Published papers

Cytochrome P450 (CYP) 3A4 is one of the major drug-metabolizing enzymes. Genetic variants of CYP3A4 with altered activity are one of the factors responsible for interindividual differences in drug metabolism. Azole antifungals inhibit CYP3A4 to cause clinically significant drug-drug interactions. In the present quantitative study, we investigated the inhibitory effects of three azole antifungals (ketoconazole, voriconazole, and fluconazole) on testosterone metabolism by recombinant CYP3A4 genetic variants (CYP3A4.1 (WT), CYP3A4.2, CYP3A4.7, CYP3A4.16, and CYP3A4.18) and compared them with those previously reported for itraconazole. The inhibition constants (Ki) of ketoconazole, voriconazole, and fluconazole for rCYP3A4.1 were 3.6 nM, 3.2 μM, and 16.1 μM, respectively. The Ki values of these azoles for rCYP3A4.16 were 13.9-, 13.6-, and 6.2-fold higher than those for rCYP3A4.1, respectively, whereas the Ki value of itraconazole for rCYP3A4.16 was 0.54-fold of that for rCYP3A4.1. The other genetic variants had similar effects on the Ki values of the three azoles, whereas a very different pattern was seen for itraconazole. In conclusion, itraconazole has unique characteristics that are distinct from those shared by the other azole anti-fungal drugs ketoconazole, voriconazole, and fluconazole with regard to the influence of genetic variations on the inhibition of CYP3A4.

In-situ rat and mouse brain perfusion data indicated that the brain distribution of ramosetron (R-ramosetron), a 5-hydroxytryptamine3 (5-HT3) receptor antagonist, was extremely low compared with that expected from its lipophilicity. We hypothesized the involvement of an efflux system(s) and investigated the contribution of P-glycoprotein to efflux transport of ramosetron across the blood-brain barrier by means of an in-vitro uptake study in cell lines that over-express P-glycoprotein. We examined the contribution of mdr1a, mdr1b and MDR1 P-glycoprotein by using LV500 cells, MBEC4 cells and LL-GA5-COL300 cells, which over-express mdr1a P-glycoprotein, mdr1b P-glycoprotein and MDR1 P-glycoprotein, respectively. The uptake of [14C]ramosetron by LV500 cells and LLC-GA5-COL300 cells was significantly lower than that by the respective parental cells. Next, we studied the effects of P-glycoprotein inhibitors, verapamil and ciclosporin, on uptake of [14C] ramosetron by these cell lines. The uptake of [14C]ramosetron by LV500 cells and LLC-GA5-COL300 cells was significantly increased in the presence of verapamil or ciclosporin, while verapamil did not affect the uptake of [14C]ramosetron by MBEC4 cells. These results indicate that the efflux of [14C]ramosetron is partly mediated by mdr1a P-glycoprotein, but not by mdr1b P-glycoprotein, and that there is a difference in substrate specificity between mdr1a P-glycoprotein and mdr1b P-glycoprotein. Further, [14C]ramosetron was confirmed to be effluxed by human MDR1 P-glycoprotein. We conclude that the limited distribution of ramosetron to the brain is due, at least in part, to efflux mediated by the P-glycoprotein at the blood-brain barrier.

Human organic anion-transporting polypeptide B (OATP-B; OATP2B1) is expressed in the human intestinal epithelial cells, and is suggested to be involved in the intestinal absorption of anionic drugs in vivo. Although citrus juices have been shown to inhibit the function of human OATP-A (OATP1A2), the effect of citrus juices on the OATP-B function remains unclear. In this study, we aimed to examine the effects of citrus juices on the function of OATP-B. The effects of citrus juices on the uptake of estrone-3-sulfate, a typical substrate for OATP-B, into human embryonic kidney 293 cells stably expressing OATP-B were evaluated. Juices were diluted with uptake buffer, adjusted to pH 7.4 and approximately 300 mOsm, and used for the experiments. Grapefruit juice (GFJ) and orange juice (OJ) at a concentration of 5% significantly inhibited the OATP-B-mediated uptake of estrone-3-sulfate by 82 and 53%, respectively. Major constituents of GFJ and OJ also significantly inhibited the OATP-B-mediated uptake of estrone-3-sulfate. Glibenclamide, a hypoglycemic drug, was identified for the first time as a substrate for OATP-B with a Kt value of 6.26 μM. GFJ and OJ inhibited the OATP-B-mediated uptake of glibenclamide. These results suggest that citrus juices may inhibit the intestinal absorption of anionic drugs, such as glibenclamide, via the inhibition of OATP-B. Copyright © 2005 by The American Society for Pharmacology and Experimental Therapeutics.

