The pharmacological implications of Smoking!

Over 4800 separate substances have been found in cigarette smoke, and the health risks of cigarette smoking are well documented.

Cigarette smoke may interfere with both the action and metabolism of a wide range of medications, some of which are relevant to anesthetic practice. Central to this is the cytochrome P450 multi-enzyme system of which there are around 30 CYP enzymes responsible for drug metabolism. Polycyclic aromatic hydrocarbons (PACs) in cigarette smoke react with these enzymes, in general inducing them, thus affecting the metabolism of a number of drugs including paracetamol, codeine and theophylline. It is only the last whose dose is significantly affected.

In addition, PACs also have an effect on a membrane bound glycoprotein called uridine diphosphate-glucuronotransferase (UGT). UGT partially metabolises codeine and morphine as well as being involved in the glucuronidation of a number of drugs including NSAIDs, amytriptyline and temazepam. It has consistently been shown that smokers have an increased requirements for opiates in the postoperative period.

Smoking decreases the potency of aminosteroid muscle relaxants (vecuronium >rocuronium) and of interest, greater than 10 hours abstinence from cigarette smoking decreases atracurium requirements.

The incidence of postoperative nausea and vomiting is reduced in smokers as is, interestingly, the prevalence of ulcerative colitis.

Reference
Sweeney BP, Grayling M. Smoking and anesthesia: The pharmacological implications. Anaesthesia 2009; 64(2): 179-86

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