OPTIMAL PLASMA CONCENTRATION OF THROMBOMODULIN ALFA TO TREAT SEPSIS-INDUCED DISSEMINATED INTRAVASCULAR COAGULATION.

ABSTRACT: Thrombomodulin alfa (TM alfa) has been shown effective for treatment of disseminated intravascular coagulation (DIC) associated with sepsis, although the optimal therapeutic plasma concentration has not been clarified. In the present study, the plasma trough concentration of TM alfa in septic patients with DIC was determined, then the cutoff value for that concentration showing influence on treatment outcome was calculated using a receiver operating characteristic curve. With a cutoff value of 1,010, the area under the curve of the receiver operating characteristic was 0.669 (95% confidence interval, 0.530-0.808), with sensitivity of 0.458 and specificity of 0.882. To evaluate its accuracy, patients were divided into those above or below the cutoff value, and 90-day survival rates were compared. The above-cutoff group showed a significantly higher 90-day survival rate (91.7%) as compared with the below-cutoff group (63.4%) ( P = 0.017), with a hazard ratio of 0.199 (95% confidence interval, 0.045-0.871). Interestingly, the incidence of hemorrhagic adverse effects was not significantly different between the groups. Based on these results, the recommended plasma trough concentration of TM alfa for treatment of septic DIC is 1,010 ng/mL, which should minimize the risk of severe bleeding while maximizing the therapeutic effect.

Prediction of treatment failure during infliximab induction therapy in inflammatory bowel disease patients based on pharmacokinetic and pharmacodynamic modeling.

BACKGROUND: In infliximab (IFX) treatment for Crohn's disease (CD) and ulcerative colitis (UC), it is difficult to predict treatment failure during the induction phase. In the present study for optimal IFX treatment, we attempted to estimate serum IFX concentration and clinical response in individual patients during the induction phase to predict the indication of therapeutic effect and the possibility of treatment failure in the maintenance phase. METHODS: We estimated pharmacokinetic and pharmacodynamic (PK/PD) parameters and predicted the serum IFX concentration and clinical response using a PK/PD model and Markov chain Monte Carlo Bayesian analysis method during the induction phase. Then, we determined whether the indication of therapeutic effect between predicted and observed clinical response were matched during the maintenance phase. RESULTS: Data obtained from 15 patients were analyzed. The correlation between predicted and observed values of serum IFX concentration (Pearson product-moment correlation coefficient, 0.700; P < 0.0001, n = 68) and clinical response of CD patients (0.790; P < 0.0001, n = 25) and UC patients (0.702; P = 0.0004, n = 21) were significantly high. The indication of therapeutic effect at the final time point of each patient (from day 115 to day 203) were successfully predicted in 14 of 15 patients (93.3%). CONCLUSIONS: This study presents prediction of serum IFX concentration and clinical response in individual patients during induction therapy, with presumption of the indication of therapeutic effect and the treatment failure in the maintenance phase. Our results show the possibility of optimizing IFX therapy during the induction phase.

Therapeutic and Adverse Effects of Thrombomodulin Alfa to Treat Sepsis-Induced Disseminated Intravascular Coagulation.

In the treatment of disseminated intravascular coagulation (DIC), which is a complication of underlying diseases such as infections and malignant tumors, effective plasma concentrations of thrombomodulin (TM) alfa range from 300 to 900 ng/mL; however, appropriate concentrations when treating sepsis-induced DIC are unknown. Thus, our aim was to determine the relationship between plasma concentrations of TM alfa and its therapeutic effects, and hemorrhagic adverse events. First, we calculated the plasma trough concentrations of TM alfa in septic DIC patients. Next, we divided patients into two groups according to their plasma concentrations into a low- and high-concentration group based on a cut-off value of 600 ng/mL. Fourteen and 35 patients were included in the low- and high-concentration groups, respectively. The Japanese Association for Acute Medicine DIC diagnostic criteria score 4 days after TM alfa administration decreased significantly by 2.06 points from baseline in the high-concentration group compared with 0.71 points in the low-concentration group. The 90-day survival rate was significantly higher in the high-concentration group (85.4%) than in the low-concentration group (49.0%) (hazard ratio, 0.27; 95% confidence interval: 0.09-0.86). In contrast, the incidence of serious hemorrhage was not significantly different between the groups. The recommended plasma concentration of TM alfa in the treatment of septic DIC was determined to be higher than 600 ng/mL, and a dose of 380 U/kg (0.06 mg/kg) was necessary to achieve this concentration.

Prediction of clinical effects of infliximab administered for inflammatory bowel disease based on pharmacokinetic and pharmacodynamic modeling.