Purpose. We examined the functional properties of choline transport across the blood-brain barrier (BBB) in mice. We compared the kinetic parameters and transport properties with those found in our in vitro uptake experiments using mouse brain capillary endothelial cells (MBEC4). Methods. The permeability coefficient-surface area product (PS) values of [3H]choline at the BBB were estimated by means of an in situ brain perfusion technique in mice. Results. [3H]Choline uptake was well described by a two-component model: a saturable component and a nonsaturable linear component. The [3H]choline uptake was independent of pH and Na+, but was significantly decreased by the replacement of Na+ with K+. Various basic drugs, including substrates and inhibitors of the organic cation transporter, significantly inhibited the [3H]choline uptake. These in situ (in vivo) results corresponded well to the in vitro results and suggest that the choline transporter at the BBB is a member of the organic cation transporter (OCT) family. Conclusion. The choline transport mechanism at the BBB is retained in MBEC4.

The characteristics of L-lactic acid transport across the trophoblast basal membrane were investigated and compared with those across the brush-border membrane by using membrane vesicles isolated from human placenta. The uptake of L-[14C]lactic acid into basal membrane vesicles was Na+ independent, and an uphill transport was observed in the presence of a pH gradient ([H+]out > [H+]in). L-[14C]lactic acid uptake exhibited saturation kinetics with a Km value of 5.89 ± 0.68 mM in the presence of a pH gradient. p-Chloromercuribenzenesulfonate and α-cyano-4-hydroxycinnamate inhibited the initial uptake, whereas phloretin or 4,4′-diisothiocyanostilbene-2,2′-disulfonate did not. Mono- and dicarboxylic acids suppressed the initial uptake. In conclusion, L-lactic acid transport in the basal membrane is H+ dependent and Na+ independent, as is also the case for the brush-border membrane transport, and its characteristics resemble those of monocarboxylic acid transporters. However, there were several differences in the effects of inhibitors between basal and brush-border membrane vesicles, suggesting that the transporter(s) involved in L-lactic acid transport in the basal membrane of placental trophoblast may differ from those in the brush-border membrane.

Aims: To assess the mechanistic relationship between doxazosin (α1-receptor antagonist) and receptor occupancy and a measure of pharmacological effect (Qmax, the maximum urinary flow rate) and to compare the mean receptor occupancy ratio at clinical doses of doxazosin, tamsulosin, terazosin and prazosin in benign prostatic hyperplasia (BPH). Methods: A ternary complex model, which described the mechanism of α1-receptor antagonists, was fitted to the pharmacological effects and receptor occupancy ratio data for doxazosin (standard tablet). In addition, mean receptor occupancy was calculated for other α1- receptor antagonists and the optimal receptor occupancy was evaluated. The clinical pharmacological effects of the controlled release formulation of doxazosin (doxazosin GITS) were estimated based on the receptor occupancy. Results: The mechanistic based model was able to describe the pharmacological effects of doxazosin. Regardless of the plasma concentrations or clinical dose of each drug, the results suggest that receptor occupancy is useful to assess quantitatively and compare the pharmacological effects of drugs with similar mechanisms of action. The clinical dosage for doxazosin GITS was estimated to be at least 8 mg and the stable pharmacological effect is expected based on the estimated receptor occupancy. Conclusions: A model for Qmax improvement in BPH based on the receptor occupancy theory was able to describe the clinical effects of the α1-receptor antagonists. Receptor occupancy is a useful index for predicting the clinical effects of α1-receptor antagonists. © 2006 The Authors.

