Compounds and methods for use in detecting gabapentin

A compound or a salt thereof for use in a gabapentin immunoassay for detecting the presence or absence of gabapentin in a sample, wherein the compound has the structure:

• wherein:
• R1, R2, or R3 is -X-W-L-Z,
• when R1 is -X-W-L-Z, X is NH, and R2 is —OH, and R3 is —H,
• when R2 is -X-W-L-Z, X is NH, R1 is —NH2, and R3 is —H, and
• when R3 is -X-W-L-Z, X is a heteroatom or lower alkyl group, R1 is —NH2, and R2 is —OH;
• W is a lower alkyl group or a carbonyl group;
• L is a linker or at least one bond between W and Z;
• and
• Z is a detectable label, wherein the detectable label comprises a fluorophore, a radioisotope, or a metal particle and wherein said fluorophore is selected from the group consisting of fluorescein derivatives, rhodamine derivatives, phycoerythrin, and Texas red.