Infliximab (IFX) is used as a therapeutic agent for ulcerative colitis (UC) and Crohn's disease (CD). Although the dosage regimen has been established through clinical trial experience, it has yet to be assessed with a pharmacokinetic and pharmacodynamic model. The present study analysed sequential changes of clinical response in patients with ulcerative colitis and Crohn's disease following repeated administrations of infliximab using the pharmacokinetic/pharmacodynamic model. In addition, the dosage regimen presently used for patients with ulcerative colitis was evaluated, as well as the potential efficacy gained by increasing the dose and/or reducing the interval of administration for patients with Crohn's disease. Furthermore, the possibility of evaluating the difference between both diseases with regard to the efficacy of infliximab was investigated. Sequential changes in the clinical response values obtained with our model were in good agreement with the observed values following administration of infliximab in patients with ulcerative colitis and Crohn's disease. The results showed the importance of a loading dose for patients with ulcerative colitis, as well as the efficacy of increasing the dose and reducing the interval for patients with Crohn's disease. Also, the efficacy of infliximab for both diseases is suggested to be similar. In conclusion, our results show a possible modeling scenario that can accommodate the clinical response to infliximab administered for ulcerative colitis and Crohn's disease. Furthermore, it provides confirmation for the present dosage regimens given for these diseases.

Comparisons of Usual Dose of Pharmaceutical Products Used in Japan and United States: Can Differences Be Explained by Pharmacokinetics Alone?

BACKGROUND: It is important to examine how a usual drug dose is established in Japan and other countries, and to evaluate that on the basis of pharmacokinetic and pharmacodynamic properties. In the present study, we examined the contributions of area under the curve (AUC) ratio and other factors on differences of usual dose between Japan and the United States. METHODS: We examined drugs approved from January 2008 to January 2011 in Japan and collected related information. For the usual dose set for the same indication in both countries, we compared the maintenance dose values between the countries. We also examined the relationships of AUC ratio and difference of usual dose in both countries. RESULTS: Our results clarified that the usual dose for the same indication is comparable between Japan and the United States for 68.75% of the examined drugs, while that for 31.25% is different. Moreover, among products with different approved doses, the dosage was set higher in the United States for 18.75% and higher in Japan for 12.50%. Our findings indicate that the difference in dose between the countries is associated with AUC ratio for 82.1% and by factors other than AUC ratio for 17.9% of the examined medications. CONCLUSIONS: The approved dose varies between the countries for about one-third of products commonly used. Additionally, it was clarified that not only AUC ratio but also other factors are involved in dosage differences. The present results provide useful information for analysis of factors related to the different usual doses between countries.

Pharmacokinetic and pharmacodynamic model for analysis of adalimumab administered for Crohn's disease.

Adalimumab (ADA) is used as a therapeutic agent for Crohn's disease (CD). Although the dosage regimen has been established through clinical trial experience, it has not been analysed theoretically. The present study analysed of sequential changes in the Crohn's disease activity index (CDAI) after repeated administrations of adalimumab using a pharmacokinetic and pharmacodynamic model. In addition, we analysed the validity of the dosage regimen, and the potential efficacy gained by increasing the dose and reducing the interval of administration. The sequential changes in CDAI values obtained with our model were in good agreement with observed CDAI values, which is considered to show the validity of our analysis. We consider that our results showed the importance of a loading dose of adalimumab to obtain remission in an early stage of active CD. In addition, we showed that patients who have an incomplete response to adalimumab can obtain similar efficacy from increasing the dose and reducing the dose interval. In conclusion, our results showed that the present model may be applied to predict the CDAI values of adalimumab for CD. They indicate the validity of the dosage regimen, as well as the efficacy of increasing the dose and reducing the dose interval.

Evaluation of Drug Efficacy of GLP-1 Receptor Agonists and DPP-4 Inhibitors Based on Target Molecular Binding Occupancy.

