Analgesic effect of microneedle with 3-acetylaconitine for neuropathic pain

Neuropathic pain is a worldwide problem that causes physical and psychological pain to many patients. 3-acetylaconitine (AAC) is a kind of non-narcotic analgesic with long-lasting action, non-tolerant and non-addiction. However, it has some cardiac toxicity and can easily cause toxic organ damage. To solve these problems, dissolvable microneedle (MN) patches were prepared and delivered subcutaneously through the skin barrier. The results showed that the solid dispersion made with AAC and polyvinyl pyrrolidone (PVP) effectively changed the solubility of AAC and improved its bioavailability. The MN shape was conical and the bending forces of AAC/PVP-MN were all approximately 1.2 N/needle, which was enough to penetrate the stratum corneum of the skin. Through the use of the neuropathic pain model (spared nerve injury) test, it was found that the soluble MN mediated AAC hypodermic delivery provided effective analgesic activity. Compared with the model group, AAC/PVP-MN could increase mechanical pain threshold and hind legs load-bearing capacity, reduce the inflammation in the body, and have certain protective effect to spinal cord neurons. This study provided an idea for the clinical treatment of neuropathic pain and also a new approach for the safe use of toxic drugs with a narrow range.