Objective

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To summarize the clinical dosage rules of Dahuang （

Radix et Rhizoma Rhei

） and its different preparations from the Eastern Han Dynasty until now， thereby providing a basis for the clinical use of Dahuang.

Methods

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Using Microsoft office excel 2016 software to establish a database of Dahuang at different doses， we selected 92 representative medical works from the Eastern Han Dynasty to the present， and entered the data including prescriptions containing Dahuang， processing methods， and dosage. According to different processing me-thods， Dahuang was divided into six categories： cleansing， wine-processed， vinegar-processed， dry-fried until charred， mixed use of raw charcoal， and no clear classification.We counted the frequency of Dahuang with different processing methods through the ages， the minimum and maximum dosage， the commonly used amount and the range.

Results

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During the Eastern Han， Tang and Song dynasties， the commonly used dose of Dahuang was 55.2 g， 41.40 g， and 41.30 g， respectively， with a range of 13.8-82.6 g. The common dose of Dahuang in the Jin Yuan period was 38.10 g， and the common range was fluctuating from 3.81 to 38.10 g. In the Ming and Qing dynasties， the commonly used dose was 7.46 g and 3.73 g， while in the Republic of China and modern times， it was 9.39 g and 6.00 g， respectively. The frequency of cleansing Dahuang was as high as 971 times， and the dosage range was 0.38-206.60 g； wine-processed Dahuang was prevalent in the Ming and Qing dynasties， with a frequency of 73 times， and is now at its peak， with a frequency of 115 times； vinegar-processed and dry-fried until charred Dahuang have few records， with vinegar-processed Dahuang mentioned about two times and dry-fried until charred Dahuang about 50 times， whose commonly used amount are within 15g.

Conclusion

2

The clinical dosage of Dahuang varies significantly with the dynasty. The commonly used dose in the Han， Tang and Song dynasties was large and the range was wide， while that was small and the range was narrow in the Jin and Yuan dynasties. Since the Ming and Qing Dynasties， the commonly used range of Dahuang was close to that in modern times. Cleansing Dahuang is most frequently used with a large amount through the ages， while wine-processed is prevalent in Ming and Qing dynasties， and reach its peak in modern times. Vinegar-processed and dry-fried until charred Dahuang are less frequently used and the dosage is low.