Drug abuse III: nicotine and smoking

CHAPTER 39


Drug abuse III: nicotine and smoking


Cigarette smoking remains the greatest single cause of preventable illness and premature death. In the United States, smoking kills more than 443,000 adults each year—about 1 of every 5 deaths. Around the world, tobacco kills over 5 million people each year. On average, male smokers die 13.2 years prematurely, and females die 14.5 years prematurely. As shown in Table 39–1, most deaths result from lung cancer (125,522), heart disease (101,009), and chronic airway obstruction (79,898). Not only do cigarettes kill people who smoke, every year, through secondhand smoke, cigarettes kill about 50,000 nonsmoking Americans, and about 600,000 nonsmokers worldwide. The direct medical costs of smoking exceed $95 billion a year. Indirect costs, including lost time from work and disability, add up to an additional $97 billion. In the United States, the prevalence of smoking among adults fell steadily from 1965 (42%) through the 1980s and 1990s, but has now leveled off, remaining constant between 2004 (20.9%) and 2008 (20.6%).



TABLE 39–1 


Average Annual Smoking-Attributable Mortality (United States, 2000–2004)*














































































































  Smoking-Related Deaths
Disease Category Male Female
Malignant Neoplasms
Lip, oral cavity, pharynx 3,749 1,144
Esophagus 6,961 1,631
Stomach 1,900 584
Pancreas 3,147 3,536
Larynx 2,446 563
Trachea, lung, bronchus 78,680 46,842
Cervix, uteri 0 447
Kidney and renal pelvis 2,827 216
Urinary bladder 3,907 1,076
Acute myeloid leukemia 855 337
Subtotal 104,472 56,376
Cardiovascular Diseases
Ischemic heart disease 50,884 29,121
Other heart disease 12,944 8,060
Cerebrovascular disease 7,896 8,026
Atherosclerosis 1,282 611
Aortic aneurysm 5,628 2,791
Other circulatory diseases 505 749
Subtotal 79,139 49,358
Respiratory Diseases
Pneumonia, influenza 6,042 4,381
Bronchitis, emphysema 7,536 6,391
Chronic airway obstruction 40,217 38,771
Subtotal 53,795 49,543
AVERAGE ANNUAL TOTAL 237,406 155,277


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*Data are for adults ages 35 and older, and do not include deaths caused by burns or secondhand smoke.


Data were obtained online at apps.nccd.cdc.gov/sammec/—the web site of the Centers for Disease Control and Prevention: Smoking-Attributable Mortality, Morbidity, and Economic Costs (SAMMEC).


Although tobacco smoke contains many dangerous compounds, nicotine is of greatest concern. Other hazardous components in tobacco smoke include carbon monoxide, hydrogen cyanide, ammonia, nitrosamines, and tar. Tar is composed of various polycyclic hydrocarbons, some of which are proven carcinogens.


What is the regulatory status of cigarettes? Good question, given that cigarettes are the single most dangerous product available to U.S. consumers. Until recently, cigarettes had avoided virtually all federal regulation. However, strong regulations are now in place. Under the Family Smoking Prevention and Tobacco Control Act, passed in June 2009, the Food and Drug Administration (FDA) now has the authority to





Basic pharmacology of nicotine




Mechanism of action

The effects of nicotine result from actions at nicotinic receptors. Whether these receptors are activated or inhibited depends on nicotine dosage. Low doses activate nicotinic receptors; high doses block them. The amount of nicotine received from cigarettes is relatively low. Accordingly, cigarette smoking causes receptor activation.


Nicotine can activate nicotinic receptors at several locations. Most effects result from activating nicotinic receptors in autonomic ganglia and the adrenal medulla. In addition, nicotine can activate nicotinic receptors in the carotid body, aortic arch, and CNS. As discussed below, actions in the CNS mimic those of cocaine and other highly addictive substances. When present at the levels produced by smoking, nicotine has no significant effect on nicotinic receptors of the neuromuscular junction.



Pharmacokinetics

Absorption of nicotine depends on whether the delivery system is a cigarette, a cigar, or smokeless tobacco. Nicotine in cigarette smoke is absorbed primarily from the lungs. When cigarette smoke is inhaled, between 90% and 98% of nicotine in the lungs enters the blood. Unlike nicotine in cigarette smoke, nicotine in cigar smoke is absorbed primarily from the mouth, as is nicotine in smokeless tobacco.


Nicotine can cross membranes easily and is widely distributed throughout the body. The drug readily enters breast milk, reaching levels that can be toxic to the nursing infant. Nicotine also crosses the placental barrier and can cause fetal harm. When inhaled in cigarette smoke, nicotine reaches the brain in just 10 seconds.


Nicotine is rapidly metabolized to inactive products. Nicotine and its metabolites are excreted by the kidney. The drug’s half-life is 1 to 2 hours.



Pharmacologic effects

The pharmacologic effects discussed in this section are associated with low doses of nicotine. These are the effects caused by smoking cigarettes. Responses to high doses are discussed under Acute Poisoning.






Effects during pregnancy and lactation.

