Development of a Novel Controlled-Release Tablet of Pregabalin: Formulation Variation and Pharmacokinetics in Dogs and Humans

Background

Novel three-layered (TL) tablet systems were compared with both monolithic matrix (MM) formulations and a commercial immediate-release (IR) capsule to develop once-a-day (OAD) pregabalin tablets.

Methods

The physical properties of the TL tablets, including dissolution and swelling rates, were compared with those of the MM tablets and the pharmacokinetic parameters of the TL tablet were compared with those of an IR capsule in beagles and humans.

Results

Our results indicated that the same amount of a hydrophilic polymer in the formulations had similar dissolution profiles at 12 h, regardless of the tablet geometry. However, the degree of tablet swelling differed, with larger amounts of polymer in the tablets showing a greater degree of swelling. In addition, TL tablets swelled more rapidly compared with MM tablets. For the pharmacokinetic study of the TL tablet, the beagles demonstrated absorption results similar to those of an IR capsule, whereas the humans demonstrated low total absorption compared with an IR capsule. The time of the peak plasma concentration at 6 h in the fed state of humans coincided with the results of the study on beagles.

Conclusion

The novel TL tablet system of pregabalin may prove to be helpful in developing improved formulations with better continuous drug absorption for OAD administration.

Comparative Pharmacokinetics of a Controlled-release Pregabalin Tablet (GLA5PR GLARS-NF1) and an Immediate-release Pregabalin Capsule in Healthy Male Volunteers

PURPOSE

Pregabalin is a widely used drug for the management of neuropathic pain. This study compared the pharmacokinetics of the GLA5PR GLARS-NF1 tablet, a 150-mg controlled-release formulation of pregabalin taken once daily, with those of a 75-mg immediate-release (IR) capsule formulation of pregabalin taken twice daily with a 12-h interval between doses.

METHODS

Two separate studies, single dose and multiple dose, were conducted with a sequence-randomized, open-label crossover design. In the single-dose study, 30 participants each received 3 treatments: two 75-mg IR capsules taken 12 h apart, each after a high-fat meal (SRF treatment); a single 150-mg GLA5PR GLARS-NF1 tablet taken after a high-fat meal (STF treatment); and a single 150-mg GLAR5PR GLARS-NF1 tablet taken in an overnight-fasted state (ST treatment). In the multiple-dose study, 24 participants each received 2 treatments, both of which occurred over 3 days: one 75-mg IR capsule in the evening after a standardized meal and a second 75-mg IR capsule the following morning after a standardized meal, for 3 days (MRF treatment); and a single 150-mg GLA5PR GLARS-NF1 tablet in the evening after a standardized meal, for 3 days (MTF treatment). Blood samples for pharmacokinetic assessments were collected over the 36 h following drug administration in each treatment period.

FINDINGS

In the single-dose study, the geometric mean ratios (GMRs) of the Cmax and the AUC_last values of the GLA5PR GLARS-NF1 tablet to those of the IR capsules (STF/SRF) were 1.047 (90% CI, 0.971-1.129) and 0.757 (90% CI, 0.694-0.826), respectively. In the multiple-dose study, the GMRs (MTF/MRF) of the Cmax and the AUC values over the dosing interval were 1.277 (90% CI, 1.210-1.348) and 0.974 (90% CI, 0.933-1.017), respectively. The systemic pregabalin exposure from the GLA5PR GLARS-NF1 tablet was higher in the fed state than in the fasted state; GMRs (STF/ST): C_max, 1.458 (90% CI, 1.353-1.573) and AUC_last, 1.655 (90% CI, 1.518-1.804).

IMPLICATIONS

The overall pregabalin exposure after multiple administrations of GLA5PR GLARS-NF1 tablets was comparable to that after multiple administrations of the IR capsules. A single administration of the GLA5PR GLARS-NF1 tablet produced lower overall pregabalin exposure than that of the same dose administered in 2 IR capsules taken every 12 h. A high-fat diet significantly increased the bioavailability of the GLA5PR GLARS-NF1 tablet. ClinicalTrials.gov identifiers: NCT01638273 and NCT02326987.

Assessment of bisphenol A exposure in Korean pregnant women by physiologically based pharmacokinetic modeling

The objective of this study was to predict the exposure to bisphenol A (BPA) after oral intake in human blood and tissues using physiologically based pharmacokinetic (PBPK) modeling. A refined PBPK model was developed taking into account of glucuronidation, biliary excretion, and slow absorption of BPA in order to describe the second peak of BPA observed following oral intake. This developed model adequately described the second peak and BPA concentrations in blood and various tissues in rats after oral administration. A prospective validation study in rats additionally supported the proposed model. For extrapolation to humans, a daily oral BPA dose of 0.237 mg/70 kg/d or 0.0034 mg/kg/d was predicted to achieve an average steady-state blood concentration of 0.0055 ng/ml (median blood BPA concentration in Korean pregnant women). This dose was lower than the reference dose (RfD, 0.016 mg/kg/d) and the tolerable daily intake established by the European Commission (10 μg/kg/d). Data indicate that enterohepatic recirculation may be toxicologically important as this pathway may increase exposure and terminal half-life of BPA in humans.

