EFFECTS OF SUBCUTANEOUS VERAPAMIL ON THE DURATION OF LOCAL-ANESTHETICBLOCKADE

Study Objectives: To determine whether a subcutaneous injection of ver apamil will provide local anesthesia and whether a mixture of lidocain e and verapamil will prolong the anesthetic effect of lidocaine alone. Design: Randomized, double-blind, placebo-controlled study. Setting: Preanesthetic area of a large metropolitan teaching hospital. Patients : 20 volunteers. Interventions: All volunteers received 4 injections o f normal saline, verapamil, lidocaine, and lidocaine-verapamil at the volar aspect of the forearm. The sites were tested with a 26-gauge nee dle to be sure the sensation of sharp could be appreciated. The inject ions were performed in a randomized, double-blind fashion using a ster ile technique. The 4 areas were tested at 1-minute intervals using a 2 6-gauge needle until the sensation of sharp was again perceived. Measu rements and Main Results: Injection sites were examined for the presen ce and degree of erythema. Volunteers were asked to rate the degree of pain felt during and immediately after injection. The time elapsed un til the person was again able to perceive sharp from a 26-gauge needle prick was measured at all 4 sites. When compared with the effects of normal saline, subcutaneous verapamil provided local anesthesia to pin prick. The mixture of verapamil and lidocaine also provided anesthesia to pinprick, but the duration of effect was less than that provided b y lidocaine alone. The use of verapamil alone and in combination with lidocaine was associated with a marked degree of erythema and edema. C onclusions: Verapamil injected subcutaneously provides a degree of loc al anesthesia. However, this effect is hampered by a local reaction at the injection site and a short duration of action. The mixture of lid ocaine and verapamil provides a shorter duration of action than does l idocaine alone.