Glucagon-like peptide-1 (GLP-1) receptor agonists (liraglutide, exenatide, lixisenatide) have recently been used as anti-diabetes drugs. We examined relationships of the binding occupancy of GLP-1 receptors (Φ) and their clinical efficacy after administration of GLP-1 receptor agonists. Next, by focusing on changes of GLP-1 concentration after administration of dipeptidyl peptidase-4 (DPP-4) inhibitors (vildagliptin, alogliptin, sitagliptin, linagliptin), we analyzed the relationship between Φ and clinical efficacy. Furthermore, using Φ as a common parameter, we compared the clinical efficacy elicited by GLP-1 receptor agonists and DPP-4 inhibitors using a theoretical analysis method. The present results showed that GLP-1 receptor agonists produced their clinical effect at a relatively low level of Φ (1.1-10.7%) at a usual dose. Furthermore, it was suggested that the drugs might achieve their full effect at an extraordinarily low level of Φ. It was also revealed that the Φ value of DPP-4 inhibitors (0.83-1.3%) was at the lower end or lower than that of GLP-1 receptor agonists at a usual dose. Accordingly, the predicted value for hemoglobin A1c (HbA1c) reduction after administration of the GLP-1 receptor agonists was higher than that of DPP-4 inhibitors. We clarified the differences between the therapeutic effects associated with GLP-1 receptor agonists and DPP-4 inhibitors theoretically. Together, the present findings provide a useful methodology for proper usage of GLP-1 receptor agonists and DPP-4 inhibitors.

Effects of FCGRIIIa-158V/F polymorphism on antibody-dependent cellular cytotoxicity activity of adalimumab.

The associations between the efficacy of IgG reagents and the FCGRIIIa-158V/F polymorphism (rs396991) have been investigated. Although the genotype frequencies in healthy Japanese have been reported, those have varied, as one study reported that the proportions of V/V, V/F, and F/F were 59.1%, 38.6%, and 2.3%, respectively, while another study found that they were 4%, 44%, and 52%, respectively. However, there are no known investigations of the association between the antibody-dependent cellular cytotoxicity (ADCC) activity of adalimumab (ADA), an IgG reagent, in combination with FcγRIIIa and the polymorphism. In this study, we analyzed healthy Japanese to clarify genotype frequency using a direct sequence method. In addition, we examined the association between the ADA-mediated ADCC activity and the polymorphism. Our results showed that the frequencies of the V/V, V/F, and F/F genotypes in healthy Japanese were 9.2%, 39.8%, and 51.0%, respectively. The average activity of ADA-mediated ADCC was 25.0%, 19.0%, and 13.3% in the V/V, V/F, and F/F genotypes, respectively. Then, the ADCC activity of V/V was significantly higher than that of F/F (p < 0.05) in therapeutic concentration. The differences in therapeutic effect of ADA among individuals can be explained, in part, by ADCC activity via the FCGRIIIa-158V/F polymorphism.

Theoretical method for evaluation of therapeutic effects and adverse effects of epidermal growth factor receptor tyrosine kinase inhibitors in clinical treatment.

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are used for non-small cell lung cancer patients with an EGFR gene mutation. However, skin disorders are known as adverse events. In the present study, we investigated whether EGFR-TK occupancy is useful as an index for assessing clinical efficacy and adverse events for the proper use and development of EGFR-TKIs. Average binding occupancies (Φ ss) of EGFR-TKIs, gefitinib and erlotinib, for the EGFR-TK of cancer or skin cells were calculated. The relationships of Φ ss with response rate (RR) or frequency of rash were analyzed using the ternary complex model. Then, the relationships between the dose of EGFR-TKIs and RR or frequency of rash were examined. Gefitinib showed a greater difference for Φ ss value for both wild-type and mutant EGFR as compared to erlotinib at usual dose. The RR increased in a nonlinear manner rapidly rising when Φ ss exceeded 95%. It was thought that a very high Φ ss value might be needed to obtain the therapeutic effect of EGFR-TKIs. Meanwhile, the frequency of rash increased in a linear manner along with elevation of Φ ss. It was shown that the K d ratio (K d for mutant/K d for wild type) was less than 0.001, when the high RR and low frequency of rash were obtained simultaneously. The results showed that the therapeutic effects and skin disorder can be assessed by using Φ ss. Furthermore, it is likely that a proper choice of drug and dose can be made by using Φ ss in EGFR-TKI therapy.

Analysis of Clinical Efficacy and Adverse Effects of ß-Blocking Agents Used Clinically for Chronic Heart Failure.

Clinical efficacy and adverse effects of the ß-blocking agents, carvedilol, bisoprolol, and metoprolol were analyzed theoretically, and then compared quantitatively, for the purpose of determining their proper use for chronic heart failure. Initially, we evaluated occupancy binding to the ß1 and ß2 receptors (Фssß1 and Фssß2) by these drugs. Thereafter, we examined the relationship between Фssß1 values and left ventricular ejection fraction (LVEF) increase rate to determine efficacy. The result showed that the efficacy with carvedilol could be attained with a lower Фssß1 value than the others. Therefore, we constructed a model under the assumption that ß-blocking agents exert both indirect action of LVEF increase through the ß1 receptor and direct action on ryanodine receptor 2. Using the model, it was suggested that these drugs have no differences in regard to the efficacy, while it was clarified theoretically that only carvedilol produces an effect that directly involves ryanodine receptor 2 at clinical doses. We also investigated decreases in heart rate and forced expiratory volume in 1 s as adverse effects of ß-blocking agents using a ternary complex model. It was indicated that carvedilol is less likely to induce a heart rate decrease. Meanwhile, it was also suggested that the risk of an asthmatic attack was higher for carvedilol at clinical doses. Our results are considered useful for selection of a proper ß-blocking agent and its administration at a reasonable dose for successful heart failure therapy.

