[Show abstract][Hide abstract] ABSTRACT: In this study, we retrospectively analyzed the relationship between headache recurrence and serotonin 5-HT1B/1D receptor occupancy (Φ1B and Φ1D). Triptans marketed in Japan (sumatriptan, zolmitriptan, eletriptan, rizatriptan, naratriptan) were investigated.
Receptor occupancies were calculated from both the pharmacokinetic and pharmacodynamic data of triptans. We examined the relationships between recurrence rate and elimination half-lives, and Ф1B and Ф1D, as calculated from the time-course of plasma drug concentration obtained from other studies. The time until Ф1B and Ф1D became 50 % or less, 40 % or less, and 30 % or less was calculated as duration time to examine the relationship with recurrence rate.
For Ф1B, eletriptan remained at a low level. For Ф1D, it was indicated that all triptans obtained an occupancy of 80 % or higher at maximum. For all items, though recurrence tended to be lower along with longer half-life, no significant statistical correlation was found. For both Ф1B and Ф1D, the recurrence rate tended to be lower as the duration became longer. In addition, a significant correlation was observed for Ф1D (p < 0.05). For clarifying the Ф value and time period most closely correlated with recurrence rate, recurrence and Ф1B and Ф1D at 6, 12, and 18 h after administration were calculated. The most significant correlation was observed between recurrence rate and Ф1D at 12 h after administration (p < 0.01).
As an index for evaluating headache recurrence following triptan administration, recurrence rate and Ф1D value at 12 h after administration were found to be most closely correlated and useful for analysis. Our results indicate that headache recurrence inhibition can be evaluated using these values.
The Journal of Headache and Pain 12/2015; 16(1):558. DOI:10.1186/s10194-015-0558-9 · 2.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: β-blocking agents are used for patients with tachycardia to improve the image quality of coronary computed tomography angiography (CCTA). In this study, we analyzed the clinical bradycardiac effects and the adverse respiratory effects of five β-blocking agents (landiolol, esmolol, propranolol, metoprolol and atenolol) used for CCTA. The changes of the occupancy binding to β1 or β2 receptor of these drugs were calculated based on the receptor occupancy theory. Thereafter, we predicted both the rate of heart rate decline ([Symbol: see text]HR) as a clinical effect and the rate of decrease in forced expiratory volume in 1 s ([Symbol: see text]FEV1) as an adverse effect, by using the ternary complex model. The results showed that the drugs with [Symbol: see text]HR greater than 10 %, necessary for CCTA, were as follows: landiolol at 13.5 %, propranolol at 11.0 %, and atenolol at 22.6 %. The [Symbol: see text]HR values at the end of CCTA for those three drugs were 0.3, 6.7, and 22.9 %, respectively. It is desirable for the bradycardiac effect to disappear at the end of CCTA. Therefore, landiolol is thought to be a preferable drug. On the other hand, [Symbol: see text]FEV1 at start and end of CCTA for those three drugs was 0.04-2.5, 34.9-40.3, and 6.0-6.1 %, respectively. Our results suggested that landiolol has the most appropriate effect and safety for patients with tachycardia who are undergoing a CCTA procedure.
European Journal of Drug Metabolism and Pharmacokinetics 12/2014; DOI:10.1007/s13318-014-0244-3 · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Triptans, serotonin 5-HT1B/1D receptor agonists, exert their action by targeting serotonin 5-HT1B/1D receptors, are used for treatment of migraine attack. Presently, 5 different triptans, namely sumatriptan, zolmitriptan, eletriptan, rizatriptan, and naratriptan, are marketed in Japan. In the present study, we retrospectively analyzed the relationships of clinical efficacy (headache relief) in Japanese and 5-HT1B/1D receptor occupancy (Phi1B and Phi1D). Receptor occupancies were calculated from both the pharmacokinetic and pharmacodynamic data of triptans.
