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

A Stratified Analysis of Supersaturation and Precipitation Effects Based on the Refined Developability Classification System (rDCS)

Supersaturation and precipitation within the gastrointestinal tract can influence oral absorption of active pharmaceutical ingredients (APIs). Supersaturation of weakly basic APIs upon transfer from the stomach into the small intestine may enhance their absorption, while salt forms of poorly soluble weak acids may generate supersaturated solutions in both stomach and intestine. Likewise, APIs with solubility-limited absorption may be developed as enabling formulations intended to produce supersaturated solutions of the API in the gut. Integrating the supersaturation/precipitation characteristics of the API into the biopharmaceutical risk classification enables comprehensive mapping of potential developability risks and guides formulation selection towards optimizing oral bioavailability (BA). The refined Developability Classification System (rDCS) provides an approach for this purpose. In this work, the rDCS strategy is revisited and a stratified approach integrating the in vitro supersaturation and precipitation behavior of APIs and their formulations is proposed.

Lipid-based systems with precipitation inhibitors as formulation approach to improve the drug bioavailability and/or lower its dose: a review

Lipid-based systems, such as self-microemulsifying systems (SMEDDS) are attracting strong attention as a formulation approach to improve the bioavailability of poorly water-soluble drugs. By applying the "spring and parachute" strategy in designing supersaturable SMEDDS, it is possible to maintain the drug in the supersaturated state long enough to allow absorption of the complete dose, thus improving the drug's bio-availability. As such an approach allows the incorporation of larger amounts of the drug in equal or even lower volumes of SMEDDS, it also enables the production of smaller final dosage forms as well as decreased gastrointestinal irritation, being of particular importance when formulating dosage forms for children or the elderly. In this review, the technological approaches used to prolong the drug supersaturation are discussed regarding the type and concentration of polymers used in liquid and solid SMEDDS formulation. The addition of hypromellose derivatives, vinyl polymers, polyethylene glycol, polyoxyethylene, or polymetacrylate copolymers proved to be effective in inhibiting drug precipitation. Regarding the available literature, hypromellose has been the most commonly used polymeric precipitation inhibitor, added in a concentration of 5 % (m/m). However, the inhibiting ability is mainly governed not only by the physicochemical properties of the polymer but also by the API, therefore the choice of optimal precipitation inhibitor is recommended to be evaluated on an individual basis.

Lipid based formulations as supersaturating oral delivery systems: From current to future industrial applications

Lipid-based formulations, in particular supersaturated lipid-based formulations, are important delivery approaches when formulating challenging compounds, as especially low water-soluble compounds profit from delivery in a pre-dissolved state. In this article, the classification of lipid-based formulation is described, followed by a detailed discussion of different supersaturated lipid-based formulations and the recent advances reported in the literature. The supersaturated lipid-based formulations discussed include both the in situ forming supersaturated systems as well as the thermally induced supersaturated lipid-based formulations. The in situ forming drug supersaturation by lipid-based formulations has been widely employed and numerous clinically available products are on the market. There are some scientific gaps in the field, but in general there is a good understanding of the mechanisms driving the success of these systems. For thermally induced supersaturation, the technology is not yet fully understood and developed, hence more research is required in this field to explore the formulations beyond preclinical studies and initial clinical trials.

Development of a sorafenib-loaded solid self-nanoemulsifying drug delivery system: Formulation optimization and characterization of enhanced properties

Sorafenib, marketed under the brand name Nexavar®, is a multiple tyrosine kinase inhibitor drug that has been actively used in the clinical setting for the treatment of several cancers. However, the low solubility and bioavailability of sorafenib constitute a significant barrier to achieving a good therapeutic outcome. We developed a sorafenib-loaded self-nanoemulsifying drug delivery system (SNEDDS) formulation composed of capmul MCM, tween 80, and tetraglycol, and demonstrated that the SNEDDS formulation could improve drug solubility with excellent self-emulsification ability. Moreover, the sorafenib-loaded SNEDDS exhibited anticancer activity against Hep3B and KB cells, which are the most commonly used hepatocellular carcinoma and oral cancer cell lines, respectively. Subsequently, to improve the storage stability and to increase the possibility of commercialization, a solid SNEDDS for sorafenib was further developed through the spray drying method using Aerosil® 200 and PVP K 30. X-ray diffraction and differential scanning calorimeter data showed that the crystallinity of the drug was markedly reduced, and the dissolution rate of the drug was further improved in formulation in simulated gastric and intestinal fluid conditions. In vivo study, the bioavailability of the orally administered formulation increases dramatically compared to the free drug. Our results highlight the use of the solid-SNEDDS formulation to enhance sorafenib's bioavailability and outlines potential translational directions for oral drug development.

