The biodistribution of triamcinolone acetonide injections in severe keloids: an exploratory three-dimensional fluorescent cryomicrotome study.

Intralesional corticosteroid injections are a first-line treatment for keloids; yet clinical treatment results are highly variable and often suboptimal. Variation in triamcinolone acetonide (TAC) biodistribution may be an important reason for the variable effects of TAC treatment in keloids. In this exploratory study we investigated the biodistribution of TAC in keloids and normal skin using different drug delivery techniques. Fluorescent-labeled TAC suspension was administered into keloids and normal skin with a hypodermic needle and an electronic pneumatic jet injector. TAC biodistribution was represented by the fluorescent TAC volume and 3D biodistribution shape of TAC, using a 3D-Fluorescence-Imaging Cryomicrotome System. Twenty-one keloid and nine normal skin samples were analyzed. With needle injections, the mean fluorescent TAC volumes were 990 µl ± 479 in keloids and 872 µl ± 227 in normal skin. With the jet injector, the mean fluorescent TAC volumes were 401 µl ± 252 in keloids and 249 µl ± 67 in normal skin. 3D biodistribution shapes of TAC were highly variable in keloids and normal skin. In conclusion, TAC biodistribution in keloids is highly variable for both needle and jet injection. This may partly explain the variable treatment effects of intralesional TAC in keloids. Future research is needed to confirm this preliminary finding and to optimize drug delivery in keloids.

Enigma of Intramuscular Triamcinolone Acetonide (Kenalog®) Efficacy.

Triamcinolone acetonide is a glucocorticosteroid used in standard clinical practice for its anti-inflammatory properties. Although it can be given via different routes of administration, the intramuscular route is unique compared with other corticosteroids-its effects remain potent over a longer period of time. We summarize the existing literature on the pharmacokinetic and pharmacodynamic mechanisms of intramuscular triamcinolone acetonide (Kenalog®). The fascinating nature of the purported efficacy of triamcinolone acetonide may be attributed to differing binding mechanisms, low solubility in blood, a low renal clearance rate, and various metabolites and other yet defined effects on skin. The enigma of the purported efficacy of triamcinolone acetonide may lie in the fact that it has a unique nature of having a long-term effect on dermatologic disease using a seemingly low dose compared with other routes of administration and other corticosteroids. Possible reasons for this may be binding differences at the intramuscular site, low solubility due to acetonide esters, a slow rate of absorption from the injected site, and a low renal clearance rate. There is still much to be learned about its mechanism of action, which may be of clinical and therapeutic significance.

Dose identification of triamcinolone acetonide for noninvasive pre-corneal administration in the treatment of posterior uveitis using a rapid, sensitive HPLC method with photodiode-array detector.

Triamcinolone acetonide (TAA) is the drug of choice in the management of ocular inflammations due to its anti-inflammatory and immuno-suppressant activity. Available marketed formulations (Triesence, Trivaris, Kenalog) are in the suspension form recommended to be administered via intravitreal injection, which has many major complications. In the present study, we have designed and evaluated Hydroxypropyl-ß-cyclodextrin (HP-ß-CD),) based conventional formulations of TAA (aqueous suspensions) with different dose strengths to identify the dose strength required for achieving the effective concentrations in vitreous humor following pre-corneal administration of the formulations. Ocular pharmacokinetic studies of conventional formulations of triamcinolone acetonide (TAA) with different dose strengths (1 mg/30µL, 2 mg/30µL, 4 mg/30µL) were performed to identify the dose strength required to produce effective concentrations of TAA in the aqueous and vitreous humor. A rapid, sensitive, selective, accurate and precise bioanalytical method utilizing a small sampling volume (<45 µL) was developed and validated for quantification of TAA in the samples obtained from the ocular pharmacokinetic studies. Aqueous suspensions of TAA with 20% HP-ß-CD produced time course profiles in the aqueous humor at all the dose strengths. However, measurable concentrations and time course of TAA in vitreous humor were achieved only with 4 mg/30µL dose strength.

