The titration hypothesis revisited: nicotine gum reduces smoking intensity.

Supplemental nicotine gum reduced the intensity of smoking in six one-and-a-half to two-pack-a-day smokers. The study involved two 4-hour self-paced smoking sessions where nicotine and placebo chewing gum were administered in a double-blind fashion. Puff volume, puff duration, inhaled volume, inhaled duration, and interpuff interval were calculated for each puff on each cigarette. Blood was drawn for nicotine levels at regular intervals as well as before and after each cigarette. Cardiovascular measures were made at regular intervals. The nicotine gum reduced smoking frequency and intensity as predicted by the titration hypothesis. Precise titration (i.e., equal nicotine blood levels on both test days) was confounded by changes in smoked nicotine delivery produced by the gum. The gum, whether placebo or active, increased smoked nicotine absorption. However, while nicotine blood levels were slightly higher on nicotine gum day, the differences may not be biologically meaningful since heart rate and blood pressure increases were similar on both days. Difficulties testing the titration hypothesis are discussed.