Nicotine exposure during gestation can harm the fetus, and nicotine in breast milk can harm the nursing infant. Nonetheless, as discussed in Box 39–1, since pharmaceutical nicotine is safer than tobacco smoke, it is reasonable to consider using nicotine therapy during pregnancy to help a woman quit smoking.



imageBOX 39–1    SPECIAL INTEREST TOPIC


SMOKING CESSATION DURING PREGNANCY


Smoking is the largest modifiable risk factor for pregnancy-related morbidity and mortality. Smoking increases the risk of ectopic pregnancy, placenta previa, placental abruption, chorioamnionitis, stillbirth, preterm birth, and spontaneous abortion. In addition, fetal exposure increases the risk of low birth weight, perinatal mortality, sudden infant death syndrome (SIDS), and cognitive, behavioral, and emotional deficits in childhood.


Of the many harmful chemicals in tobacco smoke, reproductive toxicity is due is large part to just three: nicotine, carbon monoxide, and oxidizing agents. Nicotine reduces placental blood flow (by promoting vasoconstriction), delays or impairs fetal brain development (by direct neurotoxic effects), inhibits maturation of fetal pulmonary cells, and increases the risk of SIDS. Carbon monoxide reduces the oxygen-carrying capacity of blood and, in high levels, is neuroteratogenic. Oxidizing agents increase the risk of thrombotic events and, by decreasing the availability of nitrous oxide (a smooth muscle relaxant), they contribute to placental vasoconstriction and preterm labor.


Clearly, smoking during pregnancy is dangerous and should be stopped. Ideally, women should quit prior to conception or early in pregnancy. However, quitting later is still beneficial. To aid smoking cessation, the authors of Treating Tobacco Use and Dependence: 2008 Update recommend that clinicians offer effective interventions at the first prenatal visit, and throughout the course of pregnancy as needed. Intensive, person-to-person psychosocial intervention should be offered to all pregnant smokers. Pharmacologic intervention—mainly nicotine replacement therapy (NRT)—may also be offered, but only if psychosocial intervention alone has failed. Of note, quit rates with a combination of psychosocial intervention plus NRT are higher than with psychosocial intervention alone.


What do we know about NRT during pregnancy? Not as much as we would like. Studies on the efficacy of NRT in pregnant smokers have been inconclusive—probably because the nicotine dosage was too low. (During the later stages of pregnancy, nicotine is metabolized at a high rate. Hence, if conventional NRT doses are used, nicotine blood levels may be too low to be effective.) Nonetheless, even if we are uncertain about NRT efficacy, it seems likely that NRT is much safer than smoking. After all, cigarette smoke contains thousands of harmful chemicals (in addition to nicotine), whereas NRT contains nicotine only. In fact, among women who switched from smoking to NRT, there was no evidence of serious adverse effects, and there was an important benefit: birth weight was increased.


Who should use NRT? According to a 2009 review,* use of NRT should be based on the number of cigarettes smoked. Pregnant woman who smoke no more than 5 cigarettes a day should be offered psychosocial support, but not NRT. Conversely, pregnant woman who smoke a lot should be offered NRT, along with psychosocial support.


What about bupropion and varenicline? Compared with NRT, bupropion has two advantages: (1) it lacks the potential adverse effects of nicotine and (2) it can counteract weight gain and cravings brought on by smoking cessation. One prominent voice—the American College of Obstetricians and Gynecologists (ACOG)—says that bupropion may be considered when behavioral interventions have failed. However, another prominent voice—the Motherisk Program—says that bupropion should be avoided until we know more about its safety and efficacy. As for varenicline, we have no human data on safety in pregnancy, but we do have animal data showing fetal harm. Accordingly, varenicline should not be used.



*Osadchy A, Kazmn A, Koren G: Nicotine replacement therapy during pregnancy: recommended or not recommended? J Obstet Gynaecol Can 31:744–747, 2009.



Tolerance and dependence




Acute poisoning

Nicotine is highly toxic. Doses as low as 40 mg can be fatal. Toxicity is underscored by the use of nicotine as an insecticide. Common causes of nicotine poisoning include ingestion of tobacco by children and exposure to nicotine-containing insecticides.





Chronic toxicity from smoking

According to a 2004 report from the U.S. Surgeon General, the adverse consequences of smoking are more extensive than previously understood. It is now clear that chronic smoking can injure nearly every organ of the body. We already knew that smoking could cause cardiovascular disease, chronic lung disease, and cancers of the larynx, lung, esophagus, oral cavity, and bladder. New additions to the list include leukemia, cataracts, pneumonia, periodontal disease, type 2 diabetes, abdominal aortic aneurysm, and cancers of the cervix, kidney, pancreas, and stomach. Smoking during pregnancy increases the risk of low birth weight, preterm labor, stillbirth, miscarriage, spontaneous abortion, perinatal mortality, and sudden infant death. As shown in Table 39–1, the leading causes of smoking-related death are lung cancer, ischemic heart disease, and chronic airway obstruction.

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Jul 24, 2016 | Posted by in NURSING | Comments Off on Drug abuse III: nicotine and smoking

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