查看Ch75 Dermatological Pharmacology的源代码

=== Capsaicin (辣椒素) ===

Capsaicin is an alkaloid derived from plants of the Solanaceae family (i.e., hot chili peppers). Capsaicin interacts with the transient receptor potential vanilloid type 1 (TRPV1) receptor on C-fiber sensory neurons. TRPV1 is a ligand-gated nonselective cation channel of the TRP family, modulated by a variety of noxious stimuli. Chronic exposure to capsaicin first stimulates and then desensitizes this channel to capsaicin and diverse other noxious stimuli. Capsaicin also causes local depletion of substance P, an endogenous neuropeptide involved in sensory perception and pain transmission. Capsaicin (cream, lotion, gel, roll-on, and transdermal patch) is FDA-approved for the temporary relief of minor aches and pains associated with backache, strains, and arthritis. It is also approved in patch form by prescription for postherpetic neuralgia and is used for off-label treatment of painful diabetic neuropathy and some forms of pruritus.

<b style=color:#f80>辣椒碱 (Capsaicin) </b>是一种来源于茄科植物（即辣椒）的生物碱。辣椒碱可与 C 纤维感觉神经元上的 TRPV1 受体相互作用。TRPV1 (Transient Receptor Potential Vanilloid, 瞬时受体电位香草素) 是 TRP 家族的配体门控非选择性阳离子通道，受各种有害刺激的调节。缓慢接触辣椒碱最初会刺激该通道，但很快该通道会对辣椒碱和其他各种有害刺激脱敏。辣椒碱还会导致 P 物质的局部耗竭，P 物质是一种参与感觉知觉和疼痛传递的内源性神经肽。辣椒碱（乳膏、化妆水、凝胶、滚珠和透皮贴剂）已获得 FDA 批准，用于<b style=color:#0b0>暂时缓解</b>与<b style=color:#f80>背痛</b>、<b style=color:#f80>拉伤</b>和<b style=color:#f80>关节炎</b>相关的轻微疼痛。它还被批准为<b style=color:#f80>贴剂</b>形式用于治疗<b style=color:#f80>带状疱疹后神经痛</b>，并用于<b style=color:#0b0>疼痛性</b><b style=color:#f80>糖尿病神经病变</b>和某些形式的瘙痒症的超适应症治疗。

<b style=color:#0cf>【注】</b>辣椒素可与辣椒碱互换使用。化学名：(反)-N-[(4-羟基-3-甲氧基苯基)-甲基]-8-甲基-6-壬烯基酰胺。分子式：C18H27NO3，极微溶于水 (30'C 60min 0.01mg/ml)，部分溶于乙醇 (25'C 60min 0.14mg/ml)，溶解度均随温度升高而增大，溶解度顺序：

 正丁醇 > 石油醚 > 乙酸丁酯、甲醇、乙醇、乙醚 > 乙酸乙酯 > 正己烷 > 水

辣椒碱在醇类溶剂、醚类溶剂和脂类溶剂中的溶解度均随溶剂碳链长度增加而增大，原因是随溶剂碳链长度增加，溶剂的极性逐渐降低，与弱极性辣椒碱的极性更加接近，根据相似相溶原理，辣椒碱的溶解度相应增加 。

药用乳膏辣椒碱含量为 10g:2.5mg，约 0.025%， 万分之2.5。其主要作用于 C 型感觉神经元（负责传导皮肤痛觉和瘙痒）的轴突，<b style=color:#0b0>耗竭 P 物质</b>（一种参与感觉知觉和疼痛传递的神经递质），<b style=color:#0b0>阻断痛觉传回中枢</b>。黄豆粒大小药效约 ４ 小时左右，药效过，痛觉会恢复，需再次涂抹黄豆粒大小。。。

[[文件:Capsaicin.jpg]]

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