Side-effects of analgesic kyotorphin derivatives: advantages over clinical opioid drugs.

The adverse side-effects associated with opioid administration restrain their use as analgesic drugs and call for new solutions to treat pain. Two kyotorphin derivatives, kyotorphin-amide (KTP-NH₂) and ibuprofen-KTP-NH₂ (IbKTP-NH₂) are promising alternatives to opioids: they trigger analgesia via an indirect opioid mechanism and are highly effective in several pain models following systemic delivery. In vivo side-effects of KTP-NH₂ and IbKTP-NH₂ are, however, unknown and were evaluated in the present study using male adult Wistar rats.