Patient Controlled Administration of Liquid Acetaminophen

This is a proof of concept pilot study investigating the feasibility and acceptability of patient controlled oral medication administration, using the commonly used and low risk medication in the hospital, oral acetaminophen.

Inclusion Criteria: Participants * Adult patients older than 18 years old admitted to SRC for total shoulder and reverse total shoulder arthroplasty Nurses * The nurse who will administer acetaminophen to a study patient. Exclusion Criteria: Participants * Pregnant patient * Patients that cannot swallow pills or cannot take liquid (for example due to risk of aspiration) * Emergency surgery * Chronic pain * On home opioids, any other pain modulating medications including benzodiazepine, Neurontin, ketamine. * Past medical or social history of substance abuse disorder, including ethanol misuse disorder, marijuana misuse disorder * History of any psychiatric disorders including anxiety, depression, any cognitive dysfunction * Any patients who cannot provide informed consents on their own (those who would need Legally Authorized Representatives (LARs) or surrogates) * Liver dysfunction limiting amount of safe oral acetaminophen * baseline hyperbilirubinemia (ex: chronic liver disease, Gilbert's) * patients unable to take PO * Patients with neurologic, neuromuscular, or movement disorders unable to drink from a cup. Nurses * any nurse who is not involved in the direct care of a study patient, or who is not comfortable with setting up the PCA pump.