Evocalcet Rescues Secondary Hyperparathyroidism-driven Cortical Porosity in CKD Male Rats.

To elucidate the effect of evocalcet, a new oral calcimimetic to bone of secondary hyperparathyroidism (SHPT) with chronic kidney disease (CKD), the rats were 5/6 nephrectomized and fed on a high-phosphate diet. The treated rats were then divided into vehicle groups and evocalcet administered groups. The rats in the vehicle groups exhibited increased levels of serum PTH and inorganic phosphate (Pi) levels, high bone turnover, and severe cortical porosity, mimicking SHPT (CKD-SHPT rats). The cortical bone of the CKD-SHPT rats showed broad demineralization around the osteocytes, suppression of Phex/small integrin-binding ligand N-linked glycoprotein-mediated mineralization in the periphery of the osteocytic lacunae, and increased levels of osteocytic cell death, all of which were considered as the first steps of cortical porosity. In contrast, evocalcet ameliorated the increased serum PTH levels, the enlarged osteocytic lacunae, and the cortical porosity of the CKD-SHPT rats. Osteocytes of CKD-SHPT rats strongly expressed PTH receptor and Pit1/Pit2, which sense extracellular Pi, indicating that PTH and Pi affected these osteocytes. Cell death of cultured osteocytes increased in a Pi concentration-dependent manner, and PTH administration rapidly elevated Pit1 expression and enhanced osteocytic death, indicating the possibility that the highly concentrated serum PTH and Pi cause severe perilacunar osteolysis and osteocytic cell death. It is likely therefore that evocalcet not only decreases serum PTH but also reduces the exacerbation combined with PTH and Pi to the demineralization of osteocytic lacunae and osteocytic cell death, thereby protecting cortical porosity in CKD-SHPT rats.

Predictive factors requiring high-dose evocalcet in hemodialysis patients with secondary hyperparathyroidism.

The dosage of evocalcet required to control serum parathyroid hormone (PTH) levels varies among secondary hyperparathyroidism (SHPT) patients. This post hoc analysis evaluated the dose-dependent efficacy of evocalcet on serum intact PTH (iPTH) levels, corrected calcium (Ca) and phosphate (P) levels, and safety, in an evaluation period (week 28 to week 30) by stratifying the previous phase 3 data with the final evocalcet dosages (low 1-2 mg [131 patients], medium 3-4 mg [90 patients], high 5-8 mg [92 patients]), and identified pre-treatment patient characteristics predicting the use of higher final evocalcet dosages via univariate and multivariate logistic regression models. At the end of the study at week 30, the median serum iPTH level was higher and the achievement ratio for the target range of Japanese Society for Dialysis Therapy (60-240 pg/mL) was lower in the final high-dose subgroup (216 pg/mL and 58%, respectively) than in the other subgroups (low: 149 pg/mL and 79%; medium: 149 pg/mL and 73%, respectively). Among the three subgroups, the mean serum corrected Ca and P levels demonstrated similar trends, and similar ratio of patients achieved the target range (corrected Ca, 8.4-10 mg/dL; P, 3.5-6.0 mg/dL) from week 28 to week 30. No dose-dependent safety concerns were identified. Younger age, prior cinacalcet use, higher serum levels of iPTH and corrected Ca, procollagen type 1 N-terminal propeptide, intact fibroblast growth factor-23, and larger maximum parathyroid gland volume were significantly associated with final high-dose evocalcet (p < 0.05 in all cases). Patients requiring final high-dose evocalcet had pre-treatment characteristics indicating severe SHPT, leading to a lower final achievement rate for the target PTH levels of Japanese Society for Dialysis Therapy. Therefore, the early initiation of evocalcet treatment for SHPT is critical. Trial registration: This trial was registered as follows: ClinicalTrials.gov: NCT02549391 and JAPIC: JapicCTI-153013.

Corrigendum to "Efficacy of evocalcet in previously cinacalcet-treated secondary hyperparathyroidism patients," [Kidney Int. Rep. 2021; https://doi.org/10.1016/j.ekir.2021.08.020].

[This corrects the article DOI: 10.1016/j.ekir.2021.08.020.].

Efficacy of Evocalcet in Previously Cinacalcet-Treated Secondary Hyperparathyroidism Patients.

