Arteriovenous differences in plasma concentration of nicotine and catecholamines and related cardiovascular effects after smoking, nicotine nasal spray, and intravenous nicotine

Altered disposition of repeated nicotine doses in rats immunized against nicotine

Active immunization of rats against nicotine reduces the distribution of a single intravenous dose of nicotine to brain. The current study examined the effects of immunization on the distribution of repeated doses of nicotine, and on estimates of nicotine pharmacokinetic parameters. Groups of rats received five repeated doses of nicotine over 80 min (total dose equivalent to the nicotine intake from one, three or 10 cigarettes in a human). The serum nicotine concentration in immunized rats was 160-430% higher than controls after the fifth dose, demonstrating binding of nicotine to antibody. Brain nicotine concentration in immunized rats was reduced by 30-46%. The reduction in distribution of nicotine to brain correlated with the serum hapten-specific antibody concentration, the percentage of nicotine bound in serum, and with the unbound nicotine concentration in serum. In immunized rats, nicotine had a smaller steady state volume of distribution, lower systemic clearance, and longer terminal half-life than in controls. These data demonstrate that immunization against nicotine reduces nicotine distribution to brain, even after multiple nicotine doses at rates approximating heavy cigarette smoking. Whether this reduction in nicotine distribution is large enough to alter nicotine's physiological or behavioral effects remains to be studied.

Dose-related cardiovascular and endocrine effects of transdermal nicotine

BACKGROUND

Transdermal nicotine in doses up to 21 mg/24 hr is used to facilitate smoking cessation. However, this dose does not achieve the nicotine plasma levels seen among heavy smokers, and underdosing may be one of the reasons for the limited efficacy of transdermal nicotine. There are some concerns about the adverse cardiovascular effects of nicotine, especially with concomitant smoking. Treatment with higher doses of transdermal nicotine has been proposed for highly dependent smokers, but the effects of such treatment on the cardiovascular system have not been determined. The objective of this study was to determine the cardiovascular effects of high-dose transdermal nicotine with concomitant smoking.

METHODS

Twelve healthy male smokers received three doses of transdermal nicotine (21, 42, and 63 mg/24 hr) and placebo, each for 5 days, in a balanced order. The subjects smoked during the first 4 days of each treatment and abstained from smoking during the fifth day. Ambulatory 24-hour daytime and nighttime heart rate and blood pressure values were determined for each treatment; plasma nicotine, cotinine, and carboxyhemoglobin levels and urinary catecholamines with aldosterone were measured on days 4 and 5. The data were compared by means of repeated-measures ANOVA.

RESULTS

There was no difference in heart rate or blood pressure and no changes in the pattern of circadian variations with various transdermal nicotine doses compared with smoking alone, consistent with the development of tolerance. Urinary epinephrine level was significantly higher (p < 0.05) with transdermal nicotine compared with no nicotine but was not higher with transdermal nicotine and smoking compared with smoking alone. No change was found in fibrinogen and lipid profiles with different nicotine doses.

CONCLUSIONS

High-dose nicotine treatment, even with concomitant smoking, caused no short-term adverse effects on the cardiovascular system.