Endocrine System Home > Drug Interactions With NPH Insulin/Regular Insulin

A number of medications can cause potentially dangerous NPH insulin/regular insulin drug interactions. Some of these medications include beta blockers, ACE inhibitors, fibrate cholesterol medicines, and MAOIs. These drug interactions could increase the risk of low blood sugar, which can be dangerous (even fatal) rather quickly. To prevent interactions, your healthcare provider may adjust your dosages or even prescribe a different medication.

An Overview of NPH Insulin/Regular Insulin Interactions

NPH insulin/regular insulin (Humulin® 70/30, Novolin® 70/30) has the potential to interact with numerous other medications. In fact, virtually any medication that affects blood sugar levels has the potential to interact with NPH insulin/regular insulin.
Due to the large number of potential drug interactions with NPH insulin/regular insulin (and because many such interactions are relatively insignificant), this article does not discuss every possible interaction. For instance, interactions that increase blood sugar are not discussed in this article. High blood sugar is certainly not healthy, but is usually not immediately dangerous. Typically, most people will notice higher blood sugar when testing and will adjust their insulin dosage as recommended by their healthcare provider long before these interactions become dangerous.
Other NPH insulin/regular insulin drug interactions can result in dangerously low blood sugar levels (known medically as hypoglycemia). These interactions can quickly become dangerous (even fatal), even if you check your blood sugar regularly. Some of the medicines that may cause dangerously low blood sugar when combined with NPH insulin/regular insulin include:
  • ACE inhibitors (angiotensin-converting enzyme inhibitors), such as:
    • Aspirin (Ecotrin®, Bayer®, Anacin®)
    • Choline magnesium trisalicylate (Trilisate®)
    • Diflunisal (Dolobid®)
    • Salsalate (Salflex®, Disalcid®, Amigesic®)
  • Sulfonamide antibiotics ("sulfa drugs"), such as:
    • Sulfadiazine
    • Sulfadoxine (Fansidar®)
    • Sulfamethoxazole (Bactrim®, Septra®)
    • Sulfisoxazole (Gantrisin®).
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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