生洲渚沙碛上。秋后采根。粗长坚直。色白微黄。折之易断者。为白前。细短柔韧。色
黄微白。折之不断者。白薇也。味甘辛。气微温微寒。阳中之阴。降也。手太阴肺家治咳要
药。更入手阳明足阳明经。主胸胁逆气。咳嗽上气。呼吸欲绝。（别录） 又治肺气烦闷。
贲豚肾气。（日华子） 长于降气。肺气壅实而有痰者宜之。若虚而长哽气者。不可用。（濒
湖）凡咳嗽而喉中作声者。一味白前煎服妙。久咳上气。体肿气短。昼夜倚壁不得卧。常作
水鸡声者。深师白前汤。白前紫菀半夏大戟各三两。水一斗。渍一宿。煮取三升。分数十服。
间
〔论〕白前主治。首言胸胁逆气。夫胸中固肺所治。而胁则阴阳升降之道路也。又主咳
嗽上气。呼吸欲绝。夫呼吸即升降之气。阴阳之分而合者。肺为气主。贯心脉而行呼吸。呼
吸欲绝。是有升无降。或阴或阳。皆能病之。如下之真阴不足。不能召上之阳。即无以吸上
而气不降。（此为气不归元）上之真阳不足。不能生下之阴。即无以归下而气亦不降。（此中
气大虚而失守。须大剂参 而愈。）二者皆虚证。非白前可治也。惟是后天气血之病。偏胜
所成。上实而下即虚。（如痰热上壅。阳愈失阴而亢。气固不降。）下实而上即虚。（如贲豚
肾气。阴愈逼阳而僭。其气亦不降。）随其所主之味。而以兹味为前导。庶乎近之。（此味三
阴并施。脏腑咸入。其功靡不前至。故名。）
缪氏云。走散下气。性无补益。凡咳逆气上。不由于邪客壅实者。禁用。
〔修治〕 甘草水浸。去头须。焙干用。
生长在沙洲和沙滩上。秋季之后采挖根部。根茎粗壮、长而坚硬挺直，颜色白中带微黄，折断时容易断裂的，是白前。根茎细短、柔软有韧性，颜色黄中带微白，折断时不易断裂的，是白薇（Cynanchum stauntonii, 白薇）。味道甘甜、辛，气微温或微寒，属于阳中之阴，具有沉降的作用。它是手太阴肺经治疗咳嗽的重要药物，同时也进入手阳明大肠经和足阳明胃经。主要治疗胸胁部的气逆、咳嗽气喘、呼吸急促近乎停止。（出自《名医别录》）又用于治疗肺气烦闷、奔豚肾气（一种自觉有气从少腹上冲心胸的病证）。（出自《日华子本草》）本品擅长降气，适用于肺气壅滞实证且伴有痰湿的患者。如果是虚证且表现为长期嗳气者，不可使用。（出自李时珍《本草纲目》）凡是咳嗽且喉咙中有声音的，单用一味白前煎服效果极佳。对于久咳气喘、身体浮肿、气短、白天黑夜只能靠着墙壁无法平卧、经常发出像水鸡叫声一样的喘息声的患者，可使用深师白前汤。方中白前、紫菀、半夏、大戟各三两，用水一斗，浸泡一夜，煮取三升药液，分几十次服用。
〔论述〕白前的主治功效，首先提到胸胁气逆。胸中确实是肺所主之地，而胁部则是阴阳之气升降的道路。又主治咳嗽气喘、呼吸急促近乎停止。呼吸即是升降之气，是阴阳分离又结合的过程。肺为气之主，贯通心脉并主持呼吸。呼吸急促近乎停止，意味着只有升而没有降，无论是阴还是阳的病变，都能导致这种情况。如下焦真阴不足，不能招引上方的阳气，就无法吸气而上行，导致气不下降。（这称为气不归元）上焦真阳不足，不能生发下焦的阴气，就无法使气归藏于下，导致气也不下降。（这是中气大虚而失守，需要用大剂量的参类药材才能治愈。）这两种情况都属于虚证，不是白前所能治疗的。只有后天气血的病变，由偏胜所致，上部实则下部即虚。（如痰热壅塞于上，阳气更加失去阴液的制约而亢盛，气自然不降）下部实则上部即虚。（如奔豚肾气，阴气逼迫阳气而僭越，其气也不降）根据其所主的味道，以此味作为先导，才差不多接近病机。（此药在三阴经并施，脏腑皆入，其功效没有不到达的，因此得名“前”）
缪希雍说：本品走散下气，性质没有补益作用。凡是咳逆气上，不是由于邪气客居壅实引起的，禁用。
〔炮制〕用甘草水浸泡，去掉头须，焙干后使用。
Grows on sandbars and sandy beaches. The roots are harvested after autumn. Those that are thick, long, hard, and straight, with a white color slightly tinged with yellow, and break easily when snapped, are named Baiqian (Cynanchum glaucescens, White Cynanchum Root). Those that are thin, short, soft, and flexible, with a yellow color slightly tinged with white, and do not break easily when snapped, are Baiwei (Cynanchum stauntonii, Cynanchum Root). It tastes sweet and pungent, has a slightly warm or slightly cold nature, belongs to Yin within Yang, and has a descending action. It is an essential herb for the Hand-Taiyin Lung Meridian in treating coughs, and also enters the Hand-Yangming Large Intestine Meridian and Foot-Yangming Stomach Meridian. It primarily treats rebellious Qi in the chest and hypochondrium, coughing with upward rushing of Qi, and breathing so rapid as to be nearly interrupted. (From *Bielu*) It also treats irritability due to Lung Qi stagnation and Ben Tun Shen Qi (a syndrome characterized by the sensation of Qi rushing from the lower abdomen up to the heart and chest) (From *Rihua Zi*). This herb excels at descending Qi and is suitable for cases of Lung Qi obstruction with excess and phlegm. However, it should not be used in deficiency cases presenting with chronic belching. (From Li Shizhen) For any cough accompanied by sounds