The effects of the cutaneous application of EMLA cream (a eutectic mixture of lignocaine and prilocaine in their base form) were studied in volunteers. When tested by pin-prick, EMLA cream 2.5% and 5% produced analgesia of the area tested, the cream being most effective if left in contact with the skin for 60 min. The pain produced by the insertion of an i.v. cannula was successfully blocked by the application of this formulation, especially if applied to the antecubital area. Temporary blanching of the skin areas was frequently observed on removal of the occlusive tape bandages, but prolonged, or repeated, application of 5% EMLA cream did not produce local skin reactions. Tests for delayed hypersensitivity reactions were negative. Plasma concentrations of lignocaine and prilocaine were low after a standard application.

The influence of intradermal needle insertion and fluid injection on skin blood flow was investigated using laser Doppler flowmetry. Seventeen healthy, young male volunteers participated. Four test sites on each forearm (volar surface) were used in a randomized, double-blind study. Recordings were made at 20, 40, 60 and in Group III also at 90 min after needle insertion or intradermal injection. In Group I (n = 6) different volumes of saline (0.05, 0.1, 0.2, 0.3 and 0.5 ml) were injected, producing an increase in flow, there being no differences between the various volumes. In Group II (n = 4) needle insertions were made using different needle sizes (20 G, 23 G and 30 G), the larger ones being impractical to use. Increases in flow were seen, and were somewhat higher for the larger needles. Group III (n = 12) was studied regarding the effects of three local anaesthetic agents on skin blood flow (0.1 ml, 30 G needle). Injection of bupivacaine 0.75% produced a marked increase in flow, similar to lidocaine 1% but apparently longer lasting. Bupivacaine 0.25% caused less increase in flow, similar to the flow seen with saline. Injections of ropivacaine 0.75% and 0.25%, i.e. in clinical concentrations, caused a decrease in blood flow, this being most marked after 0.25%, indicating a unique flow-decreasing effect of this new local anaesthetic drug.

Ropivacaine, a new long-acting amino-amide local anaesthetic agent, and bupivacaine, in various concentrations with or without addition of adrenaline, were tested in a randomized, double-blind study using intradermal wheals. Ten non-smoking, healthy, young male volunteers participated. In series I plain solutions of ropivacaine (0.25%, 0.5%, 0.75% and 1%) and bupivacaine (0.25%, 0.5% and 0.75%) were injected intradermally and in series II the same concentrations, with the addition of adrenaline 5 ug.ml-1 (1:200,000), were used. The same volunteers took part in both series, with an interval of at least three weeks between the experiments. Saline was included as control in both series. Pin-pricking was used to assess the dermal analgesia. Plain solutions of ropivacaine produced significantly longer durations of dermal analgesia than did plain solutions of bupivacaine, in all tested concentrations. A significant increase in duration was seen for both local anaesthetics when adding adrenaline. Local vascular effects at the injected areas were determined by visual inspection (nil, pink, pale). Local blanching (pale) was significantly more frequent for plain solutions of ropivacaine, in all tested concentrations. Local redness (pink) was significantly more frequent with plain bupivacaine, in a dose-dependent relation. An initial redness was frequently observed for both local anaesthetics containing adrenaline, followed by blanching at most sites.

No abstract

A 5% eutectic mixture of the two local anaesthetics lidocaine and prilocaine (EMLA, Astra Läkemedel AB) has been tested for application to the skin in the removal of split skin grafts. EMLA is an oil-in-water emulsion cream, containing 50 mg of active substances per ml (25 mg lidocaine, 25 mg prilocaine). The cream has been used on the donor sites of 146 patients and was applied a minimum of 1 h 30 min before surgery. 123 patients (84.3%) experienced adequate analgesia, feeling only the pressure of the dermatome or slight pain without objection to the skin graft being cut. 20 patients (13.7%) described the pain as being moderate, but the operation could be completed without further local or general anaesthesia. Three patients (2.0%) needed additional anaesthesia. Six patients complained of slight transient irritation immediately after application. After removal of the cream, erythema was present in 42 patients, pallor in 62 and oedema in 14. The concentrations of lidocaine and prilocaine in the blood were measured in 106 patients and did not exceed 1100 ng ml-1 for lidocaine and 200 ng ml-1 for prilocaine. There were no systemic side-effects.