Study of Safety Evaluation in Dispensing of Medicines-Analysis of Relationship between Dispensing Error Rate, Inspecting Error Rate, and Malpractice Rate.

In this study, we established a methodology to calculate the rate of overlooking a dispensing error (inspecting error rate) as a new index for the purpose of determining dispensing error and malpractice rates. Using data obtained from analyses of these error rates at our and two other hospitals, an inspecting error rate was calculated for each institution. Our results showed that inspecting errors occurred at a frequency 3-5 times greater as compared to dispensing errors at each of the examined hospitals. We concluded that construction of a higher quality safety management system would be enabled by incorporation of an inspecting error rate as a new index to evaluate medical safety in regard to dispensing of medicines and managing inspection accuracy.

Evaluation of drug efficacy of DPP-4 inhibitors based on theoretical analysis with pharmacokinetics and pharmacodynamics.

Dipeptidyl peptidase-4 (DPP-4) inhibitors are used clinically as therapeutic agents for the treatment of diabetes. To determine the rate of DPP-4 inhibition induced by these inhibitors, pharmacokinetic and pharmacodynamic parameters were used to theoretically examine the relationship between the rate of DPP-4 inhibition and clinical efficacy following the administration of four different DPP-4 inhibitors (sitagliptin, vildagliptin, alogliptin, linagliptin) by focusing on the increase in the level of glucagon-like peptide-1 (GLP-1) induced by their administration. On the basis of the relationship shown, changes in clinical efficacy in association with dose change were examined in order to discuss clinical dosage from the standpoint of proper usage. The results indicate that a high rate of DPP-4 inhibition is necessary for the onset of the effect of an administered the DPP-4 inhibitor and that the average value for the DPP-4 inhibition rate can be utilized as a common parameter of clinical efficacy. Furthermore, the efficacy profiles of the present DPP-4 inhibitors could be demonstrated on the basis of an increase in the GLP-1 level. It is considered that the present findings provide useful information for promoting the proper clinical use of DPP-4 inhibitors. Copyright © 2016 John Wiley & Sons, Ltd.

Investigation of Appropriate Inhalation Technique for Mometasone Furoate Dry Powder Inhaler.

The aim of this study was to establish an appropriate inhalation method with a mometasone furoate dry powder inhaler (MF-DPI). Utilizing a tone-based inhalation training device, we investigated the maximum peak inspiratory flow rate time (Tmax PIFR) and peak inspiratory flow rate (PIFR) to determine whether either had an influence on lung deposition with use of an MF-DPI. A low tone indicated a PIFR of 28 L/min and a high tone that of 40 L/min, while 60 L/min was considered to be the standard. We established an inhalation profile in consideration of a human inhalation pattern, in which Tmax PIFR was set at 0.5 s (Tmax PIFR 0.5 s) and 2.5 s (Tmax PIFR 2.5 s). The reference cut-off value derived with a cascade impactor test was used for evaluation of the rate of delivered dose in the lung, which was the amount of drug from stage 3 to 7 at all PIFRs. We then investigated the relationship of the fine particle fraction (FPF) with the claimed dose at Tmax PIFR of 0.5 s and PIFR. There were no differences among the Tmax PIFR values for the doses emitted from the device or for the rate of delivered doses in stages 3-7. However, FPF for the claimed dose at 40 L/min was significantly lower than that at 60 L/min, which was dependent on PIFR. Our results showed that PIFR but not Tmax PIFR has an effect on lung deposition after inhalation with an MF-DPI.

Effects of tumor necrosis factor α-857C/T polymorphism on the expression of tumor necrosis factor α.

