PURPOSE: To provide a sulfonamide compd. which inhibits endothelin and is useful esp. for treating hypertension.

CONSTITUTION: A compd. of formula I [wherein R is a phenyl, naphthyl, or biphenyl group optionally substd. by R1, R2, and R3; and R1 to R5 and R12 are each H, alkyl, alkenyl, alkynyl, cycloalky, aryl, aralkyl, halo, OH, CN, NO2, C(O)H, C(O)R6, CO2H, CO2R6, SH, S(O)nR6, S(O)m-OH, S(O)m-OR6, O-S(O)m0R6, O-S(O)m-OH, O-S(O)m-OR6, Z4-NR4R8, or Z4-N(R11)-Z5-NR9R10 provided R4 may combine with R5 to form alkylene or alkenylene to thereby form, together with the carbon atoms to which they are bonded, a 4- to 8-membered arom. ring, and so may R5 with R12] [e.g. N-(6-chloro-3-pyridazinyl)-5-dimethylamino-1- naphthalenesulfonamide] is provided. The compd. is obtd. by subjecting a compd. of the formula: R-SO2NH2 and a compd. of formula II to coupling in an anhydrous solvent in the presence of a base.