Tiny dexamethasone palmitate nanoparticles for intravitreal injection: Optimization and in vivo evaluation

Preparation, characterisation, pharmacokinetics and distribution of esculin microspheres administered via intravitreal injection into rabbit brain

This study explored the distribution of esculin microspheres in rabbit brain tissue following intravitreal injection and investigated the possibility of direct entry of the drug into the brain through the eye, to develop a formulation with enhanced therapeutic efficacy against Parkinson's disease.Chitosan microspheres of esculin were prepared via an emulsification cross-linking method and their characteristics were evaluated, including angle of repose, bulk density, and swelling ratio. Furthermore, the pharmacokinetic parameters and brain tissue distribution in rabbits were compared among groups administered esculin eye drops, intravitreal esculin solution, and intravitreal esculin microspheres, to determine whether esculin could enter the brain through an ocular route.The results showed that the prepared esculin microspheres were spherical and had good fluidity. Notably, intravitreal administration enhanced the area under the curve (AUC) of esculin in the thalamus. Delivery through microspheres prolonged the drug retention time in both rabbit plasma and brain tissues, as well as the brain-targeting efficiency of esculin.The collective findings indicated that there may be a direct eye-brain pathway facilitating enter of esculin microspheres into brain tissue after intravitreal injection, supporting the utility of intravitreal esculin microspheres as an effective therapeutic formulation for Parkinson's disease, a long-term chronic condition.

Adjunctive dexamethasone palmitate use for intercostal nerve block after video-assisted thoracoscopic surgery: A prospective, randomized control trial

Objectives

The efficacy of dexamethasone palmitate in extending durations of local anesthetic blocks is uncertain. In a randomized, double-blind study of patients undergoing video-assisted thoracoscopic surgery, we tested whether intravenous or perineural dexamethasone palmitate caused prolonged analgesia after intercostal nerve block.

Methods

A total of 90 patients subjected to video-assisted thoracoscopic surgery between May and December 2022 were randomly assigned to one of three intercostal nerve blocks study arms (n = 30 each), requiring the addition of 0.5% ropivacaine (23 ml) as follows: controls (C group), 2 ml saline; IV-DXP group, 2 ml saline + 2 ml (8 mg) intravenous dexamethasone palmitate; and PN-DXP group, 2 ml (8 mg) perineural dexamethasone palmitate. Time to first postoperative remedial analgesia served as primary outcome measure. Secondary endpoints included postoperative opioid consumption, pain scores by Visual Analog Scale, analgesia satisfaction, and related adverse effects.

Results

Compared with controls or the IV-DXP group, time to first postoperative remedial analgesia was longer and postoperative opioid consumption for rescue analgesia was lower in the PN-DXP group (p < 0.01). Similarly, the Visual Analog Scale scores in patients at 8, 12, 18, and 24 h postoperatively were lower in the PN-DXP group than in controls and the IV-DXP group (p < 0.01). Patient satisfaction was statistically lower in the PN-DXP group, compared with either the control or IV-DXP group (p < 0.05). Clinically, the three groups did not differ significantly in occurrences of adverse effects during the 48-h postoperative monitoring period (p > 0.05).

Conclusions

Perineural dexamethasone palmitate is a promising adjunct to ropivacaine intercostal nerve block by prolonging analgesia with almost no related adverse effects.

Modulation of release and pharmacokinetics from nanoscale lipid prodrugs of dexamethasone with variable linkage chemistry

In an attempt to tune drug release and subsequent pharmacokinetics once administered intravenously, we have synthesized three lipid-drug conjugates (LDCs) of dexamethasone (DXM) each possessing a different lipid-drug chemical linkage: namely ester, carbamate and carbonate. These LDCs were thoroughly characterized before being turned into nanoscale particles by an emulsion-evaporation process using DSPE-PEG2000 (Distearoyl-sn-Glycero-3-Phosphoethanolamine-N-(methoxy(polyethylene glycol)-2000) as the only excipient. Spherical nanoparticles (NPs) of about 140-170 nm, with a negative zeta potential, were obtained for each LDC and exhibited good stability upon storage at 4 °C for 45 days with no recrystallization of LDCs observed. LDC encapsulation efficacy was above 95% for the three LDCs, leading to a LDC loading of about 90% and an equivalent DXM loading above 50%. Although the ester and carbonate NPs did not exhibit any toxicity up to an equivalent DXM concentration of 100 μg/mL, the carbamate LDC NPs appeared very toxic towards RAW 264.7 macrophages and were discarded. Both ester and carbonate LDC NPs were shown to exert anti-inflammatory activity on LPS-activated macrophages. DXM release from LDC NPs in murine plasma was faster from ester than from carbonate NPs. Finally, pharmacokinetics and biodistribution were conducted, showing a lower exposure to DXM from carbonate LDC NPs than from ester LDC NPs, correlated with the slower DXM release from carbonate LDC NPs. These results outline the need for extended studies to find the best prodrug system for extended drug release.

Chitosan-Coated PLGA Nanoparticles Encapsulating Triamcinolone Acetonide as a Potential Candidate for Sustained Ocular Drug Delivery

The current treatment for the acquired retinal vasculopathies involves lifelong repeated intravitreal injections of either anti-vascular endothelial growth factor (VEGF) therapy or modulation of inflammation with steroids. Consequently, any treatment modification that decreases this treatment burden for patients and doctors alike would be a welcome intervention. To that end, this research aims to develop a topically applied nanoparticulate system encapsulating a corticosteroid for extended drug release. Poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) supports the controlled release of the encapsulated drug, while surface modification of these NPs with chitosan might prolong the mucoadhesion ability leading to improved bioavailability of the drug. Triamcinolone acetonide (TA)-loaded chitosan-coated PLGA NPs were fabricated using the oil-in-water emulsion technique. The optimized surface-modified NPs obtained using Box-Behnken response surface statistical design were reproducible with a particle diameter of 334 ± 67.95 to 386 ± 15.14 nm and PDI between 0.09 and 0.15. These NPs encapsulated 55-57% of TA and displayed a controlled release of the drug reaching a plateau in 27 h. Fourier-transform infrared spectroscopic (FTIR) analysis demonstrated characteristic peaks for chitosan (C-H, CONH2 and C-O at 2935, 1631 and 1087 cm-1, respectively) in chitosan-coated PLGA NPs. This result data, coupled with positive zeta potential values (ranged between +26 and +33 mV), suggests the successful coating of chitosan onto PLGA NPs. Upon coating of the NPs, the thermal stability of the drug, polymer, surfactant and PLGA NPs have been enhanced. The characteristics of the surface-modified NPs supports their use as potential candidates for topical ocular drug delivery for acquired retinal vasculopathies.