A pharmacokinetic drug-drug interaction study between pregabalin and tramadol in healthy volunteers.

PURPOSE: Combination therapy of pregabalin and tramadol is used to treat chronic neuropathic pain; however, the pharmacokinetic (PK) interactions of these drugs has not been studied. This study aimed to evaluate PK interactions between pregabalin and tramadol and the safety of combination therapy. METHODS: A randomized, open-label, multiple-dose, three-treatment, three-period, six-sequence cross-over study was conducted in healthy subjects. All subjects received the following three treatments for 4 days in each period: pregabalin 150 mg twice daily; tramadol extended-release (ER) 200 mg in the morning, and 100 mg in the evening; and co-administration of pregabalin 150 mg and tramadol ER 200 mg in the morning, and pregabalin 150 mg and tramadol ER 100 mg in the evening. RESULTS: A total of 21 subjects completed the study with no clinically significant safety issues. For pregabalin, the geometric mean ratio (GMR) (90% CI; confidence interval) of combination therapy to monotherapy for maximum concentration at steady state (Cmax,ss) and area under the concentration curve from 0 to dosing interval time at steady state (AUCτ,ss) were 0.8801 (0.8043-0.9632) and 1.0830 (1.0569-1.1098), respectively. The corresponding values for tramadol were 1.0177 (0.9839-1.0526) and 1.0152 (0.9896-1.0414), respectively. The GMR (90% CI) of combination therapy to monotherapy of O-desmethyl-tramadol for Cmax,ss and AUCτ,ss was 1.0465 (1.0095-1.0848) and 1.0361 (1.0001-1.0734), respectively. CONCLUSIONS: There were no significant drug interactions between pregabalin and tramadol, considering that all of the 90% CI of PK measures were within the conventional bioequivalence range. Both drugs were well tolerated when administered concomitantly.

Determination of mirodenafil and sildenafil in the plasma and corpus cavernous of SD male rats.

The purpose of the present study was to determine sildenafil and a novel PDE-5 inhibitor, mirodenafil in the plasma and corpus cavernosum tissue of rats to compare their pharmacokinetic properties. The concentrations of mirodenafil and sildenafil in the rat plasma and corpus cavernosum tissue samples were analyzed using LC-MS/MS after a single oral administration at a dose of 40mg/kg to rats. Although the T(max), Tlambda(1/2) and MRT were not different between mirodenafil and sildenafil, the C(max) and AUC of mirodenafil were significantly higher than those of sildenafil in the plasma and corpus cavernosum tissue. Consequently mirodenafil remained longer than sildenafil in the plasma and tissue. This may provide pharmacokinetic evidence for assessment of the in vivo efficacy of mirodenafil and sildenafil.

LC-MS/MS method for determination of hederacolchiside E, a neuroactive saponin from Pulsatilla koreana extract in rat plasma for pharmacokinetic study.

A simple, rapid, and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was applied to pharmacokinetic study of a neuroactive oleanolic-glycoside saponin, hederacolchiside E from SK-PC-B70M, a standardized extract of Pulsatilla koreana in rat. Rat plasma samples were pretreated by protein precipitation with acetonitrile, eluted from C(18) column, and analyzed using electrospray ionization (ESI)-MS/MS in negative ion mode. Digoxin was used as an internal standard. The standard curves were linear (r>0.997) over the concentration ranges of 2-500 ng/mL. The intra- and inter-day precisions were measured to be below 9% and accuracy between 90 and 111% for all quality control samples at 2, 20, 100, and 500 ng/mL (n=5). The lower limits of quantification (LLOQ) for hederacolchiside E was 2 ng/mL and the limit of detection (LOD) 0.5 ng/mL using 20 microL of plasma sample. Subsequently, hederacolchiside E was determined in rat plasma samples after oral administration of SK-PC-B70M. The mean maximum plasma concentrations of hederacolchiside E were 0.07, 0.13, and 0.36 microg/mL and the mean areas under the plasma concentration versus time curve 0.56, 1.27, and 6.46 microg h/mL at doses of 100, 200, and 400 mg/kg, respectively, which indicated non-linear pharmacokinetic pattern. In conclusion, this method was successfully applied to the pharmacokinetic study of hederacolchiside E after an oral administration of SK-PC-B70M to rats.

