A review of frequently used Kampo prescriptions: Part 2—Hangekobokuto

The origin of hangekobokuto (HKT) is from Jin Gui Yao Lue (Kinkiyōryaku in Japanese), and it has been indicated for treating throat discomfort in women.

period that was written by Sun Shimiao in 652 AD, also mentions that 'HKT is used for a woman who complains her breast is swollen and her epigastrium is stiff, or who has throat discomfort due to feeling as if a piece of meat is lodged in her throat and she can neither swallow nor spit it out' [3]. Symptoms such as breast swelling, stiffness in the epigastrium, and a feeling of throat congestion indicate qi stagnation, which is characterized by hindered qi movement throughout the body.
Daishichikito, another name for HKT, was also described in Sanin kyokuitsu by osh o h oron (in Japanese) by Chen Yan (1131-1189) in 1174, a medical book representative of the Southern Song period in China [4]. HKT was used for the pathological condition called shichiki, which represents the qi of the seven emotions of joy, anger, depression, distress, sorrow, fear, and shock, that is, for symptoms associated with excessive mental stress [5]. I kan h oron (in Japanese), the Chinese formulary edited by Ou Seki around the same time, describes HKT as shishichito and states that it can be used to treat symptoms such as throat discomfort that feels like a plum kernel stuck in the throat that patients can neither spit out nor swallow because of shichiki [6]. Shishichito (HKT) can also be used to treat patients who complain of abdominal bloating, massive phlegm and drooling, morning sickness, palpitations, and shortness of breath. The text mentioned that 'shishichito treats symptoms such as phlegm, drooling, and the feeling of a stuck plum kernel or torn cotton clinging in the throat that cannot be spat out or swallowed. These symptoms seem to be caused by the seven emotions'.
In Shuh o kiku, the medical commentary of essential prescripts written by the famous doctor Manase D osan (1507-1594), HKT has been described as follows: 'Daishichikito (HKT) treats epigastrium and abdominal bloating caused by the dysfunction of qi of the five Zang-organs, namely the liver [TM1] , heart [TM1] , spleen [TM1] , lung [TM1] , and kidney [TM1] due to an uncontrolled state of the seven emotions [7]. It also treats symptoms such as throat discomfort with massive phlegm and drooling, caused by something like a feeling of torn cotton in the throat, which cannot be spat out or swallowed, due to depression of the seven emotions. It is also useful for treating symptoms such as bloating at Ch ukan in Japanese, Zhongwan in Chinese, and Conception Vessel 12 as the meridian point 12 cm over the navel, a flushed feeling, and wheezing'. Katsuki Gy uzan (1656-1740), a physician in the mid-Edo period, mentioned in Gy uzan h ok o that shishichito can treat symptoms such as phlegm, wheezing due to depression of the qi of the seven emotions, throat discomfort that feels like a plum kernel stuck in the throat that be cannot spit out or swallowed, so-called baikakuki, or chest discomfort due to bloating of Ch ukan, and that it shows a rapid effect [8]. Yoshimasu T od o (1702-1773), an innovative medical doctor and author of Ruijuh o, stated that HKT could treat throat discomfort that feels like a piece of roasted meat is lodged in the throat, nausea, or palpitations in the epigastrium [9]. Wada T okaku (1744-1803), one of the most famous doctors of the Edo period, described in his book D osuitengen that HKT addition is useful for treating tachycardia and edema in cardiac beriberi [10]. H oi kuketsu, written by Asai Teian (1770-1829), describes how shishichito was used for wheezing caused by qi stagnation [11]. Arimochi Keiri (1758-1835) also stated in his medical book H oyogei that HKT could treat throat discomfort similar to that experienced when a piece of roasted meat is lodged in the throat [12]. Odai Y od o (1799-1870), a disciple of Yoshimasu T od o who wrote Ruijuh o k ogi, reported that the symptoms that can be treated by HKT are baikakuki and that HKT can also be used for morning sickness [13]. Asada S ohaku (1815Asada S ohaku ( -1894, a legend of the Kampo medicine world who devoted himself to the survival of Kampo medicine in opposition to the Meiji government's anti-Kampo treatment policy, wrote many descriptions of HKT. Futsugo yakushitsu h okan kuketsu, the clinical textbook that outlines instructions for using representative formulas for all ages based on his experiences, states that 'HKT is the base of the qi-regulating recipe' [14] named shishichito in Wazaikyokuh o (in Japanese), which was a formulary compiled on the order of the emperor during the Song period. It treats not only baikakuki but also various illness-related qi disorders. His book also states that 'Although it seems clear that many women have qi depression (Qi stagnation pattern [TM1] ), it is wrong to use shishichito only for women' [14]. He also described many experiences with using HKT in patients regardless of sex in Kiss oshoei [15]. Hara Nan'y o (1753-1820) and Honma S oken (1804-1872) presented their clinical experiences with HKT in S okeitei ijish ogen [16] and Naika hiroku [17], respectively. They used HKT for symptoms such as the inability to spit out or swallow, or symptoms suggestive of esophageal cancer, judged as qi stagnation, which many doctors could not cure with various Kampo medicines.
As described above, many commentaries on HKT have been written in Japan based on the Jin Gui Yao Lue written in China. After the Meiji Restoration, knowledge was passed down from generation to generation, even among doctors who had learned Western medicine. Yumoto Ky ushin (1876-1941) was a medical doctor trained in Western medicine, as certified by the Meiji government, and a new leader of the Kampo Medical Society, who made a huge effort to revive Kampo medicine. He worshipped Yoshimasu T od o and attempted to explain T od o's theory from the perspective of Western medicine. In K okan igaku, he stated that HKT was effective for nausea, vomiting, dizziness, and palpitations because HKT included shohangekabukuryoto [18], which consists of Pinellia tuber, Poria sclerotium, and ginger, as described in Jin Gui Yao Lue. After him, physicians who learned K okan igaku swept the Kampo medical world, and it is generally agreed that his disciple, Otsuka Keisetsu (1900Keisetsu ( -1980, was a crucial leader in the Kampo world during the Showa period. He used HKT to treat a man with gastroptosis, a woman with upper body edema, and a woman with neurosis, as described in Kampo shinry o 30 nen [19]. Yakazu D omei (1905Yakazu D omei ( -2002, another crucial Kampo leader who was a comrade of Otsuka Keisetsu, summarized in Kampo shuy oshoh o kaisetsu that HKT could be used to treat various symptoms such as epigastric discomfort, neurosis, laryngopharyngeal hypersensitivity, and edema [20].

