Tobacco smokers, and

Patkar, A.A.G.R., Berrettini, W.H., Weinstein, S.P., Vergare, M.J., Leone, F.T. Differences in platelet serotonin transporter sites between African-American tobacco smokers and non-smokers. Psychopharmacology. 166 221, 2003. 

It should be noted that workers exposed to benzene by dermal contact also may inhale vapors and thus receive a dual exposure. The air in many polluted areas often contains significant benzene levels as a result of the combustion of petroleum fuels. The ambient air over Los Angeles, California, in the decade 1990-2000, for example, typically contained greater than 1.0 ppm benzene.I18 Tobacco smokers and those exposed to secondhand (or environmental) smoke are further exposed to benzene. It is reasonable to anticipate that benzene-containing solvents will be used in urban and industrial areas where the air is polluted with benzene and that smokers will be among those who use such solvents. Such conditions further dictate the need for lowering the allowable benzene concentration in solvents. 

It appears that those segments of the general population with potentially high exposure to NDMA from exogenous sources would include tobacco smokers and nonsmokers who come in contact with tobacco smoke for extended periods of time, snuff dippers, people who are occupationally exposed, and people who consume large quantities of food known to contain NDMA, beer or whiskey.. ... 

Anttila, S., P Tuominen, A. Hirvonen, M. Nurminen, A. Kaijalainen, O. Hankinsonera/. (2001). CYPIAI levels in lung tissue of tobacco smokers and polymorphisms of CYPIAI and aromatic hydrocarbon receptor. Pharmacogenetics 11, 501-509. 

The manufaeturers say that population pharmaeokinetie analysis of schizophrenic patients who were enrolled in elinieal studies showed that no significant pharmacokinetic interactions occurred with benzatropine, Iorazepam or propranolol. The manufacturers also point out that since ziprasidone is not metabolised by the cytochrome P450 isoenzyme CYP1A2, smoking should not affect its pharmacokinetics. This is borne out by studies in patients, which did not reveal any differences in the pharmacokinetics of ziprasidone between tobacco smokers and non-smokers. ... 

Tobacco smokers, and non-smokers heavily exposed to tobacco smoke, may need more theophylline than non-smokers to achieve the same therapeutic benefits, because the theophylline is cleared from the body more quickly. This may also occur in those who chew tobacco or take snuff but not if they chew nicotine gum. 

Two studies found no difference between the steady-state nortriptyline plasma levels of tobacco smokers and non-smokers, but others have found that smoking tobacco lowers the plasma levels of amitriptyline, clomipramine, desipramine, imipramine" and nortriptyline. For example a 25% reduction in plasma nortriptyline levels was found in one study, and a 45% reduction in total levels of imipramine and its metabolite, desipramine, was found in another." ... 

Takizawa, H. et al. (2001) Increased expression of transforming growth factor-betal in small airway epithelium from tobacco smokers and patients with chronic obstructive pulmonary disease (COPD). American Journal of Respiratory and Critical Care Medicine, 163,... 

Prolonged high doses of beta-carotene can cause carotenodermia, a yellow-orange discoloration of the skin, which is harmless. There have been reports of increased frequencies of lung cancer in heavy tobacco smokers and asbestos workers associated with beta-carotene supplements of 30 and 20 mg/day respectively, but these are very high doses, exceeding those normally available in the diet. 

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