In Vitro Performance of Carbamazepine Loaded to Various Molecular Weights of Poly (D, L-Lactide-Co-Glycolide)

Effect of PLGA raw materials on in vitro and in vivo performance of drug-loaded microspheres

Poly(lactide-co-glycolide) and poly(lactic-co-glycolic acids) (PLGAs) play a critical role in the development of commercial long-acting injectable microsphere formulations. However, very little information is available describing the impact of PLGA manufacturer and monomer distribution along the polymer chain (e.g., glycolic blockiness (Rc) and average lactic block length (LL)) on the degradation and release behavior of PLGA drug carriers in vitro and in vivo. Here, we compared the in vitro and in vivo performance of (a) four leuprolide-loaded microsphere formulations prepared from similar low-molecular-weight acid-capped PLGAs (10-14 kD, i.e., Expansorb® DLG 75-2A, Purasorb® PDLG 7502A, Resomer® RG 752H and Wako® 7515) and (b) two triamcinolone acetonide-loaded (Tr-A) microsphere formulations from similar medium-molecular-weight ester-capped PLGAs (i.e., Expansorb® DLG 75-4E and Resomer® RG 753S). Lupron Depot® and Zilretta® were used as reference commercial products. The six 75/25 PLGAs displayed block lengths that were either above or below values expected from a random copolymer. Drug release and polymer degradation were monitored simultaneously in vitro and in vivo using a cage implant system. The four leuprolide-loaded formulations showed similar release and degradation patterns with some notable differences between each other. Microspheres from the Expansorb® polymer displayed lower LL and higher Rc relative to the other 3 PLGA 75/25 microspheres, and likewise exhibited distinct peptide release and degradation behavior compared to the other 3 formulations. For each formulation, leuprolide release was erosion-controlled up to about 30% release after the initial burst followed by a faster than erosion release phase. In vitro release was similar as that in vivo over the first phase but notably different from the latter release phase, particularly for the most blocky Expansorb® formulation. The Purasorb® and Wako® formulations displayed highly similar performance in release, degradation, and erosion analysis. By contrast, the two ester-capped Expansorb® DLG 75-4E and Resomer® RG 753S used to prepare Tr-A microspheres shared essentially identical LL and higher Rc and behaved similarly although the Expansorb® degraded and released the steroid faster in vivo, suggestive of other factors responsible (e.g., residual monomer). The in vivo release performance for both drugs from the six microsphere formulations was similar to that of the commercial reference products. In summary, this work details information on comparing the similarities and differences in in vitro and in vivo performance of drug-loaded microspheres as a function of manufacturing and microstructural variables of different types of PLGA raw materials utilized and could, therefore, be meaningful in guiding the source control during development and manufacturing of PLGA microsphere-based drug products. Future work will expand the analysis to include a broader range of LL and higher Rc, and add additional important formulation metrics (e.g., thermal analysis, and residual monomer, moisture, and organic solvent levels).

The effect of pioglitazone on pharmacokinetics of carbamazepine in healthy rabbits

Introduction

Drug–drug interactions can lead to serious and potentially lethal adverse events. In recent years, several drugs have been withdrawn from the market due to interaction-related adverse events. The objective of this study was to evaluate the pharmacokinetic interaction between pioglitazone (PG) and carbamazepine (CBZ) in healthy male rabbits.

Methods

A randomized, two-crossover design study was conducted in six healthy male rabbits. The study consisted of two periods: period one, when each rabbit received a single dose of 70 mg CBZ-suspension. Period two, when each rabbit received a single dose of 70 mg CBZ-suspension co-administered with a single dose of 1.5 mg PG with a washout period of one week between the two periods. Serial blood samples were collected over a period of 48 h. Chemiluminescent enzyme immunoassay (CLEIA) was used to measure CBZ in serum. Pharmacokinetic (PK) parameters C_max, T_max, t _1/2, AUC_0-t, AUC _0-∞, and k_e were determined for the two periods using non-compartmental analysis.

Results

In the two periods of treatment, C_max, T_max, AUC_0-t, AUC_0-∞, t _½ and k_e for CBZ were administered alone and in combination with PG. C_max, the mean peak plasma concentration was 4.33 ± 2.4 μg/mL versus 4.76 ± 2.1 μg/ml, t_max, time taken to reach, was 2.91 ± 1.11 h versus 3.6 ± 1.83 h, total area under the curve AUC_0-t was 64.90 ± 43.6 μg·h/ml versus 102.90 ± 66.9 μg·h/ml, AUC_0-∞ was 74.0 ± 52.6 μg·h/ml versus 124.3 ± 85 μg·h/mL, t _½ was 14.10 ± 2.5 h versus 16.43 ± 6.43 h and elimination rate constant k_e was 0.050 ± 0.009 h⁻¹ versus 0.057 ± 0.049 h⁻¹, respectively. No statistical differences were found in pharmacokinetic of CBZ in both cases (P > 0.05).

Conclusion

The result of the study demonstrated that PG does not affect pharmacokinetic parameters of CBZ. Therefore, no cautions regarding dose or administration pattern of CBZ with PG should be taken.