INTRODUCTION: Evocalcet is a recently approved calcimimetic agent for secondary hyperparathyroidism (SHPT). In this study, the efficacy and safety of once-daily oral evocalcet were evaluated in patients without prior cinacalcet use (nonusers) and previously treated patients (users). METHODS: This post hoc analysis of a previous phase III head-to-head comparison study included SHPT patients treated with evocalcet with or without prior cinacalcet use. Endpoints included trends in the median intact and whole parathyroid hormone (PTH), mean corrected calcium, phosphate, and bone metabolic markers, and whole-to-intact PTH ratios throughout the 30-week study period; proportions of patients achieving target intact PTH, corrected calcium, and phosphate at weeks 28 to 30; and adverse drug reactions (ADRs). RESULTS: This study included 127 nonusers and 190 users with significant differences in age; duration of dialysis; use of intravenous vitamin D receptor activators; levels of intact PTH, corrected calcium, tartrate-resistant acid phosphatase 5b, procollagen type 1 N-terminal-propeptide; and largest parathyroid gland volume (P < 0.05 for all characteristics) between 2 groups at baseline. Users required higher evocalcet dosages than nonusers. Similar efficacy results were found in the 2 groups except for a significantly higher proportion of nonusers achieving the intact PTH target (81.6% vs 67.1%, difference [95% confidence interval], -14.5% [-24.59, -3.34]), and a significant reduction in largest parathyroid gland volume from week 0 to week 30 (-120.6 [567.2] mm3, P = 0.043). No difference was found in ADRs between the 2 groups. CONCLUSION: Treatment with evocalcet is effective and safe irrespective of prior cinacalcet treatment in SHPT patients.

The effect of evocalcet on vagus nerve activity of the gastrointestinal tract in miniature pigs.

Evocalcet is a novel calcimimetic agent with fewer gastrointestinal (GI) adverse effects compared to cinacalcet. Although it is thought that cinacalcet induces GI side effects through the direct stimulation of the calcium receptor (CaR) expressed in the GI tract, the differences in the direct stimulatory effects of these two drugs on the GI tract have not been reported. In this study, we analyzed the difference in the GI effects of these two calcimimetic agents using miniature pigs by detecting vagus nerve stimulation after oral administration of the agents. Although cinacalcet induced vomiting in miniature pigs, evocalcet never induced emetic symptoms. A significant increase in the vagus nerve action potentials was observed after the administration of cinacalcet. Although the increase of that after the administration of evocalcet was mild and not significant in comparison to that in the vehicle group, it was not significantly different from the vagus nerve action potentials after cinacalcet treatment.

Long-term outcomes for Asian patients with X-linked hypophosphataemia: rationale and design of the SUNFLOWER longitudinal, observational cohort study.

INTRODUCTION: X-linked hypophosphataemic rickets/osteomalacia (XLH) is a chronic, debilitating genetic disease characterised by skeletal abnormalities and growth disorder. The burden of XLH begins in childhood and continues throughout life. Conventional medical therapy with phosphate, active vitamin D and surgery do not address the underlying pathophysiology of the disease. While treatment during childhood may improve bone deformity and growth retardation, a large proportion of adult patients still fail to reach normal stature. Furthermore, adult patients with XLH report comorbidities associated with unresolved childhood disease, as well as newly developed disease-related complications and significantly impaired quality of life (QOL). Despite the multiple negative aspects of XLH, Asian consensus statements for diagnosis and management are lacking. METHODS AND ANALYSIS: The Study of longitUdinal observatioN For patients with X-Linked hypOphosphataemic rickets/osteomalacia in collaboration With Asian partnERs study is a longitudinal observational cohort study of patients with XLH, designed to determine the medical characteristics and burdens (physical, emotional and financial) of this progressive disease and to evaluate the impact of treatment (including the use of burosumab) on clinical outcomes. The study was initiated in April 2018, and registration will remain open until 30 April 2022. The sample size planned for analyses is 160 patients, consisting of 100 patients in Japan and 60 patients in Korea. Up to 5 years of observation are planned per patient, from enrolment through to April 2023. Prospective and retrospective data will be collected to evaluate variables, including height/growth, rickets severity score, QOL, motor function and biomarkers for phosphate metabolism and bone turnover. ETHICS AND DISSEMINATION: Ethics approval was obtained from the Ethics Committee of Osaka University, the Ethics Committee of Kyowa Kirin Co and by the Ethics Committee of each participating medical institution. Two interim analyses and associated publications are planned using retrospective and enrolment data at year 1 and results at year 3. TRIAL REGISTRATION NUMBERS: NCT03745521; UMIN000031605.