Evaluation of Levels of Triamcinolone Acetonide in Human Perilymph and Plasma After Intratympanic Application in Patients Receiving Cochlear Implants: A Randomized Clinical Trial.

Importance: The use of intratympanically applied steroids is of increasing interest. Consequently, research has focused on finding an ideal drug that diffuses through the round window membrane and can be retained in the perilymph. Objective: To compare levels of triamcinolone acetonide (TAC) in perilymph and plasma after intratympanic injection. Design, Setting, and Participants: This randomized clinical trial included 40 patients receiving cochlear implants at a single tertiary care center in Vienna, Austria. Patients were randomized to 1 of 4 treatment groups receiving 1 of 2 intratympanic doses of TAC (10 mg/mL or 40 mg/mL) at 1 of 2 approximate time points (24 hours or 1 hour) before sampling the perilymph. Inclusion was carried out between November 2017 and January 2020, and data were analyzed in December 2020. Interventions: All patients underwent intratympanic injection of TAC. During cochlear implantation, perilymph and plasma were sampled for further analysis. Main Outcomes and Measures: Levels of TAC measured in perilymph and plasma. Results: Among the 37 patients (median [range] age, 57 [26-88] years; 18 [49%] men) included in the analysis, TAC was present at a median (range) level of 796.0 (46.4-7706.7) ng/mL. In the majority of patients (n = 29; 78%), no drug was detectable in the plasma after intratympanic injection. Levels above the limit of detection were less than 2.5 ng/mL. The 1-factorial analysis of variance model showed lower TAC levels in the group that received TAC, 10 mg/mL, 24 hours before surgery (median, 271 ng/mL) compared with the group that received TAC, 10 mg/mL, 1 hour before surgery (median, 2877 ng/mL), as well as in comparison with the groups receiving TAC, 40 mg/mL, 24 hours before surgery (median, 2150 ng/mL) and 1 hour before surgery (median, 939 ng/mL). The 2-factorial analysis of variance model showed lower TAC levels in the group receiving TAC, 10 mg/mL, 24 hours before surgery than the group receiving TAC, 10 mg/mL, 1 hour before surgery, and higher TAC levels in the group receiving TAC, 40 mg/mL, 24 hours before surgery compared with the group receiving TAC, 10 mg/mL, 24 hours before surgery. Patients with thickening of the middle ear had statistically significantly higher plasma levels (median, 1.4 ng/mL vs 0 ng/mL) and lower perilymph levels (median, 213.1 ng/mL vs 904 ng/mL) than individuals with unremarkable middle ear mucosa. Conclusions and Relevance: In this randomized clinical trial, TAC was shown to be a promising drug for intratympanic therapies, with similar levels in perilymph 1 hour and 24 hours after injection (distinctly in the groups receiving the 40 mg/mL dose). There was also minimal dissemination to the plasma, especially in patients with unremarkable middle ear mucosa. Trial Registration: ClinicalTrials.gov Identifier: NCT03248856.

Serum triamcinolone levels during intensive, inpatient wet-dressing therapy.

BACKGROUND: Wet dressings combined with topical corticosteroids are beneficial for patients with generalized and refractory dermatosis; however, to our knowledge, serum levels after topical corticosteroid absorption during intensive therapy have not been reported previously. AIM: To examine serum levels of triamcinolone acetonide (TAC) after topical corticosteroid application during intensive wet-dressing therapy. METHODS: We performed a retrospective study of adult patients admitted for inpatient wet-dressing therapy from 7 November 2015 to 24 June 2016. Data were collected on sex, age, body surface area, TAC serum levels, number of wet-dressing changes after 24 and 48 h, and type of wet dressing. RESULTS: In total, 29 patients (14 men, 15 women) were assessed. Median [interquartile range (IQR)] age was 57 years (51.5-67.0 years) and involved body surface area was 1.98 m2 (1.88-2.15) m2 . Before the 24-hour blood draw, patients had received 1-3 dressing changes. Median (IQR) TAC level at 24 h was 0.33 µg/dL (0.20-0.58 µg/dL), with no significant difference noted between the number of dressing changes and TAC serum level. At 48 h, results of a serum TAC test were available for 22 patients with 2-6 dressing changes. Mean (IQR) serum level was 0.30 µg/dL (0.30-0.87 µg/dL). For each additional dressing change, there was an estimated 0.21 µg/dL increase in TAC serum level (95% CI 0.11-0.31; P < 0.001). TAC serum level was not significantly associated with sex, age, body surface area or dressing type. CONCLUSIONS: Intensive, inpatient wet-dressing therapy is associated with detectable TAC serum levels. However, we suspect that topical TAC has a primarily local therapeutic effect on the skin.

