皮內注射metoclopramide有局部麻醉之作用：與lidocaine之比較

The Intradermal Local Anesthetic Effect of Metoclopramide: A Comparison with Lidocaine

靜脈內存留metoclopramide與靜脈內存留lidocaine一樣，有效地防止 propofol 之注射痛。但此種週邊之作用機轉，文獻從未提及。以雙盲之方式，我們在十位自願者之前臂皮膚內注射metoclopromide2.5毫克，lidocaine 5毫克，及生理鹽水0.5西西，注射痛與其局部麻醉之程度（針刺，輕觸，冷覺）予以定時測量。0.5% metoclopramide 和1% lidocaine一樣，在皮膚內注射時，前15分鐘比起生理鹽水有降低針刺，輕觸，冷覺之作用（p<0.01）。在皮膚內注射0.5% metoclopromide 和1% lidocaine 一樣，可產生局部麻醉之作用。

Metoclopramide administered intravenously immediately before injection of propofol;mixed with propofol;or after a rubber tourniquet for one minute before propofol injection, may reduce propofol injection pain. These 3 techniques were compared with lidocaine respectively. Metocloprarmide is a commonly used peri-operative anti-emetic. The mechanism of its analgesic effect in reducing propofol injection pain was not clearly elucidated, although a local anesthetic activity was suggested by speculation. We,therefore, undertook the following study to further evaluate whether metoclopramide processes the local anesthetic effect by intradermal injection. Lidocaine was used for comparison and normal saline was used as a control. Metoclopramide 2.5 mg, lidocaine 5 mg and normal saline (all in 0.5 ml volume) in a random order on the forearm of 10 healthy volunteers. Pain on injections and the degree of local anesthesia (tested by pinprick, light touch and cold) at each site was reported on a 0-4 scale at designated intervals. We found that 0.5% metoclopramide, similar to 1% lidocaine, demonstrated loss of sensations of pin prick, light touch and cold for 15 min after intradermal injection as compared with normal saline (p<0.01). We concluded that intradermal injection of commercially available metoclopramide, similar to lidocaine, can produce local anesthetic effect.