Evocalcet prevents ectopic calcification and parathyroid hyperplasia in rats with secondary hyperparathyroidism.

BACKGROUND: Elevated parathyroid hormone (PTH) levels in secondary hyperparathyroidism (SHPT) lead to vascular calcification, which is associated with cardiovascular events and mortality. Increased PTH production is caused by the excessive proliferation of parathyroid gland cells, which is accelerated by abnormal mineral homeostasis. Evocalcet, an oral calcimimetic agent, inhibits the secretion of PTH from parathyroid gland cells and has been used for the management of SHPT in dialysis patients. We observed the effects of evocalcet on ectopic calcification and parathyroid hyperplasia using chronic kidney disease (CKD) rats with SHPT. METHODS: CKD rats with SHPT induced by adenine received evocalcet orally for 5 weeks. The calcium and inorganic phosphorus content in the aorta, heart and kidney was measured. Ectopic calcified tissues were also assessed histologically. To observe the effects on the proliferation of parathyroid gland cells, parathyroid glands were histologically assessed in CKD rats with SHPT induced by 5/6 nephrectomy (Nx) after receiving evocalcet orally for 4 weeks. RESULTS: Evocalcet prevented the increase in calcium and inorganic phosphorus content in the ectopic tissues and suppressed calcification of the aorta, heart and kidney in CKD rats with SHPT by reducing the serum PTH and calcium levels. Evocalcet suppressed the parathyroid gland cell proliferation and reduced the sizes of parathyroid cells in CKD rats with SHPT. CONCLUSIONS: These findings suggest that evocalcet would prevent ectopic calcification and suppress parathyroid hyperplasia in patients with SHPT.

[Pharmacological and clinical profiles of a novel calcimimetic, evocalcet (ORKEDIA®)].

Calcimimetics allosterically activate the calcium receptor (CaR) and inhibit the secretion of parathyroid hormone (PTH). Cinacalcet hydrochloride (cinacalcet) has been approved as the first calcimimetic drug for the treatment of secondary hyperparathyroidism (SHPT) in patients with hemodialysis. Cinacalcet improved the achievement of target serum PTH and Ca levels and helped drastically reduce the number of parathyroidectomies. However, cinacalcet has side effects involving the gastrointestinal tract, such as nausea and vomiting, which makes it difficult to increase the dose and may result in reduced compliance. Evocalcet has been developed to improve defects of cinacalcet for management of SHPT. Evocalcet acts as an allosteric modulator of CaR, just like cinacalcet. However, its metabolic pathway is different from that of cinacalcet. The metabolism of evocalcet by cytochrome P450 is very low, so evocalcet has higher bioavailability. As a result, its pharmacologically effective dose for the inhibition of PTH secretion is lower than that of cinacalcet. Evocalcet had less of an effect on the gastrointestinal tract than cinacalcet because of the reduced dose required. In a clinical trial with a randomized, double-blind, head-to-head comparison study, it was also confirmed that the incidence of gastrointestinal-related adverse events was lower in the evocalcet group than in the cinacalcet group. Evocalcet may thus be a potent option for the management of SHPT.

Discovery of evocalcet, a next-generation calcium-sensing receptor agonist for the treatment of hyperparathyroidism.

The calcium-sensing receptor (CaSR) plays an important role in sensing extracellular calcium ions and regulating parathyroid hormone secretion by parathyroid gland cells, and the receptor is a suitable target for the treatment of hyperparathyroidism. Cinacalcet hydrochloride is a representative CaSR agonist which widely used for the hyperparathyroidism. However, it has several issues to clinical use, such as nausea/vomiting and strong inhibition of CYP2D6. We tried to improve these issues of cinacalcet for a new pharmaceutical agent as a preferable CaSR agonist. Optimization from cinacalcet resulted in the identification of pyrrolidine compounds and successfully led to the discovery of evocalcet as an oral allosteric CaSR agonist. Evocalcet, which exhibited highly favorable profiles such as CaSR agonistic activity and good DMPK profiles, will provide a novel therapeutic option for secondary hyperparathyroidism.

A novel calcimimetic agent, evocalcet (MT-4580/KHK7580), suppresses the parathyroid cell function with little effect on the gastrointestinal tract or CYP isozymes in vivo and in vitro.