Flow-through cell-based in vitro release method for triamcinolone acetonide poly (lactic-co-glycolic) acid microspheres.

The main objective of the current research was to develop a compendial flow-through cell apparatus based in vitro release testing method for sustained-release triamcinolone acetonide-loaded poly (lactic-co-glycolic) acid (PLGA) microspheres. Media-based and instrument-based parameters, such as surfactant type, concentration, media volume, flow rate, and testing temperature, were investigated. In addition, a detailed exploration was performed to reveal polymer degradation encompassing pore formation, channeling, and triamcinolone acetonide release from microspheres using freeze-fracture scanning electron microscopy. The developed USP apparatus 4 method demonstrated more than 85% drug release from the microspheres in 12 days and showcased reproducibility between different microsphere batches. Large medium volume (15 times saturation solubility) at low surfactant concentration was identified as a critical media-based parameter, with potential application in testing of other sensitive poorly soluble drugs. At 35 °C, drug release via pore channeling to the surface was evident, whereas at 39 °C, drug release slowed due to polymer plasticization. It was demonstrated here for the first time that elevated temperature-accelerated testing does not work for all PLGA-based microsphere products.

Development and validation of a LC-MS/MS method for simultaneous determination of six glucocorticoids and its application to a pharmacokinetic study in nude mice.

In this study, a simple, rapid and sensitive LC-MS/MS analytical method for simultaneous determination of six glucocorticoids including 21-hydroxy deflazacort (21-OH DFZ), prednisolone (PNL), betamethasone (BET), beclomethasone (BEC), triamcinolone acetonide (TCA), budesonide (BUD) in nude mice plasma was developed and validated. Using testosterone as internal standard, the plasma samples were prepared by precipitation with acetonitrile and separated using an ACQUITY UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 µm) with a mobile phase composed of acetonitrile and 0.1 % (v/v) formic acid aqueous solution by gradient elution at a flow rate of 0.3 mL/min. Quantitation was performed on a triple quadruple tandem mass spectrometer by multiple reaction monitoring in positive electrospray ionization mode. Calibration curves were developed over the range of 1-400 ng/mL for TCA, 5-2000 ng/mL for 21-OH DFZ, BET, BEC as well as BUD, and 10-2000 ng/mL for PNL. The accuracy, precision, matrix effect, recovery and stability were validated to be within acceptable criteria. The method was successfully applied to a preclinical pharmacokinetic (PK) study of the six GCs on female nude mice after a single oral dose of 1 mg/kg. The PK profiles of all the six GCs were described by two-compartment model with first-order absorption rate.

Triamcinolone acetonide-chitosan coated liposomes efficiently treated retinal edema as eye drops.

Macular edema (ME), which is present in various retinal diseases, leads to permanent retinal structural damage and threatens vision. The intravitreal/periocular injection of triamcinolone acetonide (TA) can improve the prognosis of ME; however, further exploration of noninvasive delivery systems is essential. Therefore, as a continuation of our previous study using TA-chitosan coated liposomes (TA-CHLs) as a topical drug delivery system, the present study aimed to determine the drug safety, stability, permeability, and bioavailability of TA-CHLs. The study was based on detecting the delivery of a fluorescent dye to the retina using optical coherence tomography angiography in rats. Marked cellular uptake was observed in cell lines. TA-CHL toxicity was investigated in cell culture. Clinical ocular safety was evaluated by measuring the corneal thickness and intraocular pressure. In preclinical studies on a laser-induced retinal edema rat model, the TA-CHL eye drops had dramatic therapeutic effect in remission of retinal edema over 10 days. These results demonstrated that TA-CHL was nontoxic and had good bioavailability in vitro and in vivo. The results of the present study indicated that this formulation could be an effective therapeutic approach and the TA-CHL eye drops may represent a new option for retinal diseases.

