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.

The primary objective of this prospective pilot study is to determine the feasibility of patient-controlled administration of liquid oral acetaminophen using recruitment rate and adherence to the study protocol rate as surrogate markers. Investigators hypothesize that patients will accept the new concept of self-controlled oral administration of liquid acetaminophen, with more than 50% patient enrollment rate and less than 20% withdrawal rate from the study group to the traditional nurse-administered acetaminophen pills.

The secondary objective of this study is to determine the preliminary efficacy of patient-controlled delivery of oral acetaminophen administration.

If the medication is spilled or otherwise not dispensed correctly, the patients will be instructed to report this instantly to the nurse. The nurse will document and provide a replacement.

All study participants have the option to call the nurse for assistance with break through pain. In addition, there is a call button to call for help with any other needs or discomfort.

All other medications, such as NSAIDs or oral opioids, will be administered as prescribed.

Participants will have to fill out a paper questionnaire and keep a pain diary, and nurses will have to fill out a questionnaire.

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.