To evaluate the total amount of exposure to drug, we calculated the area under the plasma concentration-time curve (AUCcp) and the areas under the time curves for [cyrillic capital letter ef]1B and [cyrillic capital letter ef]1D (AUC[cyrillic capital letter ef]1B and AUC[cyrillic capital letter ef]1D). Moreover, parameters expressing drug transfer and binding rates (Acp, A[cyrillic capital letter ef]1B, A[cyrillic capital letter ef]1D) were calculated.
Our calculations showed that [cyrillic capital letter ef]max1B and [cyrillic capital letter ef]max1D were relatively high at 32.0-89.4% and 68.4-96.2%, respectively, suggesting that it is likely that a high occupancy is necessary to attain the clinical effect. In addition, the relationships between therapeutic effect and AUCcp, AUCPhi1B, AUCPhi1D, and Acp[katakana middle dot]AUCcp differed with each drug and administered form, whereas a significant relationship was found between the therapeutic effect and APhi1B[katakana middle dot]AUCPhi1B or APhi1D[katakana middle dot]AUCPhi1D that was not affected by the drug and the form of administration.
These results suggest that receptor occupancy can be used as a parameter for a common index to evaluate the therapeutic effect. We considered that the present findings provide useful information to support the proper use of triptans.
The Journal of Headache and Pain 12/2014; 15(1):85. DOI:10.1186/1129-2377-15-85 · 2.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We evaluated the effectiveness of small group discussion (SGD) in association with a drug abuse prevention program for junior high school students. The students first received a lecture about drug abuse prevention, then participated in SGD. The discussion focused on how to take action when tempted to abuse drugs. We gave a questionnaire 3 times; before and after the lecture (before SGD), and after SGD. Seventy-seven students replied to these questionnaires. After the lecture, knowledge about drug abuse was improved and all students answered that they had never abused drugs. However, in answer to a different question, a few students noted that they might use drugs in some situations. We consider it necessary to give more consideration to this problem. After the lecture, 35.5% of the students felt that they had definitely acquired skills for drug abuse prevention, whereas after the SGD this was increased to 73.7%. In addition, more than 75% of the students answered that the SGD program was useful since the opinions of other students could be heard. These results suggest that more students acquired skills to prevent drug abuse by participation in SGD. Our findings showed that SGD was useful and that the students were able to more effectively understand important concepts related to drug abuse prevention.
Yakugaku zasshi journal of the Pharmaceutical Society of Japan 12/2014; 134(12):1331-45. DOI:10.1248/yakushi.14-00004 · 0.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 5-HT3 receptor antagonists are widely used as antiemetic agents in clinical setting, of which palonosetron, with a long elimination half life (t
1/2), has recently become available. It is important to evaluate the concentration of serotonin when investigating the antiemetic effects of 5-HT3 receptor antagonists, as those effects are not based solely on the t
1/2 value. We theoretically evaluated the antiemetic effects of three 5-HT3 receptor antagonists (granisetron, azasetron, palonosetron) on cisplatin-induced nausea and vomiting by estimating the time course of the 5-HT3 receptor occupancy of serotonin. We estimated the 5-HT3 receptor occupancy of serotonin in the small intestine, based on the time course of plasma concentration of each 5-HT3 receptor antagonist and the time course of concentration of serotonin near the 5-HT3 receptor in the small intestine after administration of cisplatin. The antiemetic effect of each 5-HT3 receptor antagonist was evaluated based on the normal level of 5-HT3 receptor occupancy of serotonin. Our results suggest that an adequate antiemetic effect will be provided when a dose of 75 mg/m2 of cisplatin is given to patients along with any single administration of granisetron, azasetron, or palonosetron at a usual dose. On the other hand, the 5-HT3 receptor occupancy of serotonin was found to be significantly lower than normal for several days after administration of palonosetron, as compared to granisetron and azasetron, indicating that constipation may be induced. Our results show that granisetron, azasetron, and palonosetron each have an adequate antiemetic effect after administration of 75 mg/m2 of cisplatin.
