Hossein Zia

Hot melt extrusion (HME) for amorphous solid dispersions: Predictive tools for processing and impact of drug–polymer interactions on supersaturation

The processing parameters for HME have been evaluated and the impact of solid state intermolecular drug-polymer interactions on supersaturation has been investigated. Poorly water soluble drugs Indomethacin (IND), Itraconazole (ITZ), and Griseofulvin (GSF) and hydrophilic polymers - Eudragit EPO, Eudragit L-100-55, Eudragit L-100, HPMCAS-LF, HPMCAS-MF, Pharmacoat 603, and Kollidon VA-64 were selected for this study. Solubility parameters calculations (SPCs), differential scanning calorimetry (DSC), and rheological analysis of drug-polymer physical mixtures (PMs) was performed. The solid dispersions were manufactured using HME and characterized by powder X-ray diffraction (PXRD), polarized light microscopy (PLM), Fourier transform infra-red (FTIR) Spectroscopy, and dissolution study. Results obtained by DSC correlated well with SPC, showing single glass transition temperatures for all the PMs except ITZ in Eudragit EPO that depicted the highest difference in solubility parameters. The zero rate viscosity (η₀) was dependent on the melting point and consequently the state of the drug in the polymer at the softening temperature. The η₀ of PMs was useful to estimate the processing conditions for HME and to produce transparent glassy HMEs from most of the PMs. The amorphous conversion due to HME was confirmed by PXRD and PLM. The solid state drug-polymer interactions occurred during HME could be confirmed by FTIR analysis. Highest supersaturation could be achieved for IND, ITZ, and GSF using Eudragit EPO, HPMCAS-LF, and Eudragit L-100-55, respectively where relatively higher stretching of the carbonyl peaks was observed by FTIR. Thus, the highest dissolution rate and supersaturation of poorly water soluble drugs could be attributed to drug-polymer interactions occurred during HME.

Improving the Dissolution Rate of Poorly Water Soluble Drug by Solid Dispersion and Solid Solution—Pros and Cons

The solid dispersions with poloxamer 188 (P188) and solid solutions with polyvinylpyrrolidone K30 (PVPK30) were evaluated and compared in an effort to improve aqueous solubility and bioavailability of a model hydrophobic drug. All preparations were characterized by differential scanning calorimetry, powder X-ray diffraction, intrinsic dissolution rates, and contact angle measurements. Accelerated stability studies also were conducted to determine the effects of aging on the stability of various formulations. The selected solid dispersion and solid solution formulations were further evaluated in beagle dogs for in vivo testing. Solid dispersions were characterized to show that the drug retains its crystallinity and forms a two-phase system. Solid solutions were characterized to be an amorphous monophasic system with transition of crystalline drug to amorphous state. The evaluation of the intrinsic dissolution rates of various preparations indicated that the solid solutions have higher initial dissolution rates compared with solid dispersions. However, after storage at accelerated conditions, the dissolution rates of solid solutions were lower due to partial reversion to crystalline form. The drug in solid dispersion showed better bioavailability in comparison to solid solution. Therefore, considering physical stability and in vivo study results, the solid dispersion was the most suitable choice to improve dissolution rates and hence the bioavailability of the poorly water soluble drug.

Codiffusion of propylene glycol and dimethyl isosorbide in hairless mouse skin

The in vitro percutaneous fluxes of propylene glycol (PG), cis-oleic acid (OA) and dimethyl isosorbide (DI) were determined and their effect on nifedipine (N) flux and lag time evaluated. PG, OA and DI flux through hairless mouse (HM) skin was measured in vitro by beta-scintigraphy and N permeation was measured by HPLC under finite and infinite dose conditions. Evaluation of each of the solvents separately showed that pure DI possessed the inherent ability to traverse the skin (12% in 24 h). For the tested formulation after 24 h, 57% of the PG and 40% of the DI had permeated across the skin with nearly linear permeation between 4 and 18 h and the relative order of permeation was PG > DI > N. DI permeation was further aided in the presence of PG and OA. N flux was dependent on concomitant solvent permeation. Over a 24-h test period a dose dependent response was observed for N, with 4.9-15.6 mg of N delivered from the lowest and highest doses, respectively, and the highest dose yielding zero-order flux of 146 (g/h per cm2).

A comparative pH-dissolution profile study of selected commercial levothyroxine products using inductively coupled plasma mass spectrometry

Levothyroxine (T4) is a narrow therapeutic index drug with classic bioequivalence problem between various available products. Dissolution of a drug is a crucial step in its oral absorption and bioavailability. The dissolution of T4 from three commercial solid oral dosage forms: Synthroid (SYN), generic levothyroxine sodium by Sandoz Inc. (GEN) and Tirosint (TIR) was studied using a sensitive ICP-MS assay. All the three products showed variable and pH-dependent dissolution behaviors. The absence of surfactant from the dissolution media decreased the percent T4 dissolved for all the three products by 26-95% (at 30 min). SYN dissolution showed the most pH dependency, whereas GEN and TIR showed the fastest and highest dissolution, respectively. TIR was the most consistent one, and was minimally affected by pH and/or by the presence of surfactant. Furthermore, dissolution of T4 decreased considerably with increase in the pH, which suggests a possible physical interaction in patients concurrently on T4 and gastric pH altering drugs, such as proton pump inhibitors. Variable dissolution of T4 products can, therefore, impact the oral absorption and bioavailability of T4 and may result in bioequivalence problems between various available products.

