Ketorolac Tromethamine (KT) is a non-steroidal anti-inflammatory drug (NSAID), acting as a non-selective COX inhibitor, from the class of heteroaryl acetic acid derivatives. KT has short plasma half-life (t1/2 » 5.5 h) [1]. Colloidal drug delivery systems, including nanoparti- cles (NPs), are good drug delivery candidates as they can enhance safety and efficiency of local or systemic drug delivery [2]. Methods used for formulating NPs may vary; in this study a mechanical method, spray drying was applied. Spray drying is a rapid, reproducible, continuous method for generating NPs by transforming liquid substances into solid powders. Depending on characteristics of NPs and polymer which is used, they can control the release of the drug they carry. Controlled release of a drug may provide many advantages for therapeutic control by reducing dosing frequency and decreasing side effects. Eudragit RS 100 (ERS) is a copolymer of ethyl acrylate, methyl methacrylate and low content of methacrylic acid ester with quaternary ammonium groups. The ammonium groups are present as salts and make the polymers permeable [3]. In this study, KT loaded in situ gelling system with Pluronic F-127 and ERS NPs are produced by nano spray drying method and in vitro characteristics are evaluated.