Using sleeping gas on Seth makes sense when you realize overdosing on anesthetic is just as lethal as poison and the tube wasn't properly sealed, and thus a lethal dose might have become a survivable one.
Last screen appearance of Hoyt Axton (1938-1999)
The snake's name could be a reference to the Egyptian God, Seth, who was associated with the Serpent. His primary color that he was known for was the color Red, like the cobra in this film.
Pat Morita goes up against a giant Cobra, he previously fought against a Karate dojo that was called Cobra Kai in the Karate Kid franchise.