PB
Both have been available in injectable form for years. See "parenteral" - it is indeed 10x stronger than fentanyl.
chrome-extension://oemmndcbldboiebfnladdacbdfmadadm/https://fpm.anzca.edu.au/documents/opioid-dose-equivalence.pdf
the injectable has been available since the mid 80s. Reason I recall is that the brand name for sufentanil was "Sufenta". "Souped up fentanyl".