Cinacalcet hydrochloride (cinacalcet), an oral calcimimetic agent has been widely used for the management of secondary hyperparathyroidism (SHPT) in chronic kidney disease (CKD). In sharp contrast to vitamin D receptor activators, cinacalcet suppresses SHPT without inducing hypercalcemia or hyperphosphatemia. Nevertheless, some patients remain refractory to SHPT with this agent, as the dose cannot be sufficiently increased due to gastrointestinal symptoms. In order to resolve this issue, we have developed a newly synthesized calcimimetic agent, evocalcet (MT-4580/KHK7580). In a rat model of CKD induced by 5/6 nephrectomy, oral administration of evocalcet efficiently suppressed the secretion of parathyroid hormone (PTH). With regard to the gastro-intestinal effects, cinacalcet induced a significant delay in gastric emptying in rats, while evocalcet did no marked effects on it. Evocalcet also demonstrated the less induction of emesis compared to cinacalcet in common marmosets. The pharmacological effects of evocalcet were observed at lower doses because of its higher bioavailability than cinacalcet, which may have contributed to the reduced GI tract symptoms. In addition, evocalcet showed no substantial direct inhibition of any CYP isozymes in in vitro liver microsome assay, suggesting a better profile in drug interactions than cinacalcet that inhibits cytochrome P450 (CYP) 2D6. These findings suggest that evocalcet can be a better alternative to cinacalcet, an oral calcimimetic agent, with a wider safety margin.

Phase II study of concurrent chemoradiotherapy at the dose of 50.4 Gy with elective nodal irradiation for Stage II-III esophageal carcinoma.

OBJECTIVE: Definitive chemoradiotherapy is one of the curative options for resectable esophageal squamous cell carcinoma with organ preservation. We evaluated the efficacy and toxicity of radiotherapy at a dose of 50.4 Gy concurrent with chemotherapy for Stage II-III esophageal cancer. METHODS: Esophageal cancer patients with clinical Stage II-III (T1N1M0 or T2-3N0-1M0) were eligible. Radiotherapy was administered to a total dose of 50.4 Gy with elective nodal irradiation of 41.4 Gy. Concurrent chemotherapy comprised two courses of 5-fluorouracil (1000 mg/m(2)/day) on days 1-4 and 2-h infusion of cisplatin (75 mg/m(2)) on Day 1; this was repeated every 4 weeks. Two courses of 5-fluorouracil with cisplatin were added. RESULTS: Fifty-one patients were enrolled in the study from June 2006 to May 2008. The characteristics of the 51 patients enrolled were as follows: median age 64 years; male/female, 45/6; performance status 0/1, 32/19 patients; Stage IIA/IIB/III, 9/20/22 patients, respectively. A complete response was achieved in 36 patients (70.6%). The 1- and 3-year overall survival rate was 88.2 and 63.8%, respectively. The median 1- and 3-year progression-free survival rate was 66.7% (80% CI: 57-74%) and 56.6% (80% CI: 47.1-64.9%), respectively. Acute toxicities included Grade 3/4 anorexia (45%), esophagitis (35%) and febrile neutropenia (20%). Eight patients (15.6%) underwent salvage surgery due to residual or recurrent disease. There were no deaths related to salvage surgery. CONCLUSION: Chemoradiation therapy at a dose of 50.4 Gy with elective nodal irradiation is promising with a manageable tolerability profile in esophageal cancer patients.

Effects of histamine H1-antagonists on sleep-awake state in rats placed on a grid suspended over water or on sawdust.

The present study was performed to investigate the effects of histamine H(1)-antagonists on the sleep-awake state in rats placed on a grid suspended over water in comparison with rats placed on sawdust. When rats were placed on the grid suspended over water, significant increases in the awake time and decreases in non-rapid eye movement (non-REM) sleep time were observed compared with in rats on sawdust, even when measured hourly for 6 h. Diphenhydramine, chlorpheniramine and promethazine caused a significant decrease in the awake time and increase in non-REM sleep time in rats placed on the grid suspended over water for 1-2 h and/or 2-3 h after administration. On the other hand, in rats placed on sawdust, no significant differences were observed in the awake time and non-REM sleep time with diphenhydramine and chlorpheniramine compared with the control. Different from these two drugs, promethazine caused a significant decrease in the awake time and increase in non-REM sleep time 1-2 h and 2-3 h after administration even when rats were placed on sawdust at a relatively high dose. These results clearly indicate that histamine H(1)-antagonists had potent effects on decreasing the awake time and increasing non-REM sleep time under the conditions of an activated histaminergic system.

