- Concomitant use of acetylcholinesterase inhibitors (AChEIs) is allowed but not required. Patients who are currently taking AChEIs are eligible as long as they have been using a stable dose for at least 3 months prior to screening and no change is foreseen for the duration of the study. This dose must be consistent with the product label in the concerned country. Patients who are not currently taking AChEIs but have taken them in the past are also eligible if AChEIs were stopped at least 3 months prior to screening.