Cocrystal Solubility Advantage and Dose/Solubility Ratio Diagrams: A Mechanistic Approach To Selecting Additives and Controlling Dissolution-Supersaturation-Precipitation Behavior.

Two of the main questions regarding cocrystal selection and formulation development are whether the will be stable and how fast can it dissolve the drug dose. Dissolving the drug dose may require cocrystals with a high solubility advantage over drug (SA = SCC/SD), but these may have limited potential to sustain drug supersaturation. Thus, we propose a twofold approach to mitigate the risk of drug precipitation by optimizing thermodynamic (SA) and kinetic factors (nucleation inhibitors). This risk can be evaluated by considering the cocrystal SA and drug dose/solubility ratio (D0D = Cdose/SD), which in tandem represent the maximum theoretical supersaturation that a cocrystal may generate, the driving force for drug precipitation, and the potential for dose-/solubility-limited absorption. cocrystals with SA and D0D values above critical supersaturation are prone to rapid precipitation, often negating their utility as a solubility enhancement tool. This work presents a mechanistic approach to controlling the dissolution-supersaturation-precipitation behavior of cocrystal systems, whereby relationships between SA, D0D, and the drug-solubilizing power of surfactants (SPD = SD,T/SD,aq) are used to fine-tune cocrystal-inherent supersaturation by rational additive selection. Experimental results with danazol-vanillin cocrystal demonstrate how SA, D0D, and SPD are key thermodynamic parameters to understanding the kinetic cocrystal behavior and how the risks of cocrystal development may be mitigated through the mechanistic formulation design.

Role of wetting agents and disintegrants in development of danazol nanocrystalline tablets.

Poor wetting and/or particle aggregation are the shortcomings of the dried nanocrystalline suspensions, which subsequently might hinder the superior dissolution performance of the nano-crystalline suspensions. The objective of this study was to evaluate the effect of wetting agents and disintegrants on the dissolution performance of dried nanocrystals of an active pharmaceutical ingredient (API) with poor wetting property. Danazol, a BCS Class II compound with high LogP and low polar surface area, was chosen as a model compound for this study. Danazol nanocrystalline suspension was prepared by wet-media milling and converted into powder via spray granulation either with mannitol or microcrystalline cellulose as carriers at a drug: carrier ratio of 1:9 w/w. Danazol nanocrystalline suspension showed a superior dissolution performance compared to an un-milled danazol suspension. Dried danazol nanocrystals suffered from poor wetting leading to hindered dissolution performance i.e. ~ 40% and ~ 15% drug dissolution within 15 min for the mannitol and microcrystalline cellulose-based granules, respectively. Addition of a lipophilic surfactant (i.e. docusate sodium) at a surfactant: drug ratio of 0.015: 1 w/w during granulation helped in retaining the superior drug dissolution rates i.e. more than 80% drug dissolution within 15 min for mannitol-based granules by enhancing the wettability of dried danazol nanocrystals when compared to a hydrophilic surfactant (i.e. poloxamer 188) or disintegrant (i.e. sodium starch glycolate or croscarmellose sodium). The fast-dissolving mannitol-based granules containing danazol nanocrystals and docusate sodium were compressed into a tablet dosage form. The tablets containing danazol nanocrystals with docusate sodium showed a superior dissolution performance compared to a tablet containing un-milled danazol with docusate sodium.

Lipolysis-Permeation Setup for Simultaneous Study of Digestion and Absorption in Vitro.

Lipid-based formulations (LBFs) are a delivery strategy to enhance intestinal absorption of poorly water-soluble drugs. LBF performance is typically evaluated by in vitro lipolysis studies, but these do not accurately predict the in vivo performance. One possible reason is the absence of an absorptive membrane driving sink conditions in the serosal compartment. To explore the impact of absorption under sink conditions on the performance evaluation, we developed a lipolysis-permeation setup that allows simultaneous investigation of intestinal digestion of an LBF and drug absorption. The setup consists of two chambers, an upper one for digestion (luminal), and a lower, receiving one (serosal), separated by a Caco-2 monolayer. Digestions were performed with immobilized lipase, instead of the pancreatic extract typically used during lipolysis, since the latter has proven incompatible with Caco-2 cells. Danazol-loaded LBFs were used to develop the setup, and fenofibrate-loaded LBFs were used to establish an in vitro in vivo correlation. As in regular lipolysis studies, our setup allows for the evaluation of (i) the extent of digestion and (ii) drug distribution in different phases present during lipolysis of drug-loaded LBFs (i.e., oil, aqueous, and solid phase). In addition, our setup can determine drug permeation across Caco-2 monolayers and hence, the absorptive flux of the compound. The presence of the absorptive monolayer and sink conditions tended to reduce aqueous drug concentrations and supersaturation in the digestion chamber. The drug transfer across the Caco-2 membrane accurately reflected in vivo drug exposure upon administration of three different LBFs loaded with fenofibrate, where the traditional lipolysis setup failed to predict in vivo performance. As the new setup reflects the dynamic processes occurring in the gastrointestinal tract, it is a valuable tool that can be used in the development of LBFs prior to in vivo studies.

Effect of Surfactant-Bile Interactions on the Solubility of Hydrophobic Drugs in Biorelevant Dissolution Media.

