Lidocaine transport through a cellophane membrane by alternating current iontophoresis with a duty cycle.

The purpose of this study was to determine whether lidocaine can be efficiently transported across a cellophane membrane using a square-wave alternating current (AC) with an adjusted duty cycle. Three voltages at 1 kHz with 6 duty cycles were applied for 60 min to the diffusion cells on both sides of the cellophane membrane. The donor chamber was filled with 1% lidocaine hydrochloride solution. The transport of lidocaine was enhanced in a voltage-, and duty cycle-dependent manner. These findings indicate that voltage and the direct current (DC) component of the square-wave AC play important roles in generating the driving force necessary for lidocaine delivery. Additionally, the periodic polarity alteration could reduce the electrode polarization. The higher voltages and duty cycles induced a pH change. The practical electrical conditions which are preferable for clinical application were 10 V with a 70% duty cycle or 20 V with a 60% duty cycle.

Pentazocine transport by square-wave AC iontophoresis with an adjusted duty cycle.

So far, pentazocine iontophoresis has never been studied, although pentazocine is widely used in pain management. The purpose of this study was to determine whether pentazocine transportation through a cellophane membrane could be enhanced using square-wave alternating current (AC) iontophoresis with an adjusted duty cycle and dependence on the voltage and the duty cycle. Voltages of 10, 25 and 40 V with duty cycles of 50%, 51%, 52%, 53%, 54% and 55% were applied for 60 minutes at a high frequency of 1 MHz to diffusion cells on both sides of a cellophane membrane. The donor compartment was filled with a solution containing pentazocine. Square-wave AC iontophoresis with an adjusted duty cycle enhanced pentazocine transportation at higher voltages and duty cycles. These results suggested that the direct current (DC) component of the square-wave AC played an important role in enhancing pentazocine transportation despite changes in polarity at very high frequency of 1 MHz. The higher voltages and duty cycles induced a pH change. The practical electrical conditions that could be applied clinically were 25 V with a 54% duty cycle or 40 V with a 53% duty cycle.

Age-related changes in oral mechanosensitivity of symptom-free subjects.

The purpose of this study was to determine the effect of aging on the tactile and pain sensitivity, and the factors influencing threshold change in the oral mucosa using Semmes-Weinstein Pressure Aesthesiometer. The touch and pain thresholds of 81 healthy elderly (40 males and 41 females, 77 +/- 4.5 years) were compared with those of 58 young volunteers (27 males and 31 females, 27 +/- 2.5 years). We measured the pain thresholds, the touch thresholds, PCR score and amount of salivation. Semmes-Weinstein Pressure Aesthesiometer was applied to 9 points in the oral region and 4 points in the hands; the dorsum manus, the palma manus, the incisive papilla, the palatal mucosa, the buccal mucosa, the margin of the tongue, and the dorsum of the tongue. Elderly subjects showed significantly higher touch thresholds than those of young subjects in the dorsum manus, the palma manus, the buccal mucosa, the incisive papilla, the margin of the tongue, and the dorsum of the tongue (P < 0.05). The pain thresholds of elderly subjects were significantly lower than those of young subjects in the buccal mucosa and the palatal mucosa (P < 0.05). The touch threshold was not influenced by the smoking habit, denture and amount of salivation. The pain threshold was influenced by the denture on the palate.

Transdermal delivery of lidocaine in vitro by alternating current.

The purpose of this study was to investigate whether lidocaine could be transported through excised rat skin in vitro using alternating current (AC). In addition, the relationships between factors such as voltage and frequency, and transported lidocaine concentration were studied using the in vitro model. A pair of platinum plate electrodes was installed at opposite ends of two cylindrical glass cells in parallel to the full-thickness rat skin. The donor compartment was filled with 10 % lidocaine hydrochloride, and the receptor compartment with Ringer solution. A sinusoidal wave was applied between the electrodes at 5 kinds of constant voltages at 1 kHz and at 4 kinds of frequencies at 20 volts. Our experimental system was successfully used to quantify the concentration of transported lidocaine induced by AC application. The applied sinusoidal waves evoked the transport of lidocaine through the rat skin at every voltage and frequency protocol. Our results suggest that the applied electric voltage and frequency affect the movement of the lidocaine ions. We conclude that the transdermal delivery of lidocaine by AC iontophoresis has a possibility to use for local anesthesia and the pain management of the skin.