The effects of epinastine hydrochloride and terfenadine on electrocardiographic (ECG) parameters in rats were investigated from a pharmacokinetic and pharmacodynamic perspective. Epinastine hydrochloride (1 or 3 mg kg-1 h-1) or terfenadine (5, 10 or 15 mg kg-1 h-1) was intravenously infused into rats anaesthetized with methane and α-chloralose. The changes in the QT interval derived from limb lead II and the chest lead, heart rate and PR interval were analysed. The time-course of the plasma drug-concentration of each drug was also investigated. Terfenadine prolonged the QT interval in an infusion-rate-dependent manner; its EC50 value was 792-1039 ng mL-1. An obvious QT prolongation was, moreover, observed even at a plasma terfenadine concentration of 100-200 ng mL-1, which is clinically quite high, but might be achieved under a definite condition such as a restrained terfenadine metabolism. Terfenadine also induced PR prolongation and bradycardia in an infusion-rate dependent manner. Epinastine slightly increased the heart rate, but did not affect any of the other ECG parameters even at a plasma concentration of 400 ng mL-1, which is more than 10 times the maximum concentration attained after an ordinary dosage regimen in man. We conclude that epinastine might have an advantage over terfenadine in avoiding adverse electrocardiographic reactions.

A 70-year-old Japanese woman with renal dysfunction under hemodialysis presented with vomiting and chill with fever. Over the previous 24 weeks she had been taking 75 mg of ranitidine after hemodialysis. Other medications taken were prednisolone, furosemide, α-calcidol, amlodipine and calcium carbonate. Before starting ranitidine, she had been treated with famotidine for about 2 years without complication. Hematological inspection on admission revealed agranulocytosis with WBC of 400/mm3. Ranitidine was discontinued and granulocyte colony-stimulating factor (G-CSF) was started. On Day 3, laboratory data showed slight improvement of cytopenia with WBC Of 1,000/mm3. On Day 6, her hemogram showed marked improvement with WBC of 11,700/mm3 and G-CSF was discontinued. She was discharged on Day 10. Several cases describing ranitidine-induced cytopenia are associated with the use of ranitidine at a dose of 150 mg/day or higher, and adverse reactions were found within 2 - 35 days after beginning ranitidine treatment. In the case described here, however, the adverse reaction occurred after a longer treatment period with ranitidine at a lower dose. In conclusion, ranitidine should be administered with great caution to patients with severe renal dysfunction.

The relationship between antibronchospasmic, tachycardiac, or hypokalaemic effects and plasma concentration of L‐isoproterenol (ISP) hydrochloride was investigated in guinea‐pigs in vivo. ISP was infused at the rate of 10, 30, 50, 100, and 300 ng kg−1 min−1. The antibronchospasmic effect was expressed as the attenuation of methacholine‐induced bronchospasm. The EC50 values of ISP for antibronchospasmic and tachycardiac effects were 5.12 nM and 3.95 nM, respectively. Although they were comparable to the values reported in vitro (7.23–0.358 nM, 1.77 nM), the concentration response relationship of ISP for antibronchospasmic effect was quite steep with a slope factor of more than six. Moreover, a decrease in plasma potassium level was not clearly detected. The experimental procedure in our present study was useful for evaluating antibronchospasmic and tachycardiac effects of beta‐agonists. Copyright © 1995 John Wiley & Sons, Ltd.

To assess quantitatively the risks of ophthalmic beta-blocking agents for cardiovascular and respiratory adverse reactions, we analyzed the binding kinetics of beta-blocking agents to the beta-1 and beta-2 adrenoceptors. The relationship between the occupancies for beta-1 and beta-2 adrenoceptors and the effects on the exercise pulse rate or the forced expiratory volume in one second (FEV1) after topical administration of carteolol, befunolol, timolol and betaxolol was analyzed using a ternary complex model. The beta-1 and beta-2 receptor occupancies after ophthalmic administration were calculated to be quite high as well as those after oral administration. The maximum occupancies for beta-1 and beta-2 receptors after ordinary ophthalmic administration were 52% and 88% for carteolol, 52% and 61% for befunolol, 62% and 82% for timolol, and 44% and 3% for betaxolol, respectively. Concave relationships were obtained between a decrease in exercise pulse rate and the beta-1 receptor occupancy and between a decrease in FEV1 and beta-2 receptor occupancy, respectively. Nasolacrimal occlusion was estimated to decrease the exercise pulse rate and FEV1 by 65% and 50%, respectively. The beta-1 and beta-2 adrenoceptor occupancies were proved to be the most appropriate indicators for cardiac and pulmonary adverse reactions evoked by ophthalmic beta-blocking agents.

