Inclusion Criteria:  Subject is aged 18 to 65 years at screening.  Subject is capable of providing informed consent.  A signed informed consent form must be provided before any study assessments are performed. Subject must be fluent in (oral and written) English to consent. Subject has a primary diagnosis of schizophrenia established by a comprehensive psychiatric evaluation based on the DSM-5 (American Psychiatric Association 2013) criteria and confirmed by Mini International Neuropsychiatric Interview for Schizophrenia and Psychotic Disorder Studies (MINI) version 7.0.2. Subject has not required psychiatric hospitalization, acute crisis intervention, or other increase in level of care due to symptom exacerbation within 8 weeks of screening and is psychiatrically stable in the opinion of the investigator. PANSS total score ≤ 80 at screening. Clinical Global Impression - Severity (CGI-S) score of ≤ 4 at screening At screening, subject is receiving an oral antipsychotic medication daily as maintenance therapy. Therapy must be stable, defined as the same oral antipsychotic medication for at least 8 weeks before screening and at the same dose for at least 4 weeks before screening. In the opinion of the investigator, it is clinically appropriate for the subject to discontinue current antipsychotic therapy and initiate experimental treatment with KarXT. Subject is willing and able, in the opinion of the investigator, to discontinue all antipsychotic medications prior to baseline visit. Subject has an identified reliable informant willing to be able to address some questions related to certain study visits, if needed. An informant may not be necessary if the subject has been the patient of the investigator for ≥1 year. At Day 0, subject will have been off lithium therapy for at least 2 weeks and must have discontinued all oral antipsychotic medications. Subjects taking a long-acting injectable antipsychotic could not have received a dose of medication for at least 12 weeks (24 weeks for paliperidone palmitate) before Day 0. Body mass index must be ≥ 18 and ≤ 40 kg/m2. Subject resides in a stable living situation and is anticipated to remain in a stable living situation for the duration of study enrollment, in the opinion of the investigator. Women of childbearing potential or men with sexual partners of childbearing potential must be willing and able to use at least 1 highly effective method of contraception during the study and for at least 30 days after the last dose of KarXT. Sperm donation is not allowed for 30 days after the final dose of KarXT.  Exclusion Criteria:  Any primary DSM-5 disorder other than schizophrenia within 12 months before screening (confirmed using MINI version 7.0.2 at screening). Subject has a history of moderate to severe alcohol use disorder or a substance (other than nicotine or caffeine) use disorder within the past 12 months. History or presence of clinically significant cardiovascular, pulmonary, hepatic, renal, hematologic, gastrointestinal, endocrine, immunologic, dermatologic, neurologic, or oncologic disease or any other condition that, in the opinion of the investigator, would jeopardize the safety of the subject or the validity of the study results Subject has human immunodeficiency virus (HIV), cirrhosis, biliary duct abnormalities, hepatobiliary carcinoma, and/or active hepatic viral infections based on either medical history or liver function test results. History or high risk of urinary retention, gastric retention, or narrow-angle glaucoma History of irritable bowel syndrome (with or without constipation) or serious constipation requiring treatment within the last 6 months Risk for suicidal behavior during the study as determined by the investigator's clinical assessment and Columbia-Suicide Severity Rating Scale (C-SSRS). Clinically significant abnormal finding from the physical examination, medical history, ECG, or clinical laboratory results at screening. Subjects cannot currently (within 5 half-lives before Day 0) be receiving monoamine oxidase inhibitors, anticonvulsants, tricyclic antidepressants, centrally active anticholinergics, or any other psychoactive medications other than daily antipsychotic maintenance therapy. As-needed anxiolytics and/or sleep aids are permitted. Selective serotonin reuptake inhibitors and serotonin-norepinephrine reuptake inhibitors taken at stable dose may be permitted. Subject has a history of treatment resistance to schizophrenia medications defined as failure to respond to 2 adequate courses of pharmacotherapy (a minimum of 4 weeks at an adequate dose per the label) within the past 12 months or having received clozapine within the past 3 years Pregnant, lactating, or less than 3 months postpartum. If, in the opinion of the investigator (and/or Sponsor), subject is unsuitable for enrollment in the study or subject has any finding that, in the view of the investigator (and/or Sponsor), may compromise the safety of the subject or affect his/her ability to adhere to the protocol visit schedule or fulfill visit requirements. Subjects has tested positive for coronavirus disease 2019 (COVID-19) within 2 weeks of screening. Subject has extreme concerns relating to global pandemics, such as COVID-19, that preclude study participation. Subject has had psychiatric hospitalization(s) for more than 30 days (cumulative) within the 6 months before screening. Subject has prior exposure to KarXT. Risk of violent or destructive behavior. Current involuntary hospitalization or incarceration.