Download Efficacy of Lidocaine Iontophoresis Using Either Alternating or Direct

J Med Dent Sci 2013； 60： 63－71
Original Article
Efficacy of Lidocaine Iontophoresis Using Either Alternating or Direct Current in
Hairless Rats
Atsushi Nakajima, Ryo Wakita, Haruka Haida and Haruhisa Fukayama
Section of Anesthesiology and Clinical Physiology, Department of Oral Restitution, Division of Oral Health
Sciences, Graduate School, Tokyo Medical and Dental University
The aim of this study was to determine transport
of lidocaine ions through a hairless rat skin in vivo
and to compare the efficacy of alternating current
(AC) with that of direct current (DC) iontophoresis
(IOP). We measured the concentration of lidocaine
transported through a cellophane membrane or a
hairless rat dorsal skin applying either AC-IOP or
DC-IOP. The results revealed that lidocaine
concentration increased in a time-dependent
manner in vitro in both DC-IOP and AC-IOP.
However, the in vivo study showed different
tendencies in lidocaine concentration. In the DCIOP group, lidocaine concentration reached its
maximum 20 min after current application and then
decreased rapidly; the AC-IOP group showed an
increase in lidocaine concentration in a timedependent manner. There were no side effects
such as electrical burns in the rats. In conclusion,
AC can be applied for long periods and DC for
short periods, or their application time can be
appropriately scheduled. Our study also suggests
the mechanism by which voltage waveforms affect
the skin when applied by IOP. In the future, these
findings will be a solid foundation for developing
various kinds of medical equipment such as
scheduled drug delivery system that can easily
deliver various types of drug.
Corresponding Author: Atsushi Nakajima
Section of Anesthesiology and Clinical Physiology, Department of
Oral Restitution, Division of Oral Health Sciences, Graduate School,
Tokyo Medical and Dental University 1-5-45 Yushima Bunkyo-ku,
Tokyo 113-8549, Japan
Tel: +81-3-5803-5549　Fax: +81-3-5803-0206
E-mail: [email protected]
Received February 19；Accepted June 14, 2013
Key words: Iontophoresis, Alternating current, Lidocaine,
Hairless rat, Microdialysis
1. Introduction
Iontophoresis (IOP) is one of the transdermal drug
delivery methods that utilize current to enhance the
movement of an ionic or a noncharged drug and facilitate
the penetration of the drug across the skin via three
principal mechanisms: electrorepulsion, electroosmosis,
1, 2
and electroporation . Local anesthetics, opioids,
steroids, nonsteroidal anti-inflammatory drugs (NSAIDS),
and antiviral agents among others have been used in
transdermal drug delivery studies 3, 4. Generally, direct
current (DC) IOP has often been selected because of its
higher transport efficiency. The IOP of anesthetics such
as lidocaine is used in clinical settings 5-9.
However, DC-IOP could cause some side effects such
as electrical burns, chemical burns, and erythema due
to electrolysis and attenuates the transport effect
owing to electrode polarization10, 11. This side effects
limit the DC iontophoresis duration to less than 15 min
at current density as low as 1 mA/cm2 12. Many studies
report and suggest current density of experimental
p r o t o c o l w a s a p p l i e d u p t o 0 . 5 m A / c m2 f o r D C
iontophoresis 3, 13.
Recent study shows electrochemical burns and
skin irritation were avoided by alternating current
iontophoresis (AC-IOP)11, 14 . The periodic polarity
changes of AC-IOP can neutralize pH changes. Our
study group has examined the efficiency of AC-IOP in
transporting lidocaine into the skin effectively.
We demonstrated, using by in vitro studies, that
lidocaine ions can be successfully transported through
a cellophane membrane by applying AC and that the
efficacy of lidocaine iontophoresis using a bipolar
square wave depends on the duty cycle and correlates
64
A. Nakajima et al.
J Med Dent Sci
with average voltage10, 15-21. The average voltage U ave
can be expressed as
U ave =
1
T
T
ʃ U (t )dt
(1)
0
where t is the time, U(t) is the voltage between the
electrodes at t, and T is the period of the square wave.
However, there have been fewer studies in which
the efficacy of AC-IOP is compared with that of DCIOP, which is widely used. Yan et al. reported the
good correlations between phenylalanine and mannitol
transport across human epidermal membrane during DC
and AC-plus-DC iontophoresis 22. Li et al. showed skin
resistance can be maintained at a constant level during
AC iontophoresis 23. Some studies showed that the
concentrations of drugs transported from the skin to the
target can be measured using a microdialysis system.
