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Overview

There is a potential interaction between metformin and NyQuil Severe. The nasal decongestant in NyQuil Severe, phenylephrine, can increase glucose production and decrease insulin release in the body.[1][2]

Therefore, taking NyQuil Severe can interfere with the glucose control of metformin.

If you do take a nasal decongestant and have been diagnosed with diabetes, it is important to check blood sugar regularly and learn the symptoms high and low blood sugar so you can act accordingly.

It is important to note that there are two versions of NyQuil, the original formulation and the 'Severe' formulation.

Original NyQuil does not contain phenylephrine, but the NyQuil Severe version does.

Metformin With NyQuil

NyQuil Severe is a combination ingredient cold and flu medication that contains:

  • Acetaminophen
  • Dextromethorphan
  • Phenylephrine
  • Doxylamine

The drug we are concerned about in NyQuil Severe is phenylephrine, a nasal decongestant.

Phenylephrine is classified as a sympathomimetic medication, which studies show can increase blood glucose concentrations.

Increase in blood glucose from phenylephrine occurs mostly by an increase in glucose production in the liver and inhibition of insulin secretion in the pancreas.[3]

Having said all of the above, short term use of phenylephrine will likely cause minimal changes to blood glucose (but it should be monitored nonetheless). Your doctor may recommend its use only on an intermittent, as needed, basis.

If you are planning on taking NyQuil (the non-Severe) formula, it is safe to take with metformin since it does not contain phenylephrine.[4]

Answer Summary

The phenylephrine contained in NyQuil Severe can alter blood sugar levels and may therefore interfere with metformin. NyQuil (the non-Severe formula) does not contain phenylephrine and is safe with metformin.

References
  1. ^ Elsevier ClinicalKey: Metformin Monograph
  2. ^ Drug-induced disorders of glucose metabolism. Mechanisms and management. PubMed
  3. ^ Effects of glucocorticoids and sympathomimetic agents on basal and insulin-stimulated glucose metabolism. PubMed
  4. ^ NyQuil Manufacturer Website