Nicotine Replacement Therapy (NRT) is used to help smokers quit smoking by delivering a safer alternative source of nicotine than cigarettes. Nicotine has poor oral bioavailability. Different dosage forms of nicotine are available on the market.

a) Define the term ‘oral bioavailability’ and explain why nicotine has poor oral bioavailability. (2 marks)

Oral bioavailability is the fraction or percentage of a drug that has been taken by mouth (PO) which finally ends up in the systemic circulation. In order to do this the drug needs to be absorbed via the GI route and make it through the hepatic enzyme system. If only a small fraction of drug is able to reach the systemic circulation this way then it has poor oral bioavailability.

Nicotine is poorly bioavailable via the oral route, as it undergoes extensive first pass hepatic metabolism by CYP (60-80%).

Refs:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3527900/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3864487/

SPC