The health hazards associated with the smoking of combustible cigarettes, both to the smoker inhaling the smoke and to the non-smoker exposed to the second-hand smoke, have been well documented. For this reason, combustible cigarette smoking has increasingly become prohibited in many public places, such as restaurants, airplanes, airports, hospitals, shopping malls, the work place, etc., as well as socially unacceptable when a guest in a non-smoker's home. The social pressures to create a smoke-free society, while a boon to non-smokers, have made life rather unpleasant at times for habitual smokers finding themselves unable to satisfy their cigarette cravings.
There are several factors which are known to contribute to the habitual smoker's cigarette cravings. These include the psychological factors of holding the cigarette, placing it between the user's lips, puffing on it, and experiencing the taste and aroma of the smoke, as well as the physiological factor of nicotine dependency. Combustible cigarettes satisfy the physiological needs of the smoker by releasing as a component of the cigarette smoke vaporous nicotine, which is inhaled into the user's lungs, becomes rapidly assimilated into the bloodstream, and reaches the brain via arterial systems. After crossing the blood-brain barrier, the nicotine finally binds to the nicotinic or cholinergic receptors to release adrenergic transmitters, such as epinephrine, norepinephrine and dopamine, which are generally associated with pleasure and reward.
Because of the growing social unacceptability of combustible cigarette smoking, attempts have been made to provide cigarette substitute devices for non-pyrolytic use which simulate or closely approximate the look, feel and taste of combustible cigarettes and are capable of delivering nicotine vapor to the user through inhalation. Representative of those products are those described in the Ray U.S. Pat. No. 4,284,089, issued Aug. 18, 1981; the Hill U.S. Pat. No. 4,793,366, issued Dec. 27, 1988; and the Ray U.S. Pat. No. 4,813,437, issued Mar. 21, 1989. Such devices consist of an elongated tube having the approximate dimensions of an ordinary cigarette and housing a porous polymer plug serving as a reservoir for a source of vaporizable nicotine. The nicotine vapors are delivered to the user's lungs by the air drawn through the device by suction supplied by the user. These devices have failed to gain wide acceptance as a cigarette substitute, however, due to their inability to deliver sufficient and uniform amounts of nicotine to the user's lungs, an unpleasant taste, and an unsatisfactory shelf life. Most of these problems are due to the instability of the volatile liquid nicotine employed in these devices, which decomposes in the presence of oxygen and very rapidly dissipates from the system.
Thus, there is a continuing need for an adequate substitute for combustible cigarette smoking which will satisfy both the psychological and physiological needs of the habitual smoker without offending the senses of his non-smoking neighbor.