The effect of skin thickness and time in the absorption of dexamethasone in human tendons using iontophoresis

Effects of Ice Massage Prior to an Iontophoresis Treatment Using Dexamethasone Sodium Phosphate

CONTEXT

Low current intensity iontophoresis treatments have increased skin perfusion over 700% from baseline potentially altering drug clearance from or diffusion to the targeted area.

OBJECTIVE

To determine the effects of a preceding 10-minute ice massage on subcutaneous dexamethasone sodium phosphate (Dex-P) concentration and skin perfusion during and after a 4-mA iontophoresis treatment.

DESIGN

Controlled laboratory study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-four participants (male = 12, female = 12; age = 25.6 [4.5] y, height = 173.9 [8.51] cm, mass = 76.11 [16.84] kg).

INTERVENTION(S)

Participants were randomly assigned into 2 groups: (1) pretreatment 10-minute ice massage and (2) no pretreatment ice massage. Treatment consisted of an 80-mA·minute (4 mA, 20 min) Dex-P iontophoresis treatment. Microdialysis probes (3 mm deep in the forearm) were used to assess Dex-P, dexamethasone (Dex), and its metabolite (Dex-Met) concentrations. Skin perfusion was measured using laser Doppler flowmetry.

MAIN OUTCOME MEASURE(S)

Microdialysis samples were collected at baseline, at conclusion of treatment, and every 20 minutes posttreatment for 60 minutes. Samples were analyzed to determine Dex-Total (Dex-Total = Dex-P + Dex + Dex-Met). Skin perfusion was calculated as a percentage change from baseline. A mixed-design analysis of variance was used to determine Dex-Total and skin perfusion difference between groups overtime.

RESULTS

There was no difference between groups (P = .476), but [Dex-Total] significantly increased over the course of the iontophoresis and posttreatment time (P < .001). Dex-P was measured in 18 of 24 participants with a mean concentration of 0.67 (1.09) μg/mL. Skin perfusion was significantly greater in the no ice treatment group (P = .002). Peak skin perfusion reached 27.74% (47.49%) and 117.39% (103.45%) from baseline for the ice and no ice groups, respectively.

CONCLUSIONS

Ice massage prior to iontophoresis does not alter the tissue [Dex-Total] even with less skin perfusion.

Iontophoresis in lateral epicondylitis: a randomized, double-blind clinical trial

BACKGROUND

Lateral epicondylitis (LE) is a painful condition typically caused by excessive use of tendons, resulting in tendinopathy, inflammation, pain, and sensitivity changes in the lateral elbow. Iontophoresis is a noninvasive method of systemic and local drug delivery by means of a current. The study aimed to evaluate the effects of iontophoresis in patients with LE.

METHODS

We performed a randomized, double-blind clinical trial. Twenty-four patients with LE, randomized into an iontophoresis group and a galvanic current group. The iontophoresis group received a solution of dexamethasone (4 mg/mL) and gel lidocaine-applied on the negative electrode by means of a continuous current at 5 mA for 15 minutes-and the positive electrode received a base gel solution. Patients in the galvanic current group received the same protocol but using a base gel solution on both electrodes.

RESULTS

Both groups showed a significant improvement in pain on exertion and rest; increased handgrip strength in elbow extension and flexion; and improved function, as evaluated by the Patient-Rated Tennis Elbow Evaluation scale (P < .05). Iontophoresis showed superior results compared with galvanic current in pain on exertion and rest and in the function of individuals with tennis elbow.

CONCLUSION

Iontophoresis proved to be an effective technique in reducing pain and improving strength and function in individuals with LE (tennis elbow).

The time course of dexamethasone delivery using iontophoresis through human skin, measured via microdialysis

STUDY DESIGN

Controlled laboratory study.

OBJECTIVE

To determine the time course of dexamethasone sodium phosphate (Dex-P) during iontophoresis to underlying tissues using microdialysis.

BACKGROUND

In human participants, real-time information of Dex-P transdermal delivery during iontophoresis is unknown.

METHODS

Sixty-four healthy male participants (mean ± SD age, 24.2 ± 3.3 years; height, 181.8 ± 26.1 cm; mass, 82.4 ± 11.8 kg; subcutaneous fat thickness, 0.61 ± 0.19 cm) were randomly assigned into 1 of 6 groups: (1) 1-mA current, 1-mm probe depth; (2) 1-mA current, 4-mm probe depth; (3) 2-mA current, 1-mm probe depth; (4) 2-mA current, 4-mm probe depth; (5) in vivo retrodialysis; and (6) skin perfusion flowmetry. Microdialysis probes were used to assess the combined recovery (Dex-total) of Dex-P, dexamethasone, and its metabolite.

