Biological and behavioural markers of smoking reduction

Tobacco harm reduction involves strategies designed to reduce the harms associated with tobacco use, for example by cutting down cigarette consumption and thereby reducing exposure to the risks associated with smoking. In addition to potentially reducing the harms of continued smoking, there is evidence that some harm reduction strategies are positively associated with quitting smoking entirely. A variety of interventions exist that can be used to aid both cessation and smoking reduction. However, there are limitations with using current treatments, with most attempts to change smoking behaviour ultimately ending with relapse. Numerous limitations of current treatments have been noted in the past, including that existing nicotine replacement products may not provide sufficient nicotine, and / or that the time course of nicotine delivery may not be optimal for promoting reduction. The broad objective of this thesis is to understand how smoking reduction influences smoking behaviours and cessation outcomes as well as smoking-related harm exposure. To achieve this aim, firstly, knowing the content of nicotine in supplementary products can help with interpreting the outcomes of clinical trials and with improving product design. Vaporised nicotine products (VNPs) ‚Äö- commonly known as electronic cigarettes ‚Äö- are increasingly being used by smokers to reduce their smoking, and there is some evidence that they can be effective cessation aids. A key issue with testing the effectiveness of these products, however, as been quantifying the variability in the amount of nicotine contained in products. As such, an assay was developed and applied to determine the nicotine content in one brand of VNPs which consisted of a fibrous pad in the cartridge. In addition to finding substantial variation between product batches, we also found that the measured nicotine content in the cartridge was lower than the stated content on the product label. The accurate determination of the quantity of nicotine in VNPs has important implications for both consumer safety and the further study of these devices. Secondly, smoking reduction is not only a reduction in the number of smoked cigarettes, but also an expected reduction in exposure of smoking-related harm. Biological markers can be used to indicate the intake of nicotine and smoking-related harm. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is a metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which is a tobacco specific carcinogen. As such, NNAL is considered a biological marker associated with tobacco-related harm. To measure the levels of NNAL in smokers' urine, solid phase extraction (SPE) assay has been used in previously reported studies. However, the sample preparation procedures required with these SPE assays are complicated and time consuming, limiting their use. A simple and efficient liquid-liquid extraction assay combined with ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS) was designed in this study, and applied to the smokers' urine to measure changes in harm exposure over the course of a quit attempt. As expected, the NNAL levels were significantly decreased following the quit attempt. This supports the use of NNAL as a biomarker of tobacco-related harm exposure and harm minimisation. This assay is an improvement over existing SPE-based methods in that it is substantially less complicated while maintaining adequate sensitivity and is a straightforward approach to measuring NNAL levels. The assay also demonstrated that using enzymatic hydrolysis approach of NNAL-glucuronide ‚Äö- had taken by other studies ‚Äö- as a technique for measuring the aglycone was clearly unreliable. There was a potential for significant loss of either free NNAL and NNAL aglycone. NNAL-glucuronide standards are recommended to utilise for proper validation of indirect methods such as enzymatic hydrolysis approach to measure total NNAL (free + glucuronide). Finally, we explored the mechanism through which two medications ‚Äö- specifically varenicline and nicotine patch ‚Äö- promote reduction. There has been growing research interest in using nicotine replacement medications to aid smoking reduction prior to a quit attempt. Gaining a better understanding of how treatments influence smoking reduction may allow for better tailoring of treatments and, ultimately, better cessation outcomes. The objective of the study was to test the effects of the pre-quit use of varenicline and nicotine patch on smoking rate and satisfaction with smoking. Participants in the two pre-quit treatment groups reported significant reductions in both their satisfaction with smoking and smoking rate from baseline to the end of pre-quit period; participants in the standard patch group, which started to use of nicotine patch at a quit attempt day, did not. The observed reduction of smoking rate was associated with the satisfaction with smoking, although the mediation effect of satisfaction was weak. As such, monitoring reductions in satisfaction does not appear to be a viable method of evaluating responsiveness to treatment and, or for tailoring. In summary, this research developed a sensitive and efficient assay to determine nicotine content in supplementary nicotine products, providing valuable data for further research on these products. Furthermore, an assay for determination of NNAL levels in smokers' urine was developed, which was applied to determine the reduction of smokingrelated harm exposure in a smoking cessation study. Finally, this research demonstrated that pre-quit treatment use led to reductions in satisfaction with smoking and the smoking rate, and the satisfaction was associated with the reduction in smoking rate. Monitoring such reductions may prove to be useful in evaluating responsiveness to treatment, risk of harm, and allow for tailoring of treatment.