A double blind study of the effects of smoking on heart rate: is there tachyphylaxis?

Rationale: Smoking following overnight abstention reliably increases heart rate (HR), an effect due to nicotine absorption. The effect of subsequent c igarettes on HR is less than that associated with the first cigarette of th e day, an indication of tachyphylaxis (acute tolerance). To date. smoking/H R studies have nor been conducted double-blind. Instead. control conditions have included non-smoking or some type of "sham" smoking (puffing on an un lit cigarette or a straw). Objective: We investigated the HR response to sm oking and its time course using double-blind methodology. Methods: HR was r ecorded in overnight-abstaining participants before and after smoking the f irst, second and third cigarette of the day (40 min between each cigarette) in two sessions. The experimental manipulation involved replacing the seco nd cigarette of one session with a very low nicotine-yield cigarette (0.05 mg; FTC method) compared with the other five cigarettes (1.1-mg nicotine yi eld). Results, Smoking increased HR by 15, 8 and 7 beats/min (bpm) in the s ession where all three cigarettes had the higher yield. The comparable valu es for the session in which the second cigarette had the lower yield were 1 5, -1 and 11 bpm. Conclusions: in the session where all three cigarettes ha d the higher yield, larger increase in HR after smoking the first than the second or third cigarettes indicates tachyphylaxis The HR response in the o ther session was smaller for the third cigarette than the first cigarette, indicating that a period greater than 80 min would be needed before the I-I R response was fully restored.