The use of microdialysis system that directly measures
tissue drug concentration is more appropriate for local
anesthetic studies than indirect estimations of tissue
drug concentrations from plasma drug concentrations.
The system is promising and less invasive for assessing
cutaneous drug delivery. Other studies showed the
increased percutaneous absorption of lidocaine and
prilocaine in pigs and also the percutaneous penetration
of flurbiprofen into the rat skin by DC-IOP 24, 25.
The aim of this study was to compare the efficacy of
waveforms that were set at the same average voltage
in vitro and determine the concentration of lidocaine
ions transported through a hairless rat skin in vivo applying AC-IOP and DC-IOP.
2. Materials and methods
2.1 In vitro protocol
2.1.1 Materials
Lidocaine hydrochloride (C14H22N2O·HCl; FW 270.8;
H2O content 1 mol/mol) was purchased from SigmaAldrich Co. Ltd. (St. Louis, MO, USA). One percent
lidocaine hydrochloride was prepared using distilled
and deionized water (resistivity > 18 MΩ). The pH of 1
% lidocaine was 4.6.
The cellophane membrane (Futamura Chemical Co.
Ltd., Nagoya, Japan) used was about 36 μm thick with
a pore size range of 2 - 3 nm. This pore size range is
about twice larger than the lidocaine molecule.
2.1.2 Procedure of in vitro experiments (Fig.1,
Fig.2)
To evaluate the transport of lidocaine ions through
Fig. 1 The setup of in vitro experimental system.
Fig. 2 Experimantal protocol.
the cellophane membrane, a cylindrical acryl drug
delivery cell consisting of two chambers was originally
constructed. An experimental system and methods,
prepared as previously described, were basically used
in all the in vitro experiments19.
Platinum plate electrodes with a diameter of 20 mm
and a thickness of 0.2 mm were installed at the opposite ends of two components of the cell. The length
of each component was 10 mm. The cellophane membrane was placed between the two components. The
available diffusion area was about 3.1 cm2. The donor
and receptor chambers were filled with 1 % lidocaine
hydrochloride solution (3.0 ml, pH 4.6) and distilled water (3.0 ml), respectively. Acryl cells were set in a water
bath (36.0 ℃). A thermocouple microprobe (BAT, Physitemp, NJ, USA) was inserted at the center of the donor
chamber to monitor the temperature of the solution in
Efficacy of Lidocaine IOP in Hairless Rats
Fig. 3 Experimental Waveforms.
(a) Square wave with 70 % duty cycle at 1 kHz (b) Direct current
The duty cycle is the ratio of the positive cycle to the full cycle.
EAC and EDC represent applied voltage.
In vitro experiment, EAC was 7.5 V and EDC was 3 V.
In vivo experiment, EAC was 10 V and EDC was 4 V.
Both (a) and (b) were set at the same average voltage.
the chamber. The solution in the two cell chambers was
not stirred because the bulk flow caused by stirring and
the rotator-induced magnetic field could affect lidocaine
transport.
The tube was inserted into the receptor chamber and
connected to a peristaltic pump (ALITEA XV, Sweden).
Samples were extracted from the receptor chamber
every 30 min. After collecting the first sample, voltage
was applied as described below.
A square wave (duty cycle 70 %; 7.5 V; 1kHz) and
DC (3 V) which were set at the same average voltage
(Fig. 3), were continuously applied between the parallel
platinum electrodes for 270 min using a function/
arbitrary waveform generator (Agilent Technologies,
Colorado, USA) and a high-speed power amplifier (4025,
NF Electric Instruments, Kanagawa, Japan), while the
waveform and voltage were monitored using a digitizing
oscilloscope (HP54503A, Hewlett Packard, Tokyo,
Japan) throughout the experiment.
2.1.3 Measurement system
19
Measurement system referred to Hayashiʼs protocol .
The concentration of lidocaine in the receptor chamber
was measured using a spectrophotometer (U-3310;
absorbance range, -2 - 4 Abs; precision, 0.002 Abs;
HITACHI, Tokyo, Japan) at room temperature. The
samples were diluted 25 times with distilled and
deionized water. The absorbance of the samples was
measured at a wavelength of 262 nm and an optical
path of 10 mm. Lidocaine concentration was determined
using a calibration curve 16.
