[Kinetic analysis of therapeutic doses of beta-blockers for angina pectoris based on receptor occupancy theory--relationship between beta 1-receptor occupancy or vasodilative action and dose]

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-HT_1B/1D receptor occupancy (Φ_1B and Φ_1D). 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 Ф_1B and Ф_1D, as calculated from the time-course of plasma drug concentration obtained from other studies. The time until Ф_1B and Ф_1D 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 Ф_1B, eletriptan remained at a low level. For Ф_1D, 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 Ф_1B and Ф_1D, the recurrence rate tended to be lower as the duration became longer. In addition, a significant correlation was observed for Ф_1D (p < 0.05). For clarifying the Ф value and time period most closely correlated with recurrence rate, recurrence and Ф_1B and Ф_1D at 6, 12, and 18 h after administration were calculated. The most significant correlation was observed between recurrence rate and Ф_1D at 12 h after administration (p < 0.01).

Conclusions

As an index for evaluating headache recurrence following triptan administration, recurrence rate and Ф_1D 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 analysis of efficacy of biological agent for rheumatoid arthritis based on target molecular binding occupancy

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 (Φss) 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 Φss. 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.

Analysis of Pharmacological Effects of Drugs Used for Treatment of Urinary Disturbance Based on Anticholinergic and Smooth Muscle-Relaxing Effects

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.