 The purpose of this study is to test the onset of action, offset of action, efficacy, and safety of pinaverium and an herbal medication for irritable bowel syndrome IBS for a long term over one year. Pinaverium has been in many countries, but there is no randomized, double-blind, large sample size, and placebo-controlled study on this medication yet. Tong Xie Yao Fang Formula for pain and diarrhea is a historically and contemporarily used traditional Chinese medicine that can be used for IBS. The hypothesis is that the two remedies are effective and safe for IBS treatment with no significant different onset and offset of actions when tested by modern clinical standards and criteria. 