2.2 In vivo protocol
2.2.1 Materials
Two percent lidocaine hydrochloride was purchased
from AstraZeneca (Osaka, Japan). Three percent
65
mepivacaine hydrochloride (C15H22N2O·HCl; FW
282.8) was purchased from Nippon Shika Yakuhin
Co. Ltd. (Shimonoseki, Japan). An iontophoretic patch
originally developed by TTI ellebeau Ltd, (Tokyo, Japan)
was used in this study. The patch was composed of a
silver/silver chloride electrode, a circular anode, and
a circular cathode with a nonwoven fabric reservoir
(diameter, 1.7 cm) with a capacity of 0.4 mL of a drug
solution.
2.2.2 Microdialysis system
A linear microdialysis probe (MDP) with a cellulose
membrane length of 10 mm (o.d. 0.22 mm; i.d. 0.105
mm) and a molecular weight cutoff of 50 kDa (Eicom
OP-100-10, Kyoto, Japan) was prepared. The inlet tube
of the probe was connected to a gas-tight syringe (1 ml)
on a microinjection pump (CMA/100). The outlet tube of
the probe was connected to a microfraction collector
(CMA/140) with a Teflon tube.
2.2.3 Experimental procedure in vivo (Fig. 2, Fig. 4)
Hairless rats (8-week-old males, 250-300 g) were
housed in an air-conditioned room and used for this
study. The institutional Review Board of Tokyo Medical
and Dental University approved the animal experimental
protocol. The experiment was conducted in accordance
with the guidelines of this review board.
The rats were anesthetized by the intraperitoneal
injection of sodium pentobarbital (40 mg/kg). The
surface of the dorsal skin was swabbed with alcohol
and dried before surgery. A linear microdialysis probe
was inserted into the subcutaneous tissue, unilateral
to the skin at the dorsum using a guide needle. The
guide needle was withdrawn leaving the probe. Acetate
Ringer solution was perfused at a flow rate of 2 μl /
min with 0.0015 % mepivacaine added as a recovery
calibrator (internal standard).
There was an equilibration period of 60 min to relieve
minor trauma caused by the probe insertion. Seven
samples were collected from the subcutaneous tissue
every 20 min. After collecting the first sample, the
iontophoretic device having two electrodes containing
2 % lidocaine solution (0.4 ml) and saline (0.4 ml) was
applied to the dorsal region. A square wave (duty cycle
70 %; 10 V; 1 kHz) and DC (4 V), which were set at
the same average voltage (Fig. 3), were produced by
a function generator. Either the square wave (AC-IOP
group) or DC (DC-IOP group) was applied to the rats for
120 min. The device without IOP was applied to the rats
as the passive absorption group (passive group) for 120
min. The concentration of lidocaine was determined
66
A. Nakajima et al.
J Med Dent Sci
Fig. 4 The setup of the experimental system.
by a high performance liquid chromatography (HPLC)
and compared among the three groups. After this
experiment, the dorsal skin was excised to measure
probe depth and examine skin damage. Probe depth
was assessed by H-E staining. Mathy et al. showed the
way in detail 25.
2.2.4 In vitro recovery
In vitro recovery was determined to ensure that the
probe would provide reproducible and efficient sampling
of lidocaine. The probe was placed in a 1-L beaker that
contained saline and connected to the microdialysis
system. The perfusate was 0.01 % lidocaine or 0.003
% mepivacaine. Six samples were collected every 20
min after the start of perfusion. Eight microdialysis
probes that were used in this study were examined
whether these membranes were intact. Lidocaine and
mepivacaine concentration were determined by HPLC.
2.2.5 HPLC of in vivo and in vitro samples
The HPLC system used in this study was composed
of a UV-VIS detector (SPD-10A), a column oven (CTO10A), a system controller (SCL-10A), an auto injector
(SIL-10AD), a liquid chromatograph (LC-10AD), a degasser (DGU-14A), and a column. The mobile phase consisted of 100 mM phosphate buffer (pH 6.9) and acetonitrile at a volume ratio of 45/55. The flow rate was 0.8
ml/min. Twenty-microliter samples were automatically
injected into the HPLC system for analysis. The column
oven was maintained at 40 ℃. Lidocaine was detected
at 220 nm by UV detection. Standard lidocaine solutions of 0.00002 % - 0.001 % diluted with pure water
were used to obtain standard curves, which were linear
in this range (r 2 = 0.986). Values obtained from HPLC
analysis applied to standard curve and lidocaine concentration were calculated. Using the recovery rate of
lidocaine, lidocaine concentration of the subcutaneous
tissue was identified. Mepivacaine was used to confirm
stable recovery.
