Drug and surfactant transport in Cyclosporine A and Brij 98 laden p-HEMA hydrogels

Drug transport in HEMA conjunctival inserts containing precipitated drug particles

“…The plots of % release from the inserts as a function of ffiffiffiffiffiffiffiffiffi ffi t=C p p (Fig. 6) do overlap for conjunctival inserts, which is consistent with release rates from devices that contain drugs dispersed as particles [32]. Therefore conjunctival inserts can be modeled as cylinders which contain drug embedded in a polymer matrix as particles.…”

“…Additionally, the curves in Fig. 4 are linear at long times, which is expected [32] but each curve has a non-linear curved portion at short times which is quite interesting. In fact, in the non-linear portion, the rate of drug released from each insert is the same, and is thus independent of the drug loading.…”

“…Additionally, there is a very rapid exchange of the bound and the free cyclosporine A molecules. Assuming that the exchange between the bound and free molecules is more rapid than diffusive time scales, an effective diffusivity, D, can be defined taking into account both surface and free diffusion of the bound and the free forms [32] D ¼…”

“…Below, we develop a mathematical model for drug release from the inserts that takes both resistances into account and explains all the observed trends in the drug release profiles. Since the drug loading is above the solubility limit, the hydrated conjunctival inserts contain drug in three forms [32]: (i) free drug dissolved in the fluid that hydrates the gel, (ii) drug adsorbed on the polymer surface, and (iii) drug present as aggregates/particles. On exposing the inserts to PBS, the un-aggregated drug diffuses out of the insert to reduce the free concentration of the drug below the solubility limit, which leads to dissolution of the drug particles.…”

Ocular Drug Delivery Role of Contact Lenses

“…3 Using nanoparticles/ colloid carriers to increase the release duration from the contact lenses has also been proposed by some other authors. [33][34][35][36] …”