Combined antiallodynic effects of Neurotropin®–tramadol and Neurotropin®–mirogabalin in rats with L5-spinal nerve ligation

We aimed to examine the efficacy of combination therapies of Neurotropin® with tramadol and Neurotropin with mirogabalin for neuropathic pain management. A neuropathic pain model (L5 spinal nerve ligation model: L5-SNL) using male Wistar rats was generated through tight ligation of the left fifth lumbar nerve using silk sutures. Mechanical allodynia was assessed using the 50% paw withdrawal threshold. The combined antiallodynic effects were evaluated using isobolographic analyses. Small intestinal transit was evaluated using the charcoal meal test, and motor coordination using the rota-rod test. Neurotropin (50–200 NU/kg, p.o.), tramadol (7.5–60 mg/kg, p.o.), and mirogabalin (3–30 mg/kg, p.o.) showed a dose-dependent antiallodynic effect in L5-SNL rats. The combined antiallodynic effects of Neurotropin and tramadol were additive or synergistic, whereas those of Neurotropin and mirogabalin were additive. Neurotropin (100–400 NU/kg, p.o.) did not affect the small intestinal transit, whereas tramadol (30–100 mg/kg, p.o.) significantly inhibited it. Neurotropin (100–400 NU/kg, p.o.) did not affect the walking time, whereas mirogabalin (10–100 mg/kg, p.o.) significantly decreased it. Neurotropin dose-dependently ameliorated mechanical allodynia in rats, and combination therapy with Neurotropin–tramadol or Neurotropin–mirogabalin may alleviate neuropathic pain without aggravating the adverse effects of tramadol and mirogabalin.