Osmotic minipumps containing methadone or saline were implanted in pregnant rats on E16. Pups were born and serum collected on P10(A-D) and P21 (E-H). Using a translational multiplex electrochemiluminescent platform, biomarkers were assayed. On P10, those pups exposed to perinatal methadone had significantly increased IL-1β (A), TNFα (B), IL-6 (C) and CXCL1 (D) compared to saline pups. By P21, serum levels of IL-1β (E) remained significantly increased compared to methadone pups, while other cytokines and chemokines normalized. These data reflect significant and persistent increases in pro-inflammatory proteins in the serum throughout the perinatal period, consistent with a diverse inflammatory response syndrome. *p<0.05, **p<0.01, ***p<0.001, n=3–4/group.