2.3 Statistical analyses
All values are presented as the mean ± S.D. Twoway ANOVA was carried out to determine the time and
waveform dependences of the transport efficiency of
lidocaine. One-way ANOVA was used to analyze the time
dependence of the recovery rate of microdialysis probes.
In addition, for comparison of lidocaine concentration
and cell temperature, the Dunnet test was carried out
for intragroup comparisons and the Tukey test for
intergroup comparisons. Differences were considered
significant at p < 0.05. All statistical analyses were
performed using Kyplot 5.0 (KyensLab Inc., Tokyo,
Japan).
Efficacy of Lidocaine IOP in Hairless Rats
3. Results
3.1 Probe depth and skin damage
Table 1 shows the probe depth in each group. The
mean probe depth was 1.67 ± 0.31 mm (± S.D., n =
15). No significant differences in probe depth were
found among the three groups and there were no side
effects such as an erythema or electrical burns in the
three groups.
Table 1 Probe depth in in vivo experiment.
No significant differences in probe depth were found among the
three groups.
67
where Cperfusate is the drug concentration in the perfusate
and Cdialysate is the drug concentration in the dialysate.
The samples collected from this experiment showed
that the recovery rate in vitro was 24.12 ± 4.08 % for
lidocaine and 24.28 ± 3.14 % for mepivacaine. A little
variation of recovery rate was observed among the
probes. However, no significant differences in recovery
rate were found in each probe. Fig. 5 shows recovery
rate of lidocaine maintained almost constant level
throughout the experiment. Recovery rates of lidocaine
and mepivacaine were almost the same value.
(2)
3.3 In vitro experiment
Figure 6 shows the changes in lidocaine concentration
in the receptor chamber to which the square wave,
DC, and passive diffusion were applied. The lidocaine
concentration in the receptor chamber increased in
a time-dependent manner in all the three groups. The
lidocaine concentrations in the current applied groups
(both AC-IOP and DC-IOP) were significantly elevated
after 30 min compared with that in the passive group (p
< 0.05). There were no significant differences between
the AC-IOP group and the DC-IOP group at both time
points.
The temperature of the donor chamber increased in
both the AC-IOP and DC-IOP groups (Fig. 7). It became
constant after 120 min (AC-IOP group, 37.3 ℃; DC-IOP
group, 36.0 ℃). The difference in temperature between
the two groups was statistically significant after 30 min
(p < 0.05). The DC-IOP group showed a significantly
higher temperature than the passive group (p < 0.05).
Fig. 5 Recovery rate of lidocaine determined by retrodialysis
for subcutaneous probe.
Values are means ± S.D. (n = 8). Recovery rates of lidocaine were
almost the same value and maintained almost constant level
throughout the experiment.
Fig. 6 Changes in lidocaine concentration in vitro .
(○) AC-IOP group (n = 5), (△) DC-IOP group (n = 5), (□) passive
group (n = 5). The values are plotted in the middle of each sampling
time. The error bars represent the standard deviation of the mean.
*p < 0.05 vs passive group.
Experimental
number
AC-IOP group
DC-IOP group
Passive group
1
1.75 mm
2.14 mm
1.92 mm
2
1.50 mm
1.07 mm
1.73 mm
3
2.25 mm
1.42 mm
1.54 mm
4
1.76 mm
1.60 mm
1.35 mm
5
1.47 mm
1.61 mm
1.35 mm
1.74 ± 0.31 mm
1.57 ± 0.38 mm
1.69 ± 0.25 mm
Mean ± SD
total
1.67 ± 0.31 mm (n = 15)
3.2 Recovery rate in vitro determined by retrodialysis
Disappearance rate was calculated using Eq. (2) and
taken as the recovery rate in vitro .
Recovery rate = 100 (Cperfusate ‒ Cdialysate) / Cperfusate
68
A. Nakajima et al.
J Med Dent Sci
between the AC-IOP group and the other two groups
after 60 min and thereafter (p < 0.05). At 120 min,
the lidocaine concentration in the AC-IOP group
increased through intradermal absorption, which was
approximately 6.5 times and 13 times those of the DCIOP and passive groups, respectively.
4. Discussion
Fig. 7 Temperature of donor chamber.
(○) AC-IOP group (n = 5), (△) DC-IOP group (n = 5), (□) passive
group (n = 5). The error bars represent the standard deviation of
the mean.