In silico-assisted development of supersaturable preconcentrated isotropic mixture of atazanavir for augmenting biopharmaceutical performance in the presence of H2-receptor antagonist

The therapeutic potential of atazanavir (BCS Class II drug), a highly selective inhibitor of human immunodeficiency virus (HIV-1), has been largely limited due to its low intrinsic solubility at elevated pH resulting in low oral bioavailability. Thus, the current work describes the systematic development, optimization, and evaluation of hydroxypropyl methylcellulose acetate succinate (HPMC-AS)-based supersaturable preconcentrate isotropic mixture (SP-IM) containing long-chain triglyceride to improve intestinal lymphatic transport and augment oral bioavailability of atazanavir (ATZ). A D-optimal mixture design was employed for optimization of plain IM containing corn oil, oleic acid, Tween 80, and propylene glycol, evaluating various critical quality attributes (CQAs) like particle size, polydispersity index, self-emulsification time, % transmittance, and drug content. In silico analysis and in vitro supersaturation test facilitated the selection of HPMC-AS as a best suited polymeric precipitation inhibitor (PPI) for formulating ATZ loaded SP-IM (ATZ-SP-IM). In vitro dissolution data indicated that ATZ-SP-IM exhibits superior performance in 0.025 N HCl and pH 6.8 over pure drug. Ex vivo permeation and in vivo pharmacokinetic study of ATZ-SP-IM corroborated enhanced permeation (2.03 fold) and improved drug absorption via lymphatic transport in Wistar rats. Further, the pharmacokinetic performance of ATZ-SP-IM was not affected in presence of H₂ receptor antagonist. Therefore, the results showed that ATZ-SP-IM can significantly improve the biopharmaceutical attributes of ATZ so as to lay a foundation of further research on the new dosage form of ATZ.

Lipid-based solubilization technology via hot melt extrusion: promises and challenges

INTRODUCTION

Self-emulsifying drug delivery systems (SEDDS) are a promising strategy to improve the oral bioavailability of poorly water-soluble drugs (PWSD). The excipients of SEDDS enable permeation through the mucus and gastro-intestinal barrier, inhibiting efflux transporters (e.g. P-glycoprotein) of drugs. Poor drug loading capacity and formulation instability are the main setbacks of traditional SEDDS. The use of polymeric precipitation inhibitors was shown to create supersaturable SEDDS with increased drug payload, and their solidification can help to overcome the instability challenge. As an alternative to several existing SEDDS solidification technologies, hot melt extrusion (HME) holds the potential for lean and continuous manufacturing of supersaturable solid-SEDDS. Despite being ubiquitously applied in solid lipid and polymeric processing, HME has not yet been widely considered for the preparation of SEDDS.

AREAS COVERED

The review begins with the rationale why SEDDS as the preferred lipid-based delivery systems (LBDS) is suitable for the oral delivery of PWSD and discusses the common barriers to oral administration. The potential of LBDS to surmount them is discussed. SEDDS as the flagship of LBDS for PWSD is proposed with a special emphasis on solid-SEDDS. Finally, the opportunities and challenges of HME from the lipid-based excipient (LBE) processing and product performance standpoint are highlighted.

EXPERT OPINION

HME can be a continuous, solvent-free, cost-effective, and scalable technology for manufacturing solid supersaturable SEDDS. Several critical formulations and process parameters in successfully preparing SEDDS via HME are identified.

