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.

A Novel Blue-Red Photobiomodulation Therapy Patch Effects on a Repetitive Elbow-Flexion Fatigue Task.

BACKGROUND: Photobiomodulation (laser/light) therapy has reduced skeletal muscle fatigue and improved performance in previous research. OBJECTIVE: To determine if the application of a novel blue (450 nm) and red (645 nm) light-emitting diode photobiomodulation therapy patch improves muscle function and decreases perceived exertion after an elbow-flexion fatigue protocol. PARTICIPANTS: Thirty-four strength-trained individuals (male = 32 and female = 2, age = 22.5 [2.7] y). METHODS: Participants were randomly assigned to an active or placebo treatment. On  visit 1, participants' 1-repetition maximal biceps curl was determined, and an orientation session of the fatigue task occurred to ensure no learning effects. Fifty percent of the participants' 1-repetition maximum was used during the fatigue protocol. On visit 2, participants performed biceps curl repetitions at a speed of 25 repetitions per minute until they could not physically move the weight past 90° of elbow flexion or stay with the set pace. After the fatigue protocol, a 30-minute blue/red light (wavelength = 450 and 645 nm, peak irradiance = 9 mW/cm2, duty cycle = pulsed 33%, and fluence = 5.4 J/cm2) or sham treatment was administered based on the randomized group assignment. Immediately following, the participants repeated the fatigue protocol. The number of complete repetitions was counted, and the participants rated their perceived level of exertion on the Borg scale immediately after each fatigue bout. RESULTS: Overall, fatigue occurred between the 2 exercise bouts (pretreatment = 44.1 [12.3] and posttreatment = 37.4 [9.6] repetitions, P = .02). However, less fatigue was noted in the number of participants of the active treatment group than the sham treatment group. During the posttreatment fatigue task, 29.4% of participants in the active treatment group improved compared to 0% in the sham treatment (P = .045). CONCLUSION: Nearly 30% of participants had an increase benefit during a repeated-bout fatigue task due to the blue/red light-emitting diode photobiomodulation light patch.