The cytochromes P450 (CYPs) responsible for the oxidative metabolism of tacrolimus and its in vitro major metabolite M-I, the 13-O-mono-demethylated metabolite, were characterized in human liver microsomes. Human liver microsomes and ten human CYPs expressed in Hep G2 cells were used in the experiments.
1. When ¹⁴C-labeled tacrolimus (¹⁴C-tacrolimus) was incubated with human liver microsomes, M-I formation was mainly observed in the early stage of incubation, while many peaks of the more polar metabolites, including M-VII, the 13, 15-O-di-demethylated metabolite, were detected in the late stage of incubation. When the microsomes were incubated with ¹⁴C-M-I, formation of M-VII and unidentified metabolites were observed. The rates of formation of M-I from ¹⁴C-tacrolimus in 10 different human liver microsomes correlated well with the activities of testosterone 6β-hydroxylation and tolbutamide methyl-hydroxylation, but not with the marker enzyme activities of other CYPs. The metabolism of both tacrolimus and M-I by human liver microsomes were inhibited by ketoconazole and anti-CYP3A4 antiserum.
2. After incubation of ¹⁴C-tacrolimus with Hep G2 cell lysates containing expressed human CYPs, M-I formation was observed in the reaction system with CYP3A3, 3A4 and 3A5, but not with CYP1A2, 2A6, 2B6, 2C8, 2C9, 2D6 or 2E1. After incubation of the lysates with ¹⁴C-M-I, M-VII formation was again observed only in the system with the CYP3A subfamily. Substrate disappearance of both tacrolimus and M-I was the most efficiently catalyzed by CYP3A4.
3. These results suggest that tacrolimus is metabolized to polar metabolites through M-I by human liver microsomes, and that the metabolism of both tacrolimus and M-I are mainly catalyzed by CYP3A4.

抄録全体を表示

汎用表計算ソフトウエアであるMicrosoft Excel®のマクロ機能を利用して，Visual Basic®によるモーメント解析プログラムMOMENT(EXCEL)を血中動態解析用および尿や胆汁からの排泄動態解析用にそれぞれ開発した．これらのプログラムではAUC，MRTあるいはCLなどの薬物速度論的パラメータを算出し，解析結果が入力データおよびグラフと共にエクセルシート上に整理して出力される．本解析プログラムには無限時間への外挿点の選択に，AIC法を利用した自動選択法を組み込んだ．自動選択法については，コソパートメントモデルに基づき15%の誤差乱数を加えて人工的に発生させたデータの解析によりバリデーショソを行い，自動選択法から得られるモーメント値が，モデルパラメータから導かれる理論値と良く一致することを確認した．
本解析プログラムはデータ入出力に表計算ソフトウエアをそのまま利用できるため，特に同種のデータ解析を繰り返し行う際の入力の短時間化や誤入力の低減に極めて有効である。
MOMENT(EXCEL)はインターネットによりホームページ(http://bunsekiO2.pharm.kyoto-u.ac.jp)からダウンロードが可能である．

抄録全体を表示

成熟および幼若ビーグル犬に300mg/kgの投与量でセフルプレナム(CFLP)を4週間静脈内に反復投与した際の投与初日，および投与開始27日後のCFLPの血漿中濃度を測定した．
CFLP投与後の血漿中濃度は，初日および投与27日目とも幼若ビーグル犬より成熟ビーグル犬のほうが高く，分布容積Vssは幼若ビーグル犬のほうが成熟ビーグル犬に比べて高値を示した．これは，CFLPのほとんどが血漿あるいは細胞外液にしか分布しないことから，幼若ビーグル犬の体構成成分の水分含量比が高いことに起因すると考えられた．
また，成熟ビーグル犬における血漿中濃度推移には反復投与による変化は認められなかった．一方，幼若ビーグル犬の投与初日(生後3週齢)および投与27日目(生後7週齢)におけるCFLPの総クリアランスCLtotはそれぞれ0.45±0.03 l/hr/kgおよび0.64±0.01 l/hr/kgと，投与27日目のほうが血漿中濃度の消失が速くなることが観察され，同時にクレアチニン・クリアランスCLcrの増加も観察された．これは，CFLPの反復投与による影響ではなく，幼若ビーグル犬の成長に伴う糸球体濾過機能の変化によるものと考えられた．

