Can lansoprazole (Prevacid) and metformin (Glucophage) be taken together in type 2 diabetes?

This study evaluated the effects of lansoprazole on metformin pharmacokinetics (absorption, distribution, metabolism and excretion) in healthy humans.

In type 2 diabetes, either the body does not produce enough insulin or cells no longer respond adequately to normal levels of insulin. This causes hyperglycemia (high blood glucose), which can lead to increased acidity in the stomach. 

Metformin (Glucophage) is an insulin-sensitizing agent and is the most common drug used to treat hyperglycemia in patients with type 2 diabetes mellitus. The use of metformin is associated with gastrointestinal side effects such as gastro-esophageal reflux disease. Gastro-esophageal reflux disease is a condition in which the increased stomach acids flow backwards from the stomach into the esophagus (the tube from the mouth to the stomach).

Lansoprazole (Prevacid) belongs to a class of medications called proton pump inhibitors. It works by decreasing the amount of acids made in the stomach. Metformin can be used together with lansoprazole. Since metformin is a substrate of organic cation transporters (i.e. transporters act on metformin to control its uptake, distribution and elimination), this study investigated its potential to interact with lansoprazole, an inhibitor of organic cation transporters.

This study included 20 healthy volunteers who were randomly assigned to receive metformin (single dose 1,000 mg on day 1 and single dose 750 mg on day 2, with a 12-h interval) together with either a placebo (a substance with no medical effect used as a control when testing drugs) or lansoprazole (30 mg).

Lansoprazole increased the average metformin maximum plasma concentration by 15% (showing increased availability of metformin). Lansoprazole increased total drug exposure of metformin by 17% over the 24 hours. This indicates an increase in metformin bioavailability (the proportion of the drug entering the circulation to have an active effect).

In addition, lansoprazole prolonged the half-life (the time taken for the drug in the body to be reduced by 50%) of metformin elimination from 3.9 to 4.5 hours and reduced metformin excretion from the body by 13%. The study, however, indicated that lansoprazole did not influence the action of metformin on glucose concentrations.

Co-administration of metformin with lansoprazole generally reduced side effects. Only 5% of the participants reported loss of appetite.

In summary, this study concluded that lansoprazole affected the pharmacokinetics of metformin in healthy individuals, and therefore co-administration of the two should be monitored.

This study involved a small number of participants who were only followed up for a short period (two days). Large studies involving patients with diabetes are warranted.

Consult your physician regarding the benefits and risks of co-administration of these therapies.