Evaluation of herb-drug interaction of ambrisentan with shikonin based on UPLC-MS/MS.

CONTEXT: Ambrisentan is an oral endothelin-receptor antagonist (ERA). However, there is no report on the interaction between ambrisentan and shikonin. OBJECTIVE: To investigate the effect of shikonin on ambrisentan metabolism in vivo and in vitro. MATERIALS AND METHODS: This study developed an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for simultaneous determination of ambrisentan and (S)-4-hydroxymethyl ambrisentan in rat plasma. Twelve male Sprague-Dawley (SD) rats were divided into two groups (n = 6): the control group and shikonin (20 mg/kg) group. The pharmacokinetics of ambrisentan (2.5 mg/kg) were investigated after 30 min. Additionally, human and rat liver microsomes were used to investigate the herb-drug interaction. RESULTS: The UPLC-MS/MS method was shown to be accurate, precise and reliable, and was successfully applied to the herb-drug interaction study of ambrisentan with shikonin. When co-administrated with 20 mg/kg shikonin, the Cmax and AUC(0-∞) of ambrisentan were significantly increased by 44.96 and 16.65%, respectively (p < 0.05). In addition, there were modest decreases in (S)-4-hydroxymethyl ambrisentan Cmax and AUC(0-∞) in the presence of shikonin (p < 0.05), which indicated that these results were in accordance with the inhibition of shikonin on ambrisentan metabolism. Moreover, enzyme kinetic study indicated that shikonin had an inhibitory effect on human and rat microsomes where the IC50 values of shikonin were 5.865 and 6.358 µM, respectively. CONCLUSIONS: Our study indicated that shikonin could inhibit ambrisentan metabolism. Further studies need to be carried out to verify whether similar interaction truly apply in humans and whether this interaction has clinical significance.

Development of omega-3 loxoprofen-loaded nanoemulsion to limit the side effect associated with NSAIDs in treatment of tooth pain.

The majority of newly developed drugs need to be incorporated with delivery systems to maximize their effect and minimize side effects. Nanoemulsions (NEs) are one type of delivery system that helps to improve the solubility and dissolution of drugs, attempting to enhance their bioavailability and onset of action. The objective of this investigation was to develop an omega-3 oil-based NE loaded with loxoprofen (LXP) to enhance its dissolution, in vitro release, and mucosal penetration and decrease its mucosal ulcerative effects when applied in an oral treatment. LXP-loaded NEs were formulated with varying levels of omega-3 oil (10-30%), surfactant polyoxyethylene-C21-ethers (laureth-21) (40-60%), and co-surfactant polyethylene glycol-40 hydrogenated castor oil (HCO-40) (30-50%) using an extreme vertices mixture design. The developed NEs were characterized for globule size and drug loading capacity. The optimal formulation was tested for in vitro drug release, ex vivo permeation, and ulcer index value. The developed NE acquired a globule size ranging 71-195 nm and drug loading capacity of 43-87%. Considering the results of the in vitro release study, the optimized NE formulation achieved 2.45-fold and 2-fold increases in drug permeation across tested mucosa compared to a marketed tablet and drug aqueous dispersion, respectively. Moreover, the optimum NE exhibited the best ulcer index in comparison to drug aqueous suspension and different formulations when tested in rats. Overall, this research highlights the capacity of NEs to deliver LXP with enhanced solubility, drug release, and permeation while effectively protecting the application site from side effects of the model drug.

Artepillin C: A comprehensive review of its chemistry, bioavailability, and pharmacological properties.

Artepillin C (ARC), a prenylated derivative of p-coumaric acid, is one of the major phenolic compounds found in Brazilian green propolis (BGP) and its botanical source Baccharis dracunculifolia. Numerous studies on ARC show that its beneficial health effects correlate with the health effects of both BGP and B. dracunculifolia. Its wide range of pharmacological benefits include antioxidant, antimicrobial, anti-inflammatory, anti-diabetic, neuroprotective, gastroprotective, immunomodulatory, and anti-cancer effects. Most studies have focused on anti-oxidation, inflammation, diabetic, and cancers using both in vitro and in vivo approaches. Mechanisms underlying anti-cancer properties of ARC are apoptosis induction, cell cycle arrest, and the inhibition of p21-activated kinase 1 (PAK1), a protein characterized in many human diseases/disorders including COVID-19 infection. Therefore, further pre-clinical and clinical studies with ARC are necessary to explore its potential as intervention for a wide variety of diseases including the recent pandemic coronaviral infection. This review summarizes the comprehensive data on the pharmacological effects of ARC and could be a guideline for its future study and therapeutic usage.