Effects of dihydrotestosterone on rat dermal papilla cells in vitro.

Androgenetic alopecia involves the action of dihydrotestosterone (DHT) on dermal papilla cells (DPCs) that line the base of the hair follicle. However, the mechanism of DHT action is not completely understood. The effects of DHT on DPCs, regulatory cells that function in follicle growth and the hair cycle, were examined in immortalized cells derived from rat vibrissa follicles. DHT did not affect the proliferation of immortalized DPCs. However, flow cytometry analysis revealed that DHT increased cell-cycle arrest in these cells, which was accompanied by an increase in the p27(kip1) level and by decreases in cyclin E, cyclin D1, and cyclin-dependent kinase 2 levels. DHT treatment resulted in the phosphorylation and nuclear translocation of Smad2/3, a mediator of the transforming growth factor-ß (TGF-ß) signaling pathway, which leads to the catagen phase of the hair cycle. DHT also induced the phosphorylation and nuclear translocation of heat shock protein 27 (HSP27). Moreover, DHT decreased the levels of total and nuclear ß-catenin, an important regulator of hair growth and proliferation, while lithium chloride, a glycogen synthase kinase-3ß inhibitor, attenuated the DHT-induced downregulation of the ß-catenin level. On the other hand, DHT increased the phosphorylation of mammalian target of rapamycin (mTOR), a regulator of proliferation, in immortalized DPCs. These results illustrate that DHT could shorten the duration of the hair growth cycle by initiating cell-cycle arrest, downregulating the ß-catenin level, and upregulating the TGF-ß/Smad and HSP27 level, whereas activation of mTOR by DHT could attenuate the inhibition of hair growth cycle in immortalized DPCs.

Synthesis and biological evaluation of 3-(4-substituted-phenyl)-N-hydroxy-2-propenamides, a new class of histone deacetylase inhibitors.

Inhibitors of histone deacetylases (HDACs) have been shown to induce differentiation and/or apoptosis of human tumor cells. Novel 3-(4-substituted-phenyl)-N-hydroxy-2-propenamides have been prepared as a new class of HDAC inhibitors and evaluated for their antiproliferative activity and HDAC inhibitory activity. Incorporation of a 1,4-phenylene carboxamide linker, shown by 5, and a 4-(dimethylamino)phenyl or 4-(pyrrolidin-1-yl)phenyl group as a cap substructure generated highly potent hydroxamic acid-based HDAC inhibitors 5a and 5b.

SK-PC-B70M confers anti-oxidant activity and reduces Abeta levels in the brain of Tg2576 mice.

SK-PC-B70M is an oleanolic-glycoside saponin-enriched fraction derived from the root of Pulsatilla koreana. Recently, it was reported that hederacolchiside-E is an active ingredient of SK-PC-B70M that confers a neuroprotective effect against the cytotoxicity induced by Abeta(1-42) in SK-N-SH neuroblastoma cells. SK-PC-B70M improves scopolamine-induced impairments of spatial working memory in rats. In the present study, we investigated whether SK-PC-B70M has a beneficial effect on the Tg2576 murine model of Alzheimer's disease. ELISA analysis revealed that the levels of soluble and insoluble forms of Abeta(1-42) in Tg2576 mice fed SK-PC-B70M (2000 ppm) from 11 months to 16 months of age were reduced to, respectively, 66% and 79% of the control Tg2576 mice. Anti-Abeta antibody-stained brain sections of Tg2576 mice with SK-PC-B70M (2000 ppm) consistently showed a reduction in plaque formation in the brain. Western blot analyses showed altered expressions of various cellular factors, such as up-regulation of transthyretin, phospho-ERK, and phospho-CREB in the brain treated with SK-PC-B70M. SK-PC-B70M suppressed the neuronal toxicity induced by H(2)O(2) in primary cortical culture. Moreover, biochemical and immunohistochemical analyses showed that the levels of malondialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE), oxidized by-products of lipid peroxidation, were notably reduced in the hippocampus of Tg2576 mice treated with SK-PC-B70M compared with the Tg2576 control. These results suggest that SK-PC-B70M attenuates AD-like pathology in the brain of Tg2576 mice.

