凡是后下的药物绝大多数是气味芳香，含挥发性成份的药材，久煎固使药物气味挥发，失去或减少疗效。传统方法：对气味芳香含挥发性药材在煎煮时采用后下，即在汤剂头煎将结束前5—10分钟投入同煎。中药材有效成份是由浸透加热溶出，把未经浸泡的后下药投入高温已成糊状的药材中 The vast majority of drugs that are followed are odor-smoked and contain volatile ingredients. If they are decocted for a long time, the odor of the drug will evaporate and the efficacy will be lost or reduced. Traditional method: After the aromatic ingredients containing volatile herbs are decocted, they should be cooked for 5 to 10 minutes before decocting. The active ingredients of Chinese herbal medicines are dissolved by soaking and heating, and put the untreated soda into high-temperature pastes.