PHARMACEUTICAL INFORMATION OF HANGEKOBOKUTO
Composition, description, dosage, and administration The HKT formula consists of five crude drugs: JP Pinellia tuber, JP Poria sclerotium, JP magnolia bark, JP Perilla herb, and JP ginger or fresh ginger (JP: Japanese Pharmacopeia Eighteenth edition [JP XVIII] [21]). HKT is currently available in the form of extract and decoctions in Japan. The extracts are classified into Kampo extract formulations for medical prescription (ethical Kampo formulations) and over-the-counter (OTC) Kampo extract formulations for self-medication. The decoctions include formulations prepared on the basis of doctors' prescriptions and those dispensed by pharmacists without doctors' prescriptions (in-pharmacy formulation). These forms of HKT have been approved by JP XVIII, the Guidebook of the Approval Standard for OTC Kampo Products (Revised Edition), and the Sixth Edition of the Guidelines for Pharmacy Preparation (Table 1).
The original HKT formulation was a decoction prepared by boiling a mixture of crude drugs in water at room temperature. Boiling down the mixture without Perilla herb under low heating in 500-600 mL of water reduced the volume by half. Before completion of the process of boiling down, Perilla herb was usually boiled for a few minutes to retain the maximal amount of perillaldehyde [22]. After removing the crude drug residue, the extraction fluid was divided into two or three doses per day before or between meals.
Currently, HKT extract formulations are primarily distributed in Japan. The amount of crude drug in each formulation is shown in The usual dose for adult patients consists of two or three divided doses for oral administration before or between meals. The dosage forms include granules, fine granules, and tablets. OTC HKT formulations usually contain smaller amounts of the extract than those used in medical prescriptions.