Stability of atriopeptin III in poly(d,l-lactide-co-glycolide) microspheres

Abstract The stability ofatriopeptin III (APIII) encapsulated in poly ( d,l -lactide-co-glycolide) (PLGA) microspheres has been investigated and compared to the stability of APIII alone. When the microspheres are shaken in Tris-buffered Ringers (pH 7.4) at 40°C, the APIII inside of the microspheres is completely degraded in 5 days. Though APIII is stable in microspheres that are stored desiccated at −20°C, when the microspheres are stored in 95% relative humidity at 40°C there is 20% degradation of APIII in 8 days. Concentrated APIII, on the other hand, shows no degradation after 2 weeks at 40°C and dilute APIII in water shows no loss after 1 month at 40°C. In Tris-buffered Ringers (pH 7.4) at 40°C, however, dilute APIII degrades with a half life of 8.7 days unshaken or 2.4 days when shaken. The pattern of degradation peaks seen during HPLC analysis of samples degraded in the presence of PLGA is different than that seen when APIII alone degrades in buffer solution. These experiments indicate that PLGA may not be an appropriate polymer for use with some peptides and proteins.

In vivo evaluation of spray formulations of human insulin for nasal delivery

There are many ongoing investigations to improve the nasal bioavailability of peptide and protein formulations. The presence of bioadhesive polymers in nasal formulations may increase the residence time of the drugs in the nasal cavity. A combination of bioadhesive polymers with permeation enhancers would seem to further improve nasal bioavailability. In this study, insulin spray formulations containing two bioadhesive polymers (1.5% w/v microcrystalline cellulose (MCC) and 70% w/w Plastoid L50) alone or in combination with the enhancers such as sodium taurocholate (ST), ammonium glycyrrhizinate (AG) or glycyrrhetinic acid (GA) at 1% w/v level, were evaluated in diabetic rabbits. A total volume of 100 μl of freshly prepared insulin formulation was sprayed into the nasal cavity of each diabetic rabbit. Glucose levels were monitored using a blood glucose assay and serum insulin levels were analyzed using RIA. 5 U/kg insulin in the MCC suspension alone resulted in an absolute bioavailability of 1.96% while Plastoid L50 alone resulted in 2.25% absolute bioavailability. Insulin in the MCC suspension and ST, AG or GA resulted in 8.36, 7.83 and 2.15% bioavailability, respectively. The same formulations produced a hypoglycemic effect in terms of total glucose reductions of 39.12, 15.96 and 9.36% and the maximal decreases in glucose levels were 58.37, 21.8 and 18.61%, respectively. The Plastoid formulation containing 1% ST provided nasal insulin bioavailability of 5.9% with a total glucose reduction of 17.03% and a maximal glucose decrease of 26.56%. Insulin spray formulations containing 1% ST alone and 1% AG alone resulted in bioavailabilities of 7.25 and 3.57%, respectively. These same sprays provided total glucose reductions of 25.08 and 16.97% with maximal glucose decreases of 44.56 and 19.81%, respectively. The presence of benzalkonium chloride and 2-phenylethanol as preservatives in the MCC suspension resulted in higher insulin absorption than the same formulation without preservatives (6.31% vs 1.96%).

Transdermal Delivery of Nicardipine: An Approach to In Vitro Permeation Enhancement

Nicardipine hydrochloride (NC-HCl), a calcium channel blocker for the treatment of chronic stable angina and hypertension, seems to be a potential therapeutic transdermal system candidate, mainly due to its low dose, short half-life, and high first-pass metabolism. The objective of the present study was to evaluate its flux and elucidate mechanistic effects of formulation components on transdermal permeation of the drug through the skin. Solubility of NC-HCl in different solvent systems was determined using a validated HPLC method. The solubility of drug in various solvent systems was found to be in decreasing order as propylene glycol (PG)/oleic acid (OA)/dimethyl isosorbide (DMI) (80:10:10 v/v) > PG > PG/OA (90:10 v/v) > polyethylene glycol 300 > ethanol/PG (70:30 w/w) > transcutol > dimethyl isosorbide (DMI) > ethanol > water and buffer 4.7 > 2-propanol. Propylene glycol was then selected as the main vehicle in the development of a transdermal product. As a preliminary step to develop a transdermal delivery system, vehicle effect on the percutaneous absorption of NC-HCl was determined using the excised skin of a hairless guinea pig. Vehicles investigated included pure solvents alone and their selected blends, chosen based on the solubility results. In vitro permeation data were collected at 37°C, using Franz diffusion cells. The skin permeation was then evaluated by measuring the steady state permeation rate (flux) of NC-HCl, lag time, and the permeability constant. The results showed that no individual solvent was capable of promoting NC-HCl penetration. Permeation profiles of the drug through hairless guinea pig skin using saturated solutions of drug were constructed. Among the systems studied, the ternary mixture of PG/OA/DMI and binary mixture of PG/OA showed excellent flux. The flux value of the ternary system was nearly three times higher than the corresponding values obtained for the binary solvent. A similar trend also was observed for the permeation conture stant, while the values of lag time were reversed. The ternary mixindicated was then selected as a potential absorption enhancement vehicle for the transdermal delivery of drug. In general, higher fluxes were observed through hairless guinea pig skin as compared with the human stratum corneum. Based on the results obtained from the release study of NC-HCl from saturated solutions of the drug, a novel lecithin organogel (microemulsion-based gel) composed of soybean lecithin, propylene glycol, oleic acid, dimethyl isosorbide, and isopropyl myristate was developed as a possible matrix for transdermal delivery of NC-HCl. In vitro percutaneous penetration studies from this newly developed gel system through giunea pig skin and human stratum corneum revealed that the organogel system has skin-enhancing potential and could be a promising matrix for the transdermal delivery of nicardipine. Furthermore, higher permeation rates were observed when nicardipine free base was incorporated into the gel matrix instead of hydrochloride salt.

