Q: How can I buy authorship for a medical article?
Buying authorship for an article is considered a serious form of academic misconduct. You should never consider doing this. You have not mentioned whether you are a medical practitioner or researcher, but some medical researchers who do not have the time to write their own manuscripts often assign a medical writer for the purpose. The researcher conducts the research and provides all the data to the medical writer who then writes the manuscript on behalf of the researcher. As long as the author acknowledges the use of medical writing services, this is an acceptable practice.
If you have conducted your own research, but do not have time to write the manuscript, you can consider using medical writing services. However, remember that the research and the data have to be your own.