Hi cindirs,

According to Rising Pharmaceuticals, a manufacturer of Cyclobenzaprine, the expected shelf-life of the drug is 24 months (2 years).

Reference: https://risingpharma.com/product/2392/

However, there's actually a lot of conflicting information around the topic of expired medication/shelf-life of a drug. According to a Harvard Medical School family health article, except in rare cases (i.e. tetracycline), there is little chance of danger due to taking medications even up to 15 years beyond their expiration date. This conclusion was based upon a study conducted at the request of the US military due to stockpiles of expensive drugs they could otherwise need to replace every few years. The conclusion was that 90% of those drugs remained effective 10 - 15 years after the expiration date.

But the question is whether or not the drug you have happens to be one of these drugs from the study... (I have not seen the list of drugs used in this study).

Source: health.harvard.edu/fhg/updates/update1103a.shtml

How long have you had the Cyclobenzaprine for?