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Not sure if there's RAW for this specific scenario, but I see the course of the poison (onset, saving throw frequency, number of saves) as representing the poison's metabolism. Therefore, if a character is still saving against the poison when they are ingested, it is not fully metabolized. In this case the ingesting creature might be subject to the poison. I'd set a few restrictions on that, though.
1) The ingesting creature has to kill the hero, since otherwise not enough poison would be released from the living hero's body to affect the ingesting creature.
2) The poison has to be deliverable by ingestion (Ingestion or Contact poison).
3) The ingesting creature gets the remaining dose of the poison, and therefore only has to make the number of saves vs the poison that the hero had remaining to make.
4) IIRC creatures are immune to their own poisons, and therefore a hero poisoned by a creature and then eaten by that same creature can't poison it back.
Like I said, this isn't RAW, but it feels reasonable to me.