Strategy for hypertrophic scar therapy: Improved delivery of triamcinolone acetonide using mechanically robust tip-concentrated dissolving microneedle array.

A hypertrophic scar (HS) is a cutaneous condition characterized by deposits of excessive amounts of collagen that produces a raised scar, causing physical, psychological, and cosmetic problems for the patient. The therapeutic efficacy of conventional transdermal drug delivery systems is often limited because the HS tissue is more compact than normal skin. At present, intralesional multi-injection of triamcinolone acetonide (TA) using a syringe is one of the most commonly used treatments for HS. However, the efficacy of this treatment is highly dependent on the skill of the medical professionals administering the injection. Even with co-administration of local anesthetics, traditional injection still causes pain to the patients, resulting in poor compliance. The purpose of this study was to provide an alternative treatment for HS by establishing a novel intradermal delivery system with a dissolving microneedle array (DMNA). To produce needles of higher mechanical strength for successful insertion into the compact and hard HS tissue, hydroxypropyl-ß-cyclodextrin (HP-ß-CD) was added into sodium hyaluronic acid (HA), the needle material. The hydrogen interaction between HP-ß-CD and HA restricted the mobility of the molecular chains, and subsequently increased the elastic modulus of the complex materials. The HP-ß-CD also contributed to improved loading of the hydrophobic drug molecules into the DMNA needle tips. To assess the delivery of TA to the HS site via DMNA, an HS model was established in the ventral skin of New Zealand rabbits' ears. It was found that the value of the scar elevation index was decreased to normal, together with the down regulation of mRNA expressions of Collagen I and transforming growth factor-ß1 (TGF-ß1) following the administration of DMNA containing TA (TA-DMNA). Western blotting results also revealed decreased protein expressions of both Collagen I and TGF-ß1. Hence, TA-DMNA appears to be a promising alternative to multi-injection of TA injection, providing a convenient and low-pain therapeutic strategy for HS treatment.

A Kinetic Approach to Determining Drug Distribution in Complex Biphasic Systems.

Pharmaceutical emulsions contain multiple components, such as micellar, aqueous, and oil phases, leading to complex drug transfer and equilibrium phenomena. These complex components present challenges for the bioequivalence assessment of the drug products. The objective of the study was to develop a method that can probe the underlying mechanism and process of drug distribution. The concept of drug partitioning into biphasic systems was used to simplify the complex transfer phenomenon. A kinetic method was developed taking into account the biphasic diffusion. Using this approach, both the rate (kinetics) and the extent (equilibrium) of distribution can be determined. For method development purpose, 3 model compounds (triamcinolone acetonide, difluprednate, and cyclosporine), with expected partition coefficient values ranging from 2 to 6, were tested using the kinetic method and the traditional shake-flask method. The values obtained by the 2 methods for all compounds correlated well (r2 = 0.825). Various organic and aqueous solvents which are commonly encountered in formulations were also tested to determine the impact of phase composition on drug distribution. The kinetic method was found to offer more flexibility in terms of solvent composition and can lead to better understanding for drug distribution and potential drug release in complex biphasic systems.

Glucocorticoids exert differential effects on the endothelium in an in vitro model of the blood-retinal barrier.

