Nicotine Psychopharmacology (Handbook of Experimental Pharmacology, Vol 192)
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If FDA were to issue a nicotine tobacco product standard that did not include waterpipe tobacco products within the scope, what would be the likelihood that former smokers would switch to waterpipe tobacco to maintain their nicotine addiction? What are the relative risk consequences of switching to waterpipe tobacco? As discussed throughout this document, nicotine is addictive and is the primary reason why many smokers who want to quit are unable to do so.
Accordingly, FDA is considering developing a proposed product standard to make cigarettes minimally addictive or nonaddictive by setting a maximum nicotine level, using the best available science to determine a level that is appropriate for the protection of the public health. A survey paper noted that researchers initially estimated that reducing the total nicotine content of cigarettes to 0. We specifically request comment regarding this paper's conclusions and the possible impact of higher or lower maximum nicotine levels in a potential nicotine tobacco product standard.
However, cigarette users could modify their use behaviors to compensate for this increase in ventilation. For example, the vent holes could be easily blocked by users' fingers or mouths, and larger or more frequent puffs could be taken by consumers Ref.
Sex differences in nicotine preference
The compensatory behaviors of the cigarette user were able to overcome the changes in ventilation in these higher ventilated products. VLNC cigarettes, in contrast, have relied on reducing nicotine content in the tobacco filler rather than engineering changes to the cigarette. In conventional cigarettes manufactured in the United States, nicotine accounts for approximately 1.
Certain VLNC cigarettes have much lower nicotine yields than conventional cigarettes—in the 0. Reducing the nicotine in the finished tobacco product places an absolute maximum limit on the amount of nicotine that can be extracted by the user in a given cigarette, unlike modifications such as ventilation holes, which affect nicotine yield in smoke but can be overcome through user behavior.
See section IV. C of this document for a discussion of possible compensatory smoking under a single target approach or a stepped down approach to nicotine reduction. The two types of cigarettes produced were: 1 1. Researchers also have used Quest cigarettes, produced by Vector Tobacco, to study the impact of reduced nicotine Ref.
To provide consumers with reduced risk tobacco products, companies like 22nd Century are using genetic engineering and plant breeding to produce very low nicotine tobacco for incorporation into cigarettes. In , the company was granted patents for its process to virtually eliminate the nicotine in tobacco plants Ref.
Finally, Philip Morris manufactured cigarettes with varying nicotine levels for research only Ref. Table 1 includes a list of VLNC cigarettes used in research studies and their reported nicotine levels. In , certain scientists proposed the idea of federal regulation of nicotine content, which could result in lower intake of nicotine and a lower level of nicotine dependence Ref. However, FDA acknowledges that there is individual variability in dose sensitivity to all addictive substances, making it difficult to determine a single addiction threshold which would apply across the population.
A proposal to lower the nicotine in conventional cigarettes, or any tobacco product, could merit consideration only if there were a threshold nicotine exposure level below which the nicotine did not produce significant reinforcing effects or sustain addiction in a majority of the population. Four primary study types speak to the level of nicotine in tobacco that could significantly reduce product addictiveness.
Aspectos neuropsicológicos del craving por la nicotina | Muñoz | Adicciones
The first type uses indirect estimates based on information in humans regarding nicotine intake in smokers who appear not to be addicted to nicotine to estimate a likely threshold level. A second type includes studies of VLNC use by study participants that have reported increased quit attempts and cessation even in smokers not interested in quitting. A third type includes studies that have revealed reduced positive subjective effects and increased negative effects in VLNC smokers. The fourth type includes studies measuring nicotine receptor binding, which indicate that use of VLNC cigarettes yields significantly lower nicotinic acetylcholine receptor nAChR occupancy and cerebral response.
Indirect estimates of an addiction threshold. In the review, researchers suggested that a threshold level of nicotine per cigarette should be low enough to prevent or limit the development of nicotine addiction in most young people, while providing enough nicotine for taste and sensory sensation e. In another study seeking to estimate a reinforcement threshold, scientists reviewed several studies, including one in which abstinent smokers received intravenous nicotine injections by pulling a lever in a fixed ratio task Ref.
The authors found that studies using intravenous nicotine administration suggest that the nicotine reinforcement threshold i. Although the study's authors noted potential limitations i. Despite the study limitations of both these estimates, they help provide a range on which to potentially base a nicotine level threshold.
Findings of increased cessation for VLNC cigarettes. Several studies indicate that people using significantly reduced nicotine content cigarettes as low as 0. These studies were not investigating VLNC cigarettes as cessation aids. Some studies showed that switching to VLNC cigarettes results in a reduced number of cigarettes smoked per day Ref. On the other hand, other researchers have reported the use of VLNC cigarettes did not change the number of cigarettes smoked per day Refs.
For example, in the Benowitz et al. The Mercincavage et al. The researchers found that certain biomarkers of exposure to toxic tobacco-related constituents i.
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One limitation of these studies is that they were conducted in an unregulated environment in which smokers continued to have access to the normal nicotine content NNC cigarettes. One of the more recent studies Ref. During the sixth week of the study, the average number of cigarettes smoked per day was lower for participants randomly assigned to cigarettes containing 2. Those participants using cigarettes with the lowest nicotine content 0. While these results, taken together with other studies, are promising, FDA acknowledges the inherent limitations of the available research on changes in smoking as a function of VLNC cigarettes use.
