Oral Drugs for Diabetes: Avoiding Hypoglycemia

Millions of prescriptions are filled each year for oral diabetes medications such as rosiglitazone (AVANDIA). But what patients might not know is that many other commonly used medications may affect a patient’s response to oral diabetes drugs, sometimes with dangerous results.

Most diabetes drugs are metabolized by enzymes in the liver such as CYP2C9, CYP3A4 or CYP2C8. Many other drugs inhibit these enzymes and can cause increased levels of the diabetes drug in the blood. The result of this increase may be serious hypoglycemia (very low blood sugar). See Tables 1, 2 and 3 for lists of drugs that inhibit CYP2C9, CYP3A4 and CYP2C8, respectively, as well as the diabetes drugs that are metabolized by those respective enzymes.

With any of these diabetes drugs, using another drug that inhibits the metabolizing enzyme for your diabetes drug may increase the risk of hypoglycemia.

Two diabetes drugs that are less likely to interact

Some diabetes drugs are not metabolized by liver enzymes and thus would not undergo the kinds of drug interactions described here.

For example, diabetes drugs eliminated primarily by the kidneys rather than by undergoing metabolism in the liver include the relatively new drug sitagliptin (JANUVIA) and the very old drug metformin (GLUCOPHAGE). However, because both of these drugs are excreted by the kidneys, patients taking them may be vulnerable to interactions with drugs that affect the kidneys.

Also, some drugs (and alcohol) can affect blood sugar levels on their own without affecting the blood levels of diabetes medications. Such drugs would potentially affect any diabetes drug, including insulin.

What You Can Do

People who take oral diabetes drugs should be alert for the effects of other drugs on their blood sugar.

Make sure that the person who prescribed the diabetes drug knows all the medications you are taking (including nonprescription drugs and over-the-counter products). This is especially important when starting any new medications, because hypoglycemia is more likely during the initiation of the interacting drug.

If you are monitoring your own blood sugar levels, look for changes whenever you start or stop any other drug. Make sure you are aware of the symptoms of hypoglycemia (see Box, below) to increase your chances of detecting it before it gets too severe.

Table 1. CYP2C9

 
Table 2. CYP2C8

 
Table 3. CYP3A4

* Do Not Use on WorstPills.org
** Limited Use on WorstPills.org
*** Last Choice on WorstPills.org

Updated 4/4/2012