去皮，酒洗用。恶细辛，畏萆 、女菀、卤碱，伏消石。治风宜木防己，治水宜汉
防己。
辛，苦而寒，无毒。足太阴、太阳经药。通行十二经。解脏腑之水气，泄经络之湿邪。
除脚
气之肿痛，退下焦之湿热。手足挛急之疾，关节肿痛之 。乃驱风逐水之要剂，为除湿解热
之灵丹。
出汉中川谷及黔中。二八月采根。其茎如葛蔓延，其根外白内黄，如桔梗内有黑纹。但
汉中
出者，破之文作车辐解，黄实而香，茎梗甚嫩，苗叶小类牵牛。折其茎一头吹之，气从中贯
如木通。他处者青白虚软，又有腥气，皮皱，上有丁足子，名木防己。或以木防己不任用，
而张仲景、孙思邈皆用之，是木防己亦可甚弃也。
肺痿喘嗽，汉防己末，水煎细呷。（验方第一。）
肺痿咯血，汉防己。葶苈为末，糯米汤下。（第二。）
霍乱吐利，防己、白芷末，新水下。（第三。）
目睛猝痛，酒浸为末，酒下。（第四。）
解雄黄毒，水煎服。（第五。）
小便淋涩，木防己、防风、葵子，水煎服。（第六。）
木防己汤 防己 石膏 人参 桂枝
治膈间支饮，喘满心下痞，面赤黎黑，脉沉紧者。（诸方第一。）
防己茯苓汤 防己 黄 桂枝 茯苓 甘草
水煎服。治皮水 肿，按之没指。（第二。）
防己黄 汤 防己 黄 白术 炙草 姜 枣
治风水皮肿，汗出脉浮。又治风湿相搏，关节沉痛，微肿恶风。（第三。）
去除外皮，用酒清洗后使用。与细辛相恶，畏惧萆薢、女菀和卤碱，能克制消石。治疗风证宜选用木防己，治疗水湿证宜选用汉防己。
味辛、苦，性寒，无毒。归足太阴脾经和足太阳膀胱经。通行于十二经脉。能解除脏腑间的水气，泄除经络中的湿邪。消除脚气引起的肿痛，退去下焦的湿热。对于手足拘挛抽搐的疾病，以及关节肿胀疼痛的症状，它是驱散风邪、逐除水饮的重要药剂，也是祛除湿邪、解除热毒的灵丹妙药。
产于汉中地区的山谷及黔中地区。农历二月和八月采集根部。其茎像葛藤一样蔓延生长，根部外表白色内部黄色，像桔梗内部有黑色纹理。但汉中出产的防己，折断后断面纹理呈车辐状放射，质地坚实且香气浓郁，茎梗非常嫩，幼苗叶片小得像牵牛花。折断茎的一端吹气，气流能贯通全身，如同木通。其他地方出产的则青白、虚软，又有腥味，表皮皱缩，上面有类似丁字足的突起，称为木防己。有人因为木防己不被重用而将其废弃，但张仲景、孙思邈都使用它，可见木防己也不应被完全抛弃。
肺痿伴有气喘咳嗽，将汉防己研成粉末，用水煎煮后细细咽服。（验方第一。）
肺痿伴有咯血，使用汉防己和葶苈子研成粉末，用糯米汤送服。（第二方。）
霍乱引起的呕吐腹泻，使用防己和白芷研成粉末，用新汲凉水送服。（第三方。）
眼睛突然疼痛，将药物用酒浸泡后研成粉末，用酒送服。（第四方。）
解雄黄毒，用水煎煮后服用。（第五方。）
小便淋沥涩痛，使用木防己、防风、冬葵子，用水煎煮后服用。（第六方。）
防己汤：由防己、石膏、人参、桂枝组成。
治疗膈间支饮（水饮停聚胸膈），出现喘息、胸闷、心下痞塞，面色红黑，脉象沉紧的症状。（诸方第一。）
防己茯苓汤：由防己、黄芪、桂枝、茯苓、甘草组成。
用水煎煮后服用。治疗皮水（水肿病的一种），按压凹陷不起。（第二方。）
防己黄芪汤：由防己、黄芪、白术、炙甘草、生姜、大枣组成。
治疗风水（风邪袭表引起的水肿）导致皮肤浮肿，出汗且脉浮。又治疗风湿相搏，关节沉重疼痛，轻微肿胀且怕风的症状。（第三方。）
Remove the skin and wash with wine. It is incompatible with Ephedrae Herba (Mahuang, 麻黄), fears Bletillae Rhizoma (Bixie, 萆薢), Polygala Root (Nüwan, 女菀), and Sal Natrii Sulfurati (Lujian, 卤碱), and can suppress Gypsum Fibrosum (Xiaoshi, 消石). For treating wind disorders, use Stephaniae Tetrandrae Caulis (Mu Fangji, 木防己); for treating water-dampness disorders, use Stephaniae Membranaceae Radix (Han Fangji, 汉防己).