*p < 0.05 vs DC-IOP group. †p< 0.05 vs passive group
3.4 In vivo experiments (Fig. 8)
In the AC-IOP group, lidocaine concentration
significantly increased time-dependently. In contrast,
the DC-IOP group showed unique characteristics and
the highest lidocaine concentration was detected at 20
min. The lidocaine concentration in the DC-IOP group
was about 30 times and 168 times those in the AC-IOP
and passive groups, respectively. After 40 min, both
the DC-IOP and passive groups showed low lidocaine
concentrations. There were significant differences
Fig. 8 Changes in lidocaine concentration in vivo .
(○) AC-IOP group (n = 5), (△) DC-IOP group (n = 5), (□) passive
group (n = 5). The error bars represent the standard deviation of
the mean.
*p < 0.05 vs the passive group. †p< 0.05 vs the AC-IOP group.
4.1 Skin damage after iontophoresis application
In this study, there were no signs of skin damage such
as erythema or burns in the AC-IOP or DC-IOP group,
to which electrical current was applied. Generally, DCIOP has side effects described above because of the
hydrogen and hydroxide ions generated by DC.
However, low current density less than 0.5mA/cm2
does not cause these side effects13. This study did not
measure the current flow of the skin and the current
density at direct 4 V might not reach the concerned
level. Moreover, pH changes did not occur in vivo study
possibly because the silver/silver chloride electrodes
prevented pH variation. Owing to the polarization of the
skin or electrodes surface and formation of insoluble
silver chloride, the effective current flow was limited.
Additionally, the skin was observed 120 min after
applying the DC, which was much later than 20 min.
Thus, no side effects could be observed in the skin.
Although AC-IOP also generates insoluble product,
the periodic polarity alternation neutralizes it. This fact
was capable of long-term current application. This finding indicates that AC-IOP is useful for clinical application as well as DC-IOP.
In the in vitro experiments, the temperature of the
donor cell increased in the AC-IOP group. The increase
of the vibration energy of the ion given by alternating
electric potential applied between electrodes causes
the decrease of effective Stokes radius of the ion and
plays a decisive role in the ion transport 15. However,
this vibration energy leads to increasing kinetic
energy and resulting in temperature increase of donor
chamber.
In our in vivo study, we didnʼt measure temperature
of the system. The vibration energy may cause kinetic
energy of ionized subcutaneous molecules in a timedependent manner, resulting in elevation of skin
temperature. There is a possibility that this increase
causes the skin burns. Therefore, it is necessary to
determine the optimal voltage that does not cause
human skin burns.
Efficacy of Lidocaine IOP in Hairless Rats
4.2 Recovery rate determined by retrodialysis and
compensation
In this study, the recovery rate of lidocaine was
measured by retrodialysis. It is assumed that the rate of
disappearance of compounds from the probe through
the semipermeable membrane is equal to the rate of
recovery from the extracellular medium; this assumption
was successfully employed in many studies 26. However,
the in vitro and in vivo recovery rates of compounds
usually differ. Generally, the recovery rate in vivo is
often lower than that in vitro because the diffusion in
the tissue is hardly detected compared with that in a
simple solution 27. Thus, in vitro recovery rate cannot
be used for in vivo calculations owing to differences in
transport characteristics between tissues and solutions.
To estimate lidocaine concentration, mepivacaine
was added to the perfusion as an internal standard,
because the molecular weight of mepivacaine is
almost the same as that of lidocaine. By measuring the
concentration of mepivacaine in the samples collected
in in vivo experiments, we were able to estimate the
concentration of lidocaine in the subcutaneous tissue.
Small variations in the concentration of mepivacaine
in each sample indicated that the microdialysis
probe could recover the lidocaine nearly constantly
and membranes of probes were in good condition.
Consequently, this analytical procedure enables the
precise estimation of the concentration of lidocaine at
an area applied with current.
4.3 In vitro lidocaine transport efficiency
Hayashi et al. suggested that lidocaine transport
was enhanced in a voltage- and duty-cycle-dependent
manners and was related to average voltage19. AC or
DC with the same average voltage was used in this
in vitro study. Figure 6 shows that the transport of
lidocaine ions using both waveforms showed similar
tendencies and was more efficient than the transport by
passive absorption. Therefore, this result suggests that
voltage application adds energy to lidocaine ions and
increases transport efficiency, suggesting that average
voltage is related to lidocaine transport efficiency.
