Modafinil and Cognitive Function in POTS

Inclusion Criteria: * Males and females of all races between the ages of 18 to 60 years * Diagnosed with POTS by the Vanderbilt Autonomic Dysfunction Center based on the following consensus criteria:(a) an increase in heart rate ≥ 30 beats per minute within 10 minutes of changing from the supine to standing position; (b) absence of orthostatic hypotension (defined as a decrease in systolic blood pressure ≥ 20 mmHg or diastolic blood pressure ≥ 10 mmHg upon standing); and (c) chronic symptoms (≥ 6 months) consistent with POTS that are worse with standing and are relieved by lying down * Able and willing to provide informed consent Exclusion Criteria: * Overt causes for POTS such as acute dehydration and bed rest deconditioning * Patients taking serotonin-norepinephrine reuptake inhibitors (SNRIs) or norepinephrine transporter (NET) inhibitors * Known allergies or contraindications to study medications * Pregnancy or breast-feeding * Inability to give or withdraw informed consent * Other factors which in the investigator's opinion would prevent the subject from completing the study protocol such as poor compliance during previous studies * Asthma (due to the contraindication of propranolol for asthma patients)