Abstract: Objective To explore the model of drug penetration using low-pressure needle-free injector in treating keloid. Methods The drug was injected into the dorsal skin of fragrance pigs and in vitro keloid tissues with needle-free injector. The degree of diffusion and depth under different pressures and dosages were observed, and the pattern of the drug diffusion was also inspected. Results The degree of dispersion and depth were increased with the dosage under the same pressure, and the two values also showed a rise trend with the increase of the pressure in the same dosage. Using the traditional needle injection, the drug showed a nodular distribution in the keloid tissues. However, the drug was distributed in the superficial layer of the tissues under 150 psi using needle-free injector, ＂T＂ shape under 175 psi and ＂I＂ shape under 200 psi. Conclusion Under 150 psi and 175 psi, the drug can be injected into the superficial dermis and all the layers of keloid respectively by needle-free injector, while under 200 psi, it is appropriate for the treatment of the deeper and more compact keloid.

Key words: Needle-free injector, Keloid, Injection therapy