Compounds of formula 1 are modulators of P2X3 useful for the treatment of pain and genitourinary, gastrointestinal, and respiratory disorders: ##STR00001## wherein R.sup.1 is --C(.dbd.S)CH.sub.3, pyridyl, pyrimidinyl, pyrazinyl, thiazolyl, furyl, furylcarbonyl, acetyl, or carbamoyl; R.sup.2a and R.sup.2b are independently H, methyl, or ethyl; R.sup.3 is H or methyl; Y is a bond, --(CR.sup.4R.sup.5).sub.n-- or --CR.sup.4.dbd.CR.sup.5--; wherein R.sup.4 and R.sup.5 are each independently H or methyl and n is 1 or 2; X is N or CH; A is phenyl, 5-membered heterocyclyl, or 6-membered heterocyclyl; R.sup.6, R.sup.7 and R.sup.8 are each independently H, halo, lower alkyl, cycloalkyl, alkylthio, alkylthio-lower alkyl, alkylsulfonyl-lower alkyl, di(lower alkyl)amino-lower alkyl, morpholinyl-lower alkyl, 4-methyl-piperazinyl-methyl, trifluoromethyl, pyridyl, tetrazolyl, thiophenyl, phenyl, biphenyl, or benzyl (where thiophenyl, phenyl and benzyl are substituted with 0-3 lower alkyl, halo, sulfonamido, trifluoromethyl, lower alkoxy or lower alkylthio) or R.sup.6 and R.sup.7 together form a 5-membered or 6-membered carbocyclic or heterocyclic ring substituted with 0-3 substituents selected from the group consisting of lower alkyl, lower alkoxy, oxo, halo, thiophenyl-lower alkyl, phenyl, benzyl (where phenyl and benzyl are substituted with 0-3 lower alkyl, halo, sulfonamido, trifluoro-methyl, lower alkoxy, lower alkylthio, amino-lower alkyl, lower alkylamino-lower alkyl, or di(lower alkyl)amino-lower alkyl); and pharmaceutically acceptable salts thereof; wherein when R.sup.1 is pyrimidin-2-yl, X is N, Y is a bond and A is oxazol-5-yl the carbon atom at position 4 in said oxazol-5-yl is not substituted by propyl when the carbon atom at position 2 in said oxazol-5-yl is substituted by substituted phenyl and the carbon atom at position 4 in said oxazol-5-yl is not substituted by phenyl when the carbon atom at position 2 is substituted by unsubstituted or substituted phenyl.