Frakefamide TFA is a potent analgesic that acts as a peripheral active μ-selective receptor agonist. Frakefamide is unable to penetrate the blood-brain-barrier and enter the central nervous system[1][2].
Frakefamide (LEF576) yields a dose dependent increase in morphine appropriate responding to 50% at the highest dose tested (10 μmol/kg) after infusion durations of 2 min, whereas after 15 min infusions a maximum of 25% morphine appropriate responding was occasioned at 17.5 μmol/kg[1][2].
[1]. Modalen AO, et al. A novel molecule (frakefamide) with peripheral opioid properties: the effects on resting ventilation compared with morphine and placebo. Anesth Analg. 2005 Mar;100(3):713-7. [2]. Swedberg MD, et al. Drug discrimination: A versatile tool for characterization of CNS safety pharmacology and potential for drug abuse. J Pharmacol Toxicol Methods. 2016 Sep-Oct;81:295-305.