Recent Advances in Amorphous Solid Dispersions: Preformulation, Formulation Strategies, Technological Advancements and Characterization.

Amorphous solid dispersions (ASDs) are among the most popular and widely studied solubility enhancement techniques. Since their inception in the early 1960s, the formulation development of ASDs has undergone tremendous progress. For instance, the method of preparing ASDs evolved from solvent-based approaches to solvent-free methods such as hot melt extrusion and Kinetisol®. The formulation approaches have advanced from employing a single polymeric carrier to multiple carriers with plasticizers to improve the stability and performance of ASDs. Major excipient manufacturers recognized the potential of ASDs and began introducing specialty excipients ideal for formulating ASDs. In addition to traditional techniques such as differential scanning calorimeter (DSC) and X-ray crystallography, recent innovations such as nano-tomography, transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray microscopy support a better understanding of the microstructure of ASDs. The purpose of this review is to highlight the recent advancements in the field of ASDs with respect to formulation approaches, methods of preparation, and advanced characterization techniques.

Evaluation of Formulation Parameters on Permeation of Ibuprofen from Topical Formulations Using Strat-M® Membrane.

Topical drug delivery is an attractive alternative to conventional methods because of advantages such as non-invasive delivery, by-pass of first pass metabolism, and improved patient compliance. However, several factors such as skin, physicochemical properties of the drug, and vehicle characteristics influence the permeation. Within a formulation, critical factors such as concentration of drug, physical state of drug in the formulation, and organoleptic properties affect the flux across the skin. The aim of the study was to develop and investigate topical semisolid preparations (creams and gels) with ibuprofen as the model drug and investigate the effect of various formulation parameters on the in-vitro performance across the Strat-M® membrane using flow-through cells. In addition, the physical stability of the developed formulations was investigated by studying viscosity, pH, and appearance. All the formulations developed in the study had appealing appearance with smooth texture and no signs of separation. Viscosity and pH of the formulations were acceptable. Cumulative amount of drug permeated at the end of 24 h was highest for clear gel (3% w/w ibuprofen; F6: 739.6 ± 36.1 µg/cm2) followed by cream with high concentration of ibuprofen in suspended form (5% w/w; F3: 320.8 ± 17.53 µg/cm2), emulgel (3% w/w ibuprofen; F5: 178.5 ± 34.5 µg/cm2), and cream with solubilized ibuprofen (3% w/w; F2A: 163.2 ± 9.36 µg/cm2). Results from this study showed that permeation of ibuprofen was significantly influenced by formulation parameters such as concentration of ibuprofen (3% vs. 5% w/w), physical state of ibuprofen (solubilized vs. suspended), formulation type (cream vs. gel), mucoadhesive agents, and viscosity (high vs. low). Thus, findings from this study indicate that pharmaceutical formulation scientists should explore these critical factors during the early development of any new topical drug product in order to meet pre-determined quality target product profile.

Micronized Zaleplon Delivery via Orodispersible Film and Orodispersible Tablets.

The following research study focuses on improving the solubility of zaleplon (BCS class II drug) via micronization technique in order to enhance its oral delivery in orodispersible formulations. Zaleplon along with a surfactant solution was micronized by ultrasonication. The micronization process reduced the particle size of the crystalline drug about six-fold from its original size of 155.5 µm. The micronized zalepon dispersion was lyophilized to allow for a change in the state of matter (to a powder). The superior dissolution parameters (Q5, Q30, IDR, MDR, MDT, DE, and RDR) of zaleplon in microcrystalline form over the original crystalline form in in vitro dissolution studies had unraveled that micronization technique is an efficient tool in enhancing drug solubility. The micronized zaleplon solid dispersion (after lyophilization) was loaded into orodispersible tablet (ODT) and orodispersible film (ODF) formulations. The positive quality of ODT with adequate hardness and smooth texture was attributing to the presence of Pearlitol Flash® as a ready to use ODT platform. On the other hand, the ODF loaded with micronized zaleplon and prepared with Lycoat® RS 720 (as a film former) ensured adequate tensile strength. The disintegration time of ODT and ODF was 30 ± 5 and 35 ± 5 s, respectively. Thus, the orodispersible formulations containing micronized zaleplon have a strong potential for rapid disintegration following superior absorption in solution state through oral cavity into the blood stream, envisaging better oral delivery.

Taste Masking of Griseofulvin and Caffeine Anhydrous Using Kleptose Linecaps DE17 by Hot Melt Extrusion.

The objective of this project was to investigate the potential of Kleptose Linecaps DE17 (KLD) in masking the unpleasant/bitter taste of therapeutic agents by hot melt extrusion (HME). Griseofulvin (GRI) and caffeine anhydrous (CA) were used as a bitter active pharmaceutical ingredient (API) model drugs. Thermogravimetric studies confirmed the stability of GRI, CA, and KLD at the employed extrusion temperatures. The differential scanning calorimetry (DSC) studies revealed a characteristic melting endotherm of GRI at 218-220°C and CA at 230-232°C in the physical mixtures as well as in all extrudates over the period of study, indicating the crystalline nature of drug. HME of KLD was achieved only in the presence of plasticizer. Among the several plasticizers investigated, xylitol showed improved processability of KLD at 15% w/w concentration. Dissolution studies of HME extrudates using simulated salivary medium exhibited ∼threefold less release compared to physical mixture at the end of 5 min (the lesser drug release, better the taste masking efficiency). Furthermore, the results from the sensory evaluation of products in human panel demonstrated strong bitter taste in the case of physical mixture compared to the HME formulation, suggesting the potential of Kleptose Linecaps DE17 as taste masking polymer in melt extruded form.

