Patient description: The patient is a 35-year-old woman with myasthenia gravis, class IIa. She complains of diplopia and fatigue and weakness that affects mainly her upper limbs. She had a positive anti-AChR antibody test, and her single fiber electromyography (SFEMG) was positive. She takes pyridostigmine 60 mg three times a day. But she still has some symptoms that interfere with her job. She is a research coordinator and has 3 children. Her 70-year-old father has hypertension. She does not smoke or use illicit drugs. She drinks alcohol occasionally at social events. Her physical exam and lab studies were not remarkable for any other abnormalities. BP: 110/75 Hgb: 11 g/dl WBC: 8000 /mm3 Plt: 300000 /ml Creatinine: 0.5 mg/dl BUN: 10 mg/dl Beta hcg: negative for pregnancy

Clinical trial eligibility criteria: eligible ages (years): 18.0-50.0,  Schizophrenia Schizoaffective Disorder Currently treated with a dose of at least 6 mg of risperidone daily or the equivalent of any other antipsychotic medication or a combination thereof (an equivalence table will be provided to the sites) Has a DSM-IV diagnosis of schizophrenia (295.10, 295.20, 295.30, 295.60, 295.90) or schizoaffective disorder Healthy on the basis of a prestudy physical exam, medical history, ECG, and laboratory results of blood biochemistry, hematology, and urinalysis performed within 2 weeks of randomization. If the results of the biochemistry or hematology tests or the urinalysis are not within the laboratory's reference ranges the patient can be included only if the investigator judges that the deviations are not clinically significant. For liver function tests (alanine transaminase, aspartate transaminase, and bilirubin), the values must be contained within 2 times the upper limits of the normal laboratory reference ranges and for renal function tests, the values must be within the normal laboratory reference ranges Women must be postmenopausal for at least 1 year, surgically sterile, or practicing an effective method of birth control (e.g., prescription oral contraceptives, contraceptive injections, intrauterine device, double-barrier method, contraceptive patch, male partner sterilization and at the discretion of the investigator, total abstinence) before entry and throughout the study, as well as have a negative serum pregnancy test at screening. To ensure continued women must have a negative urine test at baseline Body weight as defined by body mass index (weight [kg]/height (m)²) within a range of 15.0 to 35.0 kg/m², inclusive Willingness to spend 15 days as an in-patient during the treatment period Normotensive at screening, with supine (5 minutes) blood pressure between the range of 100 to 140 mmHg systolic, inclusive, and 60 to 90 mmHg diastolic, inclusive  Involuntarily committed in-patients Has a DSM-IV diagnosis of substance dependence within 3 months before screening evaluation. Nicotine and caffeine dependence and history of recreational use of marijuana are not exclusionary At screening, has a decrease of > = 20 mmHg systolic blood pressure or a decrease of > =10 mmHg decrease in diastolic blood pressure 2 minutes after standing, or experience symptoms of lightheadedness, dizziness, or fainting upon standing orthostatic hypotension Tests positive for the urine drug screen at screening Had an acute exacerbation of psychotic symptoms within the last 3 months before screen Relevant history or current presence of any cardiovascular, respiratory, central nervous system, neuropsychiatric (including seizures), renal, hepatic, endocrine, or immunologic diseases Has a DSM-IV Axis I diagnosis other than schizophrenia or schizoaffective disorder Suicidal or homicidal ideation