European Journal of Drug Metabolism and Pharmacokinetics 01/2014; 40(1). DOI:10.1007/s13318-014-0175-z · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: TNF inhibitors are used as therapeutic agents for rheumatoid arthritis (RA). Each has a different dosage regimen and it is thought that the differences among them have implications on efficacy. However, those differences have not been analyzed in a theoretical manner. In the present study, we tried to explain theoretically the differences. We theoretically analyzed the anti-inflammatory effect of infliximab (IFX), etanercept (ETN), and adalimumab (ADA) for RA by using a pharmacokinetic and pharmacodynamic model. Then, we simulate values for sequential changes of tender joint count (TJC) after repeated administrations of TNF inhibitors by using the model. The sequential changes of TJC obtained with our model were in good agreement with observed TJC ratio data, which was considered to show the validity of our analytical method. The following results were obtained; the onset of clinical response was fastest with IFX, the fluctuation of IFX was greater than that of the others, the clinical response with ADA was as stable as that with ETN. The present model was useful to analyze theoretically the anti-rheumatic effect of TNF inhibitors. Our results showed that different dosage regimens have implications on the onset and fluctuation of clinical response.
Drug Metabolism and Pharmacokinetics 01/2014; 29(3). DOI:10.2133/dmpk.DMPK-13-RG-090 · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A diagnostic drug containing manganese chloride tetrahydrate as a major ingredient is available since 2006. It is used in magnetic resonance imaging as a negative contrast medium for magnetic resonance cholangiopancreatography of the gastrointestinal tract. However, there is no report regarding interaction between manganese and new quinolone antibacterials. We investigated the interactions between new quinolone antibacterials and a diagnostic drug containing manganese in vitro. We evaluated the rate of formation of chelate complex by reacting new quinolone antibacterials (levofloxacin, ofloxacin, ciprofloxacin) with a diagnostic drug containing manganese. The EC(50) values of the formation of chelate complex for levofloxacin, ofloxacin, and ciprofloxacin were 5.14 ± 0.14, 5.29 ± 0.14, and 0.96 ± 0.04 mM, respectively. The rates of formation of chelate complex by levofloxacin, ofloxacin, and ciprofloxacin in a reaction with the diagnostic drug were 17.0, 18.9, and 55.5 % in clinical condition, respectively. Our results suggest that a complex of each antibacterial and manganese was formed, with ciprofloxacin causing the strongest interaction. In addition, our findings indicate that the degree of interaction may be an important problem in clinical settings with concomitant administration of a new quinolone antibacterial and diagnostic drug containing manganese.
European Journal of Drug Metabolism and Pharmacokinetics 02/2013; 38(4). DOI:10.1007/s13318-013-0120-6 · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recently, biological agents have been used for treatment of rheumatoid arthritis (RA), though the standard therapeutic doses vary among the agents utilized. To investigate the mechanisms related to those differences, we theoretically analyzed the target molecular binding occupancies of 4 biological agents: tocilizumab, infliximab, adalimumab, and etanercept. The average binding occupancy to the target molecule (Φ(ss)) was estimated to be 99.50 ± 0.44 % in a steady state after administration of the standard therapeutic dose of each agent. Furthermore, achieved American College of Rheumatology (ACR) 20, used as an index of clinical efficacy, increased in correlation with the value for Φ(ss). These results suggest that clinical effects are achieved with a high value of target molecular binding occupancy. Thus, we considered that all of the agents examined in this study are antagonists and elicit clinical efficacy by inhibiting the signaling of biologically active substances that are not necessary for life maintenance and are secreted or released specifically in pathological conditions. In addition, target molecular binding occupancy can be used as an appropriate index for evaluating the standard therapeutic dose of biological agent for RA.