In vitro experiment, pH may change using platinum
electrodes. The pH of the solution in the donor chamber
tended to decrease after applying the currency19 .
The pH of 1 % lidocaine hydrochloride solution is 4.6
and pKa of lidocaine is 7.86. Therefore, the lidocaine
molecules were almost completely dissociated and
ionized throughout experiments in the donor chamber
and pH changes in vitro study were thought to be less
influence on the result. AC-IOP does not facilitate pH
69
changes due to alternating polarities.
However, the increase in temperature in the donor
chamber could also add energy for the transport of
lidocaine ions across the cellophane membrane. A
higher temperature may enhance lidocaine transport in
the AC-IOP group compared with the DC-IOP group.
4.4 In vivo lidocaine transport efficiency
Results of in vitro experiments showed the relevance
of average voltage to transport efficiency. Therefore,
in vivo experiments were performed using waveforms
that were at the same average voltage in DC and AC
settings to determine whether both waveforms have the
same lidocaine transport efficiency. As shown in the
results, lidocaine was successfully transported through
the dorsal skin of a living hairless rat receiving both AC
and DC-IOP.
In the DC-IOP group, the lidocaine concentration
reached its maximum 20 min after the application
of current and decreased rapidly thereafter. Large
variability of the lidocaine concentration was also
shown at this point. This indicated that the maximum
concentration in the tissue could be detected between
0 and 40 min and there were differences in the amount
of transporting agent at each experiment.
Some studies showed that DC-IOP caused undesirable
effects on the skin and was considered to enhance
irritations or subcutaneous vasodilatation due to
current flow 28-30. An increased vascular blood flow
c aus e d b y v a s o dila t a t ion pr om o t e s ele c t r ol y t e
accumulation in the intracellular space, which leads
to the decrease in electrical resistance, resulting in a
greater flow of electrical current. After this phenomenon,
electropolarization, which is a disadvantage of DC
IOP, reduces current flow and increases blood flow
owing to vasodilatation. Finally, lidocaine ions flow out
of the area of application. Since Wakita et al. reported
that the application of lidocaine with epinephrine as a
vasoconstrictor has a greater anesthetic effect than
that of lidocaine only when applying DC iontophoresis,
vasodilatation has been considered one of the factors
that decrease anesthetic efficiency 20.
On the other hand, it was observed that the AC-IOP
group showed an increase in lidocaine concentration in
a time-dependent manner. The mechanism underlying
this increase is considered to be that AC changes the
polarity of electrodes periodically without generating
electropolarization and that the anesthetic could
pass through the rat skin. Comparing DC-IOP, AC-IOP
could have constant transport efficiency because of
low variability. Li et al. also reported constant skin
70
A. Nakajima et al.
resistance AC iontophoresis generally provide less
inter- and intra-subject variability than conventional
constant current DC 23 . This feature could make it
possible to infiltrate any agent into the skin at targeted
concentration.
However, the lidocaine concentration in the AC-IOP
group increased to a lesser extent than that in the
DC-IOP group. It cannot be denied that lidocaine ions
were possibly drawn “back and forth” to the electrode
because of the periodic negative phase of AC. Usually,
the skin is negatively charged, which enables the
transport of positive ions efficiently. However, when
negative voltage is applied, this may promote the
extraction of positive ions that penetrated into the
subcutaneous tissue. Some studies showed that pulsed
DC without negative components could yield a low
resistance, enhance drug delivery, and reduce the risk
of burns 31, 32. More studies are required to determine
other waveforms that may be effective.
T h e in vivo stu d y sh o we d th a t th e tra ns por t
efficiencies were significantly different between the
AC-IOP group and the DC-IOP group even when using
the same average voltage.
Hayashi et al. suggested transport efficiency is
dependent on the average voltage19. On the other hand,
our experimental model showed different tendency
of transport. This discrepancy can be derived from
these settings; in vitro or in vivo . Although transported
lidocaine ions accumulated in the receptor cell owing
to the closed system in the in vitro study, the lidocaine
ions in the in vivo study accumulated to a lesser
extent owing to the open system used in this study.
This discrepancy suggests that transport efficiency
could depend on the way current flow is applied and
further study will be needed to identify whether the
average voltage relates to transport efficiency. Yan et
al. reported that the frequency of AC is related to the
control of drug permeation, and Xu et al. showed that a
frequency lower than 1 kHz is more effective14, 33. More
studies are needed to determine the optimal frequency
of AC.
