Introduction: A phase I, open-label, multiple dose, dose-escalation clinical study was conducted to assess the safety, tolerability, maximum tolerated dose, and potential chemopreventive effect of myo-inositol in smokers with bronchial dysplasia.

Materials and methods: Smokers between 40 and 74 years of age with >or= 30 pack-years of smoking history and one or more sites of bronchial dysplasia were enrolled. A dose escalation study ranging from 12 to 30 g/d of myo-inositol for a month was first conducted in 16 subjects to determine the maximum tolerated dose. Ten new subjects were then enrolled to take the maximum tolerated dose for 3 months. The potential chemopreventive effect of myo-inositol was estimated by repeat autofluorescence bronchoscopy and biopsy.

Results: The maximum tolerated dose was found to be 18 g/d. Side effects, when present, were mild and mainly gastrointestinal in nature. Using the regression rate of the placebo subjects from a recently completed clinical trial with the same inclusion/exclusion criteria as a comparison, a significant increase in the rate of regression of preexisting dysplastic lesions was observed (91% versus 48%; P = 0.014). A statistically significant reduction in the systolic and diastolic blood pressures by an average of 10 mm Hg was observed after taking 18 g/d of myo-inositol for a month or more.

Conclusion: myo-Inositol in a daily dose of 18 g p.o. for 3 months is safe and well tolerated. The potential chemopreventive effect as well as other health benefits such as reduction in blood pressure should be investigated further.