Topical lidocaine enhanced by laser pretreatment: a safe and effective method of analgesia for facial rejuvenation.

BACKGROUND: Injectable forms of anesthesia for nonsurgical facial rejuvenation, although efficacious, are uncomfortable for the patient. Preclinical studies have demonstrated that laser pretreatment at low energies enhances absorption of topical lidocaine. OBJECTIVES: The authors assess the safety and efficacy of laser-assisted transdermal delivery of topical anesthetic. METHOD: Ten patients were split into 2 groups (A and B). All patients received 15 g of BLT (20% benzocaine, 6% lidocaine, and 4% tetracaine triple anesthetic cream) for 20 minutes with no occlusion. Then the cream was removed and the first blood draw taken. Group A patients were pretreated with the full ablative laser and group B patients with a fractional ablative laser to the full face. A further 15 g BLT was applied for another 20 minutes. Group A patients then underwent full ablative laser treatment, and group B received fractionated ablative laser treatment. Blood draws were taken at 60, 90, 120, 180, and 240 minutes after the initial topical anesthetic application, and the serum was analyzed for lidocaine and monoethylglycinexylidide (MEGX) levels. Patients were asked to rate the pain felt at intervals during the procedure. RESULTS: No patient required supplemental nerve blocks. Pain scores were equivalent at the end of the first pass for both groups (P = .436). Group A patients had significantly lower pain scores at the start of the second laser treatment (P = .045), but pain scores became equivalent by the end (P = .323). Combined serum lidocaine and MEGX levels were significantly higher in group A patients up to 90 minutes (peak average of 0.61 µg/mL for group A and 0.533 µg/mL for group B; P = .0253), which corresponded to greater initial analgesic effect. CONCLUSIONS: Data from this study demonstrate that topical anesthetic for facial rejuvenation can be enhanced with laser pretreatment while maintaining safe blood serum levels. Further studies should examine optimal application amount and time to allow safe multipass facial rejuvenation without the need for invasive nerve blocks.

Development of lidocaine-coated microneedle product for rapid, safe, and prolonged local analgesic action.

PURPOSE: To demonstrate rapid (~1 min) lidocaine delivery using 3M's solid microstructured transdermal system (sMTS) for prolonged, local analgesic action. METHODS: Polymeric microneedles were fabricated via injection molding and then dip-coated using an aqueous lidocaine formulation. The amount of lidocaine coated onto the microneedles was determined by high performance liquid chromatography (HPLC). To assess drug delivery and dermal pharmacokinetics, lidocaine-coated microneedles were inserted into domestic swine. Skin punch biopsies were collected and analyzed to determine lidocaine concentration in skin using HPLC-mass spectrometry (LC-MS). Commercial lidocaine/prilocaine EMLA (Eutectic Mixture of Local Anesthetic) cream was used as comparative control. RESULTS: Lidocaine dissolves rapidly off the microneedles and into skin such that the 1-min wear time achieves or exceeds lidocaine tissue levels needed to cause analgesia. This therapeutic threshold (100 ng/mg) was estimated by measuring the total amount of lidocaine and prilocaine in skin following a 1 h EMLA application. When co-formulated with 0.03 wt% vasoconstrictor-epinephrine, the concentration of lidocaine in tissue was maintained above 100 ng/mg for approximately 90 min. CONCLUSIONS: 3M's sMTS can be used to provide rapid delivery of lidocaine for local analgesia up to 90 min.

Percutaneous penetration kinetics of lidocaine and prilocaine in two local anesthetic formulations assessed by in vivo microdialysis in pigs.

The aim of this study was to characterize and compare the percutaneous penetration kinetics of lidocaine (L) and prilocaine (P) in two local anesthetic formulations by in vivo microdialysis coupled with HPLC. The microdialysis system for studying lidocaine and prilocaine was calibrated by a no-net-flux method in vitro and retrodialysis method in vivo, respectively. A dosage of 0.2 g/cm2 of an in-house P-L formulation (2.5% lidocaine and 2.5% prilocaine, methylcellulose-based) and commercially available Eutectic Mixture of Local Anesthesia (EMLA, 2.5% lidocaine and 2.5% prilocaine, carbopol-based) was separately but symmetrically applied in the dorsal region of pigs. Saline (0.9%, w/v) was perfused into the linear microdialysis probe at a flow rate of 1.5 microl/min. Dialysate was collected upon topical application up to 6 h at 20-min intervals and assessed by HPLC. The results demonstrated the area under the concentration-time curve (AUC(0-6 h)) of lidocaine and prilocaine in EMLA was 71.95+/-23.36 microg h/ml and 38.01+/-14.8 microg h/ml, respectively, in comparison to 167.11+/-56.12 microg h/ml and 87.02+/-30.38 microg h/ml in the P-L formulation. The maximal concentrations (Cmax) of lidocaine and prilocaine in the dermis were 29.2+/-9.08 microg/ml and 16.54+/-5.31 microg/ml in EMLA and 80.93+/-17.98 microg/ml and 43.69+/-12.87 microg/ml in the P-L formulation, respectively. This study indicates a well-calibrated microdialysis system can provide vital real-time information on percutaneous drug delivery and specifically a methylcellulose-based P-L formulation can increase percutaneous absorption of both lidocaine and prilocaine in pigs compared to carbopol-based EMLA.

Estudio sobre la condición física de la combinación de anestésicos locales y opiáceos: sus implicancias teóricas en la anestesia subaracnoidea / Study on the physical condition of the combination local anesthetics'-opiates: its theoretical implicancies in the spinal anesthesia

La baricidad de los agentes anestésicos se relaciona con la condición física del líquido cefalorráquideo (LCR), modificándose nuestra práctica cotidiana cuando utilizamos drogas hiperbaras para anestesia subaracnoidea. En la presente década se observó una tendencia creciente a utilizar combinaciones de anestésicos locales y opiáceos. En relación a dichas mezclas, se analizaron la farmacocinética y farmacodinamia pero no se profundizó el estudio respecto de su densidad y baricidad. En este trabajo se midieron las densidades de las drogas anestésicas usadas habitualmente en bloqueos regionales (a 37ºC) y diferentes combinaciones entre las mismas, comprobándose que estas últimas son menores que las de los componentes por separado. Por lo tanto, las combinaciones de anestésicos locales y opiáceos presentan un comportamiento hipobaro respecto del LCR. Tal condición debería ser tenida en cuenta al realizar un bloqueo raquídeo pues modificaría la localización y extensión del mismo.

Estudio sobre la condición física de la combinación de anestésicos locales y opiáceos: sus implicancias teóricas en la anestesia subaracnoidea / Study on the physical condition of the combination local anesthetics-opiates: its theoretical implicancies in the spinal anesthesia

La baricidad de los agentes anestésicos se relaciona con la condición física del líquido cefalorráquideo (LCR), modificándose nuestra práctica cotidiana cuando utilizamos drogas hiperbaras para anestesia subaracnoidea. En la presente década se observó una tendencia creciente a utilizar combinaciones de anestésicos locales y opiáceos. En relación a dichas mezclas, se analizaron la farmacocinética y farmacodinamia pero no se profundizó el estudio respecto de su densidad y baricidad. En este trabajo se midieron las densidades de las drogas anestésicas usadas habitualmente en bloqueos regionales (a 37ºC) y diferentes combinaciones entre las mismas, comprobándose que estas últimas son menores que las de los componentes por separado. Por lo tanto, las combinaciones de anestésicos locales y opiáceos presentan un comportamiento hipobaro respecto del LCR. T