1. Khouja T, Tadrous M, Matusiak L, Suda K (2021) Opioid Prescribing in United States Health Systems, 2015 to 2019. Value Health. https://doi.org/10.1016/j.jval.2021.04.1274
2. United Nations International Narcotics Control Board 2014. Narcotic Drugs. Estimated World Requirements for 2015, Statistics for 2013. http://www.incb.org/documents/Narcotic-Drugs/TechnicalPublications/2014/Narcotic_Drugs_Report_2014.pdf. Accessed 25 Jul 2021
3. WHO Model List of Essential Medicines: https://www.who.int/publications/i/item/WHOMVPEMPIAU2019.06. Accessed 25 Jul 2021
4. Schmidhammer H (1998) Opioid Receptor Antagonists. Prog Med Chem 35:83–132
5. Rinner U, Hudlicky T (2011) Synthesis of Morphine Alkaloids and Derivatives. In: Knölker HJ (ed) Alkaloid Synthesis. Topics in Current Chemistry, vol 309. Springer, Berlin