Constituents
The high-performance liquid chromatography profile of the HKT extract is shown in Figure 1 (provided by TSU-MURA & Co., Tokyo, Japan and Kracie Holdings, Ltd., Tokyo, Japan). JP XVIII defined the amounts of major constituents in HKT extract as follows: magnolol, not less than 2 mg and not more than 6 mg; rosmarinic acid, not less than 4 mg (for preparations prescribed with 2 g of Perilla herb) or not less than 6 mg (for preparations prescribed with 3 g of Perilla herb); and [6]gingerol, not less than 0.6 mg and not more than 2.4 mg (for preparations prescribed with 1 g of ginger), not less than 0.8 mg and not more than 3.2 mg (for preparations prescribed with 1.3 g of ginger), or not less than 0.9 mg and not more than 3.6 mg (for preparations prescribed with 1.5 g of ginger), per extract prepared with the amount specified [21]. The key characteristics of the crude drugs and their major compounds, along with their pharmacological activities, are outlined below.
Ginger JP ginger is the rhizome with (unpeeled) or without (peeled) the periderm of Zingiber officinale Roscoe (Zingiberaceae). It contains no less than 0.3% of [6]gingerol, calculated on the basis of dried material [21]. Some pharmaceutical companies use fresh ginger instead of JP ginger. Ginger has antioxidant, antiinflammatory, analgesic, antimicrobial, anticancer, antinausea, antiemetic, antiobese, and antidiabetic properties. It protects the cardiovascular and respiratory organs [34]. Its main bioactive phenolic component is [6]gingerol, which shows antiinflammatory activity by inhibiting reactive oxygen species (ROS) levels and iNOS expression through reduction of NF-κB activation and protein kinase C translation [35]. It has been also shown to reduce cytokine production and T-cell activation in an allergic rhinitis model [36]. The analgesic action of [6]gingerol is mediated through the NO-cGMP-ATPsensitive K + channel pathway and the serotoninergic system [37]. [6]-Gingerol inhibits gastric acid secretion by activating the transient receptor potential vanilloid-1 [38].

CLINICAL APPLICATIONS AND CONTROLLED TRIALS OF HANGEKOBOKUTO Method
We searched the PubMed and Traditional and Kampo Medicine databases for clinical research articles written in English using the following keywords: 'hangekobokuto', or 'hange-koboku-to', or 'Banxia Houpo Tang', or 'Banxia Houpu Tang', or 'Banxia Houpu decoction'. After excluding case reports, two nonrandomized and four randomized trials were selected (Table 3).

