5. Withdrawal, introduction, or change in dose of hormone replacement therapy and/or any drug known to substantially inhibit CYP1A2 (e.g. ciprofloxacine, fluvoxamine, cimetidine, ethinyloestradiol) or induce CYP1A2 (e.g. tobacco, omeprazole) within 7 days prior to enrolment. Subjects already on chronic therapy with any of these agents may be enrolled but doses must have remained stable from 7 days prior to enrolment through the end of the treatment period.