Without knowing what your essay has specified in it, it is not possible to suggest detailed sentences for a conclusion on aspirin. In general terms, then, the conclusion, much like the introduction, frames an essay and serves two purposes:
- It rewords the main points of the essay, acting as a reminder of these points
- It provides a sense of finality to the reader.
In order to remind the reader of the main points, the writer rewords his/her thesis statement. And, the sentence that is the final remark, so to speak, is often referred to as the "clincher." The simplest clincher is a reminder of the "hook" or motivator that has been used in the introduction. This clincher, then, brings the paper "full circle" and provides a definitive ending. So, return to your essay's introduction and form your conclusion from it.
In addition to reminding the reader of the hook of the introduction, a clincher can also extend the thought just a little further. For instance, if you have written of the scientific benefits of aspirin, you could write a sentence expressing the idea that reaching for the aspirin bottle unthinkingly when one has a headache is not merely a selfish act to relieve pain, but a beneficial one to the body.