“Combination of dextromethorphan and sitagliptin showed strongest effect in OGTT”.
A clinical trial was conducted in individuals with type-2 diabetes to identify the effects of dextromethorphan (DXM) as add-on to sitagliptin. Researchers were interested in the effects on blood glucose and serum insulin concentrations. Therefore, an investigation was performed to observe the BG-lowering effects of different strengths of DXM (30, 60 and 90 mg) in addition to 100 mg of sitagliptin. These parameters were measured individually for sitagliptin, as well as in combination of DMX and sitagliptin during an oral glucose tolerance test (OGTT). There were 20 male participants included in the study, who were all diagnosed with T2DM.
Researcher Jan Marquard, M.D., and his partners from Heinrich Heine University located in Germany, found that the combination of 60 mg DXM and 100 mg sitagliptin produced the strongest effect in the OGTT. This finding was displayed by the maximum reduction in blood glucose concentrations, which was associated with this specific combination.
The study also noted that within the first 30 minutes of the OGTT, a significantly larger increase in the baseline-adjusted AUC of serum insulin concentration was observed with the combination of 60 mg DXM and 100 mg sitagliptin compared to the 100 mg sitagliptin alone (P <0.05) or placebo (P <0.001). Researchers also claim that all strengths of the drugs used in the study, whether used alone or in combination, were well tolerated. Furthermore, there was no mention of serious adverse events or reports mentioning incidence of hypoglycemia during the study.
The authors conclude that 60 mg of dextromethorphan as an add-on to 100 mg sitagliptin can be beneficial for those suffering from type-2 diabetes. However, since the sample subjects were exclusively males, and long-term benefits have not been identified, research needs to be advanced by incorporating some of these limitations so that results can be validated and generalized to all individuals with T2DM. Furthermore, it is unclear what benefits the different strengths of DXM may have when used adjunctively with other DPP-4 inhibitors.
- The combination of 60 mg dextromethorphan plus 100 mg sitagliptin produced the strongest effect in the OGTT as it reduced maximum blood glucose concentrations
- A larger increase in the baseline-adjusted AUC of serum insulin concentration was observed with 60 mg DXM and 100 mg sitagliptin combination compared to other strengths of dextromethorphan, sitagliptin alone, or placebo
- Long-term clinical trials are warranted to identify the potential benefits of different strengths of dextromethorphan as add-on to DPP-4 inhibitors
Marquard, Jan, et al. “Effects of dextromethorphan as add‐on to sitagliptin on blood glucose and serum insulin concentrations in individuals with type 2 diabetes mellitus: A randomized, placebo‐controlled, double‐blinded, multiple crossover, single‐dose clinical trial.” Diabetes, Obesity and Metabolism (2015).