▁we aker , ▁lower ▁aff inity ▁or ▁even ▁wh olly ▁non - eff ica cious ▁comp ound ▁respectively ; ▁but ▁due ▁to ▁find ings ▁that ▁oft ent imes , ▁when ▁used ▁together , ▁such ▁two ▁mut ually ▁inferior ▁changes ▁being ▁added ▁in ▁tan dem ▁to ▁one ▁analog ue ▁has ▁the ▁potential ▁to ▁make ▁the ▁result ant ▁derivative ▁display ▁much ▁greater ▁effic acy , ▁aff inity , ▁select ivity ▁& / or ▁strength ▁than ▁even ▁the ▁parent ▁comp ound ; ▁which ▁otherwise ▁was ▁comprom ised ▁by ▁either ▁of ▁those ▁two ▁altern ations ▁when ▁made ▁alone . ▁ ▁For ▁an ▁ex position ▁& ▁all usion ▁to ▁this ▁mechanism ▁observe ▁that ▁the ▁op io id ▁o xy cod one , ▁derived ▁from ▁code ine , ▁is ▁ 1 . 5 × — 1 . 7 × ▁the ▁anal ges ic ▁pot ency ▁of ▁morph ine ▁( an ▁op io id ▁to ▁which ▁code ine ▁is ▁by ▁comparison ▁only ▁ 8 % — 1 2 % ▁as ▁pot ent ▁relatively , ▁or ▁ 0 . 1 7 th ▁its ▁strength ▁in ▁r ats ); ▁yet ▁o xy cod one ' s ▁inter medi ates ▁in ▁its ▁synth esis ▁from ▁code ine ▁are : ▁ ⅓ ▁the ▁pot ency ▁of ▁code ine ▁( i . e . ▁code in one ); ▁ 0 . 1 3 ▁that ▁of ▁morph ine ▁( i . e . ▁ 1 4 - h ydro xy code ine ) ▁in ▁r ats ▁and ▁less ▁in ▁m ice ▁( to ▁illustrate : ▁the