Inhibition Of Thromboxane B2 Generation Research Articles

Dosage exploration of meloxicam according to CYP2C9 genetic polymorphisms based on a population pharmacokinetic-pharmacodynamic model.

Meloxicam, used for treating inflammatory diseases, shows large differences in metabolism according to CYP2C9 genetic polymorphisms; however, there are few studies on dose regimen setting based on quantitative predictions. The aim of this study was to determine the appropriate meloxicam dose regimen for each genotype through population pharmacokinetic-pharmacodynamic modeling of meloxicam by considering CYP2C9 genetic polymorphisms. For modeling, previously reported pharmacokinetic (plasma concentration)-pharmacodynamic (inhibition of thromboxane B2 generation) data of meloxicam were collected for CYP2C9 genetic polymorphisms (n=43). And these data were mainly used in the modeling process. Through simulations of the established models, steady-state pharmacokinetic-pharmacodynamic profiles were obtained according to meloxicam multiple exposures for each CYP2C9 genotype, and predictions were made based on dose regimen changes. Genetic polymorphisms of CYP2C9 were identified as key covariates that significantly affected pharmacokinetic variability of meloxicam between individuals. The developed meloxicam population pharmacokinetic-pharmacodynamic model predicted pharmacokinetic results of the 7.5mg meloxicam administration groups (n=26) for CYP2C9*1/*1 and *1/*3 as an external validation. The results of model simulation revealed that the differences were 2.39-5.42 times for steady-state mean plasma concentrations and 1.21-1.71 times for the degree of inhibition of thromboxane B2 generation following multiple exposures for CYP2C9*1/*1 versus *1/*13, *1/*3, and *3/*3. This suggested that thromboxane B2 inhibition following increased plasma exposure to meloxicam differed significantly according to CYP2C9 genetic polymorphisms. The dose of meloxicam in CYP2C9*1/*13, *1/*3, and *3/*3 was randomly adjusted to 1.6-15 mg to approximate the mean thromboxane B2 inhibition for CYP2C9*1/*1 at steady state, the dose intervals varied from 24 h to 48 h. The results suggested that clinical dose adjustment of meloxicam would be necessary to account for CYP2C9 genetic polymorphisms and reduce side effects. This study suggests a clearer direction for setting up clinical therapy based on personalized medicine and quantitative predictions for meloxicam.

Strongly increased exposure of meloxicam in CYP2C9*3/*3 individuals

The effects of CYP2C9*1/*3 and *3/*3 genotypes on the pharmacokinetics and pharmacodynamics of meloxicam were evaluated in healthy Korean subjects. After oral administration of 15 mg meloxicam, the plasma concentrations of meloxicam were assessed in 11 CYP2C9*1/*1 individuals, eight CYP2C9*1/*3 individuals, and three CYP2C9*3/*3 individuals. The pharmacodynamic effects were determined by measuring thromboxane B2 generated in blood. A nine-fold lower apparent oral clearance and an eight-fold higher AUC0-∞ of single-dose meloxicam were observed in CYP2C9*3/*3 individuals when compared with CYP2C9*1/*1 individuals. CYP2C9*3/*3 individuals also showed markedly increased inhibition of thromboxane B2 generation by meloxicam. These results indicate that CYP2C9*3/*3 individuals may be at a higher risk for concentration-dependent adverse effects during long-term treatment with standard doses of meloxicam.

The H1-histamine antagonist dithiaden inhibits human platelet function in vitro

The H1-histamine receptor antagonist Dithaden® inhibited in a dose-dependent manner, human platelet aggregation in vitro that was induced with stimuli in the following rank order of potency: thrombin > A23187 > adrenaline > ADP. The aggregation of platelets in plasma induced with adrenaline was inhibited by Dithiaden (DIT) (both the first and the second phase) and the onset of the second phase was prolonged significantly. In a concentration-dependent manner DIT inhibited thrombin- and calcium ionophore A23187-induced [3H]arachi-donic acid liberation from, and peroxidation (measured as malondialdehyde formation) of membrane phospholipids. The same effect of DIT was found for the inhibition of thromboxane B2 generation. It is suggested that DIT does not inhibit stimulated platelets at specific histamine receptors sites but rather at the phospholipase A2 and thromboxane synthase level. Results from in vitro experiments should be verified in vivo.

Effects of a specific thromboxane synthetase inhibitor on thromboxane generation and excretion in healthy dogs

SUMMARY A specific thromboxane synthetase inhibitor, 3-methyl- 2 (3-pyridyl)-l-indoleoctanoic acid (CGS 12970) was administered orally to 6 healthy adult Beagles at a dosage of 30 mg/kg of body weight. Blood generation of thromboxane B2 and urinary excretion of thromboxane B2 were measured before and after administration of CGS 12970. Although 97 ± 0.4% inhibition of thromboxane B2 generation was observed within 2 hours after a single dose of CGS 12970 was administered orally, an effect on urinary excretion of thromboxane B2 was not observed. Additionally, oral administration of 30 mg/kg every 12 hours resulted in 80 ± 14% inhibition of thromboxane B2 generation but had no effect on urinary thromboxane B2 excretion.