半夏为天南星科植物半夏Pinellia ternata (Thunb.) Breit的干燥块茎，夏、秋二季采挖，洗净，除去外皮和须根，晒干。《礼记·月令》记载：五月半夏生，盖当夏之半，故名“半夏”。生半夏味辛且辣，麻舌而刺喉，临床上多使用其炮制品。

Ban-Xia, also known as the dried tuber of Pinellia ternata (Thunb.) Breit., belongs to the family Araceae. It is harvested during the summer and autumn, washed, peeled, and then dried. Ban-Xia matures in the fifth month of the lunar calendar, which is considered the middle of summer, so was named Ban-Xia, recorded in the ancient Chinese book Li Ji • Yue Ling. In clinical practice, processed forms of Ban-Xia are commonly used because its fresh form has a pungent and spicy taste, causing numbness of the tongue and throat irritation. 

半夏（图片来源于网络，侵删）

半夏，味辛，性温，有毒，归脾、胃、肺经。《神农本草经》、《本草纲目》均列半夏为下品，示其不宜与草乌、川乌、附子等中药同用。

1. Pharmacopoeia Inclusion and Categorization

Ban-Xia has a pungent taste and warm nature, belongs to the spleen, stomach, and lung meridians, and is considered toxic according to the theory of traditional Chinese medicines. It is listed as a lower-grade herb in ancient Chinese medicinal books Shennong Bencao Jing and Ben Cao Gang Mu, and cautioned its concurrent use with other traditional Chinese medicine including Cao-Wu, Chuan-Wu, and Fu-Zi.

The Pharmacopoeia of the People's Republic of China (2020 edition) included Ban-Xia and its three processed forms, namely Qing-Ban-Xia (purified Ban-xia), Jiang-Ban-Xia (ginger-processed Ban-xia), and Fa-Ban-Xia (processed Ban-xia according to specific methods).

生半夏：取原药材，去除杂质，捣碎；

清半夏：8%白矾溶液浸泡生半夏至内无干心，口尝微有麻舌感；

姜半夏：清水浸泡生半夏至内无干心，取出，另取生姜切片煎汤，加白矶与半夏共煮透，干燥；

2. Processing Methods of Ban-Xia

Method for Ban-Xia: Take the raw medicinal material, remove impurities, and crush it.

Method for Qing-Ban-Xia: Soak the raw Ban-Xia in an 8% alum solution until it is no longer dry inside, and taste it to perceive a slight numbing sensation on the tongue.

Method for Jiang-Ban-Xia: Soak the raw Ban-Xia in water until it is no longer dry inside, remove it, then take slices of fresh ginger and decoct them in water. Add alum and the Ban-Xia, then simmer until thoroughly cooked, and finally dried.

Method for Fa-Ban-Xia: Soak the raw Ban-Xia in water until it is no longer dry inside. Separately, decoct licorice twice in water, combine the decoctions, pour them into a lime solution prepared with an appropriate amount of water, stir well, and add the soaked Ban-Xia. Allow it to soak and stir until the cross-section becomes uniformly yellow and a slight numbing sensation is perceived on the tongue. The Ban-Xia is then removed, washed, and dried in the shade.

天然药物化学研究表明，半夏及其炮制品均富含生物碱、黄酮、甾体、有机酸、挥发油等化学成分，但不同炮制品所含化合物的种类和含量有所差异。半夏所含刺激性化学成分主要为原儿茶醛、2,5-二羟基苯乙酸及其葡萄糖苷、3,4-二羟基苯甲酸及其葡萄糖苷等化合物。总体而言，半夏炮制品中有毒成分及总生物碱含量均低于生半夏。其中，清半夏中总生物碱和麻黄碱含量最低；6-姜辣素为姜半夏的特有成分，姜半夏中有机酸含量最高；法半夏中甘草苷和甘草酸铵为特有成分，有机酸和半夏多糖含量最低。

3. Chemical Composition of Ban-Xia

It has been revealed that Ban-Xia and its processed forms are rich in alkaloids, flavonoids, steroids, organic acids, volatile oils, and other chemical constituents. However, the types and concentrations of compounds vary among different processed forms. The main irritant chemical components in Ban-Xia include protoanemonin, 2,5-dihydroxybenzoic acid and its glucoside, 3,4-dihydroxybenzoic acid and its glucoside, along with other related compounds. Generally, the processed forms of Ban-Xia exhibit lower levels of toxic components and total alkaloids compared to the raw Ban-Xia. Among the processed forms, Qing-Ban-Xia has the lowest content of total alkaloids and ephedrine. With 6-gingerol as the unique component, Jiang- Ban-Xia has the highest content of organic acids. While characterized by the presence of glycyrrhizin and glycyrrhizic acid, Fa-Ban-Xia has the lowest content of organic acids and polysaccharides.

半夏具有燥湿化痰、降逆止呕、消痞散结等功效，临床常以复方治疗湿痰寒痰、咳喘痰多、痰饮眩悸、风痰眩晕、痰厥头痛、呕吐反胃、胸脘痞闷诸症。生半夏及不同方法炮制后的半夏功效略有差异，生半夏镇静效果最佳，但清半夏、姜半夏、法半夏等炮制品的止咳效果均优于生半夏。现代药理学研究表明，半夏除传统的止咳、祛痰、镇吐作用外，还具备抗肿瘤、抗炎、降血脂、抗癫痫、抗腹泻及凝血等生理作用。需要注意的是半夏具有黏膜刺激性、肝肾毒性以及妊娠毒性，使用时一定要严控用量，遵医用药。

4. Pharmacological Activities of Ban-Xia

Ban-Xia possesses various bioactivities, including drying dampness, resolving phlegm, reducing rebellious qi and vomiting, and dispersing accumulation and nodules, according to the theory of traditional Chinese medicines. In clinical practice, it is commonly used in compound formulations to treat symptoms such as damp-phlegm and cold-phlegm, cough with abundant phlegm, phlegm-fluid retention with dizziness and palpitations, wind-phlegm dizziness, phlegm-induced headaches, vomiting and nausea, and chest and epigastric stuffiness. The efficacy of Ban-Xia slightly differ between raw Ban-Xia and its processed forms. Raw Ban-Xia exhibits the most pronounced sedative effect, while processed forms such as Qing-Ban-Xia, Jiang-Ban-Xia, and Fa-Ban-Xia demonstrate superior antitussive effects compared to raw Ban-Xia. It have been indicated by modern pharmacological studies that Ban-Xia also exhibits bioactivies containing anticancer, anti-inflammatory, lipid-lowering, antiepileptic, antidiarrheal, and hemostatic effects except for its traditional antitussive, expectorant, and antiemetic effects. Besides, it needs to be emphasized that strict control of dosage and adherence to medical prescriptions are necessary when using Ban-Xia, which can cause mucosal irritation, hepatorenal toxicity, and teratogenicity.