5.3.2. Low-Energy Shock Wave

The term "shock wave" indicates a high-energy sound wave that terminates in a burst of energy, similar to a mini-explosion. Shock waves, continuously transmitted sonic waves at a 16–20 MHz frequency, can carry energy from an area of positive pressure to an area of negative pressure to propagate through mediums. Shock waves (SWs) may be applied in various medical situations because of its unique physical, physical–chemical, chemical, and biological effects. Thus, LESWs per se might have therapeutic effects for inflammatory disorders, such as chronic prostatitis and cystitis. In the physical phase, the tensile force of SW creates negative pressure, which causes cavitation and molecule ionization to affect the permeability of the plasma membrane. In basic studies, high energy levels (>0.12 mJ/mm2) SWs altered cell structure and organelles. By contrast, the capability of low-energy shock waves was to increase the tissue permeability without consequent cytotoxicity temporarily; thus, LESWs can facilitate the transfer of pharmaceutical molecules into cells [31].

Through LESW induction, Chuang et al. recorded bladder urothelium leakage of Gd-diethylenetriamine pentaacetic contrast medium through magnetic resonance imaging in rats [32]. Under these circumstances, intravesical onaBoNTA can penetrate into the bladder and suppress the rat's bladder hyperactivity induced by acetic acid. Nageib et al. conducted a clinical study to prove this concept of injection-free onaBoNTA delivery through LESWs [33]. They recruited 15 refractory OAB patients who received 100 U of onaBoNTA bladder instillation along with LESWs consisting of 3000 shocks over 10 min. The study results revealed a significant decrease in OAB symptom scores in patients at the 1 and 2-month checkpoints, but not at 3 months.
