The effect of varenicline on heart rate variability in healthy smokers and nonsmokers

Effects of varenicline on motor cortical plasticity in non-smokers with schizophrenia

BACKGROUND

Nicotinic acetylcholine receptors (nAChR) have been implicated in the pathophysiology of schizophrenia, and deficits in this system may contribute to high rates of cigarette smoking in this population. nAChR stimulation may modulate neuroplasticity, or long-term potentiation (LTP), which is a key mediator of cognitive performance. Varenicline is a nAChR partial agonist that may improve cognitive deficits in both smokers and non-smokers with schizophrenia; however, the mechanism by which varenicline alters cognition in schizophrenia remains unclear. Thus, the aim of this randomized, double-blind, placebo-controlled, crossover study was to determine the effects of varenicline on LTP-like plasticity indexed through transcranial magnetic stimulation (TMS) in non-smokers with schizophrenia.

METHODS

Varenicline (0.5mg BID × 5 doses) or placebo was administered to 9 non-smokers with schizophrenia and 10 non-smoker healthy subjects. LTP-like plasticity was induced by TMS and paired associative stimulation (PAS) at 0.1Hz to the left motor cortex and measured every 15min for two hours post-PAS.

RESULTS

There was a significant diagnosis × medication interaction on peak potentiation (F (3, 34)=6.04, p<0.02) and post-hoc analyses indicated that varenicline significantly increased LTP in schizophrenia and decreased LTP in healthy subjects.

CONCLUSIONS

These preliminary findings suggest that varenicline may produce differential effects in non-smoking schizophrenia compared to control subjects. Given the role of LTP in learning and memory, these observations may suggest the potential for varenicline in the treatment of cognitive deficits in patients with schizophrenia.

Cardiovascular adverse events associated with smoking-cessation pharmacotherapies

Smoking continues to be the leading cause of preventable deaths in the USA, accounting for one in every five deaths every year, and cardiovascular (CV) disease remains the leading cause of those deaths. Hence, there is increasing awareness to quit smoking among the public and counseling plays an important role in smoking cessation. There are different pharmacological methods to help quit smoking that includes nicotine replacement products available over the counter, including patch, gum, and lozenges, to prescription medications, such as bupropion and varenicline. There have been reports of both nonserious and serious adverse CV events associated with the use of these different pharmacological methods, especially varenicline, which has been gaining media attention recently. Therefore, we systematically reviewed the various pharmacotherapies used in smoking cessation and analyzed the evidence behind these CV events reported with these therapeutic agents.

The effect of oxybutynin on cardiac autonomic modulation in healthy subjects

PURPOSE

The aim of this study was to assess the various doses of oral oxybutynin on cardiac autonomic modulation by measuring short-term heart rate variability (HRV) indexes during supine rest position.

METHODS

Eight male healthy subjects (20-23 years) participated in the double-blind crossover randomized study. The single dose of oxybutynin (2.5, 5 and 10 mg) or placebo was given to the volunteers in four sessions within 5-day intervals. Before and minutes of 30, 60, 90 and 120 after administration, lead II electrocardiogram (ECG) was recorded for 5 min. ECG extracted RR intervals data became the base of the calculation of time domain and frequency domain HRV parameters, which indicate cardiac autonomic activity. Statistical analysis was done by using the nonparametric Wilcoxon and Kruskal-Wallis tests.

RESULTS

The data analysis has revealed that MNN (P < 0.001), SDNN (P < 0.05), PNN50% (P < 0.01), RMSSD (P < 0.001), HFnu (P < 0.05) and LF/HF ratio (P < 0.05) values were significantly increased relative to baseline at various time points in all the groups except in placebo group. LFnu (P < 0.05) values were significantly increased relative to baseline at various time points in all the groups except in placebo group.

