Nicotine gum is a type of chewing gum that delivers nicotine to the body. It is used as an aid in nicotine replacement therapy (NRT), a process for smoking cessation and quitting smokeless tobacco. The nicotine is delivered to the bloodstream via absorption by the tissues of the mouth. Nicotine gum is a type of chewing gum that delivers nicotine to the body. It is used as an aid in nicotine replacement therapy (NRT), a process for smoking cessation and quitting smokeless tobacco. The nicotine is delivered to the bloodstream via absorption by the tissues of the mouth. It is currently available over-the-counter in Europe, the US and elsewhere. The pieces are usually available in individual foil packages and come in various flavors. Nicotine content is usually either 2 or 4 mg of nicotine, roughly the nicotine content of one sixth to one third of a cigarette, with the appropriate content and dosage depending on the smoking habits of the user. Popular brands include Nicotex, Nicorette, Nicogum, Nicotinell and Zonnic. Alternative nicotine replacement products include the nicotine patch, nicotine pastilles/lozenges and the nicotine inhaler. Gum should not be used less than 15 minutes after eating or drinking as doing so will reduce absorption. Users are directed to chew the gum until it softens and produces a tingling sensation or 'peppery' taste. The gum is then 'parked,' or tucked, in between the cheek and gums. When the tingling ends the gum is chewed again until it returns, and is then re-parked in a new location. These steps are repeated until the gum is depleted of nicotine (about 30 minutes) or the craving dissipates. Dosage suggested by the Dental-professional.com website is: weeks 1-6: 1 piece every 1 to 2 hours; weeks 7-9: 1 piece every 2 to 4 hours; weeks 10-12: 1 piece every 4–8 hours; no more than 24 pieces per day. Do not use for longer than 12 weeks. Pregnant women should neither smoke nor use NRT. Light smokers should use the 2 mg and heavy smokers the 4 mg; size of gum is the same for both doses. When used properly, about 3 mg is absorbed into the bloodstream from the 4 mg gum, and 1 mg from the 2 mg gum. Nicotine is a vasoconstrictor; it constricts arteries, which increases the resistance against which the heart has to pump blood, effectively making it harder for the heart to pump blood through the body. The result is enhanced shear stress on vessel walls, and repeated nicotine exposure contributes to accelerated health problems that are a function of chronic vascular injury such as coronary artery disease, acute cardiac ischemic events, and hypertension Studies have shown that nicotine exposure contributes to stroke, peptic ulcer disease, and esophageal reflux. Nicotine may also cause wounds to heal more slowly and may be associated with reproductive toxicity. Two unpleasant symptoms which affect some new users and existing users who make excessive use of nicotine gum, are hiccups and a perceived constriction of the throat muscles, as accidental swallowing of saliva containing high amounts of nicotine may cause irritation. Women who use nicotine gum and patches during the early stages of pregnancy face an increased risk of having babies with birth defects according to a 2006 study that looked at about 77,000 pregnant women in Denmark. The study found that women who used nicotine-replacement therapy in the first 12 weeks of pregnancy had a greater risk of having babies with birth defects than women who did not.