Answer:
a. Smoking cigarettes affects drug metabolism by causing the liver to metabolize drugs more slowly.
Step-by-step explanation:
Smoking impacts the activity of certain enzymes in the liver responsible for drug metabolism. Specifically, cytochrome P450 enzymes, which play a pivotal role in metabolizing drugs, can be affected by cigarette smoke. Nicotine and other compounds in cigarettes induce these enzymes, leading to an increased breakdown of drugs. However, chronic smoking can also result in the overproduction of these enzymes, which might subsequently decrease their activity due to exhaustion. As a result, the liver metabolizes drugs more slowly, affecting their clearance from the body.
The liver's enzymatic action typically follows a first-order kinetics model. If we consider a drug with a half-life of 10 hours and its metabolism affected by smoking, the half-life might extend due to the decreased enzymatic activity caused by smoking. For instance, if under normal conditions, the drug takes 10 hours to decrease its concentration by 50%, smoking might extend this time frame, say to 15 or 20 hours. This alteration can significantly impact drug efficacy and potential toxicity.
Understanding the impact of smoking on drug metabolism is crucial in clinical settings. Physicians need to adjust drug dosages for patients who smoke to ensure adequate therapeutic levels are maintained. Moreover, it underscores the importance of cessation programs for smokers, not just for their overall health but also to optimize the effectiveness of medications they might require.