Expert: Certain components of tobacco smoke interact with drugs

In his opinion, doctors who prescribe such drugs should know if their patients are smokers and adjust the dose if necessary.

Undesirable drug interactions are a serious medical problem. They occur not only between concomitant medications (of synthetic and natural origin, such as herbal medicines), but also between drugs and dietary supplements and ingredients, as well as stimulants.

In the case of smokers, certain components of tobacco smoke can interact with medicines.

"Any foreign substance that enters the body - including a drug that is a foreign substance for us - is metabolised. This metabolism takes place in the liver, with the participation of cytochrome P450 enzymes that can accelerate or decelerate the metabolism of medicines" - explains Prof. Andrzej Stańczak.

Polycyclic aromatic hydrocarbons (PAHs) that occur in tobacco smoke affect cytochrome P450. "If these polycyclic hydrocarbons induce the acceleration of metabolism, the drug is quickly eliminated from the body. Its concentration decreases and its action is weaker" - notes the expert.

The effects may also be dangerous for addicts who are in the process of quitting. Sudden shortage of enzyme-inducing agents present in tobacco smoke may contribute to changes in the pharmacokinetics of many drugs.

"If the delivered dose is normal, the medicine works, and then the patient quits smoking and suddenly there are no enzymes that speed up the metabolism, the concentration of the drug in the blood automatically increases. That means that the patient can enter the area of undesirable or toxic side effects of the drug" - says Prof. Stańczak.

The expert draws attention to one more danger that concerns passive smokers, mainly children. "Children in the environment of parents who smoke also absorb these polycyclic hydrocarbons, which may affect the level of drugs that these children should take" - he emphasises.

The drugs that interact with the components of tobacco smoke include tacrine (used in Alzheimer's disease), propranolol (a popular beta blocker used in hypertension), clozapine and memantine (used in memory disorders) and a number of drugs used in peptic ulcer disease, including cimetidine, famotidine and many other drugs in this group.

The researcher also points out that because active and passive smokers have lower levels of vitamin C in plasma and leukocytes, they should supplement 35 mg of vitamin C more than non-smokers.

According to the expert, doctors who prescribe drugs that interact with tobacco smoke should always find out whether the patient is a smoker or has just quit smoking in order to be able to properly adjust the doses of medications.

"Since in this situation both smoking and abstinence from smoking are a threat, physicians should routinely obtain information about active tobacco smoking from their patients and, if necessary, adjust doses of drugs that interact with tobacco smoke components" - emphasises Prof. Stańczak. (PAP)

Author: Kamil Szubański

Editor: Anna Ślązak

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