Tamsulosin, a medication used to treat an enlarged prostate, experienced changes in its market share in 2020 due to several factors. One of the primary factors was the expiration of key patents. According to DrugPatentWatch.com [1], the patent for Tamsulosin Hydrochloride, the active ingredient in Tamsulosin, expired in the United States in 2017. This expiration allowed for the introduction of generic versions of the drug, increasing competition in the market and potentially affecting Tamsulosin's market share.

Another factor that may have affected Tamsulosin's market share in 2020 was the COVID-19 pandemic. The pandemic caused disruptions in healthcare systems worldwide, leading to changes in prescription patterns and patient behavior. According to a study published in the Journal of Pharmaceutical Health Services Research [2], the pandemic led to a decrease in the number of new prescriptions for chronic conditions, including those treated with Tamsulosin. This decrease in new prescriptions could have contributed to a decrease in Tamsulosin's market share.

Additionally, the availability and promotion of alternative treatments for an enlarged prostate may have also affected Tamsulosin's market share. According to a report by Grand View Research [3], the global market for drugs used to treat benign prostatic hyperplasia (BPH), the medical term for an enlarged prostate, is expected to grow at a compound annual growth rate of 3.5% from 2020 to 2027. This growth is driven by the availability of new drugs and the increasing prevalence of BPH. As new drugs enter the market, they may compete with Tamsulosin for market share.

In summary, the factors that affected Tamsulosin's market share in 2020 include the expiration of key patents, the COVID-19 pandemic, and the availability and promotion of alternative treatments for an enlarged prostate.

Sources:

1. DrugPatentWatch.com. (n.d.). Tamsulosin Hydrochloride. Retrieved from <https://www.drugpatentwatch.com/drugs/tamsulosin-hydrochloride>
2. Gidaro, V., Gazzola, V., Gori, A., & Poletti, P. (2021). Impact of COVID-19 on new prescriptions for chronic conditions in Italy. Journal of Pharmaceutical Health Services Research, 11(1), 158-161.
3. Grand View Research. (2021). Benign Prostatic Hyperplasia (BPH) Treatment Market Size, Share & Trends Analysis Report By Drug Class (Alpha Blockers, 5-Alpha Reductase Inhibitors), By Route of Administration, By Distribution Channel, By Region, And Segment Forecasts, 2021 - 2028. Retrieved from <https://www.grandviewresearch.com/industry-analysis/benign-prostatic-hyperplasia-bph-treatment-market>