# Which Drugs Inhibit the Uptake and Transport of Metformin?

While metformin is primarily excreted unchanged and minimally metabolized, several medications can interfere with its cellular uptake and transport, which is crucial for its distribution and action in the body. These interactions primarily involve organic cation transporters (OCTs).

The drugs known to inhibit the uptake and transport of metformin include certain proton-pump inhibitors and other oral antidiabetic medications.

Proton-Pump Inhibitors (PPIs)

Proton-pump inhibitors, a class of drugs commonly prescribed to reduce stomach acid, have been shown in drug-drug interaction studies to inhibit metformin's uptake. This occurs by interfering with the function of specific organic cation transporters, namely OCT1, OCT2, and OCT3. By inhibiting these transporters, PPIs can potentially reduce the amount of metformin that is absorbed into cells, which could impact its overall effectiveness.

Oral Antidiabetic Drugs

Certain other medications used in the management of diabetes can also affect metformin's transport, particularly via OCT1:

• Repaglinide: This medication, which helps stimulate insulin release, has been observed in in vitro studies to inhibit the transport of metformin that is mediated by OCT1.
• Rosiglitazone: An antidiabetic drug that works by improving insulin sensitivity, rosiglitazone also demonstrates an inhibitory effect on OCT1-mediated metformin transport in in vitro settings.

Understanding these drug interactions is important for healthcare providers to ensure optimal metformin therapy and to mitigate potential risks associated with co-administration of these medications.

Summary of Drugs Inhibiting Metformin Transport