Effects of subcutaneous verapamil on the duration of local anesthetic blockade

To determine whether a subcutaneous injection of verapamil will provide local anesthesia and whether a mixture of lidocaine and verapamil will prolong the anesthetic effect of lidocaine alone.

Randomized, double-blind, placebo-controlled study.

Preanesthetic area of a large metropolitan teaching hospital.

20 volunteers.

All volunteers received 4 injections of normal saline, verapamil, lidocaine, and lidocaine-verapamil at the volar aspect of the forearm. The sites were tested with a 26-gauge needle to be sure the sensation of sharp could be appreciated. The injections were performed in a randomized, double-blind fashion using a sterile technique. The 4 areas were tested at 1-minute intervals using a 26-gauge needle until the sensation of sharp was again perceived.

Injection sites were examined for the presence and degree of erythema. Volunteers were asked to rate the degree of pain felt during and immediately after injection. The time elapsed until 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 pinprick. The mixture of verapamil and lidocaine also provided anesthesia to pinprick, but the duration of effect was less than that provided by lidocaine alone. The use of verapamil alone and in combination with lidocaine was associated with a marked degree of erythema and edema.

Verapamil injected subcutaneously provides a degree of local anesthesia. However, this effect is hampered by a local reaction at the injection site and a short duration of action. The mixture of lidocaine and verapamil provides a shorter duration of action than does lidocaine alone.