Tobacco Product Standard for Nicotine Level of Combusted Cigarettes
Furthermore, little is known about the dose-related effects of reduced nicotine. Subjective effects and relief of withdrawal symptoms associated with VLNC cigarettes. Individuals who smoke VLNC cigarettes experience some of the same subjective effects as those individuals who smoke traditional, NNC cigarettes. For example, VLNC users report experiencing reductions in certain physiological withdrawal symptoms e.
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Exposure over multiple days generally leads to a reduction in cigarettes smoked per day Ref. Furthermore, physiological responses after VLNC cigarettes, such as the increase in heart rate that is typically observed following nicotine administration, are less than those seen with higher nicotine cigarettes and are absent in some cases Ref. Thus, it appears that transitioning to VLNC cigarettes from NNC cigarettes may result in some behavioral and physiological responses commonly experienced when using standard NNC cigarettes e.
These responses, where present, are lower than those seen with standard nicotine cigarettes and get progressively lower over time. VLNC cigarettes contain some nicotine, albeit at very low levels. Although there is enough nicotine in VLNC cigarettes to bind to acetylcholine receptors in the brain, there is not enough to consistently produce the full range of subjective responses i. This supports the hypothesis that many subjective and physiological effects observed following exposure to smoke from VLNC cigarettes could be due to repeated pairing of nicotine with sensory and conditioned cues or to other psychoactive chemicals.
Given that these subjective and physiological effects have been directly linked to nicotine, it is likely that they are learned responses through repeated pairing with nicotine and not due to other chemicals in the smoke. If FDA were to propose a maximum nicotine level for cigarettes, what should be the maximum level to ensure that the product is minimally addictive or nonaddictive, using the best available science to determine a level that is appropriate for the protection of the public health?
How should the maximum level be measured e.
What would be the potential health impacts of requiring a maximum nicotine level such as 0. FDA is interested in public health impacts of requiring different maximum nicotine levels, such as 0. FDA lists four types of studies to estimate the threshold of nicotine addiction i. Should FDA rely on some or all of these types of studies? Why or why not? Is there a different method that FDA should investigate or use to determine the threshold for nicotine addiction? In addition to nicotine, minor tobacco alkaloids including nornicotine, cotinine, anabasine, anatabine, and myosamine and tobacco smoke aldehydes such as acetaldehyde are pharmacologically active and may contribute to addiction see, e.
Researchers have investigated the abuse potential of nornicotine, cotinine, anabasine, and acetaldehyde in animals Ref. However, many of these compounds are only present in tobacco smoke at low levels and are likely less potent than nicotine in mediating pharmacological response and, therefore, reinforcement Refs. In addition to setting a maximum nicotine level, should the product standard also set maximum levels of other constituents e.
If so, at what levels? If FDA were to issue a product standard establishing a maximum nicotine level for cigarettes, such a standard would need to either propose a single target where the nicotine is reduced all at once or a stepped-down approach where the nicotine is gradually reduced over time through a sequence of incremental levels and implementation dates to reach the desired maximum nicotine level. Some have suggested that any maximum nicotine level should be established as a single target rather than a stepped-down approach to limit exposure to harmful tobacco while providing similar cessation rates to those that could occur with a stepped-down approach.
Some level of compensatory smoking behavior i. According to studies involving VLNC cigarettes and other reduced nicotine cigarettes, researchers expect there could be very little or no compensatory smoking with a single target approach and that it would be self-limiting i. If individuals were to engage in compensatory smoking with a single target approach, researchers find that any compensatory smoking at the maximum nicotine levels that FDA is considering here could only be minimal and transient e.
In contrast, during a stepped-down approach, tobacco users may attempt to compensate for the loss of nicotine during the early stages of a stepped-down approach by smoking additional tobacco products or by smoking more intensely, since the intermediate-stage products could allow for extraction of nicotine through such efforts in a way that VLNC cigarettes would not e. FDA is aware of several studies that have demonstrated the impact of an immediate e. Researchers have found that the single target approach may be associated with better cessation outcomes.
While this differs from the approaches considered in this ANPRM, it provides helpful insight into the effects of a gradual vs. Scientists also found higher abstinence rates for those using the single target approach in studies comparing two levels of commercial low-yield nicotine cigarettes and nicotine lozenges Ref.
Nevertheless, some studies have found that both reduction strategies increase a smoker's probability of cessation. For example, in a study of smokers with no strong preference for a quitting method who were randomly assigned to study arms requiring either that they quit immediately or gradually reduce their cigarette consumption over 2 weeks, both the immediate and gradual cessation methods produced similar results Ref. FDA understands the argument that a stepped-down approach to limiting the nicotine levels in tobacco products Start Printed Page could undermine the public health goals of such a standard by allowing for prolonged exposure to tobacco-related toxicants during the step-down period.
Although both approaches likely would result in comparable quit rates eventually, some studies have indicated a greater likelihood of cessation success with the use of a single target. In addition, preliminary studies show that a single target approach could limit further exposure to harmful tobacco when compared with the stepped-down approach to limiting nicotine levels. FDA continues to weigh these factors, and will consider the information submitted in response to this ANPRM, as it decides the appropriate approach for a potential nicotine tobacco product standard.
What data are available to demonstrate that a single target approach to reach a maximum nicotine level would or would not result in any unintended consequences? In the alternative, what data are available to demonstrate that a stepped-down approach involving a sequence of incremental levels and implementation dates to reach a proposed nicotine level would or would not result in any unintended consequences?