Efficacy and safety of oral insulin versus placebo for patients with diabetes mellitus: A systematic review and meta-analysis

OBJECTIVE: Compliance to insulin injections is poor due to difficulty in subcutaneous administration. Hence, there is a need of an oral formulation of insulin. Oral insulin is currently under investigation. The present analysis aimed to evaluate oral insulin versus placebo for patients with diabetes mellitus (type-1 and type-2). MATERIALS AND METHODS: Results from PUBMED and MEDLINE were searched and compiled from January 1, 2000 to January 9, 2020. Postprandial blood glucose excursions (2PPG), glycated hemoglobin (HbA1c), C-peptide levels, and immune antibody (IAA) levels were compared between the arms. In addition, time to diabetes and safety of oral insulin were discussed. RESULTS: Thirteen out of 1778 trials were included to the analysis. Oral insulin was found to induce significant reduction in mean 2PPG excursion (standardized mean difference [SMD]: −1.94, 95% CI: −3.20 to −0.68, I(2) = 91.81, P < 0.005) and mean IAA levels (SMD:-0.49, 95% CI: −0.82 to -0.16, I(2) = 27.12, P < 0.005) compared with placebo. Mean C-peptide levels were notably lower in the oral insulin arm. However, the difference was not statistically significant. No significant difference was observed in mean HbA1c levels. The rate of development of type-1 diabetes was not significantly influenced by oral insulin. No deaths or treatment-related serious adverse events were reported. CONCLUSION: Oral insulin provided significant benefits for acute maintenance of diabetes mellitus. It elicited lower immune response and was well tolerated. This new formulation has potential to augment the management of diabetes mellitus. More studies are required to assess its long-term effects.