Supersaturation-Based Drug Delivery Systems: Strategy for Bioavailability Enhancement of Poorly Water-Soluble Drugs

At present, the majority of APIs synthesized today remain challenging tasks for formulation development. Many technologies are being utilized or explored for enhancing solubility, such as chemical modification, novel drug delivery systems (microemulsions, nanoparticles, liposomes, etc.), salt formation, and many more. One promising avenue attaining attention presently is supersaturated drug delivery systems. When exposed to gastrointestinal fluids, drug concentration exceeds equilibrium solubility and a supersaturation state is maintained long enough to be absorbed, enhancing bioavailability. In this review, the latest developments in supersaturated drug delivery systems are addressed in depth.

Exploring precipitation inhibitors to improve in vivo absorption of cinnarizine from supersaturated lipid-based drug delivery systems

Supersaturated lipid-based drug delivery systems are increasingly being explored as a bio-enabling formulation approach, particularly in preclinical evaluation of poorlywater-soluble drugs. While increasing the drug load through thermally-induced supersaturation resulted in enhanced in vivo exposure for some drugs, for others, such as cinnarizine, supersaturated lipid-based systems have not been found beneficial to increase the in vivo bioavailability. We hypothesized that incorporation of precipitation inhibitors to reduce drug precipitation may address this limitation. Therefore, pharmacokinetic profiles of cinnarizine supersaturated lipid-based drug delivery systems with or without precipitation inhibitors were compared. Five precipitation inhibitors were selected for investigation based on a high throughput screening of twenty-one excipients. In vivo results showed that addition of 5% precipitation inhibitors to long chain monoglyceride (LCM) or medium chain monoglyceride (MCM) formulations showed a general trend of increases in cinnarizine bioavailability, albeit only statistically significantly increased for Poloxamer 407 + LCM system (i.e. 2.7-fold increase in AUC_0-24h compared to LCM without precipitation inhibitors). It appeared that precipitation inhibitors mitigated the risk of in vivo precipitation of cinnarizine from sLBDDS and overall, bioavailability was comparable to that previously reported for cinnarizine after dosing of non-supersaturated lipid systems. In summary, for drugs which are prone to precipitation from supersaturated lipid-based drug delivery systems, such as cinnarizine, inclusion of precipitation inhibitors mitigates this risk and provides the opportunity to maximize exposure which is ideally suited in early efficacy and toxicology evaluation.

Supersaturable self-microemulsifying drug delivery system enhances dissolution and bioavailability of telmisartan

To enhance the dissolution and oral bioavailability of telmisartan (TMS), a poorly water-soluble anti-hypertensive drug, a supersaturable self-microemulsifying drug delivery system (SuSMEDDS) was developed. Amorphous alkalinized TMS (AAT) was formulated into a SMEDDS, composed of Capmul® MCM (oil), Cremophor^® RH40 (surfactant), and tetraglycol (co-surfactant). Although the SMEDDS was rapidly dissolved (>80% within 5 min) in a limited condition (500 mL, pH 6.8), drug precipitation was observed over time, resulting in a decrease in dissolution levels. The precipitation was due to drug recrystallization, as determined by differential scanning calorimetry and powder X-ray diffraction analyses. Several polymers, including Soluplus^® (SOL), were screened as precipitation inhibitors; ultimately, SuSMEDDS-SOL was prepared by admixing SOL and the SMEDDS at a 5:100 (w/w) ratio. SuSMEDDS-SOL was superior in terms of dissolution efficiency (>90% over 2 h) and dissolution-retaining time (no precipitation over 2 h). An in vivo pharmacokinetic study in rats revealed that the oral bioavailability of SuSMEDDS-SOL was 4.8-, 1.3-, and 1.2-fold greater than those of the TMS suspension, AAT solution, and SMEDDS, respectively. Therefore, SuSMEDDS-SOL is a promising candidate to enhance the dissolution and oral bioavailability of TMS.

