Pharmacotherapeutic efficacy of preservative-free intravitreal triamcinolone acetonide

Hypothalamic-pituitary-adrenal axis function following intravitreal triamcinolone acetonide injection

To evaluate the pituitary-adrenal axis function by means of the adrenocorticotropic hormone (ACTH) stimulation test following a single intravitreal injection of triamcinolone acetonide (IVTA). Prospective comparative clinical interventional study. Twenty-eight patients (28 eyes) received a single IVTA (4 mg in 0.1 ml) for macular edema. The basal cortisol level and the response to 1 μg adrenocorticotropic hormone stimulation were determined on the morning before IVTA injection and at 1 day and 1, 2, and 4 weeks after IVTA injection. Results were compared with those obtained from a control group of 50 healthy subjects. All patients in the study had normal basal cortisol and normal response to ACTH challenge before receiving IVTA. 1 day following IVTA, basal cortisol was suppressed in one patient in the study group. Fasting serum cortisol levels at 1, 2, and 4 weeks after IVTA injection were normal in all patients in the study group. 1 day following IVTA, the peak response to ACTH at 30 min was blunted in four patients (14.3 % of the study group, p = 0.05) and the cortisol response at 60 min was suppressed (p = 0.009). 1 week following IVTA, the response to ACTH challenge was blunted in only one patient. A single IVTA injection may be associated with impaired hypothalamic-pituitary-adrenal function in some patients during the first 24 h following IVTA.

Pharmacokinetics of triamcinolone acetonide for the treatment of macular edema

INTRODUCTION

The use of intravitreal triamcinolone acetonide (TA) for the treatment of various types of macular edema has been widespread, particularly for the last decade. Currently, there is a scant amount of evidence-based literature evaluating the pharmacokinetic profile of TA despite clinical data showing the efficacy of intravitreal TA for multiple forms of macular edema.

AREAS COVERED

This paper is an extensive review of human and experimental studies published on the pharmacokinetics of TA for the treatment of macular edema. The literature search was conducted via OVID, TRIP Database and EMBASE, up to April 2011.

EXPERT OPINION

The pharmacokinetic profile of TA is unpredictable and the agent has a time-limited therapeutic action due to its relatively short half-life. This has led to the need for repeated injections. Future research should investigate the pharmacokinetic profiles of TA when administered intravitreally, as well as through alternate routes in more robust studies.

Enhanced oxygen saturation in optic nerve head of non-human primate eyes following the intravitreal injection of NCX 434, an innovative nitric oxide-donating glucocorticoid

PURPOSE

Hypoxia of the retina and optic nerve head (ONH) is believed to be pivotal in the development of ocular vascular disorders, including diabetic macular edema (DME). Glucocorticoids are among the most effective agents for the treatment of back of the eye diseases. However, this class of compounds is highly liable to increase intraocular pressure (IOP) and does not improve ocular perfusion or tissue oxygenation. Nitric oxide (NO) has vasodilating properties and lowers IOP in experimental models and humans, suggesting that its properties might complement those of glucocorticoids. NCX 434 is an NO-donating triamcinolone acetonide (TA) that is less likely to increase IOP while targeting both the vascular and inflammatory components of DME.

METHODS

NCX 434 was studied in vitro with respect to its NO-releasing properties in isolated methoxamine-precontracted rabbit aortic rings and glucocorticoid-like activity in recombinant human glucocorticoid receptors. IOP and oxygen saturation in the ONH and overlaying arteries and veins were studied in the anesthetized cynomolgus monkey. Measurements were taken using, respectively, an applanation tonometer and a hyperspectral imaging system before and 7, 14, 21, 31 and 41 days after the intravitreal injection of NCX 434 (5.8 mg/eye) or TA equimolar doses (4.0 mg/eye).

RESULTS

NCX 434 inhibited (3)H-dexamethasone-specific binding (IC(50)=34±5 nM) on human glucocorticoid receptors and elicited NO-dependent aortic ring relaxation (EC(50) of 0.5±0.1 μM, E(max) 98.9%). In monkey eyes, NCX 434 enhanced, whereas TA did not, oxygen saturation in various ONH areas (*P<0.05 vs. basal), decreased it in veins, and did not affect it in the overlaying arteries. Neither NCX 434 nor TA altered IOP significantly at all time points. However, at 31 days post-treatment TA appeared to start increasing IOP (Δ(IOP)=+3.31±0.51 mmHg, 30.8%, over baseline, NS).

CONCLUSIONS

NCX 434 enhances ocular tissue oxygenation. This feature appears to depend on its NO-donating properties; thus, the compound deserves to be further investigated for the treatment of DME and other ocular disorders with impaired ocular perfusion.