Pharmacokinetics of a New, Once-Daily, Sustained-Release Pregabalin Tablet in Healthy Male Volunteers

PURPOSE

A new sustained-release (SR) pregabalin formulation (YHD1119) designed for once-daily dosing has recently been developed to improve patient adherence. This study aimed to compare the pharmacokinetics of pregabalin SR and immediate-release (IR) formulations after multiple oral doses and to assess the effect of food on the pharmacokinetic profile of the pregabalin SR formulation after a single dose in healthy individuals.

METHODS

Two clinical trials were conducted: a randomized, open-label, multiple-dose, 2-treatment, 2-period crossover study to evaluate the steady-state pharmacokinetic properties of SR treatment (pregabalin SR 300 mg once daily for 3 days) and IR treatment (pregabalin IR 150 mg twice daily for 3 days) under fed conditions and a randomized, open-label, single-dose, 2-treatment, 2-period, crossover study to evaluate the effect of food intake on the pharmacokinetic properties of the pregabalin SR formulation. Plasma concentrations of pregabalin were measured using LC-MS/MS. The AUC and C_max for pregabalin were calculated using noncompartmental method and compared between treatments in each study.

FINDINGS

Thirty-one individuals in the bioequivalence study and 23 in the food effect study completed the pharmacokinetic sampling. The geometric mean ratios of C_max,ss and AUC_0-τ between the SR and IR formulations were 1.1642 (90% CI, 1.1043-1.2272) and 0.9704 (90% CI, 0.9372-1.0047), respectively. The geometric mean ratios of C_max and AUC_0-last between the SR formulation in the fed state and in the fasted state were 1.6514 (90% CI, 1.3820-1.9732) and 1.7899 (90%CI, 1.4499-2.2097), respectively.

IMPLICATIONS

The bioavailability of the pregabalin SR 300 mg formulation is increased if taken with a high-fat meal. Once-daily pregabalin SR 300 mg is bioequivalent to twice-daily pregabalin IR 150 mg under fed conditions at steady state. The pregabalin SR formulation is expected to improve patient adherence. ClinicalTrials.gov identifiers: NCT02783183 (bioequivalence study) and NCT03191136 (food effect study).

Outside-in regulation of the readily releasable pool of synaptic vesicles by α2δ-1

The readily releasable pool (RRP) of synaptic vesicles is a key determinant of phasic neurotransmission. Although the size of the RRP is tightly regulated by intracellular factors, there is little evidence for its modification by extracellular signals. By studying the homogeneous population of synapses present in autaptic microcultures, we show that pregabalin, a prototypical gabapentinoid, decreases the effective RRP size. Simultaneous imaging of presynaptic calcium influx and recording of postsynaptic responses shows that the effect is not related to a reduction of calcium entry. The main cause is the impairment of the functional coupling among N-type calcium channels and the RRP, resembling an increase of intracellular mobile calcium buffers. The ectodomain of neurexin-1α shows a similar action to pregabalin, acting as an endogenous ligand of α2δ-1 that reduces the RRP size without affecting presynaptic calcium influx. The regulatory actions described for pregabalin and the ectodomain of neurexin-1α are mutually exclusive. The overexpression of α2δ-1 enhances the effect of pregabalin and the ectodomain of neurexin-1α on neurotransmission by decreasing their effective concentration. In contrast, knockdown of α2δ-1 causes a profound inhibition of synaptic transmission. These observations prompt to consider α2δ-1 as an outside-in signaling platform that binds exogenous and endogenous cues for regulating the coupling of voltage-gated calcium channels to synaptic vesicles.

The firing frequency of spontaneous action potentials and their corresponding evoked exocytosis are increased in chromaffin cells of CCl4 -induced cirrhotic rats with respect to control rats

High catecolamine plasma levels because of sympathetic nervous system over-activity contribute to cirrhosis progression. The aim of this study was to investigate whether chromaffin cells of the adrenal gland might potentiate the deleterious effect exerted by this over-activity. Electrophysiological patch-clamp and amperometric experiments with carbon-fibre electrodes were conducted in single chromaffin cells of control and CCl₄ -induced cirrhotic rats. The spontaneous action potential firing frequency was increased in chromaffin cells of cirrhotic rats with respect to control rats. The exocytosis evoked by that firing was also increased. However, exocytosis elicited by ACh did not vary between control and cirrhotic rats. Exocytosis triggered by depolarizing pulses was also unchanged. Amperometric recordings confirmed the lack of increased catecholamine charge released in cirrhosis after ACh or depolarization stimuli. However, the amperometric spikes exhibited faster kinetics of release. The overall Ca²⁺ entry through voltage-dependent Ca²⁺ channels (VDCC), or in particular through Cav1 channels, did not vary between chromaffin cells of control and cirrhotic rats. The inhibition of VDCC by methionine-enkephaline or ATP was not either altered, but it was increased by adrenaline in cells of cirrhotic rats. When a cocktail composed by the three neurotransmitters was tested in order to approach a situation closer to the physiological condition, the inhibition of VDCC was similar between both types of cells. In summary, chromaffin cells of the adrenal gland might contribute to exacerbate the sympathetic nervous system over-activity in cirrhosis because of an increased exocytosis elicited by an enhanced spontaneous electrical activity.

Human native Cav1 channels in chromaffin cells: contribution to exocytosis and firing of spontaneous action potentials

The present study was performed to evaluate the Ca_v1 channel subtypes expressed in human chromaffin cells and the role that these channels play in exocytosis and cell excitability. Here we show that human chromaffin cells obtained from organ donors express Ca_v1.2 and Ca_v1.3 subtypes using molecular and pharmacological techniques. Immunocytochemical data demonstrated the presence of Ca_v1.2 and Ca_v1.3 subtypes, but not Ca_v1.1 or Ca_v1.4. Electrophysiological experiments were conducted to investigate the contribution of Ca_v1 channels to the exocytotic process and cell excitability. Ca_v1 channels contribute to the exocytosis of secretory vesicles, evidenced by the block of 3μM nifedipine (36.5±2%) of membrane capacitance increment elicited by 200ms depolarizing pulses. These channels show a minor contribution to the initiation of spontaneous action potential firing, as shown by the 2.5 pA of current at the threshold potential (-34mV), which elicits 10.4mV of potential increment. In addition, we found that only 8% of human chromaffin cells exhibit spontaneous action potentials. These data offer novel information regarding human chromaffin cells and the role of human native Ca_v1 channels in exocytosis and cell excitability.