Visualizing and quantifying evoked cortical activity assessed with intrinsic signal imaging

Intrinsic signal imaging (ISI) measures changes in light reflectance from the illuminated cortex (intrinsic signals or IS) attributed to various vascular and metabolic sources that, when using illumination in the 600 nm range, appear to co-localize with neuronal activity. Given the multiple sources contributing to the collected IS, the common practice of averaging across an extended post-stimulus time epoch before dividing by baseline data typically visualizes evoked IS overlying both the cortical tissue and the large surface blood vessels. In rat PMBSF, the contribution from these vessels are problematic as they do not co-localize with known PMBSF function. Determining a means for quantifying the evoked IS area poses an additional challenge. Here, we describe how exploiting IS collected shortly after stimulus onset (within 1.5 s), which coincides with fast oxygen consumption of active neurons, visualizes evoked IS overlying the cortical tissue without the large surface vessels. We also describe how the use of absolute thresholds combined with a baseline determined from data collected immediately prior to stimulus onset (within 1 s) targets most precisely a specific evoked IS amplitude, a method that should be especially useful when evoked areas are expected to occupy a substantial portion of the total imaged area and/or when peak activity is expected to differ between subjects.

Areal extent quantification of functional representations using intrinsic signal optical imaging

An important parameter often investigated in the characterization of cortical functional organization is the areal extent of functional modules. Because it allows the visualization of functional modules with high spatial resolution in a noninvasive way to the cortex, intrinsic signal optical imaging (ISI) can be employed for the quantification of these areal extents. The present paper describes the use of the normalized threshold analysis of areal extent quantification for the objective assessment of single-whisker functional representations in the primary somatosensory cortex of adult rats. As the success of areal extent quantification depends on the ability of ISI to allow visualization of cortical representations with minimal stimulus-dependent blood vessel representations, which are commonly encountered by ISI, the present paper also describes the further development of the intratrial analysis of visualization for minimizing these vessel representations. Both analyses are discussed with respect to their advantages as well as their inherent limitations.

Suprathreshold auditory cortex activation visualized by intrinsic signal optical imaging

The suprathreshold tonotopic organization of rat and guinea pig auditory cortex was investigated using intrinsic signal optical imaging through a thinned skull. Optical imaging revealed that suprathreshold pure sine wave tone stimulation (25-80 dB) evoked activity over large cortical areas that were tonotopically organized. Three-dimensional surface plots of the activated areas revealed "patchy' auditory-evoked activity consisting of numerous local peaks and valleys building to a maximum. Subsequent detailed electrophysiological mapping in the same subjects confirmed the localization of auditory-evoked activity based on optical imaging, including responses to a test frequency at cortical loci more than 2 octaves away from the threshold-defined isofrequency contour. The success of this technique in visualizing auditory cortex functional organization at suprathreshold stimulus levels will allow for future investigations of auditory cortex frequency representation, including representational plasticity induced by a variety of experimental manipulations.

Characterization of functional organization within rat barrel cortex using intrinsic signal optical imaging through a thinned skull

We used optical imaging of intrinsic signals to characterize the functional representations of mystacial vibrissae (whiskers) in rat somatosensory cortex. Stimulation of individual whiskers for 2 s at 5 Hz resulted in a discrete area of functional activity in the cortex. Images of whisker representations were collected both through the dura and through a thinned skull. We characterized the functional representation of a whisker both spatially and temporally with two-dimensional images and three-dimensional surface plots of intrinsic signal development in the cortex in response to whisker stimulation. Single unit recordings verified that the representation of the whisker obtained with optical imaging corresponded with the electrophysiological response area of that whisker in the cortex. Lesions in the center of the functional activity were found to be in the center of the dense cytochrome oxidase patch for the corresponding whisker. In addition, a 3 x 3 matrix of whiskers was stimulated and the distances between the centers of the imaged representations and the distances between the centers of the layer IV cytochrome oxidase staining of the nine whiskers were found to be highly correlated (r = 0.98). This study shows a striking correspondence among imaging, physiology, and anatomy in the rat somatosensory cortex. Furthermore, the ability to use optical imaging through a thinned skull should allow investigations into the long-term changes in a sensory representation within a single animal.