Optimizing formulation parameters for the development of carvedilol injectable in situ forming depots

In vitro and in vivo evaluation of in situ forming polyester implants for the extended release of carvedilol

Polyester based in situ forming implants (ISFIs) are injectable long-acting drug delivery systems that offer a wide range of unique advantages. As a result of these advantages, two relatively high molecular weight, ester terminated grades of poly (D,L-lactide-co-glycolide) (PLGA) and poly(D,L-lactide) (PLA) were evaluated for their ability (i) to form ISFIs loaded with carvedilol, and (ii) to control its release both in vitro and in vivo. At a polymeric concentration of 40% w/w, implant solutions were syringeable, injectable, and able to encapsulate carvedilol to a high degree (encapsulated drug% > 97%). When visualized using scanning electron microscopy (SEM), implants were found to have a dense thin surface atop porous sublayers. As for their in vitro evaluation, PLGA and PLA implants were able to maintain drug release over the course of 49 and 84 days, respectively. On the other hand, in vivo drug release from both implants was almost identical and lasted for only 42 days. This may be due to the overriding effect of the similar host environment at the injection site that diminished the effect of polymeric physiochemistry on phase inversion and drug release. Lastly, while the polymer-free drug/NMP solution completely released its drug content within the initial half hour in vitro, the formulation extended drug release in vivo. This could be due to a yet to be investigated interaction between carvedilol and NMP under in vivo conditions. These results cement the significance of formulating carvedilol loaded ISFIs for the management of chronic conditions.

Fabrication and Optimization of a Silodosin In Situ-Forming PLGA Implants for the Treatment of Benign Prostatic Hyperplasia: In Vitro and In Vivo Study

Objectives: Lower urinary tract symptoms (LUTSs) related to benign prostatic hyperplasia (BPH) are common in older men, and alpha-adrenoceptor blockers continue to be a key part of managing these symptoms. This study aimed to formulate injectable poly (lactic-co-glycolic acid) (PLGA) in situ-forming implants (ISFIs) loaded with silodosin (SLD) to address symptoms associated with BPH. This method, which ensures prolonged therapeutic effects of SLD, is intended to decrease dosing frequency and improve treatment outcomes, leading to better patient adherence. Methods: An appropriate solvent with favorable PLGA solubility, viscosity, and in vitro release profile was selected. Additionally, an I-optimal design was employed as an optimization technique. An in vivo study in albino male rats was conducted to investigate prostate-specific antigens (PSAs), prostate weight and prostatic index, histopathology, and SLD pharmacokinetics. Results: The optimized formulation showed experimental values of 29.25% for the initial burst after 2 h and 58.23% for the cumulative release of SLD after 10 days. Pharmacokinetic data revealed that the SLD-ISFI formulation had lower Cmax and higher AUC values than subcutaneous (SC) pure SLD and oral commercial SLD capsule, indicating the controlled-release impact and improved bioavailability of the ISFI systems. SLD-ISFI produced a marked drop in the prostatic index by 2.09-fold compared to the positive control. Serum PSA level decreased significantly from 0.345 ± 0.007 to 0.145 ± 0.015 ng/mL after SLD-ISFI injection compared to the positive control. Conclusions: This study indicated that the optimized SLD-ISFI formulation proved its efficacy in managing BPH.

Development and In Vivo Evaluation of Sustained Release Microparticles Loaded with Levothyroxine for Hypothyroidism Treatment

Hypothyroidism is a chronic condition combated by a daily oral supplementation of levothyroxine. In addition to the need for frequent dosing, oral administration may result in variable absorption of the drug leading to a failure in achieving normal thyroid function. Therefore, the development of a long-acting injectable system capable of delivering the drug is necessary. This work was aimed at developing sustained release microparticles loaded with levothyroxine. The microparticles were produced through the emulsification-solvent evaporation method using 2 grades of biocompatible and biodegradable polyesters: poly(ᴅ,ʟ-lactide-co-glycolide) (PLGA) and poly(ᴅ,ʟ-lactide) (PLA). Both polymers produced microparticles with very similar sizes (1.9 µm) and zeta potential values (around -22.0 mV). However, PLA microparticles had a significantly higher drug loading (6.1% vs. 4.4%, respectively) and encapsulation efficiency (36.8%, vs. 26.1%, respectively) when compared to PLGA counterparts. While both types of microparticles displayed a biphasic release pattern in vitro, a slower rate of release was observed with PLA microparticles. Moreover, a similar biphasic release pattern was found in vivo, with an initial phase of rapid release followed by a slower phase in the subsequent 10 days. These results indicate the possibility of developing levothyroxine loaded polyester microparticles as a potential long-acting thyroid hormone replacement therapy.