| Outcome Measures: |
Primary: Ratio of Self-reported Hypoglycemic Episodes to Total Hypoglycemic Episodes Determined by Continuous Glucose Monitoring (CGM), A subject's self-reported hypoglycemic episode is defined by a hypoglycemic symptom record on the hypoglycemia diary with a confirmatory glucose value (glucometer value \< 70 mg/dL), or an incidental glucometer value \< 70 mg/dL if no hypoglycemia symptom develops. A single CGM hypoglycemic episode is defined by any CGM readings \< 70 mg/dL, followed by at least one reading ≥ 70 mg/dL from the Dexcom Professional Mobile CGM system. Self-reported and CGM assessment of hypoglycemic episodes will be conducted for two weeks before study drug intervention and two weeks after study drug intervention. The average change in the ratio of self-reported hypoglycemic episodes to total (CGM) episodes will be compared between the propranolol and placebo treatment arms, 2 weeks | Secondary: Gold Questionnaire Score for Hypoglycemia Awareness, Subjects will complete the Gold questionnaire for hypoglycemia awareness at the baseline and at the last visit of the intervention period. The Gold questionnaire is comprised of one question to evaluate the hypoglycemia awareness, with scores from 1 to 7, representing from normal to minimal/no hypoglycemia awareness. The average change in Gold questionnaire score from baseline to the last visit will be compared between the propranolol and placebo treatment arms., 4 weeks|Clarke Questionnaire Score for Hypoglycemia Awareness, Subjects will complete the Clarke questionnaire for hypoglycemia awareness at the baseline and at the last visit of the intervention period. The Clarke questionnaire is comprised of eight questions to evaluate the hypoglycemia awareness. The answer for each individual question will represent a score (0 or 1). These scores will be summed together to a final score from 0 to 7, representing from normal to minimal/no hypoglycemia awareness. The average change in Clarke questionnaire score from baseline to the last visit will be compared between the propranolol and placebo treatment arms., 4 weeks|Pederson-Bjergaard Questionnaire Score for Hypoglycemia Awareness, Subjects will complete the Pederson-Bjergaard questionnaire for hypoglycemia awareness at the baseline and at the last visit of the intervention period. The Pederson-Bjergaard questionnaire is comprised of one question to evaluate the hypoglycemia awareness, with answers of "Always", "sometimes", "occasionally", "never" or "Do not know". Each answer will represent an awareness status. The change in Pederson-Bjergaard questionnaire status from baseline to the last visit will be compared between the propranolol and placebo treatment arms., 4 weeks|Nadir Glucose Level, Nadir glucose level during each hypoglycemic episode will be detected by CGM during a 2-week interval at baseline and at the end of the treatment period. The average of nadir blood glucose levels will be calculated and the change will be compared between the propranolol and placebo treatment arms., 2 weeks|Nadir Glucose Level in Categories, Nadir glucose level during each hypoglycemic episode will be detected by CGM during a 2-week interval at baseline and at the end of the treatment period. The number of hypoglycemic events will be totaled in the severity categories of nadir glucose level: \< 70 mg/dL; \< 60 mg/dL; \< 56 mg/dL; \< 50 mg/dL; and \< 40 mg/dL. The change in the number of hypoglycemic events in these categories will be compared between the propranolol and placebo treatment arms., 2 weeks|Hypoglycemia Duration, Duration of hypoglycemia will be detected by CGM during a 2-week interval at baseline and at the end of the treatment period. The total duration of hypoglycemia (in minutes) will be calculated for each duration categories of hypoglycemia: \<15 minutes, ≥ 15 minutes, ≥ 30 minutes, ≥ 45 minutes and ≥ 60 minutes. The change in the total time of hypoglycemia in these categories will be compared between the propranolol and placebo treatment arms., 2 weeks|Blood Glucose Area Under the Curve (AUC), Blood glucose will be detected by CGM during a 2-week interval at baseline and at the end of the treatment period. The AUC of blood glucose will be calculated for each severity categories of nadir glucose level: \< 70 mg/dL; \< 60 mg/dL; \< 56 mg/dL; \< 50 mg/dL; and \< 