Publisher Summary This chapter discusses the studies regarding effects of using aspirin to treat various medical conditions and the subsequent results. Various studies on the side effects of aspirin when used as an antithrombotic drug, and their conclusions have been detailed in the chapter. The association of aspirin to Reye's syndrome is elaborated. The gastrointestinal effects because of using aspirin has been looked upon. The effects of hemorrhage in elderly patients have been discussed, along with other effects such as special senses and urinary system. The chapter also explains the effects, documented among patients using Aniline derivatives like Paracetamol, resulting in myocarditis, overdosage, effects on skin, and urinary system. There is also a discussion about the drawbacks in treating paracetamol overdosage faced by paramedics.