To improve our understanding of the pharmacokinetics of triamcinolone acetonide (TA) and TA concentration in ocular tissue, TA concentration was measured in ocular tissue after intravitreal and subtenon injection.

Fifteen rabbit eyes underwent subtenon TA injection (40 mg/1 ml), and another 15 rabbit eyes underwent intravitreal TA (4 mg/0.1 ml) injection. All eyes were enucleated at 1, 2, 4, 8, and 12 weeks after subtenon and intravitreal injection, and TA concentration in the aqueous and vitreous humor and the retina-choroid were measured by high performance liquid chromatography (HPLC).

In cases of subtenon's TA injection, TA concentrations were 0 ng/ml, 136.7 ng/ml, 178.7 ng/ml, 0 ng/ml, and 0 ng/ml in the aqueous humor; 99.1 ng/ml, 125.7 ng/ml, 726.8 ng/ml, 0 ng/ml, and 0 ng/ml in the vitreous humor; 72.7 ng/ml, 304.6 ng/ml, 459.0 ng/ml, 0 ng/ml, and 0 ng/ml in the retina-choroid after 1, 2, 4, 8, and 12 weeks, respectively. In cases of intravitreal TA injection, the measured values were 0 ng/ml, 0 ng/ml, 0 ng/ml, 654.1 ng/ml, and 0 ng/ml in the aqueous humor; 28152.2 ng/ml, 13646.4 ng/ml, 11388.8 ng/ml, 10297.2 ng/ml, and 183.0 ng/ml in the vitreous humor; and 0 ng/ml, 27.9 ng/ml, 108.3 ng/ml, 0 ng/ml, and 0 ng/ml in the retina-choroid at each time point.

Intravitreal TA injection may be more effective for drug delivery than subtenon TA injection, but subtenon TA injection seems to be an effective and safe technique.