Current Status of Supersaturable Self-Emulsifying Drug Delivery Systems

Self-emulsifying drug delivery systems (SEDDSs) are a vital strategy to enhance the bioavailability (BA) of formulations of poorly water-soluble compounds. However, these formulations have certain limitations, including in vivo drug precipitation, poor in vitro in vivo correlation due to a lack of predictive in vitro tests, issues in handling of liquid formulation, and physico-chemical instability of drug and/or vehicle components. To overcome these limitations, which restrict the potential usage of such systems, the supersaturable SEDDSs (su-SEDDSs) have gained attention based on the fact that the inclusion of precipitation inhibitors (PIs) within SEDDSs helps maintain drug supersaturation after dispersion and digestion in the gastrointestinal tract. This improves the BA of drugs and reduces the variability of exposure. In addition, the formulation of solid su-SEDDSs has helped to overcome disadvantages of liquid or capsule dosage form. This review article discusses, in detail, the current status of su-SEDDSs that overcome the limitations of conventional SEDDSs. It discusses the definition and range of su-SEDDSs, the principle mechanisms underlying precipitation inhibition and enhanced in vivo absorption, drug application cases, biorelevance in vitro digestion models, and the development of liquid su-SEDDSs to solid dosage forms. This review also describes the effects of various physiological factors and the potential interactions between PIs and lipid, lipase or lipid digested products on the in vivo performance of su-SEDDSs. In particular, several considerations relating to the properties of PIs are discussed from various perspectives.

Enhanced oral bioavailability of valsartan using a polymer-based supersaturable self-microemulsifying drug delivery system

A novel, supersaturable self-microemulsifying drug delivery system (S-SMEDDS) was successfully formulated to enhance the dissolution and oral absorption of valsartan (VST), a poorly water-soluble drug, while reducing the total quantity for administration. Poloxamer 407 is a selectable, supersaturating agent for VST-containing SMEDDS composed of 10% Capmul® MCM, 45% Tween® 20, and 45% Transcutol® P. The amounts of SMEDDS and Poloxamer 407 were chosen as formulation variables for a 3-level factorial design. Further optimization was established by weighting different levels of importance on response variables for dissolution and total quantity, resulting in an optimal S-SMEDDS in large quantity (S-SMEDDS_LQ; 352 mg in total) and S-SMEDDS in reduced quantity (S-SMEDDS_RQ; 144.6 mg in total). Good agreement was observed between predicted and experimental values for response variables. Consequently, compared with VST powder or suspension and SMEDDS, both S-SMEDDS_LQ and S-SMEDDS_RQ showed excellent in vitro dissolution and in vivo oral bioavailability in rats. The magnitude of dissolution and absorption-enhancing capacities using quantity-based comparisons was in the order S-SMEDDS_RQ > S-SMEDDS_LQ > SMEDDS > VST powder or suspension. Thus, we concluded that, in terms of developing an effective SMEDDS preparation with minimal total quantity, S-SMEDDS_RQ is a promising candidate.

A Polyvinylpyrrolidone-Based Supersaturable Self-Emulsifying Drug Delivery System for Enhanced Dissolution of Cyclosporine A

A novel supersaturable self-emulsifying drug delivery system (S-SEDDS) of cyclosporine A (CyA)—a poorly water-soluble immunosuppressant—was constructed in order to attain an apparent concentration–time profile comparable to that of conventional SEDDS with reduced use of oil, surfactant, and cosolvent. Several hydrophilic polymers, including polyvinylpyrrolidone (PVP), were employed as precipitation inhibitors in the conventional SEDDS, which consists of corn oil-mono-di-triglycerides, polyoxyl 40 hydrogenated castor oil, ethanol, and propylene glycol. PVP-incorporated pre-concentrate (CyA:vehicle ingredients:PVP = 1:4.5:0.3 w/v/w) spontaneously formed spherical droplets less than 120 nm within 7 min of being diluted with water. In an in vitro dialysis test in a biorelevant medium such as simulated fed and/or fasted state intestinal and/or gastric fluids, PVP-based S-SEDDS exhibited a higher apparent drug concentration profile compared to cellulose derivative-incorporated S-SEDDS, even displaying an equivalent concentration profile with that of conventional SEDDS prepared with two times more vehicle (CyA:vehicle ingredients = 1:9 w/v). The supersaturable formulation was physicochemically stable under an accelerated condition (40 °C/75% RH) over 6 months. Therefore, the novel formulation is expected to be a substitute for conventional SEDDS, offering a supersaturated state of the poorly water-soluble calcinurin inhibitor with a reduced use of vehicle ingredients.

