After Indra forces down Soma that Tvashtri had bewitched, his energies flow out of his limbs and become animals, plants and metals. Namuchi takes the remainder with sura. The gods ask the two Ashvins, as physicians, and Sarasvati, as healing medicine, to cure him; each asks a fee and receives the goat and the ram, the bull staying with Indra. The three take the power back from Namuchi and restore it. The rite built on this is the Sautramani. An earlier passage (5.5.4.16) says Sarasvati is speech and the cure was by speech.
Indra befriends Namuchi with an oath not to kill him with wet or dry, by night or day, then beheads him with foam in a mist. The head follows him crying that he has killed a friend. Brahma sends him to the Aruna, a stream the sages had purified and Sarasvati had filled with her water. Indra sacrifices and bathes at the confluence and is freed; the head falls into the same stream and Namuchi gains lasting worlds.
What is different here:
Indra is guilty, not ill; Sarasvati heals as a river bathed in, not as a physician; no Ashvins; the demon is also blessed.
Sources: The Satapatha-Brahmana, tr. Julius Eggeling (Sacred Books of the East 12, 41); Hymns of the Rigveda, tr. R. T. H. Griffith (1896), hymns read for the Vedic layer; The Mahabharata, tr. K. M. Ganguli (1883-96), sections read for the Vedic layer