Effect of Terazosin on ATP Levels in People With Amyotrophic Lateral Sclerosis

This will be a single center, randomized, double-blind, placebo-controlled pilot study to assess the safety and tolerability of terazosin (TZ) at a dose of 5 milligrams (mg) per os (PO) daily for patients with amyotrophic lateral sclerosis (ALS). The primary outcome of this study is to determine whether TZ increases adenosine triphosphate (ATP) levels in ALS. The investigators will measure adverse outcomes, safety, and tolerability of taking TZ. Procedures include blood draws, spirometry, fluorodeoxyglucose-positron emission tomography (FDG-PET) scans, questionnaires, and physical examinations. TZ will be titrated up to 5 mg PO daily. This is a pilot study and is not powered to assess efficacy of this medication. The investigators' hope is that this study will guide future studies of this (and similar) medications for the disease modification of ALS. This study also aims to learn more about how patients produce and use energy and if TZ can help to reverse energy deficits that appear in ALS.