Pungent, bitter, and cold in nature, non-toxic. It enters the Foot-Taiyin Spleen Meridian and Foot-Taiyang Bladder Meridian. It circulates through the twelve meridians. It resolves water qi within the zang-fu organs and drains damp-evil from the collaterals. It eliminates swelling and pain caused by jiaoqi (foot disease) and clears damp-heat from the lower jiao. For conditions involving spasms and cramps of the hands and feet, as well as joint swelling and pain, it is a crucial agent for expelling wind and driving out water, and a miraculous elixir for removing dampness and clearing heat.
It originates from the valleys of Hanzhong and Qianzhong. The roots are harvested in the second and eighth lunar months. Its stems spread like those of Puerariae Lobatae Radix (Gegen, 葛根). The root exterior is white and interior yellow, resembling the black striations inside Peucedani Radix (Jiegeng, 桔梗). However, Hanfangji produced in Hanzhong, when broken, reveals a radial pattern like chariot spokes; it is solid, fragrant, has very tender stems, and small leaves resembling Ipomoeae Nil Semen (Qianniu, 牵牛). If one end of the stem is broken and blown into, air passes through completely, similar to Akebiae Caulis (Mutong, 木通). Those from other regions are greenish-white, hollow, soft, have a fishy odor, wrinkled skin, and protrusions resembling "ding" feet on the surface; these are called Mu Fangji. Some discard Mu Fangji due to its lesser status, yet Zhang Zhongjing and Sun Simiao both used it, indicating that Mu Fangji should not be entirely abandoned.
For feiwei (lung atrophy) with wheezing and cough: Powder the Han Fangji, decoct in water, and sip slowly. (Verified Formula No. 1.)
For feiwei with hemoptysis: Use Han Fangji and Descurainiae Semen seu Lepidii Semen seu Lepidii Fructus (Tingli, 葶苈子), powdered, taken down with rice gruel. (Formula No. 2.)
For huoluan (cholera-like syndrome) with vomiting and diarrhea: Powder Fangji and Angelicae Dahuricae Radix (Baizhi, 白芷), taken down with fresh cool water. (Formula No. 3.)
For sudden eye pain: Soak in wine, powder, and take down with wine. (Formula No. 4.)
To resolve Xionghuang toxicity (realgar poisoning): Decoct in water and take. (Formula No. 5.)
For strangury with difficult urination: Use Mu Fangji, Saposhnikoviae Radix (Fangfeng, 防风), and Malvae Semen (Kuizi, 葵子), decoct in water and take. (Formula No. 6.)
Fangji Tang: Composed of Stephaniae Tetrandrae Caulis (Mu Fangji, 木防己), Gypsum Fibrosum (Shigao, 石膏), Ginseng Radix et Rhizoma (Renshen, 人参), Cinnamomi Ramulus (Guizhi, 桂枝).
Treats zhiyin (branching fluid retention) between the diaphragm, characterized by wheezing, chest fullness, epigastric stuffiness, reddish-black complexion, and a deep, tight pulse. (Primary Formula No. 1.)
Fangji Fuling Tang: Composed of Stephaniae Membranaceae Radix (Han Fangji, 汉防己), Astragali Radix (Huangqi, 黄芪), Cinnamomi Ramulus (Guizhi, 桂枝), Poria (Fuling, 茯苓), Glycyrrhizae Radix et Rhizoma (Gancao, 甘草).
Decoct in water and take. Treats pishui (skin edema), where pressing leaves an indentation that does not immediately rebound. (Formula No. 2.)
Fangji Huangqi Tang: Composed of Stephaniae Membranaceae Radix (Han Fangji, 汉防己), Astragali Radix (Huangqi, 黄芪), Atractylodis Macrocephalae Rhizoma (Baizhu, 白术), Prepared Glycyrrhizae Radix et Rhizoma (Zhi Cao, 炙草), Zingiberis Rhizoma Recens (Jiang, 姜), Jujubae Fructus (Zao, 枣).
Treats fengshui (wind-water edema) presenting with skin swelling, sweating, and a floating pulse. Also treats wind-dampness bi-syndrome with heavy joint pain, slight swelling, and aversion to wind. (Formula No. 3.)