Objective: To assess the impact of instructional guidance in the regular use of use nicotine nasal spray (NNS) on the true use of NNS during the first three weeks of smoking cessation for heavy smokers who are willing to quit.

Methods: This randomized, open, controlled trial included 50 patients who were heavy smokers, were willing to quit, and attending an academic outpatient clinic in Western Switzerland. Patients were randomised to instruction on NNS use as "ad libitum" (administration whenever cravings appear; control group) or to use NNS at least every hour when awake (intervention group). Intakes were monitored using an electronic device fixed in the spray unit (MDILogTM) during the first three weeks of use. Self reported abstinence from smoking at six months was confirmed by expired-air carbon monoxide. Using intention-to-treat analysis, random-effect GLS regression was used to calculate the mean difference of daily doses between groups controlling for lack of independence between measures from the same individual.

Inclusion Criteria:

• Highly dependent smokers in the stage of preparation according to Prochaska and Di Clemente's stages of change model

Exclusion Criteria:

• History of myocardial infarction in the preceding 3 months
• Pregnancy or breast-feeding
• Use of any form of smokeless tobacco or other nicotine replacement therapy