The correct spelling of the word "orsudan" is a bit tricky to decipher without the help of phonetic transcription. IPA phonetic notation would represent it as /ɔː.suː.dæn/. This could be interpreted as "or-sue-dan" in English orthography. By breaking the word down into its individual sounds, you can see that the "or" sound is different from "oar" and that the final syllable is spelled with a "dan" instead of "den". Careful attention to IPA phonetic transcription can help avoid errors in spelling and pronunciation.
An atoxyl derivative, containing one more methyl group than arsacetin; given in syphilis in intramuscular injections of gr. 10 (0.6).
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.