Synergistic Interaction Between Justicia spicigera Extract and Analgesics on the Formalin Test in Rats

Area of Science:

• Pharmacology
• Natural Products Chemistry
• Pain Management

Background:

• Combining analgesics with distinct mechanisms can enhance efficacy and reduce side effects.
• Investigating natural product and pharmaceutical combinations is crucial for novel pain therapies.

Purpose of the Study:

• To evaluate the antinociceptive effect of combining Justicia spicigera extract (JSE) with naproxen (NPX) or tramadol (TML) in a rat formalin test.
• To explore the underlying mechanisms, including IL-1β and COX2 levels, and the pharmacokinetic interactions.

Main Methods:

• The formalin test in rats was used to assess antinociceptive effects of JSE, NPX, TML, and their combinations.
• Dose-response curves and ED50 values were determined for various NPX:JSE and TML:JSE ratios.
• Western blot analysis measured IL-1β and COX2 levels; pharmacokinetic studies assessed NPX parameters with JSE.

Main Results:

• The NPX:JSE combination (1:3 ratio) exhibited the strongest synergistic effect (index 0.501) and lowest ED50 (73.82 mg/kg).
• The TML:JSE combination (1:3 ratio) also showed synergy with an ED50 of 29.5 mg/kg.
• JSE combination with NPX reduced COX2 and IL-1β levels without altering NPX pharmacokinetics.

Conclusions:

• The combination of Justicia spicigera extract and naproxen displays significant synergistic antinociceptive properties.
• This preclinical evidence suggests a potential therapeutic strategy for pain management by combining JSE with NPX, targeting COX2 and IL-1β pathways.
• The observed effects are achieved without adverse pharmacokinetic interactions with naproxen.