'Maidong Pingfei Yin' for Sequelae of Respiratory Tract Infection (Including Post-COVID Syndrome)

Waike Zhengzong (Orthodox Manual of External Medicine) records Maidong Pingfei Yin (Ophiopogon Lung-Calming Drink), a formula for "lung abscess" (feiyong), derived from Maidong Qingfei Yin in the Zazbing Yuanliu Xizhu (Roots and Branches of Miscellaneous Diseases). Its composition is: Renshen (Ginseng), Maimendong (Ophiopogon), Chishao (Red Peony), Binglang (Areca), Chifuling (Red Poria), Chenpi (Tangerine Peel), Jiegeng (Platycodon), each 1 qian (3 g); Gancao (Licorice) 5 fen (1.5 g). Use one bowl of water (about 300 ml), decoct down to 80% of a bowl (about 240 ml), strain, and take warm on an empty stomach twice daily.

Maidong Pingfei Yin supplements qi and nourishes yin, resolzes stasis, and expels pus. It is indicated for early-stage lung abscess with cough and panting, dull pain in the chest, and expectoration of purulent sputum; or for measles in which toxin has retired into the lung, with the lung parched and lobes upturned, presenting cough, rapid breathing, and incessant coughing, even hemoptysis, or choking on food and drink. From this description, the formula is suitable for sequelae of various respiratory infections, including the now-common post-COVID syndrome.

The formula's design shows that the ancients understood chronic respiratory disease presenting with copious sputum, panting, cough, and wheeze as "intermingled phlegm and stasis, with both deficiency and excess." They held that such chronic respiratory diseases involve concurrent righteous-qi deficiency and pathogen excess, and that "long-standing illness necessarily leads to deficiency and stasis." Treatment therefore follows the principles of "supporting righteous qi and securing the root, expelling pathogen, resolving stasis, transforming phlegm, and stopping cough."

In this formula, Renshen strongly supplements original qi; Maimendong nourishes yin and moistens the lung; Chishao activates blood and resolves stasis; Binglang moves qi and dispels phlegm; Chifuling fortifies the spleen and transforms dampness while also calming the spirit and aiding sleep; Chenpi resolves phlegm and stops cough; the Jiegeng-Gancao pair is Jiegeng Qu Tang Tang (Platycodon Expels Pus Decoction) from the Jingui Yaolue, a classic formula for cough with copious sputum. Together the herbs support righteous qi, fortify the spleen, calm the spirit, expel phlegm, transform dampness, resolve stasis, and stop cough. This design reflects TCM's holistic thinking and accounts for its therapeutic effect.

The clinical picture of lung abscess overlaps with many diseases such as lung abscess, emphysema, and COPD. Under TCM's pattern differentiation (symptomatic treatment) and the principle of "different diseases treated with the same formula," this formula suits various respiratory diseases presenting with the above symptoms. These are mostly chronic conditions with long courses, and treatment cannot be achieved in a short time. If patients respond to the decoction, they may make pills in the same proportion for continued use, or cook an electuary (gao) for gradual conditioning.