PURPOSE: Glucocorticoids (GCs) are used as treatment in diabetic macular oedema, a condition caused by blood-retinal barrier (BRB) disruption. The proposed mechanisms by which GCs reduce macular oedema are indirect anti-inflammatory effects and inhibition of VEGF production, but direct effects on the BRB endothelium may be equally important. Here, we investigated direct effects of GCs on the endothelium to understand the specific pathways of GC action, to enable development of novel therapeutics lacking the adverse side-effects of the presently used GCs. METHODS: Primary bovine retinal endothelial cells (BRECs) were grown on Transwell inserts and treated with hydrocortisone (HC), dexamethasone (Dex) or triamcinolone acetonide (TA). Molecular barrier integrity of the BRB was determined by mRNA and protein expression, and barrier function was assessed using permeability assays. In addition, we investigated whether TA was able to prevent barrier disruption after stimulation with VEGF or cytokines. RESULTS: Treatment of BRECs with GCs resulted in upregulation of tight junction mRNA (claudin-5, occludin, ZO-1) and protein (claudin-5 and ZO-1). In functional assays, only TA strengthened the barrier function by reducing endothelial permeability. Moreover, TA was able to prevent cytokine-induced permeability in human retinal endothelial cells and VEGF-induced expression of plasmalemma vesicle-associated protein (PLVAP), a key player in VEGF-induced retinal vascular leakage. CONCLUSION: Glucocorticoids have differential effects in an experimental in vitro BRB model. TA is the most potent in improving barrier function, both at the molecular and functional levels, and TA prevents VEGF-induced expression of PLVAP.

Controlled non-invasive iontophoretic delivery of triamcinolone acetonide amino acid ester prodrugs into the posterior segment of the eye.

This study investigated short duration transscleral iontophoretic delivery of four triamcinolone acetonide (TA) amino acid ester prodrugs (TA-AA) (alanine, Ala; arginine, Arg; isoleucine, Ile and lysine, Lys) using whole porcine eyes globes in vitro. Post-iontophoretic biodistribution of TA was quantified by UHPLC-MS/MS in the different ocular compartments (cornea, aqueous humor, sclera, ciliary body, choroid and retinal pigmented epithelium (RPE), neural retina and vitreous humor). Transscleral iontophoresis (3 mA/cm2 for 10 min) increased total drug delivery of the TA-AA prodrugs by 14-30-fold as compared to passive diffusion. The TA-AA prodrugs had distinct biodistribution profiles - the penetration depth achieved was dependent on their physicochemical properties (e.g. lipophilicity for TA-Ile) and susceptibility to hydrolysis (e.g. TA-Arg). Intraocular drug distribution was also influenced by prodrug binding to melanin (TA-Lys). Interestingly, under conditions of equivalent charge (6 mA/cm2 for 5 min vs. 1.5 mA/cm2 for 20 min, i.e. 1.44 C respectively) the longer duration (20 min) at lower current density resulted in ∼6 times more TA delivery into the vitreous humor. Overall, the study provided further evidence of the potential of transscleral iontophoresis for the non-invasive treatment of posterior segment inflammatory diseases.

Characterization and Pharmacokinetics of Triamcinolone Acetonide-Loaded Liposomes Topical Formulations for Vitreoretinal Drug Delivery.

PURPOSE: To achieve a safer alternative to intravitreal injection of corticosteroids, we developed and characterized triamcinolone acetonide-loaded liposomes formulations (TA-LFs) to be used topically for vitreoretinal drug delivery. METHODS: Four different 0.2% TA-LFs (TA-LF1 to TA-LF4) were generated and submitted to physicochemical characterization. Posteriorly, an ex vivo diffusion assay was performed using rabbit corneas as membranes. Finally, concentrations of triamcinolone acetonide (TA) were determined by high-performance liquid chromatography in ocular tissues from New Zealand white rabbits after multiple topical doses of TA-LF2 (6 times per day, 14 days). In addition, toxicity and tolerability of TA-LF2 was evaluated by cell viability assay and eye examination of study animals, respectively. RESULTS: TA-LF2 was the most stable formulation maintaining a stable hidrogenion potential (pH) at 30 and 40°C and even improving encapsulation with higher temperature. TA-LF2 and TA-LF3 presented the best diffusion performance in vitro reaching the highest TA concentrations after 8 h of follow-up. In vivo diffusion and pharmacokinetics analysis showed that concentrations of TA in retina and vitreous reached the highest peak at 12 h after topical administration of TA-LF2 (252.10 ± 90.00 ng/g and 32.6 ± 10.27 ng/g, respectively) and subsequently decline to 24.0 ± 11.72 ng/g and 19.5 ± 13.14 ng/g, respectively, at 14 days of follow-up. Finally, cell viability was unaffected by TA-LF2, and no increase in intraocular pressure nor ocular alterations were observed after topical administration of this formulation in rabbits. CONCLUSION: TA-loaded liposomes, administered topically, can deliver TA in the vitreous cavity and reach the retina efficiently.