Rheumatology International 01/2013; 33(7). DOI:10.1007/s00296-012-2650-7 · 1.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Kale (Brassica oleracea L. var acephala DC) is a leafy green vegetable belonging to the cabbage family (Brassicaceae) that contains a large amount of health-promoting phytochemicals. There are any reports about the effects of kale ingestion on the chemoprevention function and mechanism, but the interactions between kale and drugs have not been researched. We investigated the effects of kale intake on cytochrome P450 (CYP) metabolism by using cocktail probe drugs, including midazolam (for CYP3A4), caffeine (for CYP1A2), dextromethorphan (for CYP2D6), tolbutamide (for CYP2C9), omeprazole (for CYP2C19), and chlorzoxazone (for CYP2E1). Cocktail drugs were administered into rats treated with kale and cabbage (2000 mg/kg) for a week. The results showed that kale intake induced a significant increase in plasma levels and the AUC of midazolam, caffeine, and dextromethorphan. In addition, the plasma concentration and AUC of omeprazole tended to increase. Additionally, no almost differences in the mRNA expression levels of CYP enzymes in the liver were observed. In conclusion, kale ingestion was considered to have an inhibitory effect on the activities of CYP3A4, 1A2, 2D6, and 2C19 for a reason competitive inhibition than inhibitory changes in the mRNA expressions.
Biomedical Research 09/2012; 33(4):235-42. DOI:10.2220/biomedres.33.235 · 1.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ABSTRACT Oxycodone is an opioid widely prescribed to cancer patients for pain relief. However, the pharmacokinetics of oxycodone has not been sufficiently examined. Therefore the aim of this work was to study population pharmacokinetics of oxycodone in patients with cancer pain. The authors analyzed 108 serum oxycodone samples of 33 individuals with nonlinear mixed-effects model (NONMEM). Population pharmacokinetics was calculated using the one-compartment model of clearance, volume of distribution, bioavailability, absorption constant rate, and lag time. An exponential error model was used to determine interindividual variability and a relative error model was applied to assess residual variability. Population pharmacokinetics of oxycodone at the end point were as follows: CL(L/h) = 10.7 × [1 + (2 - Child-Pugh Classification)] (Class: A = 0, B = 1, C = 2); V(d) (L) = 193; k(a) (h(-1)) = 0.336; T(lag) (h) = 0.859; F (%) = 63.9. Interindividual variability was CL: 30.5%, V(d): 44.6%, and F: 37.0%, and residual variability was 16.2%. As the total clearance in patients with liver dysfunction (Child-Pugh class B) was reduced to 33.3%, serum concentration of oxycodone increased by 1.5. Therefore, it became clear that dose adjustments are essential when treating patients with liver dysfunction. These findings suggest that population parameters are useful for evaluating pharmacokinetics of oxycodone in patients with cancer pain.
Journal of Pain & Palliative Care Pharmacotherapy 09/2012; 26(3):220-5. DOI:10.3109/15360288.2012.702200
[Show abstract][Hide abstract] ABSTRACT: Determining the appropriate dose of transdermal fentanyl (TDF) for the alleviation of cancer pain requires determining the factors causing variations in serum fentanyl concentration after TDF treatment. The objective of this study was to identify these factors and incorporate them into a formula that can be used to predict serum fentanyl concentration after application of a TDF patch. Blood samples of cancer patients treated with a TDF patch for the alleviation of pain were collected at 24, 48, and 72 hours after application to evaluate population pharmacokinetics using the nonlinear mixed-effect model (NONMEM). Based upon this evaluation, Child-Pugh Score and use of a cytochrome P450 3A4 (CYP3A4) inducer were identified as the most significant factors in variations in serum fentanyl concentration and incorporated into the following Final Model formula: CL(fenta) (L/h) = 3.53 × (15 - Child-Pugh Score) × (1 + 1.38 × use or no use of CYP3A4 inducer). Bootstrap evaluation of the Final Model revealed a high convergence rate, suggesting that the model formula is a reliable and useful tool for determining TDF dose for the alleviation of cancer pain.
