Intervention: Atropine
Trial phase: Not Applicable
ATC code: A03BA01 | A03BA03 | A03CB03 | A03CB31 | S01FA01
SMILES: CN1C2CCC1CC(OC(=O)C(CO)c1ccccc1)C2
Sex: All
Age groups: Child | Adult
Healthy volunteers: No
Participants at risk: 31
Group description: Arm 2: Subjects receive no treatment but have access to hyoscyamine as a rescue medication.

Hyoscyamine: While not an intervention of interest to our study, patients will have hyoscyamine available as a rescue medication throughout the study. This can be taken on a PRN basis for breakthrough pain a maximum of 4x daily.
Eligibility criteria:
Inclusion Criteria:

Age 8 to 21 years.
Diagnosis of functional abdominal pain, irritable bowel syndrome or functional dyspepsia made by a pediatric gastroenterologist according to Rome III Criteria.
Mean daily intensity of pain of 25 mm in the week prior to the initiation of the study, based on the Visual Analogue Scale
Children will not be excluded if they are adhering to any specific diet. Children will be asked to report any specific established diet prior to the study or dietary modifications that could have been made during the course of the study.
Normal laboratory tests including complete blood count, erythrocyte sedimentation rate, albumin, serum amylase, lipase, liver enzymes, urine analysis, stool examination for occult blood and ova and parasites one month prior the initiation of the study. Urinary culture will be obtained if the symptoms or urinalysis suggest the possibility of a urinary infection.
Normal lactose breath test or history of lack of resolution of symptoms on a lactose-free diet (2 weeks).
Patients receiving psychological treatment, hypnosis, biofeedback or guided imagery will not be excluded of the study if those were started at least one month prior to the initiation of the study and are not planned to be discontinued during the length of the trial. Patients will need to be prescribed hyoscyamine (clinically indicated) to be considered for this study, as the placebo will be in addition to their prescribed medication.

Exclusion Criteria:

Inclusion criteria not met.
Evidence of organic gastrointestinal disease, hepatic disorders, urinary or cardiac disease.
Children below the 5th percentile for weight or height.
Hemoccult positive stools.
Patients with diagnosis of Inflammatory Bowel Disease, hyperthyroidism, CHF, cardiac arrhythmias, prostatic hypertrophy, autonomic neuropathy, biliary tract disease, children with spastic paralysis or chronic lung disease (we will consult a pulmonologist concerning the inclusion of children with chronic lung disease).
Patients who are taking any of the following drugs: AbobotulinumtoxinA, Acetylcholinesterase Inhibitors (Central), Cannabinoids, OnabotulinumtoxinA, Potassium Chloride, Pramlintide, RimabotulinumtoxinB, Secretin. Patients receiving antidepressant or anticholinergic drugs will be excluded from the study. PPIs will be allowed as long as the patient had been on a stable dose for at least 12 weeks.
Patients planning to change their diet during the time of the study will be excluded. Children will be asked to report any specific established diet prior to the study or dietary modifications that could have been made during the course of the study.
Patients planning to start psychological treatment, hypnosis, biofeedback, or guided imagery during the course of the study or have started any of these within the month prior to consent.
The participant is pregnant or is planning to become pregnant throughout the course of the research study