Microemulsion-based delivery of triamcinolone acetonide to posterior segment of eye using chitosan and butter oil as permeation enhancer: an in vitro and in vivo investigation.

The aim of the study was to formulate a microemulsion (ME) using chitosan (CH) and the butter oil (BO) as a permeation enhancer for targeting drug to the posterior segment of the eye, via topical route. Triamcinolone acetonide (TA) was selected as the model drug since it undergoes extensive first-pass metabolism, leading to poor oral bioavailability of 23%. For optimisation of BO concentration, different ratios of TA:BO were prepared by simple physical mixing in the ratio of 1:9 to 9:1 and diffusion study was performed. MEs containing TA, TA:BO and TA CH ME were formulated by water titration method. Globule sizes of TA ME, TA:BO ME and TA CH ME were found to be 66.06 ± 0.32 nm, 78.52 ± 1.50 nm and 97.30 ± 2.50 nm, respectively. In ex vivo diffusion studies using goats eye, TA:BO ME (31.33 ± 0.46 and 33.98 ± 0.23) and TA CH ME (24.10 ± 0.41 and 27.00 ± 0.18) showed higher percentage of drug diffusion in comparison to TA ME (13.29 ± 0.41and 15.56 ± 0.34) and TA solution (8.20 ± 1.04 and 10.39 ± 0.22) in presence and in absence of vitreous humour. Fluorescence intensity of coumarin-6 (as a marker) loaded ME with BO and CH was found to be higher, confirming their role in altering membrane permeability and facilitating coumarin-6 diffusion to the posterior chamber. Overall, it was concluded that BO enhances the bioavailability of TA across the retina, thereby proving its potential as permeation enhancer in facilitating drug delivery to the posterior segment of the eye.

Synthesis and Characterisation of Photocrosslinked poly(ethylene glycol) diacrylate Implants for Sustained Ocular Drug Delivery.

PURPOSE: To investigate the sustained ocular delivery of small and large drug molecules from photocrosslinked poly(ethylene glycol) diacrylate (PEGDA) implants with varying pore forming agents. METHODS: Triamcinolone acetonide and ovalbumin loaded photocrosslinked PEGDA implants, with or without pore-forming agents, were fabricated and characterised for chemical, mechanical, swelling, network parameters, as well as drug release and biocompatibility. HPLC-based analytical methods were employed for analysis of two molecules; ELISA was used to demonstrate bioactivity of ovalbumin. RESULTS: Regardless of PEGDA molecular weight or pore former composition all implants loaded with triamcinolone acetonide released significantly faster than those loaded with ovalbumin. Higher molecular weight PEGDA systems (700 Da) resulted in faster drug release of triamcinolone acetonide than their 250 Da counterpart. All ovalbumin released over the 56-day time period was found to be bioactive. Increasing PEGDA molecular weight resulted in increased system swelling, decreased crosslink density (Ve), increased polymer-water interaction parameter (χ), increased average molecular weight between crosslinks (Mc) and increased mesh size (ε). SEM studies showed the porosity of implants increased with increasing PEGDA molecular weight. Biocompatibility showed both PEGDA molecular weight implants were non-toxic when exposed to retinal epithelial cells over a 7-day period. CONCLUSION: Photocrosslinked PEGDA implant based systems are capable of controlled drug release of both small and large drug molecules through adaptations in the polymer system network. We are currently continuing evaluation of these systems as potential sustained drug delivery devices.

Investigation of dissolved cellulose in development of buccal discs for oromucosal drug delivery.