RESULTS

There was no difference in Dex-total between current intensities (P = .99), but a greater amount of Dex-total was recovered superficially at 1 mm compared to the 4-mm depth (P<.0001). Peak concentration mean ± SD values for the 1- and 2-mA currents at 1 mm were 10.8 ± 8.1 and 7.7 ± 5.5 µg/mL, and at 4 mm were 2.0 ± 0.8 and 1.3 ± 0.9 µg/mL, respectively. Peak skin perfusion was 741.4% ± 408.7% and 711.6% ± 260.8% at baseline for 1- and 2-mA intensities, respectively. Skin perfusion returned to baseline levels earlier during 1-mA intensity at a 110 mA · min dose within the treatment, compared to 2 mA at 60 minutes posttreatment.

CONCLUSION

Transdermal delivery of Dex-P during iontophoresis was successfully measured in vivo through human skin. Measurable concentrations of Dex-total were found regardless of current intensity. Although current-induced vasodilation occurred, it did not significantly affect the tissue accumulation of Dex-total.

Absorption of iontophoresis-driven 2% lidocaine with epinephrine in the tissues at 5 mm below the surface of the skin

CONTEXT

In a recent study, we were unable to measure lidocaine in the human calf at a 5-mm depth via iontophoresis. We surmised that this might be due to a lack of epinephrine in the compound. Because epinephrine is a vasoconstrictor, it might allow the drug to pass beyond the capillaries and be delivered to the deeper tissues.

OBJECTIVE

To determine if iontophoresis could deliver lidocaine with epinephrine 5 mm under the surface of human skin, as measured by microdialysis.

DESIGN

Descriptive laboratory study.

SETTING

Therapeutic modalities research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Ten volunteers (5 males, 5 females; age, 15-28 years) with less than 5 mm of adipose tissue in the area we measured and with no allergies to lidocaine participated. The measurement area had been free of any injury, swelling, or infection for at least 3 months before the study.

INTERVENTION(S)

We inserted a microdialysis probe 0.5 cm under the skin of the right lower leg. Next, microdialysis was performed through this area for 60 minutes, which allowed local skin blood flow to return to baseline. We then performed iontophoresis at 40 mA/min using 2 mL of 2% lidocaine. Iontophoresis was performed over this area for 10.5 minutes to collect the lidocaine samples. After this stage, the electrode was left in place for another 50 minutes for a total of 60 minutes.

MAIN OUTCOME MEASURE(S)

The samples of the drug were analyzed via reverse-phase high-performance liquid chromatography (RP-HPLC) in the chemistry department.

RESULTS

The RP-HPLC analysis confirmed the presence of lidocaine in all 10 participants. The mean concentration of lidocaine detected at the 5-mm depth was calculated as 3.63 mg/ mL (greater than 18% of delivered concentration).

CONCLUSIONS

We found that 2% lidocaine can be delivered up to 5 mm below the surface of the skin when the drug compound contains epinephrine and when passive delivery occurs for at least 50 minutes after the active delivery has terminated.

Microdialysis and delivery of iontophoresis-driven lidocaine into the human gastrocnemius muscle

CONTEXT

Iontophoresis is used frequently in physical medicine and rehabilitation, but many research techniques do not adequately measure it for depth of medicine delivery.

OBJECTIVE

To determine if iontophoresis delivers lidocaine 5 mm under the surface of human skin.

DESIGN

Descriptive laboratory study.

SETTING

Therapeutic modalities research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Eight men and 5 women volunteers (age range = 21± 2.3 years) who had less than 5 mm of adipose tissue in the area we measured participated in the study.

INTERVENTION(S)

We inserted a microdialysis probe 5 mm under the skin of both legs and into the triceps surae muscle groups of 10 participants. Microdialysis was performed for 60 minutes to allow a recovery period for local skin blood flow to return to baseline. We then delivered 2 mL of 1% lidocaine to the treatment leg via iontophoresis at 40 mA/min. Next, microdialysis was performed continuously in both legs during the treatment and for 30 minutes posttreatment to collect the lidocaine samples. After we had gathered the samples, several saline solutions with various amounts of lidocaine (0.005%, 0.025%, 0.05%, and 0.1 %) were prepared in vitro and analyzed. Although we did not intend to do so as a part of the original study, we also performed an identical follow-up study at 3 mm in 3 participants.

MAIN OUTCOME MEASURE(S)

Both in vitro and in vivo samples were analyzed via reverse-phase high-performance liquid chromatography (RP-HPLC). A protocol for detection and quantification of lidocaine using RP-HPLC was followed.

RESULTS

We did not detect any measurable levels or concentrations of lidocaine in the 10 control samples. According to the RP-HPLC analysis, the 10 treatment samples also were negative for the presence of lidocaine. However, when we performed the study at 3 mm, microdialysis detected lidocaine in the 3 participants at this depth in the treatment leg only.

CONCLUSIONS

Measurable levels of lidocaine were not detected at 5 mm but were found at 3 mm. More studies are needed to determine the efficacy of microdialysis in measuring iontophoresis-delivered compounds.