -(pre-mean)
b Pair = Side-by-side pre-and post-OptiMARK
* Statistically significant for both the median (Wilcoxon test) and mean (paired t test)
◊ Statistically significant for median (Wilcoxon test)
† 1 patient was excluded from this analysis because a non-contrast image was not obtained for that patient

In the two liver studies, MR images were analyzed from 199 patients with a suspected liver abnormality on a contrast CT who received OptiMARK. Patients had both pre-contrast and post-contrast MRI scans covering the entire liver. In each study, the images were read by 3 blinded readers (each reader examined approximately 1/3 of the images). Using a scale of 1 to 10, the images were evaluated by the blinded readers for the level of conspicuity of all lesions, the ability to delineate lesion borders from parenchyma/structures, the number of lesions and confidence in the number of lesions. The results are shown in Table 6. The first row of each endpoint group represents the difference in the mean score of the combined pre-and post-contrast MRI from the mean score of the pre-contrast MRI alone. Also, the table shows the number of patients whose paired MRI images were better, worse or the same as the pre-contrast MRI. Results from the contrast image alone were not evaluated. As shown in Table 6 for these endpoints, when read in combination with the non-contrast image, OptiMARK provided a statistically significant improvement over non-contrast images. In addition to these measures, the images were evaluated for the blinded reader's confidence in the diagnosis. Although improvement over baseline was noted, the trial was not designed to rigorously confirm the diagnosis.

Table 6 : Results of MRI Liver Studies with 0.1 mmol/kg OptiMARK

Endpoints Study C Study D
OptiMARK
N = 99
OptiMARK
N = 100
Conspicuity:    
Difference of Meansa 0.77 0.75
  Worse 21 (21%) 14 (14%)
  Same 37 (37%) 50 (50%)
  Better 41 (41%) 36 (36%)
Border Delineation:    
Difference of Means 0.77 0.69
  Worse 21 (21%) 15 (15%)
  Same 38 (38%) 45 (45%)
  Better 40 (40%) 40 (40%)
Number of Lesions: Difference of Means    
  Pre 2.4 3.5
  Pairb 3.0 3.8t
  Worse 13 (13%) 16 (16%)
  Same 50 (51%) 58 (58%)
  Better 36 (36%) 26 (26%)
Confidence in Number of Lesions: Difference    
  of Means 1.6 1.0
  Worse 39 (39%) 38 (38%)
  Same 2 (2%) 8 (8%)
  Better 58 (59%) 54 (54%)
a Difference of means = (Side-by-side pre-and post-OptiMARK mean) -(pre-mean)
b Pair = Side-by-side pre-and post-OptiMARK
* Statistically significant for both the median (Wilcoxon test) and mean (paired t test)
† Borderline statistical significance in paired t test

A subsequent study of 140 normal volunteers evaluated the safety of OptiMARK 0.1 mmol/kg delivered by power injector. Imaging results were not studied. The normal volunteers were randomized to receive OptiMARK injected manually, or OptiMARK or saline injected at 3 different power injector rates. At 2 mL/sec, the adverse event rates were comparable in the OptiMARK and saline controls when delivered manually and by power injector. In these small sample sizes, there was a trend towards increasing adverse events with increasing rates of power injection. Patients with abnormal vascularity were not evaluated. The safety and efficacy of power injector rates higher than 2 mL/sec has not been established.

Last reviewed on RxList: 12/15/2014
This monograph has been modified to include the generic and brand name in many instances.

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