Release behaviour of carbamazepine-loaded poly(ε-caprolactone)/poly(ethylene oxide) microspheres

Poly(ε-caprolactone) (PCL), a biodegradable and biocompatible aliphatic polyester has a great potential as a drug carrying material in controlled drug delivery/release systems. The most simple and economical way to tailor the release profile of active substances from biodegradable polymer matrix is by the addition of the second polymeric component in the polymer matrix, i.e. by blending. This study describes the preparation and characterization of a carbamazepine-loaded microspheres by the use of PCL blended with poly(ethylene oxide) as a drug carrying material. By the use of two-component hydrophilic/hydrophobic polymer blend as a microspheres' matrix material, release profile of the drug can be modified and dictated. The microspheres prepared by classical oil-in-water emulsion solvent evaporation technique were characterized with respect to particle size and morphology, polymer matrix composition, encapsulation efficiency, physical state of the drug and in vitro release behaviour. It was presented that the release profile can be modified by the presence and the amount of hydrophilic component in the starting formulation of microspheres.

Novel methods of antiepileptic drug delivery -- polymer-based implants

Epilepsy is a neurological disorder characterised by spontaneous seizures. Over one third of patients receive insufficient benefit from oral anti-epileptic drug (AED) therapy, and continue to experience seizures whilst on medication. Epilepsy researchers are consequently seeking new ways to deliver AEDs directly to the seizure focus in the brain in order to deliver higher, more effective doses to the seizure focus whilst bypassing the remainder of the brain and body to prevent side effects. The focus of this review will be polymer-based implants, which are polymeric devices loaded with AED that are designed for implantation at the seizure focus in order to achieve gradual, continuous release of AED direct into the region of the brain responsible for seizures. Polymer-based implants produced for epilepsy to date are based on a range of polymers, both biodegradable and non-biodegradable, and range from simple materials development studies through to investigations of implants in animal models of seizures and epilepsy, with varying degrees of success. This review describes the range of methods employed to manufacture polymer-based implants and compares their advantages and potential appeal to industry, and describes and compares the results and successes of polymer-based materials and devices produced to date for the treatment of epilepsy. We also discuss disadvantages and hurdles to be overcome in the field, and describe our predictions for advances to be made in the field in the coming decade.

Preparation and evaluation of PLGA microparticles as carrier for the pulmonary delivery of rhIL-2 : I. Effects of some formulation parameters on microparticle characteristics

In this study, recombinant human interleukin-2 (rhIL-2) containing poly(lactic-co-glycolic acid) (PLGA) microparticles were prepared for pulmonary administration by modified w/o/w double emulsion solvent extraction method and the effects of various formulation parameters on the physicochemical properties of the microparticles were investigated. Microparticles in suitable size for pulmonary administration (4.02 µm) were obtained by increasing dichloromethane volume used in the organic phase. Also, a very high encapsulation efficiency (99.22%) value could be reached in these microparticles. In the sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis, rhIL-2 extracted from microparticles having a similar band with native rhIL-2 showed that the protein was not affected by the encapsulation process. The release curves of microparticles exhibited a biphasic fashion, characterized by a fast release phase at initial 1 day, followed by a slower one on the remaining days. Bioactivity investigations using T cells show that rhIL-2 encapsulated in PLGA microparticles retain their biological activity.

Microparticulate based topical delivery system of clobetasol propionate

Psoriasis is a chronic, autoimmune skin disease affecting approximately 2% of the world's population. Clobetasol propionate which is a superpotent topical corticosteroid is widely used for topical treatment of psoriasis. Conventional dosage forms like creams and ointments are commonly prefered for the therapy. The purpose of this study was to develop a new topical delivery system in order to provide the prolonged release of clobetasol propionate and to reduce systemic absorption and side effects of the drug. Clobetasol propionate loaded-poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres were prepared by oil-in-water emulsion-solvent evaporation technique. Particle size analysis, morphological characterization, DSC and XRD analyses and in vitro drug release studies were performed on the microparticle formulations. Emulgel formulations were prepared as an alternative for topical delivery of clobetasol propionate. In vitro drug release studies were carried out from the emulgel formulations containing pure drug and drug-loaded microspheres. In addition, the same studies were performed to determine the drug release from the commercial cream product of clobetasol propionate. The release of clobetasol propionate from the emulgel formulations was significantly higher than the commercial product. In addition, the encapsulation of clobetasol propionate in the PLGA microspheres significantly delayed the drug release from the emulgel formulation. As a result, the decrease in the side effects of clobetasol propionate by the formulation containing PLGA microspheres is expected.