Quantitative determination of characteristic components from compound of Lysionotus pauciflorus Maxim. by LC-MS/MS and its application to a pharmacokinetic study.

Tuberculosis of cervical lymph nodes is called scrofula in Traditional Chinese Medicine (TCM). Clinical manifestation is that unilateral or bilateral neck can have multiple enlarged lymph nodes of different sizes. Current therapeutic drugs include Lysionotus pauciflorus Maxim. tablets and compound of Lysionotus pauciflorus Maxim., which have a significant effect on tuberculosis of cervical lymph nodes. This compound is composed of three herbs, Lysionotus pauciflorus Maxim., Prunella vulgaris L. and Artemisia argyi Levl.et Vant. A selective and sensitive LC-MS/MS method was established and validated in rat plasma for the first time. Chromatographic separation was achieved on a Wonda Cract ODS-2 C18 Column (150 mm × 4.6 mm, 5 µm). The mobile phase contained 0.1% formic acid aqueous solution and acetonitrile with a flow rate of 0.8 mL/min. The detection was performed in negative electrospray ionization mode and the precursor/product ion transitions of six components and internal standard (IS) sulfamethoxazole were quantified in multiple reaction monitoring (MRM) using QTRAP-3200 MS/MS. The method fulfilled US Food and Drug Administration guidelines for selectivity, sensitivity, accuracy, precision, matrix effect, extraction recovery, dilution integrity, and stability. This proposed method was then successfully applied to a pharmacokinetic study after oral administration of 10 mL/kg compound extracts in rats. The pharmacokinetic parameters and plasma concentration-time profiles would prove valuable in pre-clinical and clinical investigations on the disposition of compound medicine.

Comparison of Blood Profiles of γ-Oryzanol and Ferulic Acid in Rats after Oral Intake of γ-Oryzanol.

γ-Oryzanol (OZ), a bioactive phytochemical abundant in cereals such as rice, has been reported to be mainly hydrolyzed to ferulic acid (FA) in the body. Meanwhile, in our previous study, we revealed that a part of OZ is absorbed into the body and exists in its intact form. However, the comprehensive absorption profile of OZ and its metabolites (e.g., FA) after OZ intake has not been fully elucidated yet. Therefore, in this study, we measured the concentrations of OZ, FA, and FA conjugates (i.e., FA sulfate and glucuronide) in the blood of rats with the use of HPLC-MS/MS after a single oral administration of 300 µmol/kg body weight of rice bran OZ (RBOZ). As a result, intact OZ along with FA and FA conjugates existed in the blood, which implied that these constituents may all contribute to the physiological effects under OZ intake. Additionally, when an equimolar amount of FA (300 µmol/kg body weight) was administered, it was found that the absorption profile of FA was significantly different from that when RBOZ was administered.

Evaluation of γ-oryzanol Accumulation and Lipid Metabolism in the Body of Mice Following Long-Term Administration of γ-oryzanol.

γ-Oryzanol (OZ), abundant in rice bran oil, has gained attention due to its physiological activities (e.g., lipid-lowering effects). However, the absorption and metabolism of orally ingested OZ have not yet been fully elucidated. In this study, diets containing normal or high contents of OZ were fed to obesity model mice for 8 weeks, and OZ concentrations in plasma and organs were analyzed by HPLC-MS/MS. To evaluate the relationship between OZ accumulation and lipid metabolism in vivo, lipid concentrations in the mice plasma and liver were also measured. As a result, the accumulation of intact OZ in plasma and organs was seen in mice fed diets containing OZ, where mice fed diets containing higher OZ contents demonstrated higher levels of OZ accumulation and lower amounts of plasma lipids. These results, in combination with our additional data from a single oral administration test, suggest the possibility that intact OZ, along with its metabolites (e.g., ferulic acid), is biologically-active.

Pharmacokinetics of vitamin E, γ-oryzanol, and ferulic acid in healthy humans after the ingestion of a rice bran-enriched porridge prepared with water or with milk.

