The effectiveness of a medication depends not only on its quality but also on its dosage. Therefore, the dosage of traditional Chinese medicine (TCM) is an important factor in ensuring its therapeutic effects. Accurate understanding of the dosage of TCM is not only crucial for ensuring its clinical efficacy but also essential for medication safety.
The measurement units for TCM have evolved over time. In ancient times, there were various measurement methods, including weight (zhu, liang, qian, jin), length (chi, cun), and volume (dou, sheng, he). There were also rough measurement methods such as "dao gui," "fang cun bi," "cuo," and "mei" that could be converted to the aforementioned measurement methods. In later times, the measurement of solid medicines mainly relied on weight. Since the Ming and Qing dynasties, the decimal system (1 jin = 16 liang, 1 liang = 10 qian) has been widely adopted. The current TCM measurement standards in China use the metric system, where 1 kg = 1000 g. For the convenience of prescription and dispensing calculations, the following approximate values are used:
1 liang (decimal system) ≈ 30g
1 qian ≈ 3g
1 fen ≈ 0.3g
1 li ≈ 0.03g
The dosage of TCM, commonly referred to as the dose, generally refers to the amount of each medicine taken by an adult in a day. However, it can also refer to the amount of each medicine in a dose of medication. In a formula, it refers to the relative amount of medicine compared to other medicines. Accurately understanding the dosage is also one of the important factors for ensuring medication safety and effectiveness.
The dosage of TCM is not fixed and depends mainly on factors such as the characteristics of the medicine, the patient's condition, and the seasonal environment.
1. Characteristics of the Medicine
(a) Texture of the Medicinal Material
Generally, medicines with lighter texture, such as flowers and leaves, should be used in smaller amounts (usually 3-10g). Medicines with heavier texture, such as minerals and shells, should be used in larger amounts (usually 10-30g). Fresh ingredients also require larger amounts (usually 30-60g).
(b) Nature and Taste of the Medicine
Medicines with mild actions and less pronounced taste can be used in larger amounts, while medicines with strong actions and stronger taste should be used in smaller amounts.
(c) Toxicity
Medicines that are non-toxic or have low toxicity can have greater variations in dosage. However, for highly toxic medicines, strict adherence to the dosage specified in the pharmacopoeia is necessary.
(d) Compatibility of Medicines
When a single medicine is used, the dosage can be larger. When used in a formula, the dosage should be smaller. As the main medicine in a formula, the dosage can be larger, while as an auxiliary medicine, the dosage should be lighter.
(e) Dosage Form
In decoctions, the dosage can be larger, while in pills and powders, the dosage should be lighter.
(f) Purpose of Medication
In clinical practice, the dosage of certain medicines may vary depending on their purpose. For example, areca nut can be used for promoting digestion and relieving qi stagnation at a commonly used dosage, but for deworming purposes, a higher dosage may be required. Similarly, rhizoma arisaematis, used for purging the bowels, can have a lighter dosage when used for promoting bowel movements, but a heavier dosage when used for diuresis.
2. Patient's Condition
(a) Age
Children who are still growing and the elderly, whose vitality gradually declines, have less tolerance to medications. The dosage of medications should be lower than that of adults. Typically, children under the age of five are prescribed one-fourth of the adult dosage, while those aged five or older can take half of the adult dosage.
(b) Gender
Generally, there is not much difference in dosage between men and women. However, women should avoid excessive dosage of blood-activating, stasis-removing, and menstrual-regulating medicines during their menstrual and pregnancy periods.
(c) Constitution
Individuals with a robust constitution can tolerate a heavier dosage, while those with a weak constitution should take a lighter dosage. Even for tonic medicines, it is advisable to start with a small dosage to avoid overwhelming the weak constitution.
(d) Duration of Illness
Patients with new illnesses have less damage to their vitality, so the dosage can be slightly heavier. Patients with long-standing illnesses and weak constitutions should take a lighter dosage.
(e) Severity of Illness
For severe and critical illnesses, a heavier dosage is recommended, while for mild and non-urgent illnesses, a lighter dosage is appropriate. Excessive dosage for a severe illness may be like a drop in the ocean, making it difficult to control the condition. Conversely, excessive dosage for a mild illness may harm the vitality.
In addition, differences in occupation and lifestyle should also be considered. For example, physical laborers generally have looser skin texture than mental laborers. When using diaphoretic medicines, the dosage for physical laborers can be slightly heavier than for mental laborers.
3. Seasonal Environment
(a) Seasonal Climate
In the spring and summer seasons, when the climate is mild and the skin is loose, the dosage of dispersing and warm/hot medicines should be lighter, while the dosage of cold medicines can be heavier. In the autumn and winter seasons, when the climate is cold and the skin is tight, the dosage of dispersing and warm/hot medicines can be heavier, while the dosage of cold medicines should be lighter. This is what is meant by "adapting to the season."
(b) Living Environment
In high-altitude areas, where the skin is denser, the dosage of dispersing and warm/hot medicines can be larger.
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