Clinical applications and controlled trials
HKT has been used in patients reporting the sensation of something stuck in the throat that cannot be removed, which makes them want to clear their throat by coughing. This symptom could be similar to globus hystericus associated with a depressive state or anxiety. Accordingly, the indications for Japanese ethical HKT products are as follows: depressed feelings and a feeling of a foreign body in the throat or esophagus, palpitations, dizziness, nausea, anxiety neurosis, nervous gastritis, hyperemesis gravidarum, coughing, hoarseness, nervous esophageal stricture, anorexia, insomnia, bronchial asthma, or bronchitis [45].
Most of the controlled trials of HKT have focused on aspiration pneumonia (AP) on the basis of the indication of HKT for dysphagia. One of the reasons for the occurrence of AP is impairment of the swallowing reflex, and a decrease in the concentration of mucus substance P in saliva is related to the development of AP [46]. In 1999, Iwasaki et al. reported that the swallowing reflex of patients with stable cerebral infarction who had at least one episode of AP was significantly improved by 4-week HKT administration [44]. The concentration of substance P in the saliva was significantly increased in the HKT group. On the other hand, the swallowing reflex and the concentration of substance P did not change significantly in the control group patients who were treated with placebo (Table 3).
Iwasaki et al. examined the effects of HKT on the swallowing reflex in patients with Parkinson's disease (PD) [43]. The swallowing reflex of the PD patients significantly improved after 4 weeks of HKT treatment, but the swallowing reflex of patients with PD who were administered the placebo showed no significant changes. The concentration of substance P in the saliva did not significantly change in the HKT and placebo groups. These two clinical studies were not randomized trials.
In 2002, Iwasaki et al. conducted a randomized controlled study investigating the effect of HKT on the cough reflex in patients with cerebral atrophy and lacunar infarctions [42]. Impairment of the cough reflex is also considered a risk factor for AP [47]. They measured the cough reflex by determining the cough threshold of patients who inhaled various concentrations of nebulized citric acid. The cough threshold concentration of citric acid decreased significantly in the HKT group after 4 weeks of treatment. In the control group that received placebo, the cough threshold levels did not change.
Subsequently, Iwasaki et al. performed a randomized, observer-blinded, controlled trial to evaluate whether HKT reduced AP and pneumonia-related mortality in the elderly [41]. Ninety-five participants with dementia, cerebrovascular disease, Alzheimer's disease, or PD were randomly assigned to the HKT or placebo group and followed up for 12 months. The number of patients showing pneumonia development was significantly lower in the HKT group than in the placebo group ( p = 0.008). Pneumonia-related mortality tended to be lower in the HKT group (p = 0.05). The Cox proportional hazards model showed that the relative risk of pneumonia in the HKT group was 0.51 (95% confidence interval 0.27-0.84, p = 0.008). The number of self-ingested oral calories was significantly lower in the control group than in the HKT group (p = 0.006).
Kawago et al. conducted a double-blind, randomized study to assess the prophylactic effects of HKT on AP in patients undergoing cardiovascular surgery [39]. The participants were randomly assigned to the HKT or placebo groups and administered HKT or placebo for 14 days after cardiovascular surgery. The rate of postoperative AP in the HKT group was significantly lower than that in the placebo group (0% versus 35%, p = 0.017), but the two groups showed no significant differences in the changes in the salivary levels of substance P. The white blood cell count and C-reactive protein level on day 3 after surgery were significantly lower in the HKT group than in the placebo group (p = 0.004 and p = 0.006, respectively). The two groups also showed no significant differences in the duration of postoperative hospitalization or the duration of antibiotic treatment.
In 2010, Bo et al. reported the effect of a modified HKT decoction (HKT with Fructus Citri Sarcodactylis) in patients with globus hystericus [40]. The participants were randomly allocated to the HKT or control group and treated with the formula for clearing the throat. The therapeutic effect was graded as cured, obviously effective, effective, and ineffective. After a 3-week treatment, no significant difference was observed in the proportions of different grades between the modified-HKT and control groups. However, the depression and anxiety scores after treatment significantly improved in the modified-HKT group (p < 0.05 and 0.01, respectively), while they showed no significant difference in the control group.
These clinical trials indicate that HKT can improve the swallowing and cough reflexes in patients with dysphagia, prevent the development of AP, and ameliorate depression and anxiety. However, few clinical studies have demonstrated the effect of HKT on globus hystericus, depression, anxiety, nausea, and hyperemesis gravidarum. Some pilot studies have reported the effects of HKT on panic disorder [48], the sensation of a lump in the throat [49], and functional dyspepsia [50]. Further randomized controlled trials are required to investigate the effectiveness of HKT in these diseases.