Ginkgo biloba extract enhances antiplatelet and antithrombotic effects of cilostazol without prolongation of bleeding time.

Thrombosis and thromboembolic occlusions of major and minor blood vessels are a major complication in various peripheral vascular diseases. Antiplatelet agents (APA), key tools in the treatment of atherothrombosis, therefore became a mainstay medication for a wide range of vascular diseases. Cilostazol and Ginkgo biloba extract (GB), commonly used remedies for peripheral arterial disease, inhibit platelet aggregation with distinct therapeutic mechanisms. In this study, we have investigated if GB can potentiate the antiplatelet effects of cilostazol to explore the utility of combination therapy of cilostazol and GB against peripheral occlusive vascular diseases. GB or cilostazol was evaluated alone or in combination for the antiplatelet activity using in vitro and in vivo models. In addition, potential bleeding side effect of the combinative therapy was assessed by measuring bleeding time, prothrombin time (PT) and activated partial thromboplastin time (aPTT) in vivo after oral administration. In in vitro assays using freshly isolated human platelets, the combination of cilostazol and GB showed superior inhibition of both the shear and the collagen-induced platelet aggregation to those of each drug alone. In accordance with these enhanced in vitro antiplatelet activities, the combinative therapy showed enhanced anti-thrombotic effects in in vivo pulmonary embolism model and arterial thrombosis model. In particular, the increase of survival rate in pulmonary embolism model by combination treatment of cilostazol (25 mg/kg) and GB (20 mg/kg) was higher more than two-fold of those of the respective drugs. Notably, the combination of cilostazol and GB did not show a significant effect on the bleeding time, PT and aPTT increase, suggesting that GB may potentiate the antiplatelet effect of cilostazol without the prolongation of bleeding time or coagulation time. With these studies, we suggest that combinative therapy of GB and cilostazol might offer enhanced anti-thrombotic efficacies without increasing side-effects.

Pharmacokinetics and tissue distribution of a novel PDE5 inhibitor, SK-3530, in rats.

AIM: To investigate the pharmacokinetic profile and tissue distribution of a novel phosphodiesterase type 5 inhibitor, 5-ethyl-2-{5-[4-(2-hydroxy-ethyl)-piperazine-1-sulfonyl]-2-propoxy-phenyl}-7-propyl-3,5-dihydro-pyrrolo(3,2-d)pyrimidin-4-one (SK-3530), in rats after administration of the (14)C-labeled compound. METHODS: The pharmacokinetic parameters of SK-3530 were measured based on the total radioactivity and parent SK-3530 concentration in rat plasma after intravenous and oral administration. The tissue distribution of total radioactivity after a single oral administration of [(14)C]SK-3530 at a dose of 40 mg/kg was assayed. The plasma protein binding rates of SK-3530 were assessed by in vitro and ex vivo assay. RESULTS: The total radioactivity profiles showed linear pharmacokinetics. The maximum plasma concentration and area under the curve of the parent SK3530 were 10%-20% compared to those of the total radioactivity. After the oral administration of [14C]SK-3530, the radioactivity was widely distributed in all tissues, and the tissue/plasma ratio of the radioactivity 1 h after administration was calculated as 0.5-2.6 with the exception of excretory organs. A relatively high penetration was shown in the adrenal glands, liver, and lung. In vitro and ex vivo plasma protein binding assay by ultrafiltration showed a considerably high binding rate of more than 97%. CONCLUSION: SK-3530 was relatively well absorbed in the gastrointestinal tract and showed linear pharmacokinetics over the investigated dose range. SK-3530 had low oral bioavailability due to a high, first-pass metabolism.