This clinical trial is designed to study the effects of pregnane X receptor activator rifampicin on the glucose, lipid and hormone homeostasis in healthy volunteers. The main hypothesis is that rifampicin raises postprandial glucose studied with oral glucose tolerance test. The study is a non-randomized, one-phase, open-label trial. Twelve subjects will be given 600 mg of rifampicin a day for a week. The main outcome measures are the changes in the glucose and insulin levels during oral glucose tolerance test.

Inclusion Criteria:

• Healthy volunteer
• Age 18-45 years
• Body mass index 19-28

Exclusion Criteria:

• Any continuous medication
• Any significant disease
• Allergy to rifampicin
• Pregnancy and breast feeding
• Fear of needles and previous difficult blood samplings
• Substance abuse
• Participation in another clinical drug trial within 1 month of enrollment
• Use of soft contact lenses