Preparation of controlled release anticancer agents I: 5-fluorouracil-ethyl cellulose microspheres

Microspheres of 5-fluorouracil have been prepared, using three grades of ethyl cellulose as wall forming materials, and utilizing a solvent evaporation technique under ambient conditions. An alcoholic solution of 5-fluorouracil and polymer was dispersed in liquid paraffin containing 33.3 per cent n-heptane. The effect of stirring rate, time of stirring, drug loading, and polymer grade on drug release in two different media were evaluated. The drug loaded particles were spherical in shape and had a diameter range of 25-200 mm and were suitable for incorporating into a gel base. Drug release studies in aqueous media, showed that acidic media provide a faster release rate than neutral media. The drug release study from an aqueous gel base preparation at pH 7.0 through a synthetic membrane was found to be promising for formulation of a gel-microsphere product for the treatment of skin lesions.

Hot melt extrusion for amorphous solid dispersions: temperature and moisture activated drug-polymer interactions for enhanced stability.

Hot melt extrudates (HMEs) of indomethacin (IND) with Eudragit EPO and Kollidon VA 64 and those of itraconazole (ITZ) with HPMCAS-LF and Kollidon VA 64 were manufactured using a Leistritz twin screw extruder. The milled HMEs were stored at controlled temperature and humidity conditions. The samples were collected after specified time periods for 3 months. The stability of amorphous HMEs was assessed using moisture analysis, thermal evaluation, powder X-ray diffraction, FTIR, HPLC, and dissolution study. In general, the moisture content increased with time, temperature, and humidity levels. Amorphous ITZ was physically unstable at very high temperature and humidity levels, and its recrystallization was detected in the HMEs manufactured using Kollidon VA 64. Although physical stability of IND was better sustained by both Eudragit EPO and Kollidon VA 64, chemical degradation of the drug was identified in the stability samples of HMEs with Eudragit EPO stored at 50 °C. The dissolution rates and the supersaturation levels were significantly decreased for the stability samples in which crystallization was detected. Interestingly, the supersaturation was improved for the stability samples of IND:Eudragit EPO and ITZ:HPMCAS-LF, in which no physical or chemical instability was observed. This enhancement in supersaturation was attributed to the temperature and moisture activated electrostatic interactions between the drugs and their counterionic polymers.

Mechanistic Study of Solubility Enhancement of Nifedipine Using Vitamin E TPGS or Solutol HS-15

The objective of our study was to find mechanisms responsible for solubility enhancement of nifedipine in solid dispersions of vitamin E TPGS and/or solutol HS-15. Solid dispersions of nifedipine with selected polymers such as vitamin E TPGS, solutol HS-15, PEG1000, and lipocol C-10 of varying drug/polymer ratios were prepared by a fusion method. The solubility enhancement was found to be in the order of vitamin E TPGS > solutol HS-15 > lipocol C-10 > PEG1000. Lipocol C-10, with a similar hydrophilic-lipophilic value as vitamin E TPGS, showed a comparable retained solubility enhancement during saturation solubility studies but had lower dissolution profile. Overall, vitamin E TPGS showed the best solubility and dissolution performance, while solutol HS-15 and lipocol C-10 demonstrated moderate solubility enhancements. Solid dispersions of vitamin E TPGS as prepared by microfluidization technique initially showed slightly higher solubility compared with samples prepared by fusion method, but eventually it became the same as the study progressed. However, solid dispersion of solutol HS-15 as prepared by microfluidization demonstrated a significant, sustained increased in solubility over its sample when prepared by fusion method. Based on these results, we concluded that enhanced solubility using vitamin E TPGS and solutol HS-15 resulted from a partial conversion of crystalline drug to the amorphous form, increase in wettability of the drug by water soluble polymers, better separation of drug particles, micellar solubilization of drug by high concentrations of surfactant polymers, and interaction between polymer and drug at the molecular level.