Phenylephrine per se or Combined with Pregabalin Ameliorates Mononeuropathic Pain in Rats

Area of Science:

• Neuroscience
• Pharmacology

Background:

• Neuropathic pain (NP) affects 6.9-10% of the population, with current therapies often inadequately managing symptoms.
• The high number needed to treat (NNT) for existing NP treatments underscores the need for novel therapeutic strategies.
• Drug repurposing and combination therapies are crucial for enhancing treatment efficacy in NP management.

Purpose of the Study:

• To investigate the potential of phenylephrine (PE) as an analgesic agent for neuropathic pain.
• To evaluate the efficacy and safety of combining phenylephrine (PE) with pregabalin (PGB) for neuropathic pain treatment.
• To explore the underlying mechanisms of PE's action on neuropathic pain.

Main Methods:

• Intrathecal administration of phenylephrine (PE) in rats with mononeuropathic pain induced by partial sciatic nerve ligation.
• Assessment of PE's effects using selective α1- and α2-adrenoreceptor antagonists (prazosin and idazoxan).
• Ex vivo analysis of noradrenaline release and smooth muscle contraction in response to PE.
• Evaluation of oral PE and pregabalin (PGB) combination therapy in a rat model of mononeuropathy.

Main Results:

• Intrathecal PE significantly alleviated tactile allodynia in rats with neuropathic pain.
• Prazosin and idazoxan reversed the antiallodynic effects of PE, suggesting α-adrenoreceptor involvement.
• Oral PE and PGB combination therapy, but not individual treatments, acutely alleviated allodynia and showed enhanced efficacy upon chronic administration.
• The combination therapy was devoid of significant cardiovascular or motor side effects in preclinical models.

Conclusions:

• Phenylephrine (PE), particularly in combination with pregabalin (PGB), demonstrates significant promise for managing neuropathic pain in preclinical settings.
• The findings suggest a potential therapeutic role for PE, possibly through α-adrenoreceptor modulation, in alleviating neuropathic pain.
• Further research is warranted to elucidate pharmacokinetic interactions and confirm clinical efficacy and safety of the PE-PGB combination for neuropathic pain.