NALFURAFINE

Formulation

The table below describes the formulation of nalfurafine hydrochloride and the controls morphine sulfate and gabapentin for the following in vivo experiments.

Experiment(s) Compound Dose(s) Correction factor Dose volume mL/kg Route Vehicle Suspension / Solution
Pharmacokinetics Nalfurafine 100, 1000 1.08 1 SC PBS Solution
µg/kg
Irwin (1-30 µg/kg), Nalfurafine 1, 3, 10, 30 1.08 1 SC PBS Solution
Rotarod (1-30 µg/kg) µg/kg
Irwin (100-3000 µg/kg), Nalfurafine 100, 300, 1000, 3000 1.08 3 SC PBS Solution
Rotarod (100-3000 µg/kg) µg/kg
Plantar incision, Nalfurafine 0.3, 1, 3, 10 1.08 1 SC PBS Solution
L5/L6 SNL µg/kg
Plantar incision Morphine 6 mg/kg 1.33 1 SC Saline Solution
L5/L6 SNL Gabapentin 60 mg/kg 1.00 1 PO Saline Solution

L5/L6 SNL = L5/L6 spinal nerve ligation; PO = per os; SC = subcutaneous; PBS = phosphate buffered saline (pH 7.2)


Results

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Method: Protein binding
A table shows the results of rapid equilibrium dialysis to assess protein binding and percent recovery of nalfurafine. In rat plasma, nalfurafine was 67.3% bound to protein and 32.7% unbound and had a recovery of 102.3%. In rat brain homogenate, nalfurafine was 39.5% bound to protein and 60.5% unbound and had a recovery of 97.4%. Analysis of nalfurafine returned values consistent with literature values.

Method: Rotarod Animals were balanced across treatment groups based on body weight. Animals that achieved a latency of 40 seconds during the baseline trial were included in the study. Experimenters assessing behavior were masked to treatment. Group size was determined using power analysis.
Two graphs show the latency for male or female rats to fall off a rotarod apparatus. Responses are shown at the following time points: baseline (before treatment) and at 30, 60, and 90 minutes after treatment with vehicle (phosphate buffered saline, delivered SC) or nalfurafine (1, 3, 10, or 30 μg/kg, delivered SC). There were 10 rats per group. Males but not females had a significant interaction of time x treatment in a two-way repeated measures ANOVA. In males, the latency to fall in the 30 μg/kg nalfurafine group was approximately 30 seconds at each post-treatment time point, but this was not significantly different from the 40 second latency seen in the vehicle group. Data were analyzed using GraphPad Prism version 10.0.2.

Method: Rotarod Animals were balanced across treatment groups based on body weight. Animals that achieved a latency of 40 seconds during the baseline trial were included in the study. Experimenters assessing behavior were masked to treatment. Group size was determined using power analysis.
Two graphs show the latency for male or female rats to fall off a rotarod apparatus. Responses are shown at the following time points: baseline (before treatment) and at 30, 60, and 90 minutes after treatment with vehicle (phosphate buffered saline, delivered SC) or nalfurafine (100, 300, 1000, or 3000 ìg/kg, delivered SC). There were 10 rats per group. A significant interaction of time x treatment was found in a two-way repeated measures ANOVA for each sex. Dunnett’s tests found a significant decrease in latency to fall relative to the vehicle group in males at 30 minutes post-treatment with 300, 1000, or 3000 ìg/kg nalfurafine (p<0.05, 0.0001, 0.0001, respectively); at 60 minutes post-treatment with 300, 1000, or 3000 ìg/kg nalfurafine (p<0.05, 0.0001, 0.0001, respectively); and at 90 minutes post-treatment with 1000 ìg/kg nalfurafine (p<0.0001) and 3000 ìg/kg nalfurafine (p<0.0001). Dunnett’s tests found a significant decrease in latency to fall relative to the vehicle group in males at 30 minutes post-treatment with 1000 ìg/kg nalfurafine (p<0.05) and 3000 ìg/kg nalfurafine (p<0.0001); at 60 minutes post-treatment with 300, 1000, or 3000 ìg/kg nalfurafine (p<0.01, 0.01, 0.001, respectively); and at 90 minutes post-treatment with 100, 300, 1000, or 3000 ìg/kg nalfurafine (p<0.05, 0.0001, 0.0001, 0.0001, respectively).


This work was conducted by PsychoGenics Inc. (Paramus, NJ) in collaboration with PSPP, NINDS, NIH under contract # 75N95019D00026 and 75N95024D00038. Prescribing information for clinically used controls can be found at labels.fda.gov. Information for icons representing experimental design details can be found through the NINDS Office of Research Quality https://go.nih.gov/Yw2tHGI.