Endothelial Function and Autonomic Regulation After Short-term Smoking Cessation: Varenicline Versus Placebo
The purpose of this study is to evaluate endothelial function and autonomic regulation (for example, heart rate and blood pressure) in smokers before and after short-term smoking cessation. The endothelium is the thin layer of cells that lines the interior surface of blood vessels. The endothelium releases nitric oxide, which promotes dilation of the blood vessels and inhibits inflammation. Previous studies have shown that tobacco use is associated with endothelial dysfunction, and tobacco use increases heart rate and blood pressure.
We hypothesize that 2 weeks of smoking cessation will improve endothelial function. We will also determine if endothelial function and autonomic regulation after short-term smoking cessation differs for patients that achieve abstinence with the smoking cessation agent varenicline compared to placebo.
|Study Design:||Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double Blind (Subject, Investigator)
Primary Purpose: Basic Science
|Official Title:||Endothelial Function and Autonomic Regulation After Short-term Smoking Cessation: Varenicline Versus Placebo|
- Arterial Endothelial Function as Measured by Flow-mediated Dilation [ Time Frame: 2 weeks after participants quit smoking (study visit 3, day 15) ] [ Designated as safety issue: No ]Flow-mediated dilation of the brachial artery will be measured using high-resolution ultrasound. Arterial diameter will be measured above the small cavity in the elbow joint from ultrasound images at rest in response to an increase in blood flow to the area. This blood flow will be induced by inflation of a blood pressure cuff placed around the forearm to a pressure of at least 50 mm Hg above systolic pressure for 5 min, followed by release. The ultrasound image of the artery will be recorded continuously from 30 sec before until 2 min after cuff release.
- 24-hour Ambulatory Blood Pressure [ Time Frame: 2 weeks after participants quit smoking (study visit 3, day 15) ] [ Designated as safety issue: No ]Ambulatory blood pressure will be measured using the Spacelabs 90202 recorder. Systolic and diastolic blood pressure during the 24-hour period will be analyzed.
|Study Start Date:||March 2007|
|Study Completion Date:||February 2010|
|Primary Completion Date:||February 2009 (Final data collection date for primary outcome measure)|
Active Comparator: Varenicline
Participants on this arm will receive varenicline tablets for 15 days.
Smoking cessation assistance: study days 1-3: 0.5 mg once daily, study days 4-7: 0.5 mg twice daily, study days 8-15: 1 mg twice daily; study day 16: 1 mg once. The tablets should be taken orally after food intake with 200 ml of water.
The treatment phase may be prolonged up to a maximum of 2 weeks under the following conditions: 1) the participant voluntarily agrees to the prolongation of the study, 2) both the participant and investigator are confident that the participant will be able to completely refrain from smoking for at least 10 days until the final study day.
Other Name: Chantix
Placebo Comparator: Placebo
Participants on this arm will receive placebo tablets for 15 days.
The pharmacy will prepare tablets that match the varenicline tablets. The tablets should be taken orally after food intake with 200 ml of water.
Smoking is a major cardiovascular risk factor and is associated with arterial endothelial dysfunction, a key event in atherosclerosis. Previous observations have suggested that smoking-related endothelial dysfunction is dose-related and potentially reversible after withdrawal from smoking. To our knowledge, no data are available regarding potential improvement of arterial endothelial function in the first weeks of smoking cessation. This time frame is especially important because due to smoke-free policies in healthcare facilities, all smokers requiring surgery are abstinent from tobacco for at least some period of time.
Varenicline, a partial agonist at α4β2 neuronal nicotinic acetyl-choline (nAChR) receptors, received FDA approval as a novel medication for helping cigarette smokers to stop smoking. Given the anticipated common use of varenicline, it is important to define if the drug alters endothelial function and/or autonomic effects. Based on the lesser potency of varenicline (compared to nicotine) at nAChR receptors in peripheral ganglia and on endothelial cells of blood vessels, it may be hypothesized that varenicline has less or no influence on autonomic control of blood pressure and heart rate, and less or no influence on endothelial function.
Therefore, the aims of this study are 1) to determine the effects of short-term smoking cessation on endothelial function and autonomic regulation, and 2) to determine if these effects will be altered during treatment with varenicline.