The serial designation "IP 190" is stamped on 500-milligram oral tablets of naproxen. Naproxen is prescribed for humans for the treatment of chronic back pain and a number of other conditions and works by reducing inflammation.
Naproxen is available in various dosage levels, but these have different stampings. IP189, for example, is stamped on the 375-milligram tablet. The drug is not classed as a controlled substance as its mechanism for action is as a nonsteroidal cyclooxygenase inhibitor, rather than as a narcotic or other drug with a high potential for abuse. Though pills can usually be identified by their stampings, any pill of unknown composition or origin should be safely disposed of rather than ingested.