The aim of the present study is to examine the relationship between dopamine D2-receptor gene (DRD2) polymorphisms (Taq1A, Taq1B, -141C Ins/Del) and the risk of extrapyramidal adverse effects (EPS), assessed according to the Drug-Induced Extra-Pyramidal Symptoms Scale (DIEPSS), or the maintenance dose of antipsychotics in schizophrenic patients. The DIEPSS score was significantly higher in patients bearing the -141C Del allele than in those without it. Taq1A and Taq1B restriction fragment length polymorphisms (RFLPS) did not significantly affect the DIEPSS score. On the other hand, maintenance doses of neuroleptics and antiparkinsonian drugs were significantly higher in patients with the B1 allele of Taq1B RFLP than in those without it, while the Taq1A RFLP and -141C Ins/Del polymorphisms were not significantly related to the maintenance doses. In conclusion, the risk of EPS may be increased in patients with the -141C Del allele of the DRD2 gene. In these patients, antipsychotics should be administered with caution. ©2005 Dustri-Verlag Dr. K. Feistle.

Objective: To report a case of second-degree atrioventricular block associated with concomitant use of aprepitant and amlodipine. Case: A 73-year-old man with lung cancer was treated with aprepitant for prophylactic use for the prevention of nausea and vomiting, concomitantly with cisplatin, gemcitabine, and an investigational drug (anti-epidermal growth factor receptor monoclonal antibody). He was diagnosed with first-degree atrioventricular block and was taking amlodipine for hypertension. During the first cycle of chemotherapy, 5 days after the start of aprepitant, he experienced Wenckebach second-degree atrioventricular block (Mobitz type I), and amlodipine was discontinued. After day 6, the atrioventricular block was not shown. According to the Naranjo adverse drug reaction scale, a score of 7 was obtained (causality: probable). In addition, using the Drug Interaction Probability Scale, a score of 6 was obtained (causality: probable). Conclusion: The drug-drug interaction between aprepitant and amlodipine was considered to have deteriorated his atrioventricular block, conceivably due to the inhibition of cytochrome P450 (CYP) 3A-mediated metabolism of amlodipine by aprepitant.

Objectives: The present study aimed to evaluate the effects of CYP3A4 genetic variation on the kinetics of mechanismbased inhibition (MBI) of both inhibitors using midazolam as a substrate for comparison with our previous study, as midazolam and testosterone have different binding sites. Background: The genetic variation of cytochrome P450 (CYP) 3A4 affects MBI, expressed as the maximum inactivation rate constant (kinact,max) and the inhibitor concentration required to achieve half-maximal inactivation (KI). We previously showed, using testosterone as a substrate, that the MBI kinetics of erythromycin and clarithromycin differ among CYP3A4 variants. Materials and methods: Midazolam 1'-hydroxylation inactivation profiles of erythromycin and clarithromycin were assessed using recombinant CYP3A4.1, .2, .7, .16, and .18 expressed in Escherichia coli. MBI parameters were calculated from changes in the inactivation rate constant (Δkobs) by the inhibitors. Results: Both inhibitors increased Δkobs value in a concentration- and preincubation time-dependent manner, and MBI kinetics differed among variants. Trends of differences in MBI parameters among variants were similar to those assessed using testosterone as a substrate; KI decreased for CYP3A4.7, and kinact,max decreased for CYP3A4.2, .7, and .16. Conclusion: The genetic variation of recombinant CYP3A4 affects the MBI profile of CYP3A4 by erythromycin and clarithromycin, while the influence of genetic variation was similarly observed regardless of substrates. Our findings are of clinical relevance because the residual enzyme activity of CYP3A4 in the presence of inhibitor was estimated to vary among genetic variants.

ドラッグストアを訪れた消費者を対象に、青汁を飲む動機、青汁の安全性と有効性についての認識、サプリメント一般に関する情報の必要性など青汁の使用実態をアンケート調査した。2006年2〜3月に北海道、東北、関東地方のツルハの調剤併設ドラッグストア68店を訪れた患者、消費者563名を調査対象とした。青汁服用者は65歳以上の高齢者、降圧薬、抗アレルギー薬、糖尿病治療薬の長期間服用者で有意に多かった。33.2%は効果があると考えていたが、55%はわからないと答えた。青汁服用による体調不良は2.4%で起った。その他、毎日服用(55.5%)、注意事項不読(27%)などであった。青汁服用は長期医薬品服用の高齢者に多いことが判明した。青汁服用の効果と副作用についての証拠を集め、消費者に注意事項が確実に伝わる方法を検討する必要がある。

