Doctor Patel is a mentioned-only character.
He is first mentioned by Mary Cooper in "The Luminous Fish Effect" (S01E04), who says she knows him from her church in Texas, and that he offers 50% discounts at his pharmacy to all the congregation. She says that he is the only 'colored' person in her church group.
He is later mentioned by Missy in "The Porkchop Indeterminacy" (S01E15) as the only other Indian person she had met.