The influence of ultrasound waves upon the permeation of theophylline through
cellophane membrane and rabbit skin was studied in vitro. Sonication was carried out with
continuous mode at intensities (0.5, 1, 1.5, & 2 W/cm2) at constant frequency 800 KHz for one
hour. Different gel formulations with (hydroxypropylmethyl cellulose, sodium
carboxymethylcellulose and carbopol 934P) in different concentrations (1-4% w/w) were
utilized. Phonophoresis of theophylline through rabbit skin were significantly less than that
obtained with the cellophane membrane. Ultrasound application has showed a significant
increase in the amount of theophylline permeation with increasing intensity. For all the tested
gelling agents, the amount of drug released was decreased by increasing polymer
concentrations. The Flux values were 5.99, 3.69 & 2.4 (μg/min cm2) for 2% HPMC, 4% Na
CMC and 2% carbopol 934P gels respectively. It was found that drug release from HPMC gels
obeys Zero-Order model while its release from Na CMC & carbopol 934P were fitted with
First-Order and Higuchi-diffusion model respectively.