The short version
Just 2 companies supply this market — thin enough that a single exit would be felt immediately. The price has fallen 33% in a year, to $1.05 per mL — and generics that get this cheap tend to get abandoned rather than defended. Historically, drugs in this position went on to a new shortage within 90 days about 0.4% of the time — roughly 3× the typical drug (0.1%).