It was reported that homozygosity for a lymphotoxin α (LTA) 1-1-1-1 haplotype (LTA NcoI-TNFc-aa13L-aa26) may identify subgroups with a poor response to infliximab in Crohn's disease patients. Previously, we found a genetic polymorphism that linked with the LTA 1-1-1-1 haplotype and noted that it was a tumor necrosis factor (TNF) α-857 T allele. To investigate the effects of the -857C/T (rs1799724) polymorphism on the expression of TNFα, we compared levels of transcriptional activity of the gene, mRNA, and protein of the TNFα. The change in transcriptional activity of the -857T allele was higher than that of the -857C allele. Furthermore, the accumulated transcriptional activity of the -857T allele was 1.3-fold higher than that of the -857C allele up to 48 h. The levels of mRNA and protein of the TNFα after stimulation were also shown to be significantly higher in -857C/T as compared to the -857C/C genotype. Our results suggested that TNFα promoter -857T is higher than -857C in the levels of transcriptional activity of the gene, mRNA, and protein of the TNFα. The differences in therapeutic effect of TNF inhibitors among individuals can be explained in part by the induction ability of TNFα via the -857C/T polymorphism.

Prediction of Therapeutic Effect of Rasburicase on Hyperuricemia Associated with Chemotherapy Based on Theoretical Model.

Rasburicase has a strong and fast effect for reducing blood levels of uric acid. However, there have been no reports of theoretical analysis for the rational dose and interval of administration. Thus we constructed a pharmacokinetic and pharmacodynamic model to determine changes in uric acid level after rasburicase administration at various doses and regimens. The time courses of uric acid level predicted using our model were in good agreement with observed data, indicating adequate performance for our model. The therapeutic effects after a single infusion at various rates of generation of uric acid were predicted. The maximum effect was not a large difference, in spite of the generation rate. Then, the therapeutic effects of repeated administrations were predicted. The effect did not change when rasburicase was administered at more than the usual dose. Besides, as the administration interval increased, the difference between minimum and maximum level of uric acid became greater. However, in all doses and regimens, adequate therapeutic effects were obtained. In conclusion, the model was found useful for predicting therapeutic effect of rasburicase and individually determining rational dosage regimen of rasburicase.

Evaluation of clinical bradycardiac effect and respiratory adverse effect of ß-blocking agents in coronary computed tomography angiography based on theoretical analysis.

ß-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 ß-blocking agents (landiolol, esmolol, propranolol, metoprolol and atenolol) used for CCTA. The changes of the occupancy binding to ß1 or ß2 receptor of these drugs were calculated based on the receptor occupancy theory. Thereafter, we predicted both the rate of heart rate decline (▲HR) as a clinical effect and the rate of decrease in forced expiratory volume in 1 s (▲FEV1) as an adverse effect, by using the ternary complex model. The results showed that the drugs with ▲HR greater than 10 %, necessary for CCTA, were as follows: landiolol at 13.5 %, propranolol at 11.0 %, and atenolol at 22.6 %. The ▲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, ▲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.

Theoretical analysis of headache recurrence in patients administered triptans for migraine based on receptor occupancy.

BACKGROUND: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

Theoretical evaluation of antiemetic effects of 5-HT3 receptor antagonists for prevention of vomiting induced by cisplatin.

5-HT(3) 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-HT(3) receptor antagonists, as those effects are not based solely on the t(1/2) value. We theoretically evaluated the antiemetic effects of three 5-HT(3) receptor antagonists (granisetron, azasetron, palonosetron) on cisplatin-induced nausea and vomiting by estimating the time course of the 5-HT(3) receptor occupancy of serotonin. We estimated the 5-HT(3) receptor occupancy of serotonin in the small intestine, based on the time course of plasma concentration of each 5-HT(3) receptor antagonist and the time course of concentration of serotonin near the 5-HT(3) receptor in the small intestine after administration of cisplatin. The antiemetic effect of each 5-HT(3) receptor antagonist was evaluated based on the normal level of 5-HT(3) receptor occupancy of serotonin. Our results suggest that an adequate antiemetic effect will be provided when a dose of 75 mg/m(2) 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-HT(3) 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/m(2) of cisplatin.

Theory-based analysis of clinical efficacy of triptans using receptor occupancy.

BACKGROUND: 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 (Φ1B and Φ1D). Receptor occupancies were calculated from both the pharmacokinetic and pharmacodynamic data of triptans. METHODS: 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 Ф1B and Ф1D (AUCФ1B and AUCФ1D). Moreover, parameters expressing drug transfer and binding rates (Acp, AФ1B, AФ1D) were calculated. RESULTS: Our calculations showed that Фmax1B and Фmax1D 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, AUCΦ1B, AUCΦ1D, and Acp · AUCcp differed with each drug and administered form, whereas a significant relationship was found between the therapeutic effect and AΦ1B · AUCΦ1B or AΦ1D · AUCΦ1D that was not affected by the drug and the form of administration. CONCLUSIONS: 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.