Nicotine is of considerable medical significance because of its presence in tobacco. It is a natural alkaloid, colourless, a volatile base that turns brown and acquires the odor of tobacco on exposure to air. It s ultimate response on any system represents the summation of stimulatory and inhibitory effects of nicotine. The major action of nicotine consists initially of transient stimulation and subsequently of a more persistent depression of all autonomic ganglia. The effects of nicotine on the neuromuscular junction are similar to those on the ganglia, the stimulant phase is largely obscured by the rapidly developing paralysis. In the later stage, nicotine also produces neuromuscular blockade by receptor desensitization. Stimulation of the central nervous system with large doses is followed by depression and death which results from failure of respiration due to both central paralysis and peripheral blockade of the muscles of respiration. Nicotine is readily absorbed from the respiratory tract and bucal membranes. Absorption from the stomach is limited being a relatively strongbase. The average cigarette contains 60 to 11mg of nicotine and delivers about 1-3mg of nicotine systematically to the smoker (Henning field 1995, Benowitz 1998). Nicotine administered orally as a gum or as transdermal pitch is effective in achieving abstinence from tobacco use. The milk of heavy smokers may contain 0.5mg per litre of nicotine. Poisoning from nicotine may occur in children from ingestion of tobacco products. Smoking tobacco usually contains 1-2% nicotine. Respiratory difficulty and death from respiratory failure are features of acute toxicity. Nicotine provides the reinforcement for the smoking of cigarettes. The dependence can be extremely durable and explains the high failure rate among smokers who try to quit (American Psychicentric Association). Cigarette addiction is synonymous with nicotine addiction. Few individuals who may smoke cigarettes smoke a small enough quantity (five cigarettes or fewer per day to avoid dependence). Each puff produces some discrete reinforcement. With 10 puffs per cigarette, the one-pack-per day smoker reinforces the habbit 200times daily. The timing, setting, situation and preparation all become associated repetitively with the effects of nicotine. Smokers may be smoking to achieve the reward of nicotine effects to avoid the pain of nicotine withdrawal or most likely a combination of the two. A cigarette is a smooth round stick; it gives the smoker a psychological sense of well-being and warmth but distributes enough amount of nicotine for addiction. Cigarette smoke contains several substances with different pharmacological effects such as carcinogenicity due to tar, phenol, carbazole B-Naphthylamine, radon and hydrazine. Respiratory tract irritant such as nitrogen oxide, carbon monoxide interfere with gaseous exchange and nicotine interferes with respiratory muscle function due to its neuromuscular blocking effects. Cigarette smoking causes chronic obstructive pulmonary diseases responsible for most deaths in smokers. Non smokers have longer life span than smokers, the reduced life span in smokers may be due to diseases associated with the smoking especially diseases of the respiratory tract. The peak expiratory flow rate is reduced in conditions causing airflow obstruction and is a good indicator of the severity of the obstruction. The measurement has therefore become popular in clinical practice because of its speed and simplicity and the use into serial measurements can be made. This simple measurement is of value in distinguishing between some types of respiratory disorders as well as in providing an index of their severity.