Preclinical studies on the effects of hangekobokuto on depression and anxiety
Based on the monoamine hypothesis, depression is primarily treated with selective serotonin reuptake inhibitors (SSRIs) and serotonin-noradrenaline reuptake inhibitors (SNRIs). Subsequently, several hypotheses have been proposed, including the hypothalamic-pituitary-adrenal (HPA) axis hypothesis, the neuroplasticity hypothesis, and the inflammatory hypothesis, and connections among these hypotheses have also been suggested. Many studies have reported that HKT exhibits therapeutic activity by modulating several biomarkers in experimental models. Behavioral tests have confirmed behavioral improvements in the acute stress model [51][52][53] and chronic stress model [54][55][56][57].
Regarding the effects of HKT on brain monoamines, a healthy rodent model showed an increase in serotonin (5-hydroxytryptamine, 5-HT) and noradrenaline (NA) levels, and a decrease in their turnover in the hypothalamus. It also showed an increase in dopamine (DA) level, and a decrease in its turnover in the striatum [58]. In an acute stress model, HKT improved 5-HT levels and increased the levels of its metabolite, 5-hydroxyindoleacetic acid (5-HIAA), in the striatum and hippocampus [53]. In addition, the polysaccharide fraction of HKT improved the reduction of 5-HT and DA levels in the whole brain [52]. In a chronic stress model, 5-HT and 5-HIAA levels were decreased in the cortex, hippocampus, striatum, and oblongata, but both were improved only in the striatum by HKT [55]. Similarly, HKT improved the reductions in 5-HT and DA levels in the prefrontal cortex, and the improved anxious behaviors were inhibited by a 5-HT 1A receptor antagonist [57].
Elevated levels of the inflammatory cytokines interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6 as well as increased levels of neutrophils and monocytes have been reported in the peripheral blood of depressed patients. Chronic stress increases IL-6 levels in the brainstem, which is markedly decreased by HKT [57]. The NOD-like receptor family pyrin domain containing 3 (NLRP3), a pattern recognition receptor involved in innate immunity, senses uric acid crystals and hyperglycemia, forms inflammasomes, releases cytokines, and is involved in many pathological conditions. NLRP3 was recently shown to also sense stress. In a chronic stress model, NLRP3 inflammasome activation was observed in the liver, hypothalamus, hippocampus, and prefrontal cortex, but was suppressed by HKT. The consequent IL-1β maturation in these sites were also suppressed by HKT treatment [54].
The activity of natural killer (NK) and lymphokineactivated killer (LAK) cells has been reported to decrease in patients with depression. Decreased NK and LAK cell activities in a chronic stress model were ameliorated by HKT. The levels of IL-2, which is involved in NK cell activation and LAK cell induction, is also increased [55]. Some reports have also evaluated the hormones in the HPA axis. Serum corticosterone and corticotropin-releasing factor (CRF) levels increased in a chronic stress model and were decreased by HKT [54,57].
Immediate genes (IEGs) are expressed in response to various stressors. c-Fos, an IEG, is present in many parts of the central nervous system and is an indicator of neural activity. Brain c-Fos levels, which were increased in the chronic stress model, were decreased by HKT [56]. Increased monoamine catabolism, activation of immune-inflammatory processes, and abnormal lipid metabolism result in overproduction of ROS, causing increased activation of antioxidant enzymes and increased lipid peroxidation. In an acute stress model, the levels of malondialdehyde (MDA), a marker of oxidative stress, were increased in the serum and liver and decreased by HKT [53]. In a chronic stress model, the superoxide dismutase (SOD) and nitric oxide synthase (NOS) activity in the liver as well as the serum MDA level increased, but these were decreased by HKT [55].
Nutritional abnormalities are common in depressed patients, who are at risk of developing type 2 diabetes and have higher rates of obesity and lipid abnormalities than healthy individuals. In a chronic stress model, HKT administration improved oral glucose tolerance and abnormalities in insulin signaling [54]. Similarly, while blood total cholesterol and high-and low-density lipoprotein cholesterol levels decreased and triglyceride levels increased in a chronic stress model, these were restored by HKT [55].

Effects on the laryngeal reflex
Reflex responses to electrical stimulation were recorded in the laryngeal nerves of cats. After a single administration of HKT, the response gradually decreased, disappeared, and then gradually recovered [59].

Effects on gastrointestinal motility
In a mouse model of postoperative ileus, HKT suppressed the infiltration of neutrophils and macrophages and restored delayed intestinal transit. In addition, it decreased the production of inducible NOS (iNOS) and increased the expression of nerve growth factor (NGF) and decreased nuclear factor-κB (NFκB), respectively, which are associated with iNOS (3) Improvement in glucose tolerance and insulin signaling impairment in the liver, hypothalamus, and prefrontal cortex (4) Alleviation of the activity of the NLRP3 inflammasome and decreased IL-1β level in the liver [54] (2017) Kampo extract formulation induction. In contrast, the increased IL-1β and IL-6 expressions associated with iNOS induction were not restored by HKT, and no increase in NGF expression was seen [60].

Effects on chronic intermittent hypoxia
Obstructive sleep apnea (OSA) causes chronic intermittent hypoxia (CIH), resulting in mitochondrial dysfunction and production of ROS in the heart. Iron metabolism and mitochondrial function are closely related, and iron enhances apoptotic signaling through its role in ROS production. HKT improved CIH-induced cardiac dysfunction and histological changes, attenuated mitochondrial damage and apoptosis, and activated mitophagy to resist cardiac injury. In addition, HKT suppressed ROS generation in cardiac tissue and reduced CIH-induced iron deposits in the mitochondria [61].

Decrease in spontaneous movement and prolongation of sleep time
After a single administration of HKT, the spontaneous locomotor activity of mice decreased, especially during the dark period. The treatment also prolonged the sleep time of hexobarbital-treated mice [59].

