Toshiro Fukami

P-glycoprotein mediates brain-to-blood efflux transport of buprenorphine across the blood-brain barrier

The involvement of P-glycoprotein (P-gp) in buprenorphine (BNP) transport at the blood–brain barrier (BBB) in rats was investigated in vivo by means of both the brain uptake index technique and the brain efflux index technique. P-gp inhibitors, such as cyclosporin A, quinidine and verapamil, enhanced the apparent brain uptake of [3H]BNP by 1.5-fold. The increment of the BNP uptake by the brain suggests the involvement of a P-gp efflux mechanism of BNP transport at the BBB. [3H]BNP was eliminated with an apparent elimination half-life of 27.5 min after microinjection into the parietal cortex area 2 regions of the rat brain. The apparent efflux clearance of [3H]BNP across the BBB was 0.154 ml/min/g brain, which was calculated from the elimination rate constant (2.52 × 10− 2 min− 1) and the distribution volume in the brain (6.11 ml/g brain). The efflux transport of [3H]BNP was inhibited by range from 32 to 64% in the presence of P-gp inhibitors. The present results suggest that BNP is transported from the brain across the BBB via a P-gp-mediated efflux transport system, at least in part.

Characterization of multicomponent crystal formed between indomethacin and lidocaine

Purpose: Crystalline complex was formed between indomethacin (IDM) and lidocaine (LDC) at molar ratio 2:1 from ethanol solution. The purpose of this study was elucidation of an interactive manner between IDM and LDC in ethanol solution and mechanism of the complex formation through solid state as well as liquid state. Methods: The chemical and physical nature of the complex was clearly elucidated by the alliance of powder X-ray diffractometry, differential scanning calorimetry, and infrared spectroscopy. The complex was also formed via solid-state reaction by cogrinding and heating treatment without any solvent. Results: The complexation process was estimated to be as follows: (i) mixing and contact of two components, (ii) disorder of crystalline LDC by grinding or fusion, and then (iii) crystal growth by heating. In addition, 1H-NMR coupled with microchanneled cell for synthesis monitoring revealed that a primary interactive force between IDM and LDC molecule was coulomb energy.

Novel pharmaceutical cocrystal consisting of paracetamol and trimethylglycine, a new promising cocrystal former

Paracetamol (APAP), a frequently used antipyretic drug, has poor compression moldability. In this study, we identified a novel cocrystal consisting of APAP and trimethylglycine (TMG) that exhibits improved tabletability. TMG was used instead of oxalic acid (OXA), which is a coformer reported previously. The cocrystal (APAP-TMG at a molar ratio of 1:1) was characterized by X-ray analysis, infrared spectroscopy, and thermal analysis. The crystal structure of APAP-TMG revealed that it was a cocrystal, since no proton was transferred between the APAP and TMG molecules. The compression and dissolution properties of APAP-TMG were similar to that of the APAP-OXA cocrystal. In addition, taste sensing measurements suggested that TMG has a sweet and umami taste, indicating that TMG should suppress the bitterness of APAP. From these results, TMG could be a safe and promising cocrystal former that could replace OXA, which can irritate tissues.

Involvement of an Influx Transporter in the Blood-Brain Barrier Transport of Naloxone

Naloxone, a potent and specific opioid antagonist, has been shown in previous studies to have an influx clearance across the rat blood–brain barrier (BBB) two times greater than the efflux clearance. The purpose of the present study was to characterize the influx transport of naloxone across the rat BBB using the brain uptake index (BUI) method. The initial uptake rate of [3H]naloxone exhibited saturability in a concentration‐dependent manner (concentration range 0.5 µM to 15 mM) in the presence of unlabeled naloxone. These results indicate that both passive diffusion and a carrier‐mediated transport mechanism are operating. The in vivo kinetic parameters were estimated as follows: the Michaelis constant, Kt, was 2.99±0.71 mM; the maximum uptake rate, Jmax, was 0.477±0.083 µmol/min/g brain; and the nonsaturable first‐order rate constant, Kd, was 0.160±0.044 ml/min/g brain. The uptake of [3H]naloxone by the rat brain increased as the pH of the injected solution was increased from 5.5 to 8.5 and was strongly inhibited by cationic H1‐antagonists such as pyrilamine and diphenhydramine and cationic drugs such as lidocaine and propranolol. In contrast, the BBB transport of [3H]naloxone was not affected by any typical substrates for organic cation transport systems such as tetraethylammonium, ergothioneine or L‐carnitine or substrates for organic anion transport systems such as p‐aminohippuric acid, benzylpenicillin or pravastatin. The present results suggest that a pH‐dependent and saturable influx transport system that is a selective transporter for cationic H1‐antagonists is involved in the BBB transport of naloxone in the rat. Copyright

Ascorbyl dipalmitate/PEG-lipid nanoparticles as a novel carrier for hydrophobic drugs.

