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

Conceptualization and Investigation of Multicomponent Polymer Networks as Prospective Corticosteroid Carriers

Dexamethasone (DXM) is a highly potent and long-acting synthetic glucocorticoid with anti-inflammatory, anti-allergic, and immunosuppressive effects. However, the systemic application of DXM can cause undesirable side effects: sleep disorders, nervousness, heart rhythm disorders, heart attack, and others. In the present study, multicomponent polymer networks were developed as potential new platforms for the dermal application of dexamethasone sodium phosphate (DSP). First, a copolymer network (CPN) comprising hydrophilic segments of different chemical structures was synthesized by applying redox polymerization of dimethyl acrylamide onto poly(ethylene glycol) in the presence of poly(ethylene glycol) diacrylate (PEGDA) as a crosslinker. On this basis, an interpenetrating polymer network structure (IPN) was obtained by introducing a second network of PEGDA-crosslinked poly(N-isopropylacrylamide). Multicomponent networks obtained were characterized by FTIR, TGA, and swelling kinetics in different solvents. Both CPN and IPN showed a high swelling degree in aqueous media (up to 1800 and 1200%, respectively), reaching the equilibrium swelling within 24 h. Additionally, IPN showed temperature-responsive swelling in an aqueous solution as the equilibrium swelling degree decreased considerably with an increase in the temperature. In order to evaluate the networks' potential as drug carriers, swelling in DSP aqueous solutions of varied concentration was investigated. It was established that the amount of encapsulated DSP could be easily controlled by the concentration of drug aqueous solution. In vitro DSP release was studied in buffer solution (BS) with pH 7.4 at 37 °C. The results obtained during DSP loading and release experiments proved the feasibility of the developed multicomponent hydrophilic polymer networks as effective platforms for potential dermal application.

Trilayer microneedle array assisted transdermal and intradermal delivery of dexamethasone

Dexamethasone is a synthesised glucocorticoid that is widely used in the treatment of various inflammatory skin conditions. Novel trilayer dissolving microneedle arrays were manufactured to assist dexamethasone delivery via the skin. Both transdermal delivery and intradermal delivery of dexamethasone can be achieved this way. Additionally, we proposed a novel strategy of co-formulating dexamethasone and its pro-drug dexamethasone sodium phosphate into the same dissolving microneedle array, with a view to achieving a fast onset of action and also sustained treatment. Here, a 3D-printing technique was employed, for the first time, to fabricate a baseplate for these microneedle arrays. The 3D-printed baseplates provided strong support to aid the insertion of the drug-encapsulated tips. A simple and rapid HPLC method was developed, and validated, to separate and quantify dexamethasone and dexamethasone sodium phosphate in the same sample. Ex-vivo studies found that these trilayer dissolving microneedle arrays could achieve a delivery efficiency of over 40% in intradermal delivery and over 50% in transdermal delivery. Trilayer microneedle-assisted delivery of this glucocorticoid provided a promising alternative to oral and parenteral routes of dexamethasone administration.

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.

Dexamethasone Sodium Phosphate Penetration During Phonophoresis at 2 Ultrasound Frequencies

CONTEXT

The effect of ultrasound frequency on phonophoresis drug delivery in humans is unknown.

OBJECTIVE

To determine if a low (45-kHz) or high (1-MHz) frequency delivered a higher dexamethasone (Dex) concentration through the skin.

DESIGN

Controlled laboratory study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 40 healthy men between the ages of 18 and 45 years (age = 23.1 ± 2.6 years, height = 176.1 ± 7.2 cm, mass = 88.5 ± 19.4 kg, posterior calf subcutaneous thickness measured using musculoskeletal ultrasound imaging = 0.6 ± 0.2 cm).

INTERVENTION(S)

Participants were randomly assigned to 1 of 4 groups (ultrasound frequency at microdialysis probe depth): (1) 45-kHz frequency at 1 mm, (2) 45-kHz frequency at 4 mm, (3) 1-MHz frequency at 1 mm, or (4) 1-MHz frequency at 4 mm (n = 10 in each group). Three linear microdialysis probes were inserted at the desired tissue depth. We rubbed dexamethasone sodium phosphate (Dex-P) into the skin and then applied a 15-minute phonophoresis treatment.

MAIN OUTCOME MEASURE(S)

Dialysate was collected during the treatment and 60 minutes posttreatment and analyzed for Dex-P, Dex, and the metabolite form of Dex. The sum of the 3 analytes was calculated as total dexamethasone (Dex-total), and differences between the 45-kHz and 1-MHz treatment groups were determined by a repeated-measures analysis of variance.

RESULTS

At 1 mm, 3 (30%) participants in the 45-kHz and 4 (40%) participants in the 1-MHz group had measurable levels of Dex-P. Total dexamethasone increased after the treatment ceased, independent of ultrasound frequency (P < .001), with a trend of the 45-kHz treatment to produce a greater increase in drug concentration (P = .006). At 4 mm, 5 (50%) participants in the 45-kHz and 1 (10%) participant in the 1-MHz group had measurable levels of Dex-P. We observed no difference in Dex-total concentration between treatment groups at 4 mm (P = .72).

CONCLUSIONS

Phonophoresis provided a mechanism for Dex-total delivery at the 1- and 4-mm tissue depths. However, the effectiveness of the ultrasound frequencies varied between the 2 measured tissue depths.

Wireless Versus Wired Iontophoresis for Treating Patellar Tendinopathy: A Randomized Clinical Trial

CONTEXT

The efficacy of the relatively new wireless iontophoresis patch compared with the traditional wired dose controller is unknown.

OBJECTIVE

To determine the differences among 2 iontophoresis drug-delivery systems (wireless patch versus wired dose controller) and a sham treatment in treating patellar tendinopathy.

DESIGN

Randomized controlled clinical trial.

SETTING

Physical therapy clinic.

PATIENTS OR OTHER PARTICIPANTS

Thirty-one participants diagnosed with patellar tendinopathy (men = 22, women = 9, age = 24.5 ± 5.9 years).

INTERVENTION(S)

Participants were randomly assigned into 1 of 3 treatment groups: wireless patch, wired dose controller, or sham treatment. Participants in the active treatment groups received six 80 mA/min iontophoresis treatments using 2 mL of 4% dexamethasone sodium phosphate. During each visit, clinical outcome measures were assessed and then the assigned treatment was applied.

MAIN OUTCOME MEASURE(S)

Clinical outcome measures were Kujala Anterior Knee Pain Scale, pressure sensitivity, knee-extension force, and sit-to-stand pain assessment using a numeric rating scale. For each clinical outcome measure, we used a repeated-measures analysis of covariance to determine differences among the treatment groups over the treatment period.

RESULTS

Participants reported a clinically important improvement on the Kujala Anterior Knee Pain Scale across all treatment groups, with no differences among groups (P = .571). A placebo effect was observed with pressure sensitivity (P = .0152); however, the active treatment decreased participants' pain during the sit-to-stand test (P = .042).

CONCLUSIONS

A placebo effect occurred with the sham treatment group. Generally, improvement was noted in all groups regardless of treatment type, but greater pain reduction during a functional task was evident within the active treatment groups during the sit-to-stand test. The wireless patch and wired dose controller treatments were equivalent across all variables.