46歳女性にKPテープ先発品Aを1日1回痛みに応じて、腰部と膝関節に貼付していたが、後発品Bに変更した後、使用感の相違が生じた。そこでA使用者39名(男6名、女33名、20〜86歳)とB使用者27名(男7名、女20名、39〜85歳)を対象に、テープ剤、外袋、ライナーについて調べ、テープ剤の評価を行い、貼付後の患部の状態についても調べた。先発品Aと後発品Bには使用感に差があり、先発品Aは後発品Bに比較し高く評価される傾向が認められた。先発品A使用経験を有する患者は使用経験がない患者に比べ、後発品Bに対する評価が低い傾向がみられた。貼付剤の使用感に関する比較試験は採用薬の選定や製剤切り替え時の服薬指導に有用である。

常用量以下の曝露量における全身性副作用の用量依存性について検討した。解析対象薬物として、常用量製剤に加えて、低曝露製剤として、貼付剤、点眼薬などといった局所適用製剤、あるいは低用量の経皮剤などといった全身曝露量の少ない全身作用型製剤が使用されている薬物を選択した。NSAIDsは、常用量製剤が27成分、低曝露製剤が17成分が上市され、常用量製剤と低曝露製剤の療法が上市されているのは10成分であった。β-ブロッカーでは、常用量製剤が22成分、低曝露製剤が7成分あり、両製剤が上市されているのは5成分であった。免疫抑制剤・ステロイドでは、常用量製剤が10成分、低曝露製剤が17成分あり、両製剤が上市されているのは5成分であった。AUCが常用量製剤の概ね20%以上では全身性副作用の発現は明らかであり無視できず、概ね3〜20%程度の曝露でも、減少はするものの完全には消失しないことが示唆された。

In Japan, purchasing drugs via Internet auction is prohibited by law. The aim of the present study was to clarify the current status of unapproved drug transactions via Internet auction in Japan. We created five sets of keywords corresponding to five therapeutic categories, ie, hair growth, gastrointestinal treatment, skin care, anti-aging therapy, and anti-cancer therapy. The searches were first performed on the website "Yahoo-oku" (Yahoo auction, Japan) using the above sets of keywords within five days, followed by secondary searches in the same manner after a forty-day interval. The searched items together with their explanations were evaluated independently by two researchers to determine whether they were illegal. The illegal items in the anti-cancer category were further monitored after submitting violation reports to the website. In two search phases within five days each, 571 and 581 illegal items were identified, respectively. After submission of the violation reports, only 1.1％ and 3.4％ of the items in the anti-cancer category were withdrawn by the site administrator and seller, respectively, and 38％ of the monitored items were sold. Taken together, unapproved drug transactions via the Internet are a serious problem. The government and site administrators may need to take effective measures to monitor and avoid such transactions, as well as providing notices and education to customers.

「インターネットを用いた薬剤師間情報交換・研修システム」を介して,塩酸ドネペジルの添付文書に規定されている用法・用量から逸脱した症例を確認した.中でも「初回から3mgあるいは5mg未満の量で1〜2週間後も継続されている」という,有効性が期待できない用量での処方が最も多く認められた.アンケート調査の結果および河野らの報告を考慮すると,3mg/日以下の投与量で有効で,かつ副作用が軽減される患者が存在する可能性は高いが,現段階では,医療用添付文書に定められた用法および用量を遵守する必要があり,規定外の投与は推奨できない.よって,臨床試験により,血中濃度と治療効果の関係を明らかにするとともに,低用量における治療効果を評価する必要性が示唆された

薬薬連携の中での疑義照会の現状と問題点を明らかにし、今後の疑義照会のあり方を探ることで適正な薬物治療を実施する上で有用な情報を構築することを目的にアンケート調査を行った。院外処方せんを発行する際に、処方鑑査を行っているかとの問いに関して、半数近くの47%が薬剤部の関与していないと回答した。院外処方せん発行後の〜次疑義照会先は薬剤部であるとの回答が74%を占め、一次疑義照会先を医師へ直接と決めている病院は12%にとどまった。保険薬局薬剤師の半数が、ほとんど近隣の医療機関からの処方せんを受けていると回答し、回答者の約98.5%が疑義照会の経験があると回答した。疑義照会先は、医師に電話(23.7%)、外来受付に電話、薬剤部に電話ほぼ同程度であった。疑義照会の内容としては、用法の不備、規格、単位の不備が大多数を占めた。