麻黄（三两去节） 芍药（三两） 五味子（半升） 干姜（二两） 甘草（二两炙） 桂枝（三
两） 半夏（三两洗） 细辛（三两）
上八味。以水一斗。先煮麻黄。减二升。去上沫。纳诸药。煮取三升。去滓。温服一升
。
此治太阳寒水之法也。虽同名青龙。却与大青龙主治迥别。太阳表邪不解。与阳热相搏
。宜大
青龙发之。太阳表邪不解。与寒饮相格。宜小青龙逐之。经云。伤寒表不解。心下有水气。
干呕。发热而咳。此为小青龙的对之证。故方中用麻黄桂枝细辛之属。以散寒而解表。用半
夏干姜五味之属。以蠲饮而降逆。复以芍药甘草。两和表里。但表里错杂之邪。病出恒不一
致。若微利者。水已下趋。故去麻黄。加芫花。顺其势以导之也。若渴者。寒已化热。故去
半夏。加栝蒌根。反其用以治之也。若噎者。寒格上焦也。故去麻黄。加附子以散寒。若小
便不利。少腹满者。水蓄下焦也。故去麻黄。加茯苓以利水。若喘者。水邪射肺也。故去麻
黄。加杏仁以下肺气。此方本不至发汗。故或用麻黄。或去麻黄。皆相表里证之轻重。而为
加减之圆机活法也。
按大青龙发汗以除阳热。犹龙之乘云上天而布甘霖。小青龙逐水以散阴寒。犹龙之翻波
逐浪而归江海。制方之妙。亦犹龙之变化而不可测乎。
Ephedrae Herba (Mahuang, 麻黄) [3 liang, stems removed], Paeoniae Radix Alba (Baishao, 白芍) [3 liang], Schisandrae Fructus (Wuweizi, 五味子) [0.5 sheng], Zingiberis Rhizoma Recens (Ganjiang, 干姜) [2 liang], Glycyrrhizae Radix et Rhizoma Praeparata cum Melle (Zhi Gancao, 炙甘草) [2 liang], Cinnamomi Ramulus (Guizhi, 桂枝) [3 liang], Pinelliae Rhizoma Praeparatum (Banxia, 法半夏) [3 liang, washed], Asari Radix et Rhizoma (Xixin, 细辛) [3 liang].
The above eight ingredients. Use one dou of water. First decoct Ephedrae Herba until the volume is reduced by two sheng. Remove the foam on the surface. Add the remaining herbs. Decoct to obtain three sheng of liquid. Strain the dregs. Take one sheng warm.
This is the method for treating Taiyang Cold-Water disease. Although both share the name "Qinglong" (Azure Dragon), their indications are distinctly different from those of Da Qinglong Tang (Major Azure Dragon Decoction). When exterior pathogens in the Taiyang stage remain unresolved and contend with Yang heat, Da Qinglong Tang should be used to disperse them. When exterior pathogens in the Taiyang stage remain unresolved and clash with cold-fluid retention, Xiao Qinglong Tang (Minor Azure Dragon Decoction) should be used to expel them. The Classics state: "In cold damage, if the exterior syndrome is not resolved, there is fluid accumulation in the epigastrium, accompanied by dry retching, fever, and cough." This constitutes the specific indication for Xiao Qinglong Tang. Therefore, the formula employs herbs such as Ephedrae Herba, Cinnamomi Ramulus, and Asari Radix to dispel cold and resolve the exterior. It uses Pinelliae Rhizoma, Zingiberis Rhizoma Recens, and Schisandrae Fructus to eliminate fluid retention and direct rebellious Qi downward. Furthermore, Paeoniae Radix Alba and Glycyrrhizae Radix et Rhizoma harmonize the interior and exterior. However, when pathogenic factors complicate both the interior and exterior, clinical manifestations may vary. If mild diarrhea occurs, it indicates that water has moved downward; thus, Ephedrae Herba is omitted and Daphnes Genkwa Flos (Yuanhua, 芫花) is added to guide the pathogen along its course. If thirst is present, it suggests that cold has transformed into heat; thus, Pinelliae Rhizoma is omitted and Trichosanthis Radix (Gualougen, 瓜蒌根) is added to counteract the original action and clear heat. If a sensation of choking or obstruction occurs, it indicates cold blocking the Upper Jiao; thus, Ephedrae Herba is omitted and Aconiti Lateralis Radix Praeparata (Fuzi, 附子) is added to dispel cold. If urination is difficult and the lower abdomen is full, it indicates water retention in the Lower Jiao; thus, Ephedrae Herba is omitted and Poria (Fuling, 茯苓) is added to promote diuresis. If wheezing or asthma occurs, it indicates water pathogens attacking the Lung; thus, Ephedrae Herba is omitted and Armeniacae Semen Amarum (Xingren, 杏仁) is added to descend Lung Qi. This formula is not primarily intended to induce sweating; therefore, the use or omission of Ephedrae Herba depends on the severity of the interior-exterior syndromes, representing a flexible and adaptive modification strategy.
Note: Da Qinglong Tang induces sweating to eliminate Yang heat, akin to a dragon riding the clouds to heaven to distribute sweet rain. Xiao Qinglong Tang expels water to disperse Yin cold, akin to a dragon turning waves and chasing currents to return to the rivers and seas. The subtlety in formulating this prescription is also as unpredictable and transformative as the dragon itself.