The Purpose of This Pilot Study is to Assess the Impact of KUVAN® (Sapropterin Dihydrochloride) on Gastric Relaxation in Women With Diabetic Gastroparesis.

Inclusion Criteria:Inclusion Criteria

Patients with moderate to severe symptoms of diabetic gastroparesis will be studied (GCSI >21). Patients should not have post-surgical gastroparesis or dyspeptic symptoms with normal gastric emptying. In order to qualify for inclusion in the trial, patients must satisfy the following inclusion criteria:

1. Diagnosis of diabetes mellitus > 5 years requiring medical therapy
2. Female gender
3. Ages 18-65 years
4. Documentation of delayed gastric emptying on gastric emptying scintigraphy (within 2 years of enrollment)
5. Symptoms of gastroparesis for at least 6 months with Gastroparesis Cardinal Symptom Index (GCSI) score > 21 indicating moderate to severe symptoms
6. Recent negative upper endoscopy or upper GI series within 2 years of enrollment (no evidence of mechanical obstruction or peptic ulcer disease)

Exclusion Criteria:Exclusion Criteria

Patients who satisfy any of the following exclusion criteria will be ineligible for enrollment in the study:

1. Diabetes diagnosed < 5 years prior to the study
2. Male gender
3. Normal gastric emptying
4. Gastroparesis from post-surgical etiologies
5. Another active disorder, which could explain symptoms in the opinion of the investigator
6. Pregnancy
7. History of significant cardiac arrhythmias and/or prolonged QTc
8. Daily use of narcotic analgesics for abdominal pain
9. Contraindications to gastric emptying breath test: patients with a known allergy to egg, wheat, or algae.
10. Underlying seizure disorder
11. Known history of cardiac ischemia
12. Recent clinically significant gastrointestinal bleeding
13. Patients taking Levodopa
14. Any other condition, which in the opinion of the investigator would impede compliance or hinder the completion of the study
15. Failure to give informed consent
16. Surgery for placement of a gastric stimulator within the past 6 months (patients > 6 months post-op with persistent symptoms and delayed gastric emptying are eligible).
17. A normal upper endoscopy not performed within 2 year of study entry.
18. Patients taking phosphodiesterase inhibitors such as sildenafil, vardenafil, tadalafil
19. Patients with renal impairment (i.e. Creatinine > 2.5 mg/dL)
20. Patients with hepatic dysfunction (i.e. ALT and AST values > 2.5x ULN and T. bilirubin > 1.5x ULN)
21. Patients with uncontrolled diabetes, such as HbA1c > 10 mg/dl at screening/baseline will be excluded.