Correct spelling for the English word "ludyl" is [lˈʌdɪl], [lˈʌdɪl], [l_ˈʌ_d_ɪ_l] (IPA phonetic alphabet).
Trade name of an organic arsenical compound having properties similar to those of galyl and, like the latter, employed in the treatment of syphilis and diseases of protozoal origin.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.