Fuente: WIPO "tomato" The present invention concerns the field of antibodies. More specifically, it relates to an antibody which specifically binds to a hapten being fentanyl or a derivative thereof, said antibody binding to the hapten with an equilibrium dissociation constant (Kd) of at most 1.000 pM, at most 800 pM, at most 600 pM, at most 400 pM, at most 200 pM, at most 100 pM or at most 75 pM, wherein the binding pocket for the hapten comprises amino acids from all three complementary determining regions (CDRs) of each chain. The present invention also relates to a polynucleotide encoding said antibody, a vector or expression construct comprising the poly-nucleotide, a host cell comprising the polynucleotide or the vector or expression construct or a non-human transgenic organism comprising said polynucleotide or said vector or expression construct. The invention also relates to said antibody or said polynucleotide for use as a medicament for treating and/or preventing a disease or condition in a subject associated with administration fentanyl or a derivative thereof.