Delsym Box With Text - Interaction With Crestor


Most online 'drug interaction checkers' do not list an interaction between Delsym (dextromethorphan), a cough suppressant, and Crestor (rosuvastatin), a statin cholesterol-lowering medication.[1]

However, our own interaction checker, which utilizes the database does list a potential interaction:

The metabolism of Dextromethorphan [Delsym] can be decreased when combined with Rosuvastatin [Crestor].
PharmacistAnswers DrugBank Interaction Checker

Most interaction tools don't list this because it has not been reported in studies and isn't thought to be of clinical significance.

However, based on the known metabolism of both drugs, it does appear possible the metabolism of dextromethorphan can be decreased if used at the same time as Crestor. A decrease in metabolism may increase the overall effect of the drug.

Overall though, the likelihood of this being clinically significant as to make an impact on someone's therapy is considered to be minimal at best.

The Details

Delsym (dextromethorphan) is metabolized by a variety of enzymes in the liver, including CYP2D6 and CYP3A4.[2][3]

Crestor (rosuvastatin) is thought to be only minimally metabolized via liver CYP enzymes. The prescribing information for the drug specifically states that it doesn't appear to be at all affected by the CYP3A4 enzyme (which is partially responsible for dextromethorphan metabolism):[4]

Rosuvastatin [Crestor] clearance is not dependent on metabolism by cytochrome P450 3A4 to a clinically significant extent.

However, studies have shown that Crestor can inhibit CYP3A4 to a very mild degree.[5]

If CYP3A4 is inhibited, dextromethorphan metabolism may be slightly decreased as well.

Why It Isn't Significant

The reason why online 'interaction checkers' don't list the potential interaction between Crestor and Delsym is likely because there isn't thought to be any clinical significance to it. This is for multiple reasons:

  • Delsym (dextromethorphan) is primarily metabolized by CYP2D6, not, CYP3A4.
  • Crestor [rosuvastatin] only minimally inhibits CYP3A4.

Dextromethorphan is, for the most part, metabolized by CYP2D6. Crestor is not known to affect this enzyme at all.

Crestor only inhibits CYP3A4 minimally.

Since Crestor only inhibits CYP3A4 is a very mild degree, and dextromethorphan is mostly metabolized by another enzyme anyway (CYP2D6), the risk of a noticeable interaction between the two drugs is small, if not practically non-existent.

In most cases, you can feel safe taking them together.


Delsym (dextromethorphan) metabolism may be decreased slightly if taken with Crestor (rosuvastatin), but the interaction is not thought to be clinically significant.

  1. ^ Elsevier ClinicalKey: Interactions. ClinicalKey
  2. ^ CYP3A4 drug interactions: correlation of 10 in vitro probe substrates. PubMed
  3. ^ Elsevier ClinicalKey: Dextromethorphan Monograph. ClinicalKey
  4. ^ Crestor Prescribing Information. AccessFDA
  5. ^ Effects of acid and lactone forms of eight HMG-CoA reductase inhibitors on CYP-mediated metabolism and MDR1-mediated transport. PubMed