DC-IOP has higher transport efficiency than ACIOP but it is unsuitable for long-term application. In
contrast, AC-IOP is inferior to DC in terms of rapid
drug permeation, but it is suitable for long-term
application. These findings indicate the possible clinical
primary and secondary applications of DC and AC
respectively, that is, DC is applied to rapidly increase
lidocaine concentration, followed by AC to maintain the
concentration. If the application time relates the dose of
transdermal absorption and long-term AC-IOP maintains
J Med Dent Sci
the local concentration of the target area, it will enable
each patient to administer appropriate drug dose and
prevent them from overdosing. For example, this could
be very useful device especially for elderly persons
who might have hepatic or renal dysfunction. Further
studies are also required for the applications of both
DC-IOP and AC-IOP.
5. Conclusions
Our experimental system was successfully applied to
the evaluation of the effects of both AC-IOP and DC-IOP
on lidocaine transport across a living hairless rat skin.
Following the application of DC-IOP, the concentration
of lidocaine in the subcutaneous tissue immediately
increased and then decreased rapidly. On the other
hand, AC-IOP gradually increased the concentration
in a time-dependent manner. The results of our study
indicated that AC-IOP and DC-IOP have different effect
on transporting lidocaine ions in vivo . Consequently,
this study suggests that both AC and DC-IOP protocol
should be adjusted to increase and maintain the drug
concentration at target tissue according to clinical
situations.
1.
2.
3.
4.
5.
6.
7.
8.
References
Guy RH, Kalia YN, Delgado-Charro MB, Merino V,
López A, Marro D. Iontophoresis: electrorepulsion and
electroosmosis. J Control Release. 2000; 64(1-3): 129-32.
Singh P, Maibach HI. Iontophoresis in drug delivery: basic
principles and applications. Crit Rev Ther Drug Carrier
Syst. 1994; 11(2-3): 161-213.
Kalia YN, Naik A, Garrison J, Guy RH. Iontophoretic drug
delivery. Adv Drug Deliv Rev. 2004; 56(5): 619-58.
Chien YW, Siddiqui O, Sun Y, Shi WM, Liu JC. Transdermal
iontophoretic delivery of therapeutic peptides/proteins. I:
Insulin. Ann N Y Acad Sci. 1987; 507: 32-51.
Zeltzer L, Regalado M, Nichter LS, Barton D, Jennings S,
Pitt L. Iontophoresis versus subcutaneous injection: a
comparison of two methods of local anesthesia delivery
in children. Pain. 1991; 44(1): 73-8.
Galinkin JL, Rose JB, Harris K, Watcha MF. Lidocaine
iontophoresis versus eutectic mixture of local anesthetics
(EMLA) for IV placement in children. Anesth Analg. 2002;
94(6): 1484-8, table of contents.
Greenbaum SS, Bernstein EF. Comparison of iontophoresis
of lidocaine with a eutectic mixture of lidocaine and
prilocaine (EMLA) for topically administered local
anesthesia. J Dermatol Surg Oncol. 1994; 20(9): 579-83.
Maloney JM, Bezzant JL, Stephen RL, Petelenz TJ.
Iontophoretic administration of lidocaine anesthesia in
office practice. An appraisal. J Dermatol Surg Oncol. 1992;
18(11): 937-40.
Efficacy of Lidocaine IOP in Hairless Rats
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
Irsfeld S, Klement W, Lipfert P. Dermal anaesthesia:
comparison of EMLA cream with iontophoretic local
anaesthesia. Br J Anaesth. 1993; 71(3): 375-8.
Umino M, Oda N, Yasuhara Y. Experimental and
theoretical studies of the effect of electrode polarisation
on capacitances of blood and potassium chloride solution.
Med Biol Eng Comput. 2002; 40(5): 533-41.
Howard JP, Drake TR, Kellogg DL. Effects of alternating
current iontophoresis on drug delivery. Arch Phys Med
Rehabil. 1995; 76(5): 463-6.
Yan G, Li SK, Peck KD, Zhu H, Higuchi WI. Quantitative
study of electrophoretic and electroosmotic enhancement
during alternating current iontophoresis across synthetic
membranes. J Pharm Sci. 2004; 93(12): 2895-908.
Wang Y, Thakur R, Fan Q, Michniak B. Transdermal
iontophoresis: combination strategies to improve
transdermal iontophoretic drug delivery. Eur J Pharm
Biopharm. 2005; 60(2): 179-91.
