Open flow microperfusion (OFM) is an in-vivo sampling technique used to collect tissue-specific concentrations of molecules regardless of molecular weight or lipophilicity. It works by push pull perfusion through patented membrane-free probes. OFM probes have macroscopic openings that allow the perfusate to mix directly with surrounding interstitial fluid (ISF). Continuous and repeated sampling of bound and unbound drugs, neurotransmitters, antibodies, peptides, cells, and other molecules. OFM reduces cost and development time by providing the pharmacological profile of a drug at an earlier phase in drug development. Combine with BASi’s Movement Responsive Caging System, RaturnTM, and Fraction Collector for a hands-free approach to sample collection in awake, freely moving animals.