Stability of Opioid Growth Factor ([Met 5 ]‐Enkephalin) in Solution Using HPLC and Photodiode Array Detection

A reversed phased HPLC method with photodiode array detection was used to monitor the stability of opioid growth factor (OGF; [Met 5 ]-enkephalin) in sterile saline for 1, 2, and 8 weeks, and stored at -17°C, 4°C, and 23°C. Samples maintained at -17°C had 97% of the initial OGF concentration after 2 months, whereas those stored at 4°C had 94% of the original concentration. Preparations housed at 22°C had reductions of 6–12% by the 8th week. These data provide important information about storage of OGF for clinical applications.