ADVERSE EFFECTS OF HANGEKOBOKUTO
In Japan, all drugs causing adverse events, including suspected causal drugs and drugs for which a causal relationship cannot be ruled out, are required to be reported to the Pharmaceutical and Medical Devices Agency (PMDA) by pharmaceutical companies, attending physicians, and pharmacists who identify the adverse events. The Japanese Adverse Drug Event Report database of the PMDA included 68 cases of adverse reactions related to HKT that were reported between 2004 and 2022 [64]. Of these, 18 cases were reported with HKT as the suspected causal drug, and the remaining cases were reported with concomitant medications as the causal drug. In these 18 cases, the most frequent adverse effect was liver injury (six cases), followed by interstitial lung disease (four cases). However, a closer examination of these cases revealed that they involved concomitant treatment with Scutellariae Radix-containing agents, such as saikokeisikankyoto and bofutsushosan. Therefore, whether HKT was the true cause of adverse effects in these F I G U R E 2 The overview of clinical and preclinical studies of hangekobokuto on stress, depression, anxiety, swallowing function, chronic intermittent hypoxia, and gastrointestinal motility.
cases is unknown. These cases included one case each of anaphylactic reaction, acute pyelonephritis, hemorrhagic stroke, dementia, leukopenia, and toxicity from various substances and two cases of Fanconi syndrome. Anaphylactic reactions can occur with any drug and should be carefully monitored.
Arai et al. extracted information on adverse drug reactions due to Kampo medicines from the Japanese Adverse Drug Reactions Relief Database for fiscal years 2008-2014 and estimated the incidence of adverse drug reactions due to Kampo medicines by estimating the number of people taking Kampo medicines from the production value, drug price, and administration period [65]. In their study, HKT was estimated to cause interstitial pneumonia in 0.38 per 100 000 patients and liver damage in 0.89 per 100 000 patients. However, no postmarketing studies on the frequency of adverse drug reactions have been conducted for ethical HKT extract preparations.

SUMMARY
The original text of HKT is Jin Gui Yao Lue, and it was originally described as being useful for treating throat discomfort in women. HKT smoothens qi circulation and improves symptoms such as breast swelling, stiffness in the epigastrium, and throat congestion, which reflect qi stagnation. The HKT formula consists of five crude drugs. Figure 2 shows the overview of clinical and preclinical studies of hangekobokuto on stress, depression, anxiety, swallowing function, chronic intermittent hypoxia, and gastrointestinal motility. Clinical studies have shown several clinical effects of HKT, including improving the swallowing reflex by increasing substance P levels in saliva; improving swallowing reflex; improving cough reflex; reducing pneumonia in patients with dementia, cerebrovascular disease, AD, or PD; reducing postoperative AP in patients who undergo cardiovascular surgery; and improving depression and anxiety scores in patients with globus hystericus. Preclinical studies have also reported that HKT increases 5-HT and noradrenaline levels in the hypothalamus and the DA level in the striatum in a healthy rodent model, improves 5-HT levels in the striatum and hippocampus and ameliorates the reduction in 5-HT and DA levels in the whole brain in an acute stress model, improves 5-HT levels in the striatum and the reductions in 5-HT and DA levels in the prefrontal cortex in a chronic stress model, and decreases corticosterone and CRF levels in a chronic stress model. The adverse events associated with HKT are reported as so rare.

CONCLUSION
HKT, which is widely used in clinical settings, has a low rate of adverse events. Several clinical studies have reported on the effects of HKT in reducing AP and improving depression and anxiety. Some of these effects are explained by the regulation of monoamines and stress hormones in the brain and substance P levels in the oral cavity.

AUTHOR CONTRIBUTIONS
Shin T designed the study. Tomoko S wrote 'Historical background of hangekobokuto'. Ryutaro A wrote 'Pharmaceutical information of hangekobokuto'. Akiko K wrote 'Clinical applications and controlled trials of hangekobokuto'. Akiyo K wrote 'Preclinical studies on hangekobokuto'. Tatsuya N wrote 'Adverse effects of hangekobokuto'. Natsumi S made Figure 2. Shin T wrote the abstract, summary, and conclusion. from the Department of Kampo Medicine, Tokai University, School of Medicine to which they belonged, and received a research grant from TSUMURA & CO., which was not related to this review.