Efficacy and safety of oral insulin compared to subcutaneous insulin: a systematic review and meta-analysis

Introduction A systematic review and meta-analysis of interventional studies was conducted to compare the efficacy and safety of oral insulin versus subcutaneous (SC) insulin in diabetic patients. Methods Medline, Scopus, ISI Web of Knowledge and Cochrane Central Register of Controlled Trials were searched. Two independent reviewers evaluated studies for eligibility and quality and extracted the data. The primary outcomes were fasting blood glucose (FBG), 1h and 2h postprandial blood glucose, HbA(1c), AUC of insulin, C-max and T-max of insulin, and T-max of glucose infusion rate. Secondary outcomes were adverse events. Results Eleven studies (n = 373) met the inclusion criteria. Meta-analyses showed that there is no significant difference between oral and SC insulin in controlling HbA(1c), FBG, 1 and 2 h postprandial blood glucose and producing C-max of insulin (P > 0.05); however oral insulin had faster action as indicated by the shorter T-max, compared to SC insulin (P < 0.05). The most included studies were varied in their methodological quality. Conclusion This systematic review and meta-analysis showed that oral insulin is comparable to SC insulin with regard to glycemic efficacy and safety. However, is necessary to conduct additional studies in which oral insulin administered to large number of patients for long enough periods of time.