in the throat, decocting and taking a single dose of Baiqian yields excellent results. For chronic cough with upward rushing of Qi, bodily swelling, shortness of breath, inability to lie flat day or night but only leaning against walls, and frequent wheezing sounds resembling those of a water frog, use Shenshi Baiqian Tang. The formula contains Baiqian, Ziwan (Asteris Radix), Banxia (Pinelliae Rhizoma Preparatum), and Daji (Euphorbiae Pekinensis Radix), each three liang. Use one dou of water, soak overnight, boil to obtain three sheng of liquid, and divide into dozens of doses for administration.
[Discussion] The primary indications of Baiqian first mention rebellious Qi in the chest and hypochondrium. The chest is indeed governed by the Lung, while the hypochondrium serves as the pathway for the ascending and descending of Yin and Yang. It also treats coughing with upward rushing of Qi and breathing so rapid as to be nearly interrupted. Respiration is the Qi of ascending and descending, representing the separation and union of Yin and Yang. The Lung is the master of Qi, penetrating the Heart vessels and governing respiration. Breathing so rapid as to be nearly interrupted indicates rising without descending; whether due to Yin or Yang pathology, both can cause this condition. For instance, if the True Yin in the lower jiao is insufficient and cannot attract the Yang Qi from above, there will be no inhalation upwards, leading to non-descending Qi. (This is referred to as "Qi failing to return to its origin.") If the True Yang in the upper jiao is insufficient and cannot generate the Yin from below, the Qi cannot descend and store itself, leading to non-descending Qi. (This is severe deficiency of Middle Qi with loss of control, requiring large doses of Ginseng herbs to cure.) Both scenarios are deficiency syndromes and are not treatable by Baiqian. Only pathological conditions of acquired Post-Heaven Qi and Blood, resulting from excessive dominance, fit this indication: Upper Excess leads to Lower Deficiency (e.g., Phlegm-Heat obstructing the upper, causing Yang to become hyperactive due to lack of Yin restraint, thus Qi fails to descend); Lower Excess leads to Upper Deficiency (e.g., Ben Tun Shen Qi, where Yin forces Yang to rebel, causing Qi to fail to descend). Guided by the specific flavors and using this herb as a pioneer, one approaches the correct treatment principle. (This herb acts on all three Yin meridians and enters all Zang-Fu organs; its efficacy reaches everywhere, hence the name "Qian" meaning "before" or "pioneer".)
Miao Xi Yong stated: It disperses and descends Qi, possessing no tonifying properties. It is strictly contraindicated for coughing and rebellious Qi that does not arise from pathogenic invasion and excess obstruction.
[Processing] Soak in Licorice Water, remove the root heads and whiskers, then dry by baking before use.