<qa>  What do the Principal Investigator or co-workers designated by himher do not involve?13. Having taken medication regularly in the month prior to the start of the study or symptomatic medication in the week before the start of the study, except for oral contraceptives, vitamins, herbal remedies, or dietary supplements that, according to the Principal Investigator or co-workers designated by himher, do not involve a risk for the subjects and do not interfere with the objectives of the study. 