The goal of this clinical trial is to learn about baclofen in pediatric patients with rumination syndrome. The main question it aims to answer is whether baclofen is effective in treating children with rumination syndrome. Participants will be asked to take baclofen or placebo for 4 weeks and fill out surveys regarding symptoms.

Rumination syndrome is a functional gastrointestinal disorder characterized by effortless, repetitive regurgitation of recently ingested meal. The objective of this study is to evaluate the efficacy of baclofen, a GABA-b agonist, in children with rumination syndrome. The investigators hypothesize that children with rumination syndrome who are treated with baclofen in addition to standard behavioral treatment will have greater clinical improvement compared to those who receive placebo.

After enrollment into the study, participants will be randomized into one of two parallel groups in a 1:1 ratio: (a) baclofen or (b) placebo control. The research team will be blinded to randomization. Participants will subsequently meet with investigational pharmacist and receive four-week supply of either baclofen 0.5 mg/kg/day up to 15 mg divided three times a day or matching placebo three times a day in liquid formulation. At baseline, the research team will collect information on demographics, medical, and surgical history, relevant diagnostic testing, and relevant past treatments (including working with a psychologist). Patients/families will complete a baseline questionnaire (rumination severity questions, PedsQL, route of nutrition, medications) and then the patient will start taking study drug or placebo in addition to their usual care as determined by the patient's primary gastroenterologist. Participants/families will complete follow-up questionnaires at week 1, week 2, week 4, and then week 8. The questionnaires will be filled out by the patient or guardian electronically via REDCap. The research team will closely monitor for side effects. In addition to asking about any side effects at follow-up timepoints, the research team will also emphasize that families should contact the team using the research team phone number with any instances of suspected side effects even before the next follow-up timepoint. After the 4-week drug or placebo period, participants are free to start or continue baclofen, or use other treatment modalities, as determined by their primary GI team.

Inclusion Criteria:

• Children 4-18 years of age who meets Rome IV diagnostic criteria for rumination syndrome and are see at NCH GI clinic

Exclusion Criteria:

• Patients who have contraindications to baclofen due to medical history and/or current medications
• Patients who are non- English speaking
• Patients who are pregnant

Participants will be randomized into one of two parallel groups in 1:1 ratio. The specific details of randomization sequence will be managed by investigational pharmacy. The participant, care provider, and research team are blinded to randomization.