The short version
22 companies supply this market — deep enough that no single failure threatens the supply. The generic price has fallen 68% in a year, to $0.7249 per unit — and generics that get this cheap tend to get abandoned rather than defended. The brand (Gralise) runs $14.67 per unit — 163× more. Put together: this looks like a healthy supply — the boring kind, which is exactly what you want.
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