Patient description: An 89-year-old man was brought to the emergency department by his wife and son after six months of progressive changes in cognition and personality. He began to have poor memory, difficulty expressing himself, and exhibited unusual behaviors, such as pouring milk onto the table and undressing immediately after getting dressed. He is unable to dress, bathe, use the toilet, or walk independently. On examination the patient's temperature was 36.5C (97.7F), the heart rate 61 bpm in an irregular rhythm, the blood pressure 144/78 mm Hg, and the respiratory rate 18 bpm. The patient was alert and oriented to self and city but not year. He frequently interrupted the examiner. He repeatedly reached out to grab things in front of him, including the examiner's tie and face. He could not spell the word "world" backward, could not follow commands involving multiple steps and was unable to perform simple calculations. His speech was fluent, but he often used similar-sounding word substitutions. He could immediately recall three out of three words but recalled none of them after 5 minutes. Examination of the cranial nerves revealed clinically significant paratonic rigidity. Myoclonic jerks were seen in the arms, with symmetrically brisk reflexes. The reflexes in

Clinical trial eligibility criteria: eligible ages (years): 18.0-75.0,  Long QT Syndrome All Individuals Be a nonsmoker or consume < 20 cigarettes per day Have a calculated body mass index (BMI) from 18 to 36 kg/m^2, inclusive, at study screening Have either a normal 12-lead electrocardiogram (ECG) or one with abnormalities that are considered clinically insignificant by the investigator Screening labs within defined thresholds Individuals with mild, moderate, or severe renal impairment must also meet the following additional to be eligible for participation in this study Must have diagnosis of chronic (> 6 months), stable renal impairment with no clinically significant changes within 3 months (90 days) prior to study drug administration (Day 1) Individuals with severe renal impairment, creatinine clearance (CLcr) must be 15-29 mL/min, inclusive (using the Cockcroft-Gault method) based on serum creatinine and actual body weight as measured at the screening evaluation. If an individual's score changes during the course of the study, the score at screening will be used for classification Individuals with moderate renal impairment, CLcr must be 30-59 mL/min, inclusive (using the Cockcroft-Gault method) based on serum creatinine and actual body weight as measured at the screening evaluation. If an individual's score changes during the course of the study, the score at screening will be used for classification Individuals with mild renal impairment , CLcr must be 60-89, inclusive mL/min (using the Cockcroft-Gault method) based on serum creatinine and actual body weight as measured at the screening evaluation. If an individual's score changes during the course of the study, the score at screening will be used for classification  History of meningitis or encephalitis, epilepsy, seizures, migraines, tremors, myoclonic jerks, narcolepsy, obstructive sleep apnea, anxiety, syncope, head injuries or a family history of seizures Presence or history of cardiovascular disease (including history of myocardial infarction based on ECG and/or clinical history, any history of ventricular tachycardia, congestive heart failure, cardiomyopathy, or left ventricular ejection fraction < 40%), cardiac conduction abnormalities, a family history of Long QT Syndrome, or unexplained death in an otherwise healthy individual between the ages of 1 and 30 years Syncope, palpitations, or unexplained dizziness Implanted defibrillator or pacemaker Medical history of renal carcinoma or hepatorenal syndrome Individuals receiving or anticipating use of hemodialysis, peritoneal dialysis, or any other renal replacement therapy or other medical procedure that serves as a surrogate for renal function during the study Individuals with fluctuating or rapidly deteriorating renal function. Assessment of the stability of the individual's renal function will be determined by the investigator Renal allograft recipients Experienced hypertensive crisis, required the addition of ≥1 antihypertensive drug, or required more intensive antihypertensive therapy (eg, addition of a new drug class) in the last 3 months