L-ascorbyl 2,6-dipalmitate (ASC-DP), a fatty ester derivative of ascorbic acid, is poorly soluble in water and does not spontaneously form micelles or liposomal structures in water. In this study, we attempted to prepare an ASC-DP/surfactant nano-sized complex as a carrier for hydrophobic drugs. Samples were prepared by hydrating a solvent-evaporated film of ASC-DP/surfactant at a molar ratio of 1:1. Among the surfactants tested, distearoylphosphatidylethanolamine-polyethylene glycol 2000 (DSPE-PEG) was found to form stable nanoparticles with ASC-DP (average particle size: ca. 67 nm). Several hydrophobic drugs were incorporated in the ASC-DP/DSPE-PEG nanoparticles. Stability, toxicity, and blood residence of the drug-containing ASC-DP/DSPE-PEG nanoparticles were evaluated using amphotericin B (AmB) as the model drug. By intravenously administering mice with the formulations, we determined the minimum lethal dose of Fungizone, a formulation of AmB solubilized with sodium deoxycholate, was 3.0 mg/kg, while that of AmB/ASC-DP/DSPE-PEG nanoparticles was 10.0 mg/kg. When 2.0 mg/kg, Fungizone was administered, the mice showed higher renal and hepatic toxicities. Intravenously administered AmB/ASC-DP/DSPE-PEG nanoparticles demonstrated higher concentration in plasma than Fungizone. Thus, the ASC-DP/DSPE-PEG nanoparticle system appears to be a promising delivery system for hydrophobic drugs.

Pharmaceutical evaluation of steroidal ointments by ATR-IR chemical imaging: Distribution of active and inactive pharmaceutical ingredients

We recently used micro attenuated total reflection infrared (ATR-IR) spectroscopy to conduct imaging analysis of ointments and evaluate the distributions of the active pharmaceutical ingredient (API) and excipients. An alclometasone dipropionate (ALC) ointment was used as a model product. Almeta, a brand-name product, had a domain with absorbance at 1656 cm(-1) attributable to the carbonyl group of ALC, the API. Absorbances at 1040 and 3300 cm(-1) were also noted in this domain, indicating the presence of the solubilizer, propylene glycol. Data also suggested the presence of benzyl alcohol in this domain. More detailed analysis showed the distribution of surfactants and other excipients in the base. Similar results were obtained for Vitra, a generic version of Almeta. Imaging analysis with micro ATR-IR confirmed that both ointments are liquid droplet dispersions with ALC dissolved in propylene glycol and dispersed in a base. However, minor differences in the ingredient distributions of the two ointments were detected and reflect differences in excipient concentrations and type, or manufacturing differences. In summary, we used micro ATR-IR for imaging analysis of an original ointment, Almeta, and its generic form Vitra, and established a method for visually evaluating the distributions of the API and excipients in these ointments.

Comparative pharmaceutical evaluation of brand and generic clobetasone butyrate ointments

In the present study, we performed comprehensive pharmaceutical evaluation among an original clobetasone butyrate (CLB) ointment product and three generic products. Although spherocrystal images were observed under a polarizing microscope for only Kindavate®, the original product, distribution of active and inactive ingredients was chemically equivalent between the original and generic medicine by the attenuated total reflection infrared spectroscopy. These results suggest that the spherocrystals observed in Kindavate® are composed of hydrocarbon. On GC/MS, it was revealed that linear alkanes having 25-27 carbon atoms are densely present in Sun White®, the base used in Kindavate®. On the other hand, linear alkanes having 22-31 carbon atoms were broadly distributed in most other white petrolatums. In the CLB ointment products, the distribution equivalent of linear alkane to Sun White® was observed only in Kindavate®. Thus, the GC/MS method is extremely useful for identification of white petrolatum used in the ointment. A similar amount of CLB among the pharmaceutical products was detected in the skin tissue by skin accumulation test, although there were the differences in rheological properties and the quality of white petrolatum. The present results will be very useful for pharmacists in selecting medicine products that match the needs of the patient. Such pharmaceutical information will help spread objective knowledge about products in the future, and will contribute to the appropriate selection of medication.

