So just by stopping smoking I can affect the way certain medicines work in my body?
The answer is yes. If you stop smoking, whether you use a form of NRT or not, you may alter your body's response to certain medications. Smoking tends to increase the body's metabolism and thereby lowers the blood levels of drugs like caffeine, theophylline (an asthma medication), phenacetin, imipramine (an antidepressant), oxazepam, propranolol, insulin, paracetamol and pentazocine (a pain medication) through enzyme induction. When you stop smoking you may actually increase the blood levels of these drugs. Stopping smoking can also decrease the absorption of some other drugs, like glutethimide for example. This is why it is best that you consult with your doctor or pharmacist if you are unsure about how quitting smoking can interact with any other medication that you are taking.