Evaluation of topical anesthetics by laser-induced sensation: comparison of EMLA 5% cream and 40% lidocaine in an acid mantle ointment.
OBJECTIVE
Current techniques for assessing local anesthetics (e.g., pin-prick test) cannot elicit a specific afferent activity without contamination from mechanosensitive receptors. This study was aimed to validate the use of non-scarring laser pulses as a reproducible method to assess effectiveness of topical anesthetics by comparing EMLA 5% cream and 40% lidocaine ointment.


METHODS
Thirty-two evaluations per compound were achieved in a total of eight healthy subjects. Non-scarring pulses from a 585 nm Pulsed-dye laser and a double-frequency Nd:YAG laser were investigated as pain inducers and the results were statistically analyzed by using a Student t-test.


RESULTS
Discrimination of anesthesia was better assessed with the 1,064 nm Nd:YAG laser. Anesthesia obtained by EMLA 5% cream was significantly higher than for 40% lidocaine ointment (P <0.0001). For EMLA cream, the number of evaluations with complete anesthesia was twice as much as for 40% lidocaine.


CONCLUSIONS
Non-scarring laser pulses are reliable and reproductive pain inducers for assessing topical anesthetics showing a low intra-individual variation. This technique demonstrated that EMLA 5% cream is significantly more effective than 40% lidocaine ointment.
Laser Center, Dermatology Department, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.
E
E
Hernández
S
S
González
E
E
González
D000279:Administration, Cutaneous; D000538:Aluminum Silicates; D000772:Anesthesia, Local; D019162:Anesthetics, Combined / Q000008:administration & dosage*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D018592:Cross-Over Studies; D006801:Humans; D007834:Lasers; D008012:Lidocaine / Q000008:administration & dosage*; D000077442:Lidocaine, Prilocaine Drug Combination; D008465:Mechanoreceptors / Q000187:drug effects / Q000502:physiology; D009354:Neodymium; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D009824:Ointments; D017288:Pain Threshold / Q000187:drug effects; D011318:Prilocaine / Q000008:administration & dosage*; D015203:Reproducibility of Results; D012677:Sensation / Q000502:physiology*; D016037:Single-Blind Method; D012867:Skin / Q000187:drug effects / Q000294:innervation; D015019:Yttrium
D000538:Aluminum Silicates; D019162:Anesthetics, Combined; D000779:Anesthetics, Local; D000077442:Lidocaine, Prilocaine Drug Combination; D009824:Ointments; D011318:Prilocaine; D009354:Neodymium; D015019:Yttrium; D008012:Lidocaine