Journal of Pain & Palliative Care Pharmacotherapy 06/2012; 26(2):98-104. DOI:10.3109/15360288.2012.679725
[Show abstract][Hide abstract] ABSTRACT: In Japan, the recommended dosage regimens of infliximab (IFX) for treatment of rheumatoid arthritis (RA) and Crohn's disease (CD) are different. However, the differences have not been analyzed theoretically. In a previous study, we constructed a pharmacokinetic-pharmacodynamic model to investigate the effects of IFX for CD and found it useful to establish a rational dosage regimen of IFX for individual patients with CD. In the present study, we investigated whether the theory-based model could be used for cases of RA and also used it to evaluate the validity of the dosage regimen. The results obtained with our model were in good agreement with observed tender joint count (TJC) ratio data, which was considered to show the validity of our analysis. Thus, we concluded that the model could be used for patients with RA. Furthermore, a second administration of IFX given 2 weeks after the first infusion was important to achieve remission in the early stage of RA. We also compared the estimated pharmacodynamic parameters of RA with those of CD. The elimination rate constant of inflammation in RA was greater than that in CD, suggesting that the recovery from inflammation in RA is faster than that in CD, and indicating a reason for the difference in dosage between RA and CD. In conclusion, use of our model in light of the individual quantitative factor of tumor necrosis factor (TNF)-α allows establishment of IFX dosage regimens for individual patients.
Rheumatology International 01/2012; 32(1):145-50. DOI:10.1007/s00296-010-1553-8 · 1.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The educational intervention could improve knowledge about rational drug use in the junior high school. Improving knowledge about rational drug use at an early age may be a good way to increase the population's awareness of health, medicines and self-medication. To educate the rational drug use, it is desirable that the school pharmacists participate in this educational program in the junior high school. So we conducted an educational lecture by school pharmacists to promote rational drug use and self-medication in junior high school students. The study compared participant responses before and after a lecture. After the first questionnaire, we lectured the mentioned above to them. Afterward, second questionnaire was conducted. In the second questionnaire, more than 95% of the students understood the contents of the lecture to some extent. After a lecture, students who answered that 'I don't have confidence that I can buy medicines rightly by myself' decreased from 42.7% to 11.7%. And students who answered that 'I don't have confidence that I can use medicines rightly by myself' decreased from 25.2% to 12.6%. It was possible to achieve a favorable modification of attitudes to rational use of medicines in junior high school students. Continuous interventions might allow better effects and could help to fill the gap in health education of the general population.
[Show abstract][Hide abstract] ABSTRACT: Kale is a cruciferous vegetable (Brassicaceae) that contains a large amount of health-promoting phytochemicals. The chronic ingestion of cabbage of the same family is known to accelerate conjugating acetaminophen (AA) and decrease the plasma AA level. Therefore, we examined to clarify the effects of kale on the pharmacokinetics of AA, its glucuronide (AA-G) and sulfate (AA-S). AA was orally administered to rats pre-treated with kale or cabbage (2000 mg/kg/day) for one week. Blood samples were collected from the jugular vein, and the concentrations of AA, AA-G and AA-S were determined. In results, kale ingestion induced an increase in the area under the concentration-time curve (AUC) and a decrease in the clearance of AA, whereas cabbage had almost no influence. In addition, there were significant differences in the AUC of AA-G between the control and kale groups. mRNA expression levels of UDP-glucuronosyltransferases, the enzymes involved in glucuronidation, in the kale group were significantly higher than those in the control group. In conclusion, kale ingestion increased the plasma concentrations of both AA and AA-G. The results suggest that kale ingestion accelerates the glucuronidation of AA, but an increase of plasma AA levels has a different cause than the cause of glucuronidation.
