Failure to detect dexamethasone phosphate in the local venous blood postcathodic lontophoresis in humans

Selected Medicines Used in Iontophoresis

Iontophoresis is a non-invasive method of systemic and local drug delivery using an electric field. Iontophoresis enables diffusion of the selected drug via skin, mucosa, enamel, dentin, and other tissues. The amount of delivered therapeutic molecules is about 10⁻2000 times greater than conventional forms of delivery. Among other fields, this method is used in dentistry, ophthalmology, otorhinolaryngology, and dermatology. According to related literature, the most important drugs studied or administered by iontophoresis are: Local anesthetics, opioids, steroids, non-steroidal anti-inflammatory drugs, antibacterial drugs, antifungal drugs, antiviral drugs, anticancer drugs, fluorides, and vitamins. The present review covers current available data regarding the selected medicines used in iontophoresis. Furthermore, indications and conditions of iontophoresis application are reviewed.

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.

Temporomandibular disorders. Part 2: conservative management

Appropriate management of temporomandibular disorders (TMD) requires an understanding of the underlying dysfunction associated with the temporomandibular joint (TMJ) and surrounding structures. A comprehensive examination process, as described in part 1 of this series, can reveal underlying clinical findings that assist in the delivery of comprehensive physical therapy services for patients with TMD. Part 2 of this series focuses on management strategies for TMD. Physical therapy is the preferred conservative management approach for TMD. Physical therapists are professionally well-positioned to step into the void and provide clinical services for patients with TMD. Clinicians should utilize examination findings to design rehabilitation programs that focus on addressing patient-specific impairments. Potentially appropriate plan of care components include joint and soft tissue mobilization, trigger point dry needling, friction massage, therapeutic exercise, patient education, modalities, and outside referral. Management options should address both symptom reduction and oral function. Satisfactory results can often be achieved when management focuses on patient-specific clinical variables.

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.

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

STUDY DESIGN

Experimental laboratory study.

OBJECTIVES

To measure the transmission of dexamethasone sodium phosphate (DEX-P) using iontophoresis as a function of skinfold tissue thickness and time elapsed between treatment and tissue extraction.

BACKGROUND

Iontophoresis is a modality used in physical therapy with the intent to drive medications through the skin to underlying tissues using a direct electrical current. DEX-P is the most commonly used medication with iontophoresis and is used to treat a variety of connective tissue conditions.

METHODS AND MEASURES

Sixteen adults undergoing anterior cruciate ligament reconstructive surgery using the semitendinosis/gracilis autograft received a 40-mA-min dose of iontophoresis with 0.4% DEX-P superficial to a slip of the distal semitendinosis tendon prior to surgery. The tendon slip was extracted within 4 hours. Time between treatment and tissue extraction and skinfold thickness were measured. Analysis was performed on the slip of the semitendinosis using high-performance liquid chromatography mass spectrum.

RESULTS

Of the 16 subjects (10 female, 6 male; mean age, 33 years), 7 had measurable amounts of DEX-P in the tendon slip (4 female, 3 male; mean age, 34 years). The average concentration in the 16 subjects was 2.9 ng/g of tendon tissue. There was no correlation between DEX-P absorbed and skinfold thickness (r = -0.08, P = .79) or time elapsed (r = 0.25, P = .38). In a subset of the 7 individuals that showed measurable levels of DEX-P absorbed, the average concentration of DEX-P was 6.6 ng/g of tendon tissue, and there was a relationship between DEX-P concentrations and time elapsed that did not reach statistical significance (r = 0.71, P = .11).

CONCLUSIONS

Iontophoresis appears to facilitate the transmission of dexamethasone to connective tissues in humans with skinfold thickness up to at least 30 mm. The absorption of the dexamethasone seemed to continue to occur for up to 4 hours after delivery. It is not clear why DEX-P was measured in only 7 of the 16 subjects.

LEVEL OF EVIDENCE

Therapy, level 5.

Absorption of dexamethasone sodium phosphate in human connective tissue using iontophoresis

BACKGROUND

Iontophoresis ostensibly facilitates the delivery of medications through the skin to underlying tissues using a direct electrical current. Dexamethasone is the most commonly used medication with iontophoresis to treat a variety of connective tissue disorders.

HYPOTHESIS

Iontophoresis will facilitate the absorption of dexamethasone into connective tissue compared with diffusion.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty-nine adults undergoing anterior cruciate ligament reconstructive surgery using the semitendinosus/gracilis autograft were randomly assigned to either a true iontophoresis (TI) or sham iontophoresis (SI). In the TI group, a 40-mA/min dose of iontophoresis using a 0.4% (4 mg/mL) solution of dexamethasone was used targeting the semitendinosus tendon just before surgery. The SI group underwent the same treatment, but the machine was not turned on. Tissue was extracted within 4 hours of treatment and analyzed for dexamethasone. In addition, 2 control samples were sent to the laboratory for analysis.

RESULTS

There was a statistically significant difference in dexamethasone concentrations between the groups (P = .0216). Of the 16 samples in the TI group, 8 had measurable amounts of dexamethasone, with an average concentration of 2.906 ng/g of tendon tissue. In the SI group, 1 of the 13 samples had measurable amounts of dexamethasone with an average concentration of 0.205 ng/g of tendon tissue. The control samples contained no dexamethasone.

CONCLUSION

Iontophoresis facilitates the transmission of dexamethasone to connective tissues in humans.

CLINICAL RELEVANCE

Iontophoresis can deliver dexamethasone to connective tissues in humans.