Pharmacokinetic aspects and in vitro-in vivo correlation potential for lipid-based formulations

Lipid-based formulations have been an attractive choice among novel drug delivery systems for enhancing the solubility and bioavailability of poorly soluble drugs due to their ability to keep the drug in solubilized state in the gastrointestinal tract. These formulations offer multiple advantages such as reduction in food effect and inter-individual variability, ease of preparation, and the possibility of manufacturing using common excipients available in the market. Despite these advantages, very few products are available in the present market, perhaps due to limited knowledge in the in vitro tests (for prediction of in vivo fate) and lack of understanding of the mechanisms behind pharmacokinetic and biopharmaceutical aspects of lipid formulations after oral administration. The current review aims to provide a detailed understanding of the in vivo processing steps involved after oral administration of lipid formulations, their pharmacokinetic aspects and in vitro in vivo correlation (IVIVC) perspectives. Various pharmacokinetic and biopharmaceutical aspects such as formulation dispersion and lipid digestion, bioavailability enhancement mechanisms, impact of excipients on efflux transporters, and lymphatic transport are discussed with examples. In addition, various IVIVC approaches towards predicting in vivo data from in vitro dispersion/precipitation, in vitro lipolysis and ex vivo permeation studies are also discussed in detail with help of case studies.

Characterization of supersaturatable formulations for improved absorption of poorly soluble drugs

With the increasing number of poorly water-soluble compounds in contemporary drug discovery pipelines, the concept of supersaturation as an effective formulation approach for enhancing bioavailability is gaining momentum. This is intended to design the formulation to yield significantly high intraluminal concentrations of the drug than the thermodynamic equilibrium solubility through achieving supersaturation and thus to enhance the intestinal absorption. The major challenges faced by scientists developing supersaturatable formulations include controlling the rate and degree of supersaturation with the application of polymeric precipitation inhibitor and maintenance of post-administration supersaturation. This review is intended to cover publications on this topic since April 2009. Scientific publications associated with characterization of supersaturatable systems and related preclinical and clinical pharmacokinetics (PK) studies are reviewed. Specifically, this review will address issues related to assessing the performance of supersaturatable systems including: (1) Diversified approaches for developing supersaturatable formulations, (2) meaningful in vitro test methods to evaluate supersaturatable formulations, and (3) in vivo PK study cases which have demonstrated direct relevance between the supersaturation state and the exposure observed in animal models and human subjects.

Improved oral bioavailability of poorly water-soluble indirubin by a supersaturatable self-microemulsifying drug delivery system

BACKGROUND

Indirubin, isolated from the leaves of the Chinese herb Isatis tinctoria L, is a protein kinase inhibitor and promising antitumor agent. However, the poor water solubility of indirubin has limited its application. In this study, a supersaturatable self-microemulsifying drug delivery system (S-SMEDDS) was developed to improve the oral bioavailability of indirubin.

METHODS

A prototype S-SMEDDS was designed using solubility studies and phase diagram construction. Precipitation inhibitors were selected from hydrophilic polymers according to their crystallization-inhibiting capacity through in vitro precipitation tests. In vitro release of indirubin from S-SMEDDS was examined to investigate its likely release behavior in vivo. The in vivo bioavailability of indirubin from S-SMEDDS and from SMEDDS was compared in rats.

RESULTS

The prototype formulation of S-SMEDDS comprised Maisine™ 35-1:Cremophor(®) EL:Transcutol(®) P (15:40:45, w/w/w). Polyvinylpyrrolidone K17, a hydrophilic polymer, was used as a precipitation inhibitor based on its better crystallization-inhibiting capacity compared with polyethylene glycol 4000 and hydroxypropyl methylcellulose. In vitro release analysis showed more rapid drug release from S-SMEDDS than from SMEDDS. In vivo bioavailability analysis in rats indicated that improved oral absorption was achieved and that the relative bioavailability of S-SMEDDS was 129.5% compared with SMEDDS.

CONCLUSION

The novel S-SMEDDS developed in this study increased the dissolution rate and improved the oral bioavailability of indirubin in rats. The results suggest that S-SMEDDS is a superior means of oral delivery of indirubin.