Use of a Phosphodiesterase Type 5 Inhibitor to Improve Anabolic Resistance in Older Adults

Inclusion Criteria: * Ages 60-75 yrs * Recently prescribed 5mg of tadalafil daily for clinical purposes Exclusion Criteria: * History of diabetes * history of hypotension including orthostatic hypotension * History of malignancy or chemo/radiation therapy in the 6 months prior to enrollment * History of short gut syndrome, gastrointestinal bypass/reduction surgery (Lap band, gastric sleeve, etc.) * Subjects who cannot refrain from using protein or amino acid supplements for 7 days prior to Visit 2 and 3. * Alcohol consumption of ≥ 5 units/servings per day * Concomitant use of * oral or injectable corticosteroids * testosterone, insulin like growth factor-1, or similar anabolic agent * riociguat (Adempas) * nitroglycerin * isosorbide dinitrate (Isordil) * isosorbide mononitrate (Imdur, Monoket) * doxazosin (Cardura) * prazosin (Minipress) * terazosin (Hytrin) * Any other disease or condition that would place the subject at increased risk of harm if they were to participate, at the discretion of the study physician