CONCLUSIONS

Our findings have revealed that acute consumption of 2.5, 5 and 10 mg oxybutynin (an anticholinergic compound) in the juvenile healthy male subjects produces a cholinergic effect according to time and frequency domain of HRV indexes.

Short-term effectiveness of smoking-cessation treatment on respiratory function and CEA level

Aim: Tobacco smoke contains many chemicals that are harmful and cause carcinogenesis. The aim of this study was to confirm the relationship between smoking and changes in respiratory functional and laboratory parameters comparing, in particular, smoking-cessation treatment’s outcomes between smokers who reduce tobacco consumption (reducers) and smokers who quit completely (quitters). Materials & methods: A total of 181 current smokers were prospectively enrolled. All of the participants completed a sociodemographic questionnaire and underwent 3 months of varenicline plus nicotine-replacement therapy combined with basic counseling. Laboratory tests and clinical and lung-function parameters were evaluated at entry and after 3 months of therapy. After 3 months of smoking-cessation treatment, subjects were sorted into two subgroups: quitters and reducers. Results: After 3 months of combined therapy, 56% of the subjects (101 patients) stopped smoking; the remaining patients reduced. Significant improvements in pulmonary-function tests (especially in the 25–75% forced expiratory volume testing) were recorded. The most significant improvements were obtained in quitters: carboxyhemoglobin was reduced by 1.06%, the average expiratory flow between 25 and 75% of vital capacity increased by 16% from predicted, mean serum CEA level decreased by 1.83 ng/ml, heart rate decreased by approximately 16 beats/min on average and forced 1 s expiratory flow increased by 2.57% from predicted. The Fagerström scores showed a positive correlation with the corresponding blood carboxyhemoglobin levels. Conclusion: Just 3 months of smoking-cessation treatment achieved significant improvements in lung-function parameters and a decrease in serum CEA, mostly in subjects who totally quit smoking. This result confirms the effectiveness of our smoking-cessation treatment and suggests the utility of the selected parameters as tools to motivate and monitor patients.

Cardiovascular effects of pharmacologic therapies for smoking cessation

Tobacco dependence is a potent risk factor for cardiovascular (CV) diseases and, despite known harms of smoking and benefits associated with smoking cessation, approximately 20% of the adult population with CV diseases or hypertension continue to smoke. Extensive research has demonstrated that nicotine replacement, varenicline, and bupropion sustained-release are superior to placebo for short- and intermediate-term smoking cessation. Because of their mechanisms of action, some smoking cessation therapies have been thought to have the potential to increase CV risk, particularly if the pharmacotherapies are taken while individuals are still smoking. Hence, we have analytically reviewed the literature describing the CV effects of therapies for smoking cessation, particularly as they apply to patients with CV disease.

Cardiac autonomic function in healthy young smokers

The present study examined the heart rate turbulence (HRT) and heart rate variability (HRV) parameters in healthy young smokers (<40 years) to assess the effects of smoking on cardiac autonomic function. The study included 75 smokers with a history of habitual smoking for at least 1 year (41 males and 34 females; mean age, 29.3 ± 7.3 years) and 30 nonsmokers (hospital staff; 16 males and 14 females; mean age, 29.0 ± 6.1 years). Addiction to smoking was evaluated using the modified Fagerström test for nicotine-dependence index (NDI). HRT, HRV, basic clinical and echocardiographic, and Holter test parameters were compared between groups. No significant differences between the two groups were found in the basic clinical and echocardiographic variables. Turbulence onset (TO) was significantly higher in the smoking group than in the controls, and turbulence slope was significantly lower in the smokers, than in the controls (p < 0.05). Standard deviation of all normal-to-normal (NN) interval index (SDNNI) was the only HRV parameter that was significantly different between the smoking and control groups (p < 0.05). The NDI was positively correlated with the TO (p < 0.05). Smoking impairs the baroregulatory function in healthy young smokers, particularly the HRT parameters and SDNNI. Our findings highlight the importance of complete smoking cessation.