Send to

Choose Destination
J Ocul Pharmacol Ther. 2013 Sep;29(7):633-8. doi: 10.1089/jop.2012.0226. Epub 2013 Apr 18.

The effect of ocular pigmentation on transscleral delivery of triamcinolone acetonide.

Author information

Wenzhou Medical College, Institute of Ocular Pharmacology, School of Ophthalmology and Optometry, Wenzhou, China.



To determine the capacity and kinetics of the binding between triamcinolone acetonide (TA) and the ocular pigment for a better understanding of the transscleral delivery.


In the in vitro study, natural melanin (sepia officinalis, Sigma-Aldrich) was incubated at 37°C with different concentrations of TA and the binding capacity/binding affinity was measured. The TA releasing profile from the melanin was also studied through repeated incubation of TA-melanin in fresh phosphate-buffed saline. In the ex vivo study, the effect of the choroidal pigment on the trans sclera/choroid permeability of TA was investigated through Franz-type vertical diffusion cells using both a TA suspension and a saturated TA solution.


The amount of TA bound to melanin increases with the increase of the TA concentration and with an increase in the incubation time. A Scatchard analysis revealed that the maximum number of moles of TA bound to melanin is predicted to be 22.43 nmol/mg, with a binding affinity of K=2.4×10(-5) nM(-1). TA released from a pigment showed a fast phase within the first 24 h and a slow phase thereafter. About 40% of the bound TA released in the first day and 73.94% of accumulative release was observed after 5 days. The TA suspension showed more TA penetration through the scleral-choroid complex than the saturated solution (P=0.0104). The apparent permeability coefficients for the suspension across the sclera-choroid of pigmented and albino rabbits are 7.48±1.53×10(-6) cm/s and 10.78±2.49×10(-6) cm/s, respectively.


TA can bind to and release from the ocular pigment, which may extend the TA ocular half-life and therapeutic duration when TA is delivered through a subtenon injection. A further in vivo study is warranted to validate the findings and to quantitate the magnitude of the difference between pigmented and albino animals.

[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Atypon Icon for PubMed Central
Loading ...
Support Center