过去分词、目前分词被动式、目前分词完成被动式有什么区别，要具体状况具体剖析。就你提供的句子而言，______ in time, this medicine will be quite effective. 这是分词短语作条件状语的使用方法。
▲在此状况下，用过去分词taken 即可。转换成从句是If it is taken in time，由于“目前分词被动式”being taken 表示“被动和进行”，所以不符合条件句的需要。
being done 形式不是不能做状语，而是在那种情况下才能。比如，以下状况就能用：
Being watched by so many people then, she felt very nervous at the stage. “当时因为那样多人在观看她，所以她在台上非常紧张”。说明“被其他人看着”是在进行的状况下。
Being tired out after a long walk, they had to sTOP at the foot of the mountain for a rest.
作状语时，分词表示“状况”而不是“动作”的状况下，“过去分词”和“目前分词被动式”都可以用，意思几乎没差别。
▲再看过去分词和目前分词完成被动式有什么区别：
1. Compared with them, we still have a long way to go. 和他们相比，大家还有非常长的路要走。
2. Having been shown around the library, we were taken to the lab. 携带参观了图书馆后，大家又被带去参观实验室。
过去分词”Compared with them 作条件状语，与句子谓语动词发生的时间没先后之分，或者先后时间不清楚。句1等于If we are compared with them, we still have a long way to go. 而“目前分词完成被动式”Having been shown the library 肯定早于句子谓语动词发生的时间，句2等于After we had been shown around the library, we were taken to the lab. 通常来讲，只须动作早于谓语动词发生的时间，而且又是被动意义，就应用“目前分词完成被动式”。又如：
Having been bitten twice, the postman refused to deliver our letters unless we chained our dog up. 由于被狗咬了两次，邮递员要大家把狗拴起来，不然就不给大家送信了。（因果关系，缘由一直在前，所以用完成式。）