Mucoadhesive formulations have a wide scope of application for both systemic and local treatment of various diseases. In the case of recurrent aphthous stomatitis, to ensure effective therapy, the concentration of corticosteroids, and/or anesthetics at the mouth ulcer side should be maintained with minimal systemic absorption. Therefore, the aim of the study was to investigate cellulose-based formulations, in achieving suitable hardness, mucoadhesiveness, and sustained release of the active ingredients directed towards the mucosa for an extended period of time (∼4 h). This was examined by creating polymer reinforced cellulose composites which consisted of porous cellulose discs (CD) and different polymer components namely polyethylene glycol 6000 (PEG6000), polyethylene glycol 400 (PEG400), and ethyl cellulose. Empty CDs were formed by dropping dissolved cellulose into coagulation medium. The empty porous CDs were immersed into different drug loading solutions which were prepared by dissolving three different concentrations of triamcinolone acetonide and lidocaine hydrochloride in five different ratios of PEG 6000:PEG 400:ethanol (w:w:w %) solutions. All formulations were investigated regarding drug content, release, hardness, and mucoadhesive properties. The results indicate that the non-dispersing buccal discs had sufficient hardness, drug content and in vitro release properties, but further studies are needed to achieve proper mucoadhesiveness.

Synovial and systemic pharmacokinetics (PK) of triamcinolone acetonide (TA) following intra-articular (IA) injection of an extended-release microsphere-based formulation (FX006) or standard crystalline suspension in patients with knee osteoarthritis (OA).

OBJECTIVE: Intra-articular (IA) corticosteroids relieve osteoarthritis (OA) pain, but rapid absorption into systemic circulation may limit efficacy and produce untoward effects. We compared the pharmacokinetics (PK) of IA triamcinolone acetonide (TA) delivered as an extended-release, microsphere-based formulation (FX006) vs a crystalline suspension (TAcs) in knee OA patients. METHOD: This Phase 2 open-label study sequentially enrolled 81 patients who received a single IA injection of FX006 (5 mL, 32 mg delivered dose, N = 63) or TAcs (1 mL, 40 mg, N = 18). Synovial fluid (SF) aspiration was attempted in each patient at baseline and one post-IA-injection visit (FX006: Week 1, Week 6, Week 12, Week 16 or Week 20; TAcs: Week 6). Blood was collected at baseline and multiple post-injection times. TA concentrations (validated LC-MS/MS, geometric means (GMs)), PK (non-compartmental analysis models), and adverse events (AEs) were assessed. RESULTS: SF TA concentrations following FX006 were quantifiable through Week 12 (pg/mL: 231,328.9 at Week 1; 3590.0 at Week 6; 290.6 at Week 12); post-TAcs, only two of eight patients had quantifiable SF TA at Week 6 (7.7 pg/mL). Following FX006, plasma TA gradually increased to peak (836.4 pg/mL) over 24 h and slowly declined to <110 pg/mL over Weeks 12-20; following TAcs, plasma TA peaked at 4 h (9628.8 pg/mL), decreased to 4991.1 pg/mL at 24 h, and was 149.4 pg/mL at Week 6, the last post-treatment time point assessed. AEs were similar between groups. CONCLUSION: In knee OA patients, microsphere-based TA delivery via a single IA injection prolonged SF joint residency, diminished peak plasma levels, and thus reduced systemic TA exposure relative to TAcs.

Distribution of fluorescein sodium and triamcinolone acetonide in the simulated liquefied and vitrectomized Vitreous Model with simulated eye movements.