40 mg/dL. The change in AUC of these categories will be compared between the propranolol and placebo treatment arms., 2 weeks|Duration of Hypoglycemia Onset-to-Diagnosis, The time of hypoglycemic symptom and glucometer reading of each hypoglycemic episode will be documented by study subjects in the hypoglycemia diary, and the onset time of hypoglycemia will be detected by CGM during a 2-week interval at baseline and at the end of the treatment period. The duration of hypoglycemia onset-to-diagnosis will be calculated as the time difference between hypoglycemia onset as recorded on CGM, and documented hypoglycemic symptom and glucometer reading, whichever is the earliest. The change in the average duration of hypoglycemia onset-to-diagnosis will be compared between the propranolol and placebo treatment arms., 2 weeks|Duration of Hypoglycemia Onset-to-Treatment, The time of hypoglycemia treatment of each hypoglycemic episode will be documented by study subjects in the hypoglycemia diary, and the onset time of hypoglycemia will be detected by CGM during a 2-week interval at baseline and at the end of the treatment period. The duration of hypoglycemia onset-to-treatment will be calculated as the time difference between hypoglycemia onset as recorded on CGM, and documented hypoglycemia treatment. The change in the average duration of hypoglycemia onset-to-treatment will be compared between the propranolol and placebo treatment arms., 2 weeks|Duration of Hypoglycemia Diagnosis-to-Recovery, The time of hypoglycemic symptom and glucometer reading of each hypoglycemic episode will be documented by study subjects in the hypoglycemia diary, and the recovery time of hypoglycemia will be detected by CGM during a 2-week interval at baseline and at the end of the treatment period. The duration of hypoglycemia diagnosis-to-recovery will be calculated as the time difference between the documented hypoglycemic symptom and glucometer reading, whichever is the earliest, and hypoglycemia recovery as recorded on CGM. The change in the average duration of hypoglycemia diagnosis-to-recovery will be compared between the propranolol and placebo treatment arms., 2 weeks|Duration of Hypoglycemia Treatment-to-Recovery, The time of hypoglycemia treatment of each hypoglycemic episode will be documented by study subjects in the hypoglycemia diary, and the recovery time of hypoglycemia will be detected by CGM during a 2-week interval at baseline and at the end of the treatment period. The duration of hypoglycemia treatment-to-recovery will be calculated as the time difference between the documented hypoglycemia treatment and hypoglycemia recovery as recorded on CGM. The change in the average duration of hypoglycemia treatment-to-recovery will be compared between the propranolol and placebo treatment arms., 2 weeks|Total Hypoglycemia Episodes, Hypoglycemia will be reported by patients detected by CGM during a 2-week interval at the baseline and at end of the treatment period. The total number of hypoglycemic episodes as defined by CGM readings of \< 70 mg/dL will be counted, and the changes in the number will be compared between the propranolol and placebo treatment arms., 2 weeks|Total Severe Hypoglycemia Episodes, Severe hypoglycemia is a clinical event defined by any hypoglycemic episode requiring outside help in the treatment administration of the particular hypoglycemic episode. Severe hypoglycemia episodes will be recorded by hypoglycemia diary during a 2-week interval at baseline and at the end of the treatment period. The total number of hypoglycemia/severe hypoglycemia episodes as defined by CGM readings of \< 70 mg/dL will be counted and the change will be compared between the propranolol and placebo treatment arms., 2 week|Fear of Hypoglycemia Score, Subjects will complete the Fear of Hypoglycemia Questionnaire at baseline and the last visit of the intervention period. The average change in Fear of Hypoglycemia Questionnaire score from baseline to 4 weeks will be compared between the propranolol and placebo treatment arms., 4 weeks|Mean Blood Glucose, Blood glucose will be detected by CGM during a 2-week interval at the baseline and at the end of the treatment period. The average change will be compared between the propranolol and placebo treatment arms., 2 weeks
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