Biomedical Research 12/2011; 32(6):357-62. DOI:10.2220/biomedres.32.357 · 1.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to develop an effective learning system for patient interview training as a part of a pre-education clinical pharmacy. We devised a learning system for performing pharmaceutical care training and then investigated its usefulness. The learning content was a first interview with a simulated patient (SP). All students were divided into 8 groups of 5. Each student practiced interviewing an SP while 2 other students checked the performance of the interviewer, with roles rotated within each group. Additionally, the teachers also rotated among the groups to check the students. We evaluated the results contained in 55 check sheets used by teachers to evaluate the learning system, 223 check sheets used by students, and 110 check sheets used by the SPs. We found that there was a significantly greater number of students rated as unable to perform by the teachers as compared to those rated by the other students. In addition, the ratings for the items, "other symptom is confirmed" and "the severity and properties of the symptom are confirmed" were similar to the above result. Furthermore, there was a significantly greater number of students rated as unable to perform by the teachers as compared to those rated by the SPs in regard to the item "interviewed using open-ended questions." After the students had performed their first attempt at a first interview, 28.6% were rated as unable to perform by the teachers, which was significantly reduced to 15.8% after the fourth attempt and 10.4% after the fifth attempt. Our results indicate that students must practice the first interview at least 4 times before reaching a level of competency. In addition, our findings suggest that both teachers and SPs should undertake pre-education training in clinical pharmacy practice, as the evaluations were significantly different among the teachers, students, and SPs in the present study.
Yakugaku zasshi journal of the Pharmaceutical Society of Japan 01/2011; 131(1):153-9. DOI:10.1248/yakushi.131.153 · 0.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to estimate interindividual differences in the antiemetic effects of 5-HT(3) receptor antagonists by evaluating the influence of pharmacokinetics on 5-HT(3) receptor occupancies, based on receptor occupancy theory.
We analyzed interindividual differences of 5-HT(3) receptor occupancies and antiemetic effects after the oral and/or intravenous administration of standard doses of the following 5-HT(3) receptor antagonists: azasetron, granisetron, indisetron, ondansetron, ramosetron, and tropisetron.
The interindividual difference between maximum and minimum 5-HT(3) receptor occupancies after oral administration ranged from 0.6% to 64.0%, and that difference after intravenous administration ranged from 0.6% to 29.6%. Following oral administration, the interindividual difference between maximum and minimum complete vomiting inhibition rates ranged from 0.2% to 16.1%. After intravenous administration, that difference ranged from 0.8% to 52.5%.
Interindividual differences in the clinical effects of 5-HT(3) receptor antagonists could be evaluated based on receptor occupancy theory, and the differences varied among drugs. Drug selection considering these individual variations might be useful for the patients who experienced vomiting associated with chemotherapy.
International Journal of Clinical Oncology 12/2009; 14(6):518-24. DOI:10.1007/s10147-009-0912-5 · 2.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To investigate the influence of single nucleotide polymorphisms (SNP) on transcription of the 17beta-hydroxysteroid dehydrogenase (HSD17B7) gene.
Luciferase reporter genes containing a 5'-flanking of the HSD17B7 gene, as well as the sequence around the SNP, were transfected into LNCaP and DU145 cells. Then, luciferase assays were carried out.
The presence of the G allele resulted in an increase of transcriptional activity derived from the 5'-flanking region of the HSD17B7 gene by 270% and 370% in LNCaP and DU145 cells, respectively. Transcriptional activity of the HSD17B7 gene containing the G allele was higher than that of the C allele.
The transcriptional activity of the HSD17B7 gene containing the G allele is higher than that of the C allele. This difference in HSD17B7 expression may regulate the risk of peripheral edema as an adverse reaction induced by estramustine phosphate sodium.