Changes of sleep patterns in rats with chronic constriction injury under aversive conditions.

In the present study, we investigated the changes of sleep parameters in rats with chronic constriction injury (CCI) under aversive conditions. The electroencephalogram (EEG) in the frontal cortex of CCI rats and electromyogram (EMG) were measured over 6 h by placing rats on sandpaper as an aversive condition, to compare with rats placed on sawdust. Six days after CCI surgery, the rats exhibited significant mechanical allodynia, and also had neuropathic pain. When rats were placed on sawdust, no significant difference was observed between the CCI group and sham-operated control group in sleep latency, total waking time, total non-REM sleep time and total REM sleep time. On the other hand, when CCI rats were placed on sandpaper, a significant increase was observed in sleep latency and total waking time compared with the sham group; however, no significant difference was observed in the total non-REM sleep time and total REM sleep time between these two groups. These results indicate that an important factor of sleep disturbance in CCI rats is not only damage to the nerves but also being under aversive conditions. In addition, it was found that CCI rats placed on sandpaper as an aversive condition can serve as a new sleep disturbance model.

Effect of tandospirone on sleep latency in rats placed on a grid suspended over water.

The present study was performed to examine the effect of tandospirone on sleep latency in a new insomnia animal model by placing rats on a grid suspended over water. For investigating the mechanism of tandospirone, the effect of tandospirone on sleep latency was also studied using rats that were depleted with neuronal serotonin (5-HT) after p-chlorophenylalanine administration. Tandospirone caused a shortening of sleep latency dose-dependently, and a significant effect was observed at 20 mg/kg, p.o. or more. A shortening of sleep latency was observed by administration of p-chlorophenylalanine (300 mg/kg, i.p.) for 2 days. On the other hand, tandospirone exerted no potentiating effect on the shortening of sleep latency induced by p-chlorophenylalanine. From these findings, a shortening of sleep latency induced by tandospirone may occur through the pre-synaptic 5-HT(1A) receptors in rats.

[Effect of santalol on the sleep-wake cycle in sleep-disturbed rats].

Sandalwood oil is widely used in aromatherapy for alleviating various symptoms. Santalol, a major component of sandalwood oil, has been reported to have central nervous system depressant effects such as sedation. In the present study, we investigated the effect of santalol on the sleep-wake cycle in sleep-disturbed rats. When inhaled at a concentration of 5 X 10(-2) ppm, santalol caused a significant decrease in total waking time and an increase in total non-rapid eye movement (NREM) sleep time. In order to clarify the mechanism of action, olfactory hypofunction was caused in rats by intranasal application of 5% zinc sulfate solution, and thereafter the effects of inhalation of fragrances were evaluated. In this study, it was found that the impairment of the olfactory system showed no significant effect on the changes in sleep parameters induced by santalol. This result suggests that santalol may act via the circulatory system rather than the olfactory system. That is, santalol is thought to be absorbed into the blood through the respiratory mucosa, and then exert its action. From these results, it is concluded that santalol may be useful in patients having difficulty maintaining sleep without being affected by individual differences in perfume-related preference.

Effect of valerian extract preparation (BIM) on the sleep-wake cycle in rats.

In the present study, we studied the effect of valerian extract preparation (BIM) containing valerian extract, golden root (Rhodiola rosea L.) extract and L-theanine (gamma-glutamylethylamide) on the sleep-wake cycle using sleep-disturbed model rats in comparison with that of valerian extract. A significant shortening in sleep latency was observed with valerian extract and the BIM at a dose of 1000 mg/kg. On the other hand, valerian extract and the BIM caused no significant effects on total times of wakefulness, non-rapid eye movement (non-REM) sleep and REM sleep. Valerian extract and the BIM at a dose of 1000 mg/kg also had no significant effect on delta activity. In conclusion, it became clear that the BIM could be useful as a herbal medicine having a sleep-inducing effect without causing an alteration of the sleep-wakefulness cycle.

Effects of some H1-antagonists on the sleep-wake cycle in sleep-disturbed rats.

