药物在人体中的作用时间各不相同,有的较短,亦有较长者。短效药物一般只能维持治疗水平4小时左右,每天须服药3～4次。有些药如口服避孕药,虽每天仅服药一次,但必须连续服药一个周期方能达到避孕目的。这种短效药物,常因没有按时服药而不能达到治疗或预防目的。此外,短效药物“一天数次”的服用方法,所产生的血药浓度时高时低(图1),高时往往可超过最适宜的治疗浓度,以致发生各种毒性反应;低时则远在所需要的治疗浓度以下,以致无显著疗效。鉴于上述存在问题,药物长效化的研究已引起了普遍注意。这方面的研究工作,包括用 The role of drugs in the human body varies in time, some shorter, but also older. Short-acting drugs generally can only maintain the treatment level of about 4 hours a day to take 3 to 4 times. Some drugs such as oral contraceptives, although only once a day medication, but must take a cycle of continuous medication to achieve the purpose of contraception. This short-acting drug, often not because of medication on time and can not achieve the purpose of treatment or prevention. In addition, short-acting drugs taken “several times a day”, the resulting blood concentration is high and low (Figure 1), high often exceed the optimal treatment concentration, resulting in a variety of toxic reactions; low Far below the required therapeutic concentration, resulting in no significant effect. In view of the above problems, the study of drug long-term has attracted widespread attention. Research work in this area, including use