Transdermal iontophoretic delivery of a liquid lipophilic drug by complexation with an anionic cyclodextrin.

Iontophoresis is now established as one of the methods of enhancing transdermal delivery of drugs. However, its application to enhance the delivery of highly lipophilic compounds is limited due to lack of any charge and poor water solubility of molecules. Propofol, a sedative and anesthetic drug was chosen as a model lipophilic drug in this study. Propofol was complexed with sulfobutyl ether-ß-cyclodextrin (SCD), a ß-cyclodextrin derivative carrying ionizable groups to render propofol amenable to iontophoresis. The phase solubility studies of propofol with SCD revealed an AL type curve indicating a stoichiometry of 1:1. The complex was characterized by UV-spectrophotometry and (1)HNMR. Transport studies were performed using Franz diffusion cells across porcine epidermis. The passive permeation flux of propofol was enhanced by fourfold due to complexation with SCD. Application of iontophoresis (0.5mA/cm(2)) to SCD-propofol solution enhanced the transport of propofol by an additional fourfold. The enhancement in the transport of propofol after complexation was found to be due to multiple mechanisms such as transport of intact complex, enhanced thermodynamic activity of drug at the interface and prolonged recovery of barrier disrupted due to iontophoresis. The pharmacokinetic studies were performed in Sprague-Dawley rats to assess the feasibility of transdermal iontophoretic delivery in vivo, of a lipophilic drug complexed with SCD.

Minimally invasive transdermal delivery of iron-dextran.

Iron deficiency is one of the most prevalent and serious health issues among people all over the world. Iron-dextran (ID) colloidal solution is one among the very few US Food and Drug Administration (FDA)-approved iron sources for parenteral administration of iron. Parenteral route does not allow frequent administration because of its invasiveness and other associated complications. The main aim of this project was to investigate the plausibility of transdermal delivery of ID facilitated by microneedles, as an alternative to parenteral iron therapy. In vitro permeation studies were carried out using freshly excised hairless rat abdominal skin in a Franz diffusion apparatus. Iron repletion studies were carried out in hairless anemic rat model. The anemic rats were divided into intact skin (control), microneedle pretreated, and intraperitoneal (i.p.) groups depending on the mode of delivery of iron. The hematological parameters were measured intermittently during treatment. There was no improvement in the hematological parameters in case of control group, whereas, in case of microneedle pretreated and i.p. group, there was significant improvement within 2-3 weeks. The results suggest that microneedle-mediated delivery of ID could be developed as a potential treatment method for iron-deficiency anemia.

Transdermal iontophoretic delivery of propofol: a general anaesthetic in the form of its phosphate salt.

The main objective of this study was to investigate the feasibility of delivery of propofol phosphate (PP), a prodrug of propofol, via transdermal route using iontophoresis in combination with chemical permeation enhancers (CPEs). PP, a prodrug, was synthesized and its structure was characterized. In vitro passive and iontophoretic drug transport studies were carried out using Franz diffusion cell across freshly excised hairless rat skin at different concentrations of PP in combination with CPE. Among all the CPEs screened, 0.1% sodium dodecyl sulfate (SDS) increased the passive transdermal flux to 13.43 ± 0.73 µg/(cm(2) h) from 8.52 ± 0.82 µg/(cm(2) h) (control). Cathodal iontophoresis in combination with 0.1% SDS synergistically enhanced the flux [249.24 ± 6.12 µg/(cm(2) h)] of PP. The Pharmacokinetic studies were performed in rat model to assess the feasibility of transdermal delivery of PP. The amount of propofol present in plasma samples in control group (passive) was below the detectable levels at all the time points during the study. The plasma concentration-time profile of iontophoresis group of rats was fit to a noncompartmental model and the pharmacokinetic parameters were calculated. These studies suggest the plausibility of achieving therapeutically relevant levels of propofol when delivered via transdermal route by combining iontophoresis with CPE.

Ungual and transungual drug delivery.

Topical therapy is desirable in treatment of nail diseases like onychomycosis (fungal infection of nail) and psoriasis. The topical treatment avoids the adverse effects associated with systemic therapy, thereby enhancing the patient compliance and reducing the treatment cost. However the effectiveness of the topical therapies has been limited due to the poor permeability of the nail plate to topically applied therapeutic agents. Research over the past one decade has been focused on improving the transungual permeability by means of chemical treatment, penetration enhancers, mechanical and physical methods. The present review is an attempt to discuss the different physical and chemical methods employed to increase the permeability of the nail plate. Minimally invasive electrically mediated techniques such as iontophoresis have gained success in facilitating the transungual delivery of actives. In addition drug transport across the nail plate has been improved by filing the dorsal surface of the nail plate prior to application of topical formulation. But attempts to improve the trans-nail permeation using transdermal chemical enhancers have failed so far. Attempts are on to search suitable physical enhancement techniques and chemical transungual enhancers in view to maximize the drug delivery across the nail plate.