PURPOSE: In this study, we investigated the absorption and excretion kinetics of antioxidant dietary phytochemicals (vitamin E, γ-oryzanol, and ferulic acid) in healthy humans after the ingestion of an oatmeal porridge supplemented with rice bran extract (RBE) prepared with water or with whole milk, and we compared it with the intake of an equivalent dose of the rice bran content, in the form of RBE oil. METHODS: Twelve healthy volunteers (6 men and 6 women) orally ingested RBE oil (2 g) or RBE-enriched porridge (35 g, including 2-g RBE) with water or with milk, in a three-armed, crossover trial. Blood and urine samples were collected at baseline and up to 24 h after intake. Vitamin E (α-, ß-, γ-, and δ-tocopherols and tocotrienols), ferulic acid (FA), and γ-oryzanol (ORY) were quantified by HPLC. RESULTS: The ingestion of RBE-fortified oatmeal porridge and RBE oil significantly increased FA concentrations in plasma, showing faster absorption and higher maximum plasma concentrations after the intake of the porridges, irrespective of the addition of water or milk. At least part of the FA could have been hydrolyzed from ORY. However, plasma vitamin E concentrations did not increase from baseline, and no intact FA esters (cycloartenyl ferulate, 24-methylenecycloartanyl ferulate, campesteryl ferulate, and ß-sitosteryl ferulate) were detected in plasma or urine with any of the meal treatments. CONCLUSIONS: Rice bran extract-enriched porridge and, to a lesser extent, RBE oil, provide relevant sources of bioaccessible and bioavailable ferulic acid, and could be further developed into functional foods with health potential.

Effects of Acanthopanax senticosus on Brain Injury Induced by Simulated Spatial Radiation in Mouse Model Based on Pharmacokinetics and Comparative Proteomics.

The active compounds in Acanthopanax senticosus (AS) have different pharmacokinetic characteristics in mouse models. Cmax and AUC of Acanthopanax senticosus polysaccharides (ASPS) were significantly reduced in radiation-injured mice, suggesting that the blood flow of mouse was blocked or slowed, due to the pathological state of ischemia and hypoxia, which are caused by radiation. In contrast, the ability of various metabolizing enzymes to inactivate, capacity of biofilm transport decrease, and lessening of renal blood flow accounts for radiation, resulting in the accumulation of syringin and eleutheroside E in the irradiated mouse. Therefore, there were higher pharmacokinetic parameters-AUC, MRT, and t1/2 of the two compounds in radiation-injured mouse, when compared with normal mouse. In order to investigate the intrinsic mechanism of AS on radiation injury, AS extract's protective effects on brain, the main part of mouse that suffered from radiation, were explored. The function of AS extract in repressing expression changes of radiation response proteins in prefrontal cortex (PFC) of mouse brain included tubulin protein family (α-, ß-tubulin subunits), dihydropyrimidinase-related protein 2 (CRMP2), γ-actin, 14-3-3 protein family (14-3-3ζ, ε), heat shock protein 90ß (HSP90ß), and enolase 2. The results demonstrated the AS extract had positive effects on nerve cells' structure, adhesion, locomotion, fission, and phagocytosis, through regulating various action pathways, such as Hippo, phagosome, PI3K/Akt (phosphatidylinositol 3 kinase/protein kinase B), Neurotrophin, Rap1 (Ras-related protein RAP-1A), gap junction glycolysis/gluconeogenesis, and HIF-1 (Hypoxia-inducible factor 1) signaling pathways to maintain normal mouse neurological activity. All of the results indicated that AS may be a promising alternative medicine for the treatment of radiation injury in mouse brain. It would be tested that whether the bioactive ingredients of AS could be effective through the blood-brain barrier in the future.

Preclinical evaluation of saroglitazar magnesium, a dual PPAR-α/γ agonist for treatment of dyslipidemia and metabolic disorders.

1. Saroglitazar, a novel peroxisome proliferator-activated receptor (PPAR) agonist, regulates lipid and glucose metabolism. The objective of this report is to provide a preclinical evaluation (in vitro/in vivo) of ADME properties of saroglitazar. In vitro studies included determination of permeability, metabolic stability, plasma protein binding, CYP reaction phenotyping and CYP inhibitory liability. In vivo studies included oral bioavailability and pharmacokinetic assessment in mouse, rat and dog. The excretion of saroglitazar was determined in rats. Exploratory metabolism of saroglitazar was evaluated using in vitro and in vivo samples. 2. Saroglitazar was metabolically more stable in human liver microsomes as compared to rat and dog liver microsomes, highly protein bound (98-99.6%) with high Caco2 permeability (104 nm/s) with <2 efflux ratio. In vitro metabolism in rat, dog and human liver microsomes revealed three putative metabolites corresponding to di-hydroxylation, mono-oxygenation and dehydrogenation moieties. 3. Oral bioavailability was 100%, 72% and 47% in mouse, rat and dog, respectively. The intravenous clearance and volume of distribution of saroglitazar were 3.6, 8.5 and 6.9 mL/min/kg and 1.3, 4.8 and 1.8 L/kg for mouse, rat and dog, respectively. The elimination half-life of saroglitazar ranged between 6 and 15 h. Saroglitazar appeared to be eliminated via hepatobiliary route with negligible renal excretion.

