AbstrakPencampuran sediaan parenteral (iv admixture) yang sudah dilaksanakan secara umum di rumah sakit mempunyai kemungkinan terjadinya kegagalan baik berupa inkompatibilitas obat maupun gangguan stabilitas obat. Penelitian ini bertujuan mengetahui angka inkompatibilitas obat dalam pencampuran sediaan parenteral di RSUD Prof. Dr. Margono Soekarjo Purwokerto yang mengalami inkompatibilitas fisika yang teramati secara organoleptis. Penelitian ini merupakan penelitian deskriptif prospektif. Data yang telah dikumpulkan lalu dianalisis secara deskriptif. Dari 667 pencampuran sediaan parenteral di bangsal bedah saraf RSUD Prof. Dr. Margono Soekarjo selama bulan Februari 2010, dapat disimpulkan angka inkompatibilitas potensial sebesar 0,45% dan inkompatibilitas aktual sebesar 2,55%. Inkompatibilitas aktual yang terjadi berupa kristal 0,17%, endapan 0,17%, dan kabut sementara 2,04% pada pencampuran fenitoin dengan NaCl atau ringer laktat. However, it has a possibility of failures, like incompatibilities and changes in drug stabilities. The aim of this study was to determine the rate of drug incompatibilities in mixing parenteral preparations in neurosurgery ward in Prof. Dr. Margono Soekarjo Regional Public Hospital which undergo physical incompatibility observed in organoleptic. This study was a prospective descriptive research for one month period. Data were collected and analyzed descriptively. The results showed that from 667 parenteral admixtures in neurosurgery ward in Prof Dr Margono Soekarjo Hospital in February 2010, there were 0.45% potential incompatibility and 2.55% actual incompatibility happened. Actual incompatibility shown as crystal 0.17%, sediment 0.17%, and 2.04% was non-permanent haze in phenytoin and sodium chloride or ringer lactate admixtures.