Under stressful conditions, many cells release adenosine to minimize tissue damage. Inhibition of intracellular adenosine kinase (AK) increases the local extracellular concentration of adenosine and its effect on traumatized tissue. The synthesis and SAR of a new series of pyridopyrimidines for the inhibition of AK are described. It was found that a range of analogs with position five substituted by an amine or ether functionality increased aqueous solubility while retaining the in vitro potency of initial leads. A narrower range of analogs was active in vivo in a rat inflammatory hyperalgesia model.