TABLE 5

Nalmefene and naloxone: a comparison of affinities at μ opioid receptors and pharmacokinetic properties following intranasal administration

ParameterNalmefeneNaloxone
Ki (nM)1.0a5.4a
t1/2 (h)7.11b2.08c
Tmax (h)0.25b0.5c
Cmax (ng/ml)4.45b4.83c
  • a Ki values were estimated using [3H]alvimopan binding to cloned human μ opioid receptors (Cassel et al., 2005). The ∼5-fold higher affinity of nalmefene compared with naloxone is consistent with both Ki values obtained (0.13 and 0.62 nM, respectively) using [3H]DAMGO as a radioligand in monkey brain membranes (Emmerson et al., 1994) and pA2 values of 9.38 and 8.51, respectively, in functional assays using guinea pig ileum and mouse vas deferens (Toll et al., 1998).

  • b Data from Table 2.

  • c Data from https://www.accessdata.fda.gov/drugsatfda_docs/label/2015/208411lbl.pdf.