Inclusion Criteria:
* Ability to provide informed consent.
* Aged between 18 and 65 years (inclusive) at the time of screening.
* Self-identified as milk intolerant or milk avoider.
* Agree to refrain from all treatments and products for milk intolerance (e.g., laxatives, stool softeners, Pepto Bismol®, Lactaid® Dietary Supplements) during the study.
* Willing to return for all study visits and complete all study-related procedures.
* Understand and provide written informed consent in English.
Exclusion Criteria:
* Any known allergy to Naloxone.
* Allergic to milk.
* Currently pregnant, lactating or considering pregnancy.
* Cigarette smoking or other use of tobacco or nicotine containing products within 3 months of screening.
* Diagnosed with any of the following disorders associated with abnormal gastrointestinal motility, such as: gastroparesis, amyloidosis, neuromuscular diseases (e.g., Parkinson's disease), collagen vascular diseases, alcoholism, uremia, malnutrition, untreated hypothyroidism.
* History of surgery that alters the normal function of the gastrointestinal tract, including:
gastrointestinal bypass surgery, bariatric surgery, gastric banding, vagotomy, fundoplication, pyloroplasty. (Note: A history of uncomplicated abdominal surgeries, such as appendix removal more than 12 months before screening, will not be excluded).
* Past or present diagnosis of any of the following: organ transplant, chronic pancreatitis or pancreatic insufficiency, symptomatic biliary disease, celiac disease, chronic constipation, diverticulosis, inflammatory bowel disease (e.g., ulcerative colitis, Crohn's disease), small intestine bacterial overgrowth syndrome, gastro-esophageal reflux disease (GERD), irritable bowel syndrome (IBS), any other medical condition with symptoms that could confound data collection (e.g., gas, diarrhea, bloating, cramps, stomach pain, fecal urgency).
* Diagnosed with active ulcers, or history of severe ulcers.
* Diagnosed with diabetes mellitus (type 1 and type 2)
* Diagnosed with Congestive Heart Failure (CHF)
* Diagnosed with Human Immunodeficiency Virus (HIV), Hepatitis B or Hepatitis C
* Weigh less than 16.5 kg or have a BMI greater than 35 kg/m².
* Had recent bowel preparation for endoscopic or radiologic investigation within 4 weeks of screening (e.g., colonoscopy prep).
* Have used treatments for milk intolerance (e.g., laxatives, stool softeners, Pepto Bismol®, Lactaid®) within 7 days of screening.
* Chronic antacid or proton pump inhibitor (PPI) use.
* Used systemic antibiotics within 30 days prior to screening (you may participate one month after discontinuing antibiotics).
* Used a high colonic enema within 30 days prior to screening. 8MAY2025 IRB-2024-731 Page 3 of 11
* Had symptoms or diseases that interfere with the assessment of milk intolerance symptoms (e.g., gas, diarrhea, bloating, cramps, stomach pain, fecal urgency).
* History of alcohol abuse.
* History of opioid drug abuse (e.g., oxycodone, hydrocodone, heroin, fentanyl, morphine).
* Currently undergoing chemotherapy.
* Have used any investigational drug or participated in an investigational study within 30 days prior to screening.
* Have any cardiac pacemaker, any type of prosthesis (eye, penile), implanted cardiac defibrillator, heart valve prosthesis/stents, aneurysm clip, shunt (spinal/intraventricular), neuro or bone stimulator, wire sutures or surgical staples, insulin or infusion pump, bone/joint pin, screw, nail, plate, implanted drug infusion device, body tattoos, cochlear, otologic or ear implant, tattooed makeup (eyeliner, lip, etc.), prostate radiation seeds, breast tissue expander, IUD (intrauterine device), hearing aids, transdermal medicine patch (Nitro), body piercing(s), any metallic implants or objects, internal electrodes or wires\*\*
* Have claustrophobia (fear of closed spaces)
* Cannot lie still for up to 75 minutes for any reason (e.g., movement disorder, severe cold with coughing).
* Worked with metal (grinding, fabrication, etc.) or had an injury to the eye involving a metallic object (e.g., metallic slivers, foreign body), injured by a metallic object that may NOT have been completely removed (e.g., bullets, shrapnel, BBs), had surgery or any similar invasive procedure, had a reaction to a contrast medium used for MRI or CT, diagnosed with epilepsy/seizure \*\*Exceptions to the Exclusion Criteria are allowed in the following circumstances: Certain implants, tattoos, metallic objects, or jewelry may be allowed and can be considered safe to image after having been reviewed and approved of by the Purdue MRI Staff. If it is safe, you will be able to participate in the study.
