Shengmai-San: Treating Lung Dryness and Fatigue from Sweating

Prescribe for Fatigue, Spontaneous Sweating, Cough, and Thirst

By Jubong Kang, KMD

Actions and Diagnosis

Shengmai-San restores symptoms such as lassitude, thirst, sweating, cough, dizziness, and loss of appetite caused by a deficiency of both qi and yin. These symptoms typically occur during midsummer heat, while working, or after recovering from fever. They may also appear when overwork, tension, and stress persist for a long time.

When more heat is generated due to febrile disease, summer heat, or overwork, the lungs initially discharge more fluid through breathing. Heat that cannot be sufficiently removed escapes through the pores with sweat. With excessive fluid loss, the lungs dry up, vigor decreases, and a qi– and yin-deficiency syndrome is formed.

This process is described as “fire restrains metal” in traditional Asian Medicine, referring to the relationship between heart-fire, the heat of the heart, and lung-metal, the ability of the lungs to endure that heat. When heart-fire becomes excessive, the body fluid—the water-qi that supports lung-metal—decreases, causing dryness and the “deficiency of both qi and yin of the lung.” Prescriptions for treating this include Maimendong-Tang, Zhuye-Shigao-Tang, Baihe-Gujin-Tang, and Qingzao-Jiufei-Tang, as well as Shengmai-San. They restore the balance by normalizing “fire restrains metal.”

Among the constituent drugs, Renshen is the monarch drug. It reinforces primordial qi, invigorates the spleen and lung, produces body fluids, quenches thirst, eases the mind, and alleviates symptoms of shortness of breath, weakness, exhaustion, dizziness, amnesia, and poor appetite.

Maimendong is the minister drug that nourishes the lung, heart, and stomach and invigorates yin. It improves dry tongue and thirst, dry cough, vexation, sleeplessness, constipation, hematemesis, and hemoptysis, all caused by yin-deficiency. Pharmacologically, it also has a blood sugar–reducing effect.

Wuweizi is an adjuvant drug that promotes fluid production, constrains perspiration, astringes essence, and stops diarrhea. It improves spontaneous perspiration, night sweating, chronic cough, chronic diarrhea, nervous exhaustion, and chronic hepatitis.

In diagnosis, a patient who benefits from Shengmai-San typically exhibits lassitude, perspiration, cough, thirst, inappetence, and a weak, rapid pulse. It’s often used as a single prescription or combined with Buzhong-Yiqi-Tang, Bazhen-Tang, Shuanghe-Tang, and Liuwei-Wan, depending on the condition.

Application: Used when lethargy, sweating, thirst, or low blood pressure occur due to summer heat. Also applicable when the pulse is weak and fast, with lethargy, poor appetite, and dry mouth and tongue caused by overwork or stress.

Distinction: If Wuweizi is removed and Dazao and Banxia are added, Shengmai-San becomes Maimendong-Tang. If sweating occurs with Maimendong-Tang symptoms, add Wuweizi; if cough with sputum appears in Shengmai-San, add Banxia.

Contents in the Source Text: “This prescription treats symptoms such as short breath, fatigue, thirst, sweating a lot, and cough due to lung deficiency; these were caused by heat damaging primordial qi.” (Nei Wai Shang Bian Huo Lun)

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