Disclosed are benzoxazines and benzothiazines of formula (I) wherein Q is O-(CHR6)1-3 or S-(CHR6)1-3, R1 andeach R 6 is H, optionally substituted [C1-6 alkyl, C1-4alkaryl, C1-4alkheterocyclyl, C2-9 heterocyclyl, C3-8 cycloalkyl, C1-4 alkcy-cloalkyl] or -(CR1A R1B)nNR1c R1D wherein R1A R1B R1C R1D are independentlyhydrogen, optionally substituted [C1-6 alkyl,C1-4alkaryl, Cl-4 alkheterocyclyl, C2-9 heterocyclyl, C3-8 cycloalkyl, etc ]or wherein R1A and R1B combine to form =0, or whereinR1C and R1D combine to form an optionally substituted C2-9 heterocyclyl, and nis an integer between 1-6, each of R2 and R3 is H,hal, optionally substituted [C1-6 alkyl, C6-10aryl, C1-6alkaiyl, C2-9heterocyclyl, C1-6 alkoxy, C1-6 thioalkoxy, (CH2)r2NHC(NH)R2A,CH2)r2NHC(S)NHR2A, Cl-4 alkheterocyclyl] or hydroxy, wherein r2 is an integerfrom 0 to 2, R2A is optionally substituted [C1-6alkyl, C6-10aryl, C^alkaryl, C2-9 heterocyclyl, C1-4 alkheterocyclyl,C1-6thioalkoxy, Cl-4 thioalkaryl, aryloyl, Cl-4thioalkheterocylyl,or amino], each R4 and R5 is H, hal, (CH2)r2NHC(NH)R2A or CH2)r2NHC(S)NH R2A,Y' and Y 2 are together =0 or Y1 and Y2 areindependently H, optionally substituted [C1-6 alkyl, C6-10aryl, C1-6alkaryl,C2-9 heterocyclyl, C1-6 alkoxy, C1-6 thioalkoxy,C1-4alkheterocyclyl] or hydroxy； wherein only one of R2 , R3, R4 and R5 is(CH2)r2NHC(NH)R2A or CH2)r2NHC(S)NH R2A, or apharmaceutically acceptable salt or prodrug thereof Said benzoxazines andbenzothiazines of formula (I) inhibitnitric oxide synthase (N O S), particularly selectively inhibit neuronalnitric oxide synthase (n N O S) in preference to other N O S iso-formsThe N O S inhibitors of formula (I), alone or in combinatioon with otherpharmaceutically active agents, can be used fortreating or preventing various medical conditions