The present study was undertaken to investigate the effects of some H(1)-antagonists on the sleep-wake cycle in sleep-disturbed rats in comparison with those of nitrazepam. Electrodes were chronically implanted into the frontal cortex and the dorsal neck muscle of rats for the electroencephalogram (EEG) and electromyogram (EMG), respectively. EEG and EMG were recorded with an electroencephalograph. SleepSign ver. 2.0 was used for EEG and EMG analysis. The total times of waking, non-rapid eye movement (non-REM), and rapid eye movement (REM) sleep were measured from 10:00 to 16:00. Nitrazepam showed a significant decrease in sleep latency, total waking time, and delta activity and an increase in the total non-REM sleep time. A significant decrease in the sleep latency was observed with diphenhydramine, chlorpheniramine, and cyproheptadine. Cyproheptadine also caused a significant decrease in the total waking time and increases in total non-REM sleep time, REM sleep time, slow wave sleep, and delta activity, although no remarkable effects were observed with diphenhydramine and chlorpheniramine. In conclusion, cyproheptadine can be useful as a hypnotic, having not only sleep inducing-effects, but also sleep quantity- and quality-increasing effects.

Effect of seed coat extract from black soybeans on radial maze performance in rats.

1. In the present study, we tested the effect of seed coat extract from black soybeans on eight-arm radial maze performance in rats. 2. Rats were fed a diet containing 5% seed coat extract from black soybeans or a normal diet for 40 days. 3. One week after the start of feeding, rats were tested for learning ability related to two types of memory, reference memory and working memory, with a partially (four of eight) baited eight-arm radial maze. 4. A significant decrease in the total number of errors was observed 30 (mean value of five trials of 26-30 days) and 35 days (30-35 days) after the intake of the diet containing seed coat extract compared with the control group. In addition, the mean number of days taken to reach this criterion was significantly decreased after the intake of the diet containing the seed coat extract. 5. The number of reference memory errors was significantly decreased 30 and 35 days after the intake of the diet containing seed coat extract. However, no significant decrease was observed in the number of working memory errors. 6. From these results, it is concluded that the intake of seed coat extract from black soybeans effectively enhances memory and learning ability, especially long-term memory, in rats.

Hypnotic activities of chamomile and passiflora extracts in sleep-disturbed rats.

In the present study, we investigated hypnotic activities of chamomile and passiflora extracts using sleep-disturbed model rats. A significant decrease in sleep latency was observed with chamomile extract at a dose of 300 mg/kg, while passiflora extract showed no effects on sleep latency even at a dose of 3000 mg/kg. No significant effects were observed with both herbal extracts on total times of wakefulness, non-rapid eye movement (non-REM) sleep and REM sleep. Flumazenil, a benzodiazepine receptor antagonist, at a dose of 3 mg/kg showed a significant antagonistic effect on the shortening in sleep latency induced by chamomile extract. No significant effects were observed with chamomile and passiflora extracts on delta activity during non-REM sleep. In conclusion, chamomile extract is a herb having benzodiazepine-like hypnotic activity.

Effects of kava-kava extract on the sleep-wake cycle in sleep-disturbed rats.

RATIONALE: Kava-kava extract may be useful as an herbal medicine for treatment of insomnia and anxiety. OBJECTIVES: The present study was undertaken to investigate the effects of kava-kava extract on the sleep-wake cycle in comparison with that of flunitrazepam using sleep-disturbed rats. METHODS: Electrodes for measurement of electroencephalogram (EEG) and electromyogram (EMG) were implanted into the frontal cortex and the dorsal neck muscle of rats. EEG and EMG were recorded with an electroencephalogram. SleepSign ver.2.0 was used for EEG and EMG analysis. Total times of wakefulness, non-rapid eye movement (non-REM) and REM sleep were measured from 09:00 to 15:00. RESULTS: A significant shortening of the sleep latency in sleep-disturbed rats was observed following the administration of kava-kava extract at a dose of 300 mg/kg, while no effects were observed on the total waking and non-REM sleep time. On the other hand, flunitrazepam showed a significant shortening in sleep latency, decrease in total waking time and increase in total non-REM sleep time. Although the effects of flunitrazepam were antagonized by the benzodiazepine receptor antagonist flumazenil, the effect of kava-kava extract was not antagonized by flumazenil. Kava-kava extract showed a significant increase in delta activity during non-REM sleep in sleep-disturbed rats, whereas a significant decrease in delta power during non-REM sleep was observed with flunitrazepam. Flumazenil caused no significant effect on the changes in delta activity induced by both kava-kava extract and flunitrazepam. CONCLUSIONS: Kava-kava extract is an herbal medicine having not only hypnotic effects, but also sleep quality-enhancement effects.