One pack of cigarettes contains 20 cigarettes. Pack years are the number of packs a person has smoked, multiplied by the number of years. For example, someone who smokes 1 pack a day for 1 year has a 1 pack-year history of smoking. Similarly, someone who has smoked half a pack a day for 2 years also has a 1-year pack history (2 years x 0.5 pack = 1 pack year).
There are three major types: nicotine replacement therapy (NRT), varenicline or bupropion. NRT is typically prescribed for 2 weeks, whilst varenicline or bupropion are prescribed for 3-4 weeks.
NRT provides a low level of nicotine without the addition of harmful compounds found in cigarette smoke – these can help reduce relapses. Different types of NRT exist, and which one to use is mainly up to the patient. Examples include:
Using methods of NRT that deliver an intermittent dose such as chewing gum may be more beneficial in patients who are pregnant, as opposed to a continuous method like patches.
Bupropion is a dopamine and noradrenaline re-uptake inhibitor, and is also started 1-2 weeks prior to the patient’s stop date.
Varenicline a nicotinic receptor agonist and helps to reduce cravings. It is started 1-2 weeks prior to the patient’s stop date.
Smoking induces the hepatic enzyme CYP1A2 which increases the metabolism of certain drugs. Thus, patients may be prescribed higher doses whilst they are smoking. If they suddenly stop smoking, the CYP1A2 activity levels return to normal, potentially resulting in higher plasma concentrations of certain drugs. Examples of drugs to be mindful of include:
https://pubmed.ncbi.nlm.nih.gov/19490292/
https://cks.nice.org.uk/smoking-cessation#!scenarioBasis:2
https://cks.nice.org.uk/smoking-cessation#!prescribingInfoSub:15
https://cks.nice.org.uk/smoking-cessation#!prescribingInfoSub:7
