Inclusion Criteria:  Medically-stable volunteers of either gender between 35 and 50 years old or over the age of 65 No medication changes anticipated for the duration of the study except as defined in protocol  Exclusion Criteria:  Insulin-dependent diabetes Psychiatric or neurologic disease affecting cognition in a way that may interfere with study outcomes in the opinion of the investigator Unstable Coronary Artery Disease (active angina, MI within 6 months, stent placement within 6 months, cardiac surgery within 6 months) Estimated CrCl < 30 mL/min using the Cockroft-Gault equation based on ideal body weight or total body weight Any malignancy actively being treated or not in remission Currently taking any CNS stimulant or depressant medications that may interfere with study outcomes in the opinion of the investigator unless using as defined in the protocol Positive toxicology test for marijuana at screening visit or visit 2 or using marijuana not as defined in the protocol Active or recent history of a substance use disorder within one year Any medical condition that in the opinion of the investigator would disqualify the subject from participation in the study Female subjects who are pregnant, planning to become pregnant, or breastfeeding on any study day Female subjects of childbearing potential unwilling to use acceptable method of contraception during the study as defined in the protocol Contraindication, known allergy, or suspected intolerability to study medication Receipt of an antihistamine within 5 half-lives prior to the start of study visit 1 or study visit 2, as determined by the investigator Positive toxicology test for a drug that is inconsistent with permitted medication use (defined in the protocol) as interpreted by the investigator Participation in any other investigational drug study during the study or within 4 weeks prior to screening