Hi

Niacin by FDA is not recognized or proposed as a strong CYP inhibitor please check.

https://www.fda.gov/drugs/drug-interactions-labeling/drug-development-and-drug-interactions-table-substrates-inhibitors-and-inducers#table3-2

I think this paper (maybe not exactly the case of Simcor) concludes the situation very well:

"There is a small pharmacokinetic drug interaction between ER niacin and ezetimibe/simvastatin and although this is not considered to be clinically significant, the concomitant use of these drugs should be appropriately monitored, especially during the niacin titration period."

Article Assessment of potential pharmacokinetic interactions of ezet...

Best regards

Tomasz

There are many iso enzymes that metabolism drug ,not necessarily the both Niacin and statin have same iso enzyme.

Important other important factor is the dose of Niacin may be very low to elicit metaboliic process.