Complex sentence: The article was subsequently cited extensively as evidence that addiction was very rare among patients who were prescribed narcotics (more specifically, opioids), despite the fact that the original letter was not peer-reviewed and did not include the analysis on which it was based.
Split into simpler sentences: The article was subsequently cited extensively as evidence that addiction was very rare among patients who were prescribed narcotics (more specifically, opioids). The original letter was not peer-reviewed and did not include the analysis on which it was based.