Mirabegron in Achalasia: A Clinical and Manometric Proof of Concept Pilot Study

Inclusion Criteria: * 18 years old \< Age \< 75 years old with prior diagnosis of achalasia via manometry and/or radiographically Exclusion Criteria: * \< 18 years old or \> 75 years old * History of hypertension not controlled on oral medications (blood pressure \> 160/100 mm Hg) * No prior history of hypertension with a blood pressure \> 160/100 mm Hg * History of bladder outlet obstruction * History of angioedema * Pregnant or breast-feeding women: Women between 18 and 40 years old who are enrolled in the study will be required to use a form of birth control during the study * Patients currently receiving certain medications (digoxin, warfarin, any overactive bladder medications, thioridazine, flecainide, propafenone, phosphodiesterase inhibitors) * Patients with prolonged QTc interval or risk factors to develop it: * Baseline QTc on EKG of \> 450 milliseconds * History of additional risk factors for Torsades de Pointes (heart failure, family history of long QT syndrome) * Concomitant medications that prolong the QTc interval: ranolazine, sotalol, dofetilide, procainamide, disopyramide, propafenone, azole antifungals, fluoroquinolones, macrolide antibiotics, HIV antiretrovirals, chemotherapy, beta-2 agonists, tricyclic antidepressants, selective serotonin reuptake inhibitors * Prior surgeries for achalasia * \< 2 months since last endoscopic botulinum toxin injection into LES or endoscopic dilation * Stage 4 Chronic kidney disease (severe renal impairment with GFR 15-29 ml/min), Stage 5 Chronic Kidney disease (GFR \< 15 ml/min or on dialysis) * Childs Pugh B (moderate) or C (severe) Cirrhotic (hepatic impairment)