Abstract: AIMTo evaluate the feasibility and accuracy of continuous monitoring of drug with a fiber optic chemical sensor (FOCS) in animal. METHODSAn accurate optical design was used to enhance the intensity of light from a 100-micron optic fiber and the fluorescence signal could be detected. A new sol-gel method was used to fix the fluorescence substance 4-(N,N-dioctyl)amino-7-nitrobenz-2-oxa-1,3-diazole (D-70) on the body fiber. The vary quenching means the vary of the concentration of adriamycin (ADM) in rabbit blood. ADM was determined by FOCS based on the fluorescence multiple quenching. In a simple animal model, the carotid artery was catheterized with a cannula, housing a 100-micron optic fiber. RESULTSThe recovery of ADM was 99.4%～106.2%,the within-run and between-run RSDs were 6.6%～11.4% and 5.9%～11.7% respectively. The method permitted detection limits as low as 0.057 μg·mL^-1 at a signal-to-noise ratio of 3. CONCLUSIONFiber-optic chemical sensor is potentially useful for monitoring blood drug in biomedical field.