I ended up clicking this video and then landing on Chuck Norris's explination of why Bruce Lee died.
Apparently (according to chuck) he had a reaction between a muscle relaxant he was taking for a back injury he had previously, and a antibiotic given to him by his costar.
There's a completely different explanation involving an analgesic, but as it turns out Chuck's description actually has at least one person indirectly supporting that theory in a medical journal.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3581776/
Apparently antibiotics and muscle relaxants can create problems when used together.