Clinical Diathermy Performance Evaluation of Multi-hour Sustained Acoustic Medicine Treatment with 2.5% Diclofenac Ultrasound Coupling Patch

BACKGROUND: Low-intensity Continuous Ultrasound (LICUS) therapy heals soft tissue injuries. It alleviates acute and chronic musculoskeletal pain by activating multiple healing processes through its diathermic and mechanotransducive properties. Diclofenac has been FDA-approved as a Non-Steroidal Anti-Inflammatory Drug (NSAID). It is an analgesic and anti-inflammatory drug available in oral and topical forms. Adding 2.5% diclofenac sodium to ultrasound coupling gel can be used to deliver LICUS in addition to the analgesic effects of diclofenac sodium without altering the diathermic and acoustic effects of the ultrasound penetration with no undesired adverse effects. OBJECTIVE: To determine the effects of adding 2.5% diclofenac sodium to standard aqueous ultrasound gel on the ultrasound coupling and diathermic properties of a long duration Sustained Acoustic Medicine (SAM) treatment. METHODS: In a two-phase study, first, the acoustic and diathermic changes were determined in bovine tissue during 4-hour-long SAM stimulation at 1 cm, 2 cm, and 5 cm with aqueous and 2.5% diclofenac ultrasound coupling patch. Then, in the second phase, the heating profiles were recorded with and without 2.5% diclofenac gel in 54 healthy adult subjects at the forearm and calf during the SAM treatment. RESULT: The addition of 2.5% diclofenac sodium significantly increased coupling gel density, acoustic impedance, and signal propagation (p<0.0001) with little or no effect on the diathermic profiles at 1 cm, 2 cm, and 5 cm depth. The coupling gel with 2.5% diclofenac sodium sustained the therapeutic ultrasound intensity longer than the aqueous coupling gel (5.5 cm relative to 4.5, p<0.0009). No significant diathermic difference was recorded on the calf and forearm skin with a 2.5% diclofenac ultrasound gel coupling patch. CONCLUSION: Adding 2.5% diclofenac sodium to ultrasound gel increases acoustic impedance, improves ultrasound signal coupling into deep tissue, and provides longer sustained deep tissue heating without negatively impacting the diathermic profile during SAM treatment.