Yan G, Li SK, Higuchi WI. Evaluation of constant current
alternating current iontophoresis for transdermal drug
delivery. J Control Release. 2005; 110(1): 141-50.
Shibaji T, Yasuhara Y, Oda N, Umino M. A mechanism of
the high frequency AC iontophoresis. J Control Release.
2001; 73(1): 37-47.
Kinoshita T, Shibaji T, Umino M. Transdermal delivery of
lidocaine in vitro by alternating current. J Med Dent Sci.
2003; 50(1): 71-7.
Haga H, Shibaji T, Umino M. Lidocaine transport through
living rat skin using alternating current. Med Biol Eng
Comput. 2005; 43(5): 622-9.
Ogami S, Hayashi S, Shibaji T, Umino M. Pentazocine
transport by square-wave AC iontophoresis with an
adjusted duty cycle. J Med Dent Sci. 2008; 55(1): 15-27.
Hayashi S, Ogami S, Shibaji T, Umino M. Lidocaine transport
through a cellophane membrane by alternating current
iontophoresis with a duty cycle. Bioelectrochemistry. 2009;
74(2): 315-22.
Wakita R, Oono Y, Oogami S, Hayashi S, Umino M. The
relation between epinephrine concentration and the
anesthetic effect of lidocaine iontophoresis. Pain Pract.
2009; 9(2): 115-21.
Wakita R, Nakajima A, Haida Y, Umino M, Fukayama H.
The relation between the duty cycle and anesthetic
effect in lidocaine iontophoresis using alternating current.
Pain Pract. 2011; 11(3): 261-6.
Yan G, Higuchi WI, Szabo A, Li SK. Correlation of
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
71
transdermal iontophoretic phenylalanine and mannitol
transport: test of the internal standard concept under DC
iontophoresis and constant resistance AC iontophoresis
conditions. J Control Release. 2004; 98(1): 127-38.
Li SK, Higuchi WI, Zhu H, Kern SE, Miller DJ, Hastings MS.
In vitro and in vivo comparisons of constant resistance
AC iontophoresis and DC iontophoresis. J Control
Release. 2003; 91(3): 327-43.
Wei H, Chen Y, Xu L, Zheng J. Percutaneous penetration
kinetics of lidocaine and prilocaine in two local anesthetic
formulations assessed by in vivo microdialysis in pigs.
Biol Pharm Bull. 2007; 30(4): 830-4.
Mathy FX, Lombry C, Verbeeck RK, Préat V. Study of the
percutaneous penetration of flurbiprofen by cutaneous
and subcutaneous microdialysis after iontophoretic
delivery in rat. J Pharm Sci. 2005; 94(1): 144-52.
Kreilgaard M. Assessment of cutaneous drug delivery
using microdialysis. Adv Drug Deliv Rev. 2002; 54 Suppl
1: S99-121.
Simonsen L, Jørgensen A, Benfeldt E, Groth L. Differentiated
in vivo skin penetration of salicylic compounds in hairless
rats measured by cutaneous microdialysis. Eur J Pharm
Sci. 2004; 21(2-3): 379-88.
Durand S, Fromy B, Bouyé P, Saumet JL, Abraham P.
Vasodilatation in response to repeated anodal current
application in the human skin relies on aspirin-sensitive
mechanisms. J Physiol. 2002; 540(Pt 1): 261-9.
Horiuchi Y, Droog EJ, Henricson J, Wikström T, Lennquist
S, Sjöberg F. Role of histamine release in nonspecific
vasodilatation during anodal and cathodal iontophoresis.
Microvasc Res. 2004; 67(2): 192-6.
Tartas M, Bouyé P, Koïtka A, Jaquinandi V, Tan L,
Saumet JL, et al. Cathodal current-induced vasodilation
to single application and the amplified response to
repeated application in humans rely on aspirin-sensitive
mechanisms. J Appl Physiol. 2005; 99(4): 1538-44.
Pikal MJ, Shah S. Study of the mechanisms of flux
enhancement through hairless mouse skin by pulsed DC
iontophoresis. Pharm Res. 1991; 8(3): 365-9.
Meyer PF, Oddsson LI. Alternating-pulse iontophoresis for
targeted cutaneous anesthesia. J Neurosci Methods.
2003; 125(1-2): 209-14.
Xu Q, Kochambilli RP, Song Y, Hao J, Higuchi WI, Li SK.
Effects of alternating current frequency and permeation
enhancers upon human epidermal membrane. Int J
Pharm. 2009; 372(1-2): 24-32.