Studies on preparation of carbamazepine (CBZ) supersaturatable self-microemulsifying (S-SMEDDS) formulation and relative bioavailability in beagle dogs

The main purpose of this work was to develop a supersaturatable self-microemulsifying drug delivery system (S-SMEDDS) of carbamazepine (CBZ). S-SMEDDS of CBZ was prepared and drug precipitation behavior, dissolution rate in vitro and particle size distribution were evaluated. The relative bioavailability of S-SMEDDS formulation of CBZ was evaluated in beagle dogs compared with a commercial tablet. The results showed that the presence of a small amount of polymeric precipitation inhibitor (PVP) effectively sustained the supersaturated state by retarding precipitation kinetics. The mean particle size of S-SMEDDS formulation after dispersion was about 33.7?nm and the release rate from S-SMEDDS was significantly higher than the commercial tablet in vitro. In pharmacokinetic parameters of S-SMEDDS formulation, AUC(0?t) and C(max) were 9.83???2.47??g?ml(?1)?h and 4.96???1.16??g?ml(?1), compared to the conventional tablet which were 1.67???1.19??g?ml(?1)?h and 0.74???0.19??g?ml(?1), respectively. AUC(0-t) of S-SMEDDS increased nearly five times compared to the market tablet with the same administration dose of 200?mg. On the other hand, AUC(0?t) of S-SMEDDS with a dose of 50?mg was about 85.9% compared to the commercial tablet with a dose of 200?mg. Thus, it was concluded that S-SMEDDS provide an effective approach for improving the extent of absorption of CBZ with a low surfactant level.

Optimization of preparation conditions of poly(ε-caprolactone) microspheres for controlled release of carbamazepine

Poly (?-caprolactone), PCL, is an aliphatic polyester suitable for controlled drug release due to its biodegradability, biocompatibility, non-toxicity and high permeability to many therapeutic drugs. This study investigates the effect of the preparation parameters on the size and the morphology of the PCL microspheres and on the release profile of carbamazepine from these microspheres. The PCL microspheres were prepared using oil-in-water (o/w) emulsion solvent evaporation method with the poly(vinyl alcohol), PVA, as the emulsion stabilizer. The influence of the stirring rate applied during the emulsion formation, the homogenization time and the emulsifier concentration on diameter and size distribution of the microspheres was analyzed by scanning electron microscope (SEM). The initial emulsion was formed applying high stirring rates of 10000, 18000 and 23000 rpm, for homogenization times: 5, 10 and 15 min. The diameter was strongly influenced by the stirring rate, and the average particle size decreased from 9.2 to 2.8 ?m with the increase of the stirring rate. Increasing the amount of PVA in the water phase from 0.2 to 1 mass% improved stabilization of the oil droplets and led to a slight decrease of the average particle diameter. Drug-loaded microspheres were prepared by the same technique using different amounts of carbamazepine (10 and 15 mass%), under given conditions (1 mass% PVA, stirring rate of 18000 rpm for a period of 5 min of emulsion formation). Additionally, microspheres were prepared by applying low stirring rate of 1000 rpm with 10 and 15 mass% of the drug. The SEM analysis showed that microspheres created with 18000 rpm stirring rate, had average diameters of 3-4 ?m, and the microspheres prepared with 1000 rpm stirring rate were larger than 100 ?m. It was also observed that, in the case of the large microspheres, carbamazepine was deposited on their surfaces, while the small microspheres had smooth surfaces without observable drug crystals. The encapsulation efficiency and the release behavior of the carbamazepine were examined using high performance liquid chromatography-ultraviolet spectroscopy (HPLC-UV). The drug encapsulation efficiencies were in the range from 69 to 81%, and were increasing with the increase of the amount of carbamazepine in both series. In vitro release experiments were carried out in the phosphate buffer solution (pH 7) at 37?C. The release rate was influenced by the microspheres size and morphology. The larger microspheres released more carbamazepine (85-95%) compared to the small ones (50-65%) for the same period. This behavior was attributed to the different drug distribution in the PCL matrix. Different mathematical models were used to describe drug release kinetics. It was concluded that the mechanism of the carbamazepine release from the microspheres was diffusion-controlled, independent on the type of microspheres. The kinetic parameters showed that the release of carbamazepine was slower from the smaller microspheres, probably as a result of more even distribution of the drug in the polymer matrix.

Formulation, release characteristics and bioavailability study of oral monolithic matrix tablets containing carbamazepine

This study examined the release of carbamazepine (CBZ) from hydrophobic (Compritol 888 ATO) and hydrophilic-hydrophobic matrix combination (Compritol 888 ATO-hydroxpropyl methylcellulose, HPMC). Hydrophobic matrix tablets were prepared by hot fusion technique, while hydrophilic-hydrophobic matrix tablets were prepared by wet granulation technique. The properties of the compressed matrix tablets were determined according to the US Pharmacopoeia. Both matrix formulations displayed a controlled-release profile when compared to the reference formulation (Tegretol CR 200). The bioavailability of CBZ formulations and Tegretol CR 200 were evaluated in beagle dogs. Carbamazepine presented a significant higher bioavailability from matrix tablets containing hydrophilic polymer (HPMC) than that obtained from Tegretol CR200. The average inter-subject plasma concentration variability CV% was the least with tablet containing hydrophilic polymer (HPMC) and was the highest with Tegretol CR 200 (33.8 and 54.1, respectively). Analysis of variance applied to log AUC(0-alpha) and log C(max) showed statistical significant differences among the three formulations (P < 0.05). Plotting the fraction of CBZ released in vitro and fraction absorbed showed a statistically significant relationship (R(2) = 0.935-0.975) for the three matrix tablets examined.