Blood–brain barrier transport of naloxone does not involve P-glycoprotein-mediated efflux

The blood-brain barrier (BBB) transport of naloxone, a potent and specific opioid antagonist, was investigated in rats using the brain uptake index method and the brain efflux index method. The apparent influx clearance of [(3)H]naloxone across the BBB was 0.305 mL/min/g brain. [(3)H]naloxone was eliminated from the brain with an apparent elimination half-life of 15.1 min after microinjection into the parietal cortex area 2 regions of the rat brain. The apparent efflux clearance of [(3)H]naloxone across the BBB was 0.152 mL/min/g brain, which was calculated from the elimination rate constant (4.79 x 10(-2) min(-1)) and the distribution volume in the brain (3.18 mL/g brain). The influx clearance across the BBB was two times greater than the efflux clearance. The elimination of [(3)H]naloxone from the brain was not inhibited in the presence of the typical P-glycoprotein (P-gp) inhibitors such as quinidine, verapamil, vinblastine, and vincristine, indicating that naloxone is not a P-gp substrate in the rat. In vitro experiments by using human multidrug resistance 1 (MDR1)/P-gp overexpressing HeLa cells showed that the uptake of naloxone by the cells did not change in the presence of the P-gp inhibitors. In conclusion, the present results obtained from in vivo and in vitro studies suggest that P-gp is not involved in the BBB transport of naloxone.

In vivo evidence for the efflux transport of pentazocine from the brain across the blood-brain barrier using the brain efflux index method.

The efflux transport of pentazocine (PTZ) from the brain across the blood–brain barrier (BBB) was investigated using the Brain Efflux Index method. PTZ was eliminated with the apparent elimination half-life of 13.0 min after microinjection into the parietal cortex area 2 region of the rat brain. The apparent efflux clearance of PTZ across the BBB was 137 μl/min/g brain, which was calculated from the elimination rate constant (5.35 × 10−2 min−1) and the distribution volume in the brain (2.56 ml/g brain). The efflux transport of PTZ was decreased in the presence of unlabeled PTZ, suggesting that PTZ is eliminated by a carrier-mediated transport system across the BBB. To characterize the efflux transport of PTZ from the brain in vivo, the effects of several compounds on the efflux transport of PTZ were investigated. P-glycoprotein (P-gp) inhibitors (verapamil and quinidine) reduced the PTZ efflux transport. In addition, the efflux transport of PTZ was inhibited by organic cations such as l-carnitine and tetraethylammonium (TEA), whereas organic anions such as p-aminohippuric acid, probenecid and taurocholate did not affect the PTZ efflux transport. The present results suggest that PTZ is transported from the brain across the BBB via l-carnitine/TEA-sensitive carrier-mediated efflux transport system(s) in addition to P-gp.

Solid dispersions of efonidipine hydrochloride ethanolate with improved physicochemical and pharmacokinetic properties prepared with microwave treatment

Drug absorption into the body is known to be greatly affected by the solubility of the drug itself. The active pharmaceutical ingredient efonidipine hydrochloride ethanolate (NZ-105) is a novel 1,4-dihydropyridine calcium antagonist that has a very low solubility in water. It is classified as a poorly soluble drug, and improvements in its solubility and higher bioavailability with oral administration are needed. In this study, employing microwave technology as a new means to improve solubility, we established a method for preparing solid dispersions using hydroxypropyl methylcellulose acetate succinate as a polymeric carrier and urea as a third component. This effective method has a treatment time of several minutes (simple) and does not require the use of organic solvents (low environmental impact). The third component, urea, acts to lower the melting point of NZ-105, which promotes amorphization. This greatly improves the solubility compared with the microwave-treated product of NZ-105/HPMC-AS binary system. The solid dispersion prepared with this method, in addition to evaluation in vitro, was tested in vivo using beagle dogs and shown to be effective from the eightfold improvement in absorption compared with NZ-105 alone based on the area under the curve.