The effect of induction of CYP3A4 by St John's wort on ambrisentan plasma pharmacokinetics in volunteers of known CYP2C19 genotype.

To evaluate the impact of CYP2C19 polymorphisms on ambrisentan exposure and to assess its modification by St. John's wort (SJW), 20 healthy volunteers (10 CYP2C19 extensive, four poor and six ultrarapid metabolizers) received therapeutic doses of ambrisentan (5 mg qd po) for 20 days and concomitantly SJW (300 mg tid po) for the last 10 days. To quantify changes of CYP3A4 activity, midazolam (3 mg po) as a probe drug was used. Ambrisentan pharmacokinetics was assessed on days 1, 10 and 20, and midazolam pharmacokinetics before and on days 1, 10, 17 and 20. At steady state, ambrisentan exposure was similar in extensive and ultrarapid metabolizers but 43% larger in poor metabolizers (p < 0.01). In all volunteers, SJW reduced ambrisentan exposure and the relative change (17-26%) was similar in all genotype groups. The extent of this interaction did not correlate with the changes in CYP3A activity (midazolam clearance) (rs = 0.23, p = 0.34). Ambrisentan had no effect on midazolam pharmacokinetics. In conclusion, SJW significantly reduced exposure with ambrisentan irrespective of the CYP2C19 genotype. The extent of this interaction was small and thus likely without clinical relevance.

[Comparative pharmacokinetics of syringin, eleutheroside E and isofraxidin in rat plasma after intravenous administration of each monomer and Ciwujia injection].

To compare the pharmacokinetics of syringin, eleutheroside E and isofraxidin after intravenous administration of each monomer and Ciwujia injection. Twenty-four Sprague-Dawley rats were randomly divided into four groups and intravenously administrated with syringin, eleutheroside E, isofraxidin, and Ciwujia injection, respectively. The concentrations of the three components in rat plasma were determined by LC-MS/MS. DAS 2.0 software was applied to calculate the pharmacokinetic parameters while the SPSS 17.0 software was used for statistical analysis. Significant difference (P < 0.05) was found between each monomer and the injection on the main pharmacokinetic parameters such as AUC, CL and t1,/2. Compared with the injection, the group treated with the syringin has obvious decrease in AUC, and increase in CL while the group treated with eleutheroside E has obvious increase in AUC, and decrease in CL The t1/2 of isofraxidin was prolonged in Ciwujia injection. Pharmacokinetic characters of the ingredients in the injection varied greatly from the monomer. Other constituents in the injection may have an impact on the pharmacokinetic profiles of these three components.

Optimization, in vitro release and bioavailability of gamma-oryzanol-loaded calcium pectinate microparticles reinforced with chitosan.

Response surface methodology was used to optimize coating conditions, including chitosan concentration (X(1)) and coating time (X(2)), for sustained release of chitosan-coated Ca-pectinate (CP) microparticles containing oryzanol (OZ). The optimized values of X(1) and X(2) were found to be 1.48% and 69.92 min, respectively. These optimized values agreed favorably with the predicted results, indicating the utility of predictive models for the release of OZ in simulated intestinal fluid. In vitro release studies revealed that the chitosan-coated CP microparticles were quite stable under acidic conditions, but swell and disintegrate under alkaline conditions. In vivo release study of OZ, physically entrapped within chitosan-coated CP microcapsules, demonstrated the sustained release of OZ and could be used to improve the bioavailability of OZ following oral administration.

[Effect of several penetration enhancers on transdermal absorption in vitro of syringin, chologenic acid and rutin in Xuelian cataplasm].