Intravitreal administration is the method of choice for drug delivery to the posterior segment of the eye with special emphasis on the vitreous body and its surrounding retinal vasculature. In order to gain a better understanding of the underlying distribution processes, an in vitro model simulating the vitreous body (Vitreous Model, VM) and a system simulating the impact of movement on the VM (Eye Movement System, EyeMoS) was previously developed. In the study reported here, these systems were modified in regard to a standardized injection procedure, the diversity of simulated eye movements, extended periods of investigation, the opportunity to simulate the state after vitrectomy and in considering the physiological temperature. Fluorescein sodium (FS) and triamcinolone acetonide (TA) were used as (model) drugs to examine the drug distribution within the VM. Vitrectomy was simulated by replacing half the volume of the polyacrylamide gel that was used as vitreous substitute with the clinically used Siluron® 5000 whereas for a simulated liquefaction half the volume of the gel was replaced by buffer. A simulated liquefaction caused a 12-fold faster distribution of FS compared to the simulated juvenile VM, which was most likely caused by convective forces and mass transfer. Also, the injection technique (injection into the gel or into the buffer compartment) influenced the resulting distribution pattern. Without any liquefaction, the previously described initial injection channel occurred with both (model) drugs and, in the case of TA, remained almost unchanged during the investigation period of 72h. Simulating vitrectomized eyes, TA did not spread uniformly, but either remained in the depot or strongly sedimented within the VM suggesting that a homogenous distribution of a TA suspension is highly unlikely in vitrectomized eyes. High variabilities were observed with ex vivo animal eyes, demonstrating the limited benefit of explanted tissues for such distribution studies. The combination of the modified VM and EyeMoS seems a valuable tool for characterizing intravitreal dosage forms in a reproducible simulation of diversified eye movements and a partially liquefied or vitrectomized vitreous body.

Subconjunctival Delivery of p75NTR Antagonists Reduces the Inflammatory, Vascular, and Neurodegenerative Pathologies of Diabetic Retinopathy.

Purpose: The p75NTR is a novel therapeutic target validated in a streptozotocin mouse model of diabetic retinopathy. Intravitreal (IVT) injection of small molecule p75NTR antagonist THX-B was therapeutic and resolved the inflammatory, vascular, and neurodegenerative phases of the retinal pathology. To simplify clinical translation, we sought a superior drug delivery method that circumvents risks associated with IVT injections. Methods: We compared the pharmacokinetics of a single 40 µg subconjunctival (SCJ) depot to the reported effective 5 µg IVT injections of THX-B. We quantified therapeutic efficacy, with endpoints of inflammation, edema, and neuronal death. Results: The subconjunctival depot affords retinal exposure equal to IVT injection, without resulting in detectable drug in circulation. At week 2 of diabetic retinopathy, the SCJ depot provided therapeutic efficacy similar to IVT injections, with reduced inflammation, reduced edema, reduced neuronal death, and a long-lasting protection of the retinal structure. Conclusions: Subconjunctival injections are a safe and effective route for retinal delivery of p75NTR antagonists. The subconjunctival route offers an advantageous, less-invasive, more compliant, and nonsystemic method to deliver p75NTR antagonists for the treatment of retinal diseases.

Targeted intracorneal delivery-Biodistribution of triamcinolone acetonide following topical iontophoresis of cationic amino acid ester prodrugs.

The aim was to investigate intracorneal iontophoresis of biolabile triamcinolone acetonide (TA) amino acid ester prodrugs (TA-AA). Arginine and lysine esters of TA (TA-Arg and TA-Lys, respectively) were synthesized and characterized; quantification was performed by HPLC-UV and UHPLC-MS/MS. The aqueous solubility of the prodrugs (at pH 5.5) was ∼1000-fold greater than TA. Anodal iontophoresis (10min at 3mA/cm2) of TA-AA was investigated using isolated porcine cornea. Although no statistically significant difference was observed in total intracorneal delivery of TA (468.25±59.70 and 540.85±79.16nmolTA/cm2, for TA-Arg and TA-Lys, respectively), the different susceptibilities of the prodrugs to hydrolysis influenced intracorneal biodistribution. Quantification of TA in twenty-five 40µm thick corneal lamellae revealed significantly deeper penetration of TA following TA-Lys iontophoresis. Its superior resistance to hydrolysis enabled sustained electromigration into the deeper cornea suggesting judicious prodrug selection might enable targeted regioselective drug delivery. The intracorneal biodistribution following anodal iontophoresis of TA-Arg (2.3mM; 10min, 3mA/cm2) was visualized by full field optical coherence tomography providing qualitative confirmation of the extensive intracorneal penetration of TA. Short duration iontophoresis of TA-AA prodrugs may improve deep corneal bioavailability and efficacy in vivo, constituting a "single-shot" treatment option for corneal allograft rejection.