Study of Promethazine for Treatment of Diabetic Gastroparesis

Inclusion Criteria: * adult patients 18-65 years of age * clinical diagnosis of diabetic gastroparesis. * EGD without evidence of gastric outlet obstruction within the past five years * gastric emptying scintigraphy test demonstrating \>10% solid food retention at 4 hours within the past three years. Exclusion Criteria: * the inability or unwillingness to provide informed consent * currently pregnant or breast feeding * prior placement of a gastric stimulator * pyloric botulinum toxin injection within the past 12 months * prior gastric surgery * history of a connective tissue disorder * use of narcotic medication within the past four weeks * hemoglobin A1C \>12 mg/dL within the past 3 months * current or recent (within past 4 weeks) use of promethazine, metoclopramide or domperidone * hypersensitivity or prior adverse reaction to promethazine * concomitant use of phenothiazines (i.e. prochlorperazine, chlorpromazine) or other agents likely to increase extrapyramidal reactions * concomitant use of tiotropium or ipratropium * narrow angle glaucoma * urinary retention * Parkinson's disease * significant psychiatric disease * history of seizure.