OBJECTIVE: To study the effects of different penetration enhancers on the transcutaneous permeability of syringin, chologenic acid and rutin in Xuelian cataplasm in vitro and to determine the effective enhancer. METHOD: Using improved Franz-type diffusion cell and excised big mouse skin in vitro as transdermal barrier, the kinetics parameters of syringin, chologenic acid and rutin in Xuelian cataplasm such as cumulative permeation quantity, permeation rate were determined by HPLC. The enhancement ability of azone (A-zone), propylene glycol (PG) was investigated when used either uniquely or combinatively. RESULT: With the 7% azone, the syringin, chologenic acid and rutin in Xuelian cataplasm could penetrate through the skin of rats well. CONCLUSION: The selection of the best penetration enhancers provide reference for Xuelian cataplasm.

Allometric prediction of the human pharmacokinetic parameters for naveglitazar.

Compounds that belong to the class known as dual (alpha,gamma) peroxisome proliferator-activated receptors (PPARs) show interesting pharmacological properties--regulation of blood glucose, fatty acids, and lipid parameters. Using the recently published preclinical data of naveglitazar, an allometric method was used to predict the human pharmacokinetic parameters (CL/F and Vss/F). The predicted parameters were compared to observed/predicted values of other important dual (a,y) PPAR compounds. The allometry data suggested that naviglitazar (CL/F) was at least 4 times faster than that of ragaglitazar, while the Vss was either equal to or 40% lower as compared to that of ragaglitazar.

Preclinical pharmacokinetics and interspecies scaling of ragaglitazar, a novel biliary excreted PPAR dual activator.

Allometric scaling has been used as an effective tool for the prediction of human pharmacokinetic parameters. Allometry has been a useful approach for the analysis of compounds that are eliminated unchanged in the urine and/or exhibit similar metabolic patterns across species. However, it has been a challenging issue to correctly predict human pharmacokinetic parameters for drugs that are eliminated intact and/or as conjugates in the bile. Ragaglitazar is a novel, non-thiazolidinedione peroxisome proliferator-activated receptor (PPAR) alpha- and gamma-agonist. In our investigation, preclinical pharmacokinetic data on ragaglitazar were gathered for several animal species (mice, rats, rabbits and dogs). Ragaglitazar when administered orally has shown a low clearance rate (Cl/F; < 5% of hepatic blood flow) in mice, rats and rabbits and a moderately high Cl/F in dogs (> 15% of hepatic blood flow). A qualitative estimation of rat bile has unequivocally confirmed the elimination of ragaglitazar in the bile. The human pharmacokinetic data are also indicative of the involvement of enterohepatic biliary recycling. In order to predict key parameters such as Cl/F and volume of distribution (V/F), simple allometry was the approach adopted at the onset. Although V/F scaled adequately, it failed to accurately predict human Cl/F. Therefore, standard correction factors such as maximum life span potential (MLP) and brain weight were also included. Although such modifications improved the linearity (r2 > 0.9), they failed to predict the investigated values. Further incorporation of correction factors particularly relevant to biliary excreted drugs improved the prediction of these values. Interestingly, the exclusion of dog data from the interspecies scaling considerably improved the prediction of both Cl/F and V/F.

Determination and pharmacokinetic study of syringin and chlorogenic acid in rat plasma after administration of Aidi lyophilizer.

A high-performance liquid chromatographic (HPLC) method was developed for the first time to simultaneously quantify syringin and chlorogenic acid in rat plasma using wavelength-transfer technology. The analysis was performed on a Diamonsil C(18) column (200 x 4.6 mm i.d., 5 microm particle size) with isocratic mobile phase consisting of acetonitrile-0.05% phosphoric acid (12:88, v/v). The linear ranges were 0.20-10 and 0.25-30 microg/mL, respectively. The lower limits of quantification were 0.20 and 0.25 microg/mL, respectively. The method was shown to be reproducible and reliable with intraday precision below 8.5 and 6.1%, interday precision below 7.1 and 5.5%, accuracy within +/-7.1 and +/-8.6%, and mean extraction recovery excess of 92.1 and 80.9%, respectively, which were all calculated from the blank plasma sample spiked with syringin and chlorogenic acid at three concentrations of 0.20, 1.0 and 6.0 microg/mL for syringin and 0.25, 2.0 and 20 microg/mL for chlorogenic acid. This method was validated for specificity, accuracy and precision and was successfully applied to the pharmacokinetic study of syringin and chlorogenic acid in rat plasma after intravenous administration of Aidi lyophilizer.

Anti-oxidant activities of Acanthopanax senticosus stems and their lignan components.

