Topical anaesthesia of intact skin: liposome-encapsulated tetracaine vs EMLA.
In this randomized, double-blind study, we have compared the ability of 5% liposome-encapsulated tetracaine (amethocaine) (LET) vs 5% eutectic mixture of local anaesthetics (EMLA) to produce local anaesthesia of intact skin in 40 healthy volunteers. Volunteers had both preparations applied to their forearms under an occlusive dressing for 1 h. Superficial anaesthesia was measured by a total of nine 1-mm pinpricks on each arm. Deeper anaesthesia was assessed by single insertion of a sterile 22-gauge needle to a depth of 3 mm and pain was reported on a visual analogue scale (VAS). If the volunteer perceived greater than four of the 1-mm pinpricks, the 3-mm insertion was not performed. Results showed that the number of pinpricks perceived was significantly less (P < 0.01) for LET (median 1.0; range 0-9) vs EMLA (1.5; 0-9). In volunteers who had deeper anaesthesia assessed, there was no significant difference (P = 0.065) in VAS scores for LET (mean 1.5 (SD 1.4); n = 34) vs EMLA (2.4 (2.1); n = 28). Overall anaesthetic effect, as ranked by all of the subjects, was significantly better for LET compared with EMLA (P = 0.024). We have demonstrated that when applied in equal volumes, 5% LET produced better superficial local anaesthesia than EMLA.
Fisher
R
R
Memorial University of Newfoundland, St John's, Canada.
Hung
O
O
Mezei
M
M
Stewart
R
R
D000279:Administration, Cutaneous; D000328:Adult; D000772:Anesthesia, Local / Q000379:methods; D000779:Anesthetics, Local / Q000008:administration & dosage*; D004311:Double-Blind Method; D004337:Drug Carriers; D005260:Female; D006801:Humans; D008012:Lidocaine; D000077442:Lidocaine, Prilocaine Drug Combination; D008081:Liposomes; D008297:Male; D008875:Middle Aged; D009824:Ointments; D011318:Prilocaine; D013748:Tetracaine / Q000008:administration & dosage*
D000779:Anesthetics, Local; D004337:Drug Carriers; D000077442:Lidocaine, Prilocaine Drug Combination; D008081:Liposomes; D009824:Ointments; D011318:Prilocaine; D013748:Tetracaine; D008012:Lidocaine