International Journal of Urology 10/2009; 16(10):836-41. DOI:10.1111/j.1442-2042.2009.02374.x · 2.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We established a network meeting system program and used it to review a prior pharmaceutical practice training session. Pharmacists at Tokai University Hachioji Hospital gave lectures about dispensing and other tasks performed by clinical pharmacists to third-year undergraduate students at Tokyo University of Pharmacy and Life Sciences. After the lectures, discussions were held using the network meeting system, after which a questionnaire was completed by the students. The questionnaire was answered by 530 students, of whom approximately 90% expressed interest in the program, 80% noted approval of the media used in the system, and 94% thought that the program was useful. Thus, we concluded that the students were motivated by the program to remember what they had learned in the lectures. We also found that the quality of data communication had an effect on the interests and motivation of the students. Based on their evaluation of the media, it was considered that improvements in communication regarding the system were necessary, though the evaluation of the utility of the program was not influenced by the quality of data communication. As a result, we concluded that our network meeting system program was useful to review prior learning of pharmaceutical practice.
Yakugaku zasshi journal of the Pharmaceutical Society of Japan 01/2008; 127(12):2027-33. DOI:10.1248/yakushi.127.2027 · 0.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Propiverine hydrochloride, oxybutynin hydrochloride and terodiline hydrochloride have both anticholinergic and antispasmodic effects, and are used for the management of urinary frequency and incontinence. The average standard therapeutic doses of these drugs differ greatly. We retrospectively analyzed their pharmacological effects with consideration given to muscarinic acetylcholine receptor binding affinities, anticholinergic activities, and inhibitory effects on KCl-induced contraction. Muscarinic acetylcholine receptor occupancies and the inhibitory ratios of the drugs for both acetylcholine-induced and KCl-induced contraction in a steady state after oral administration of standard doses were calculated based on pharmacokinetics and the receptor occupancy theory. The average muscarinic acetylcholine receptor occupancy and inhibitory ratio of acetylcholine-induced contraction were estimated to be 12.6+/-1.06% and 3.27+/-0.74%, respectively, with no significant differences found between the drugs for those parameters. A significant linear relationship was found between muscarinic acetylcholine receptor occupancy and the maximum ratio of increase in bladder urinary capacity. On the other hand, the inhibitory ratios of KCl-induced contraction varied from 0.01 to 0.48%. The present results suggest that muscarinic acetylcholine receptor occupancy is a principal determinant of the therapeutic effect of a drug used for treatment of urinary disturbance.
[Show abstract][Hide abstract] ABSTRACT: Antineoplastic drugs have been shown to exert direct effects on the gut and induce the release of serotonin from the enterochromaffin cells of small intestinal mucosa. It is thought that released serotonin stimulates vagal afferent fibers through 5-HT3 receptors located in the vagal afferent terminals in the gastrointestinal tract and initiates sensory signals to the area postrema and the emetic center, thereby initiating nausea and vomiting. A 5-HT3 antagonist competitively inhibits serotonin at its specific binding sites, 5-HT3 receptors, and thereby elicits an antiemetic effect. Therefore 5-HT3 receptor occupancy of serotonin may be an appropriate indicator of the antiemetic activity of 5-HT3 antagonists. We analyzed 5-HT3 receptor occupancy of serotonin by integrating pharmacokinetic and receptor-binding kinetic parameters based on the receptor occupancy theory to compare the strength of the antiemetic effects of three dosage regimens of azasetron hydrochloride. The inhibitory effects on the binding of serotonin to 5-HT3 receptor of regimen 2 (an intravenous bolus injection of 5 mg of azasetron hydrochloride before and 8 h after chemotherapy) and regimen 3 (an intravenous bolus injection of 2.5 mg followed by 7.5 mg continuous intravenous infusion for 24 h) were longer-lasting than those of regimen 1 (an intravenous bolus injection of 10 mg before the start of chemotherapy). Furthermore, a positive relationship was found between the time of inhibitory effects on the binding of serotonin to 5-HT3 receptor and antiemetic effects of azasetron hydrochloride. From these results, dosage regimens 2 and 3 were considered to be more effective in the long term than regimen 1 in prophylaxis of nausea and vomiting induced by cisplatin.
Yakugaku zasshi journal of the Pharmaceutical Society of Japan 03/2007; 127(2):353-7. · 0.26 Impact Factor