Correct spelling for the English word "sterule" is [stˈɛɹuːl], [stˈɛɹuːl], [s_t_ˈɛ_ɹ_uː_l] (IPA phonetic alphabet).
Trade name for a flask-shaped glass capsule containing a sterile solution of an alkaloid or other drug, chiefly for hypodermic or ophthalmic use; the neck of the flask is broken when it is desired to use the solution.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.