The antioxidant activities of Acanthopanax senticosus stems were evaluated in CCl4-intoxicated rats. The n-butanol fraction from the water extract of the stems, when pretreated orally at 200 mg/kg/day for 7 consecutive days in rats, was demonstrated to exhibit significant increases in antioxidant enzyme activities such as hepatic cytosolic superoxide dismutase, catalase and glutathione peroxidase by 30.31, 19.82 and 155%, respectively. The n-butanol fraction whereas showed a significant inhibition of serum GPT activity (65.79% inhibition) elevated with hepatic damage induced by CCl4-intoxication. Eleutheroside B, a lignan component, isolated from the n-butanol fraction was found to cause a moderate free radical scavenging effect on DPPH, its scavenging potency as indicated in IC50 value, being 58.5 microM. These results suggested that the stems of A. senticosus possess not only antioxidant but also hepatoprotective activities.

Novel tricyclic-alpha-alkyloxyphenylpropionic acids: dual PPARalpha/gamma agonists with hypolipidemic and antidiabetic activity.

Synthesis and structure-activity relationships of tricyclic alpha-ethoxy-phenylpropionic acid derivatives guided by in vitro PPARalpha and PPARgamma transactivation data and computer modeling led to the identification of the novel carbazole analogue, 3q, with dual PPARalpha (EC(50) = 0.36 microM) and PPARgamma (EC(50) = 0.17 microM) activity in vitro. Ten days treatment of db/db mice with 3q improved the insulin sensitivity, as measured by OGTT, better than that seen with both pioglitazone and rosiglitazone treatment, suggesting in vivo PPARgamma activity. Likewise, 3q lowered plasma triglycerides and cholesterol in high cholesterol fed rats after 4 days treatment, indicating in vivo PPARalpha activity. Investigations of the pharmacokinetics of selected compounds suggested that extended drug exposure improved the in vivo activity of in vitro active compounds.

Renal carcinogenesis induced by ferric nitrilotriacetate in mice, and protection from it by Brazilian propolis and artepillin C.

The protective effect of Brazilian propolis and its extract Artepillin C against ferric nitrilotriacetate (Fe-NTA)-induced renal lipid peroxidation and carcinogenesis was studied in male ddY mice. Fe-NTA-induced renal lipid peroxidation leads to a high incidence of renal cell carcinoma (RCC) in mice. Administration of propolis by gastric intubation 2 h before or Artepillin C at either the same time, 2 h, or 5 h before the intraperitoneal injection of Fe-NTA (7 mg Fe/kg) effectively inhibited renal lipid peroxidation. This was evaluated from the measurement of renal thiobarbituric acid-reactive substances (TBARS) or histochemical findings of 4-hydroxy-2-nonenal (4-HNE)-modified proteins and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Repeated injection of Fe-NTA (10 mg Fe/kg per day, twice a week for a total of 16 times in 8 weeks) caused subacute nephrotoxicity as revealed by necrosis and pleomorphic large nuclear cells in the renal proximal tubules, and gave rise to RCC 12 months later. A protective effect from carcinogenicity was observed in mice given propolis or Artepillin C. Furthermore, the mice given Fe-NTA only developed multiple cysts composed of precancerous lesions with multilayered and proliferating large atypical cells. Mice treated with propolis and Artepillin C also had cysts, but these were dilated and composed of flat cells. These results suggest that propolis and Artepillin C prevent oxidative renal damage and the carcinogenesis induced by Fe-NTA in mice.

[Stereoselective chronopharmacokinetics of hydratropic acid in rats].

The circadian rhythms of hydratropic acid (HTA) pharmacokinetic parameters were studied by using consinor method. Under standard light-dark cycle, the T1/2 beta and CL of S(+)-HTA, T1/2 beta of R(-)-HTA and CL, MRT of RS (+/-)-HTA were found to have circadian rhythm. Circadian rhythms were also found in the T1/2 beta and AUC of S (+)-HTA, CLS of R(-)-HTA and RS(+/-)-HTA under reverse light--dark cycle. Stereoselective circadian rhythms were found in CL of S(+)-HTA under standard light-dark cycle and in T1/2 beta and AUC of S(+)-HTA and CL of R(-)-HTA under reverse light-dark cycle. After ip administration of RS(+/-)-HTA to rat under two different light-dark cycles, the peak phases of circadian rhythms in the biotransformation of R(-)-HTA to S(+)-HTA in rat were both at the end of the dark phase. This suggests that administration of the drug at early morning is a recommendable scheme for chronotherapy with HTA.