Isotopically labeled bile acid derivatives

A compound of Formula I

• or a pharmaceutically acceptable salt thereof, wherein
• R1 is OH, O-glucuronide, OSO3H, SO3H, CO2R5, 14CO2R5, C(O)R6, 14C(O)R6;
• R2 is H, D, or OH;
• R3 is OH or O-glucuronide;
• R4 is OH or O-glucuronide;
• R5 is H or substituted or unsubstituted alkyl;
• R6 is NH(CH2)2SO3H, NHCH2CO2H, or N(CH3)CH2CO2H or glucuronic acid moieties,
• wherein hydrogens in can be replaced with deuterium;
• R11 is Z11b, hydroxy, halogen, alkoxy, or oxo when Z11a is not present;
• R16 is Z16a, hydroxy, halogen, alkoxy, or oxo when Z16b is not present;
• R23 is Z23a or alkyl;
• and
• Z1a, Z1b, Z2a, Z2b, Z3, Z4a, Z4b, Z5, Z6, Z7, Z8, Z9, Z11a, Z11b, Z12, Z14, Z15a, Z15b, Z16a, Z16b, Z17, Z18, Z19, Z20, Z21, Z22a, Z22b, Z23a, Z23b, Z24a, Z24b, or Z25 is independently selected from H (hydrogen) or D (deuterium), and at least one of Z1a, Z1b, Z2a, Z2b, Z3, Z4a, Z4b, Z5, Z6, Z7, Z8, Z9, Z11a, Z11b, Z12, Z14, Z15a, Z15b, Z16a, Z16b, Z17, Z18, Z19, Z20, Z21, Z22a, Z22b, Z23a, Z23b, Z24a, Z24b, or Z25 is D;
• and
• any carbon atom is 12C, 13C, or 14C.