抄録全体を表示

The absorption, distribution, and excretion of radioactivity were investigated following a single oral administration of ¹⁴C-pramipexole to rats at a dose of 0.5 mg/kg. The protein binding of the drug was also investigated in vitro and in vivo.
1. The total radioactivity in plasma reached the maximum at about 1.5 hr after oral administration of ¹⁴C-pramipexole to male and female rats. The half-lives of radioactivity in plasma were about 48 and 41 hr in male and female rats, respectively, as determined from the data at 24 to 72 hr after administration. The C_max was decreased in the presence of food, but total absorption of radioactivity remained unaffected. ¹⁴CPramipexole was well absorbed throughout the duodenum, jejunum and ileum, but not in the stomach. 2. The radioactivity in most tissues after oral administration of ¹⁴C-pramipexole to male rats reached Cmax at 2 hr, being higher in liver, kidney, hypophysis and salivary gland. The radioactivity in the whole brain was higher than that in plasma at 2 and 6 hr after administration. At 48 hr after oral administration, the radioactivity in most tissues except blood had decreased to below 1/10 of the respective maximum concentration. The ratio of the concentration in blood cells to that in plasma was in the range of 1.63-7.15 at 0.5 to 48 hr after oral administration.
3. The binding of ¹⁴C-pramipexole at concentrations of 10-1000 ng/ml to rat plasma protein in vitro was about 15-18% and that at concentrations of 0.5-50 ng/ml to human serum protein in vitro was about 17-26%.
The percentage of radioactivity bound to rat plasma protein within 2 hr after oral administration of ¹⁴Cpramipexole to male rats was below 20%. After 2 hr, the ratio of plasma protein binding increased with time, and then the percentage of radioactivity bound to rat plasma protein was about 67% at 48 hr.
4. The amount of radioactivity excreted in urine and feces within 168 hr after oral administration of ¹⁴C-pramipexole to male rats were 59.0% and 44.0% of the dose, respectively. Within 48 hr after intraduodenal injection of the bile obtained from other rats which had been administered ¹⁴C-pramipexole (0.1 mg/kg) intravenously, about 4% of the injected radioactivity was excreted in the bile.
5. The radioactivity in milk after oral administration to lactating rats was 2-5 times higher than that in plasma at all times from 0.5 to 48 hr, but the half-life of radioactivity in milk was shorter than that in plasma.

抄録全体を表示

The absorption and distribution of radioactivity were investigated following a 14-day period of daily oral administration of ¹⁴C-pramipexole (0.5 mg/kg/day) to male rats.
1. When measured 24 hr after each of 14 repeated daily administrations of ¹⁴C-pramipexole to male rats, the level of radioactivity in plasma rose as the number of doses increased, and reached a steady state after 12 or 13 doses. The elimination of radioactivity from the plasma after the last dose was similar to that after a single administration.
2. At 1 hr after the 14th administration, the level of radioactivity reached the maximum in most tissues. High levels were observed in the liver and kidney, being about 22 and 14 times higher than that in the plasma, respectively. At 168 hr after the last dose, the levels of radioactivity in the liver and kidney were very much higher than that in plasma. The elimination of radioactivity from most tissues after the last dose was parallel to that from plasma, except the spleen and kidney, where an accumulation was observed.
3. After the last administration, the ratio of the concentration in blood cells to that in plasma gradually increased with the lapse of time. The elimination of radioactivity from blood cells was very much slower than that from plasma. The relative increase of radioactivity in blood cells at the late stage after drug administration may be attributed to metabolites of pramipexole.

抄録全体を表示

Peptide and protein drugs are becoming a very important class of therapeutic agents. However, the oral bioavailability of peptide and protein drugs is generally poor because they are extensively degraded by proteases in the gastrointestinal tract and impermeable through the intestinal mucosa. For systemic delivery of peptide and protein drugs, parenteral administration is currently required to achieve their therapeutic activities. However, these administration are poorly accepted by patients and may cause allergic reactions and serious side effects. Therefore, various approaches have been examined to overcome the delivery problems of these peptides when they administered orally. These approaches include (1) to use additives such as absorption enhancers and protease inhibitors, (2) to develop an administration method for peptides that can serve as an alternative to oral and injection administration, (3) to modify the molecular structure of peptide and protein drugs to produce prodrugs and analogues, and (4) to use the dosage forms to these peptide drugs. Of all these approaches, we demonstrated that transmucosal absorption of various peptides including insulin, calcitonin, tetragastrin and thyrotropin releasing hormone (TRH) could be improved by using these approaches. Therefore, these approaches may give us basic information to improve the transmucosal absorption of peptide and protein drugs.

抄録全体を表示