The present invention relates to compounds of the formula (I) ##STR00001## or a tautomer or prodrug thereof, or a pharmaceutically acceptable salt of said compound, tautomer or prodrug, wherein: R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are each independently selected from H, halo, CN, CF.sub.3 and CONH.sub.2; compositions containing such compounds and the uses of such compounds as antiparasitic agents.