Biorelevant dissolution media (BDM) methods are commonly employed to investigate the oral absorption of poorly water-soluble drugs. Despite the significant progress in this area, the effect of commonly employed pharmaceutical excipients, such as surfactants, on the solubility of drugs in BDM has not been characterized in detail. The aim of this study is to clarify the impact of surfactant-bile interactions on drug solubility by using a set of 12 surfactants, 3 model hydrophobic drugs (fenofibrate, danazol, and progesterone) and two types of BDM (porcine bile extract and sodium taurodeoxycholate). Drug precipitation and sharp nonlinear decrease in the solubility of all studied drugs is observed when drug-loaded ionic surfactant micelles are introduced in solutions of both BDM, whereas the drugs remain solubilized in the mixtures of nonionic polysorbate surfactants + BDM. One-dimensional and diffusion-ordered 1H NMR spectroscopy show that mixed bile salt + surfactant micelles with low drug solubilization capacity are formed for the ionic surfactants. On the other hand, separate surfactant-rich and bile salt-rich micelles coexist in the nonionic polysorbate surfactant + bile salt mixtures, explaining the better drug solubility in these systems. The nonionic alcohol ethoxylate surfactants show intermediate behavior. The large dependence of the drug solubility on surfactant-bile interactions (in which the drug molecules do not play a major role per se) highlights how the complex interplay between excipients and bile salts can significantly change one of the key parameters which governs the oral absorption of poorly water-soluble drugs, viz. the drug solubility in the intestinal fluids.

Micellar solubilization of poorly water-soluble drugs: effect of surfactant and solubilizate molecular structure.

OBJECTIVE: This study aims to clarify the role of surfactant and drug molecular structures on drug solubility in micellar surfactant solutions. SIGNIFICANCE: (1) Rationale for surfactant selection is provided; (2) the large data set can be used for validation of the drug solubility parameters used in oral absorption models. METHODS: Equilibrium solubility of two hydrophobic drugs and one model hydrophobic steroid in micellar solutions of 19 surfactants was measured by HPLC. The drug solubilization locus in the micelles was assessed by UV spectrometry. RESULTS: Danazol is solubilized much more efficiently than fenofibrate by ionic surfactants due to ion-dipole interactions between the charged surfactant head groups and the polar steroid backbone. Drug solubilization increases linearly with the increase of hydrophobic chain length for all studied surfactant types. Addition of 1-3 ethylene oxide (EO) units in the head group of dodecyl sulfate surfactants reduces significantly the solubilization of both studied drugs and decreases linearly the solubilization locus polarity of fenofibrate. The locus of fenofibrate solubilization is in the hydrophobic core of nonionic surfactant micelles and in the palisade layer of ionic surfactant micelles. CONCLUSIONS: Highest drug solubility can be obtained by using surfactants molecules with long chain length coupled with hydrophilic head group that provides additional drug-surfactant interactions (i.e. ion-dipole) in the micelles.

Heme Modification Contributes to the Mechanism-Based Inactivation of Human Cytochrome P450 2J2 by Two Terminal Acetylenic Compounds.

The mechanism-based inactivation of human CYP2J2 by three terminal acetylenic compounds: N-(methylsulfonyl)-6-(2-propargyloxyphenyl)hexanamide (MS), 17-octadecynoic acid (OD), and danazol (DZ) was investigated. The loss of hydroxyebastine (OHEB) carboxylation activity in a reconstituted system was time- and concentration-dependent and required NADPH for MS and OD, but not DZ. The kinetic constants for the mechanism-based inactivation of OHEB carboxylation activity were: KI of 6.1 µM and kinact of 0.22 min-1 for MS and KI of 2.5 µM and kinact of 0.05 min-1 for OD. The partition ratios for MS and OD were ∼10 and ∼20, respectively. Inactivation of CYP2J2 by MS or OD resulted in a loss of the native heme spectrum and a similar decrease in the reduced CO difference spectrum. A heme adduct was observed in the MS-inactivated CYP2J2. The possible reactive metabolite which covalently modified the prosthetic heme was characterized by analysis of the glutathione conjugates formed by MS or OD following oxygenation of the ethynyl moiety. Liquid chromatography-mass spectrometry showed that inactivation by MS or OD did not lead to modification of apoprotein. Interaction of CYP2J2 with DZ produced a type II binding spectrum with a Ks of 2.8 µM and the IC50 for loss of OHEB carboxylation activity was 0.18 µM. In conclusion, heme modification by MS and OD was responsible for the mechanism-based inactivation of CYP2J2. The results suggest that the ethynyl moiety of MS and OD faces the heme iron, whereas the isoxazole ring of DZ is preferentially oriented toward the heme iron of CYP2J2.

Toward Successful Cyclodextrin Based Solubility-Enabling Formulations for Oral Delivery of Lipophilic Drugs: Solubility-Permeability Trade-Off, Biorelevant Dissolution, and the Unstirred Water Layer.

The purpose of this work was to investigate key factors dictating the success/failure of cyclodextrin-based solubility-enabling formulations for oral delivery of low-solubility drugs. We have studied the solubility, the permeability, and the solubility-permeability interplay, of the highly lipophilic drug danazol, formulated with different levels (8.5, 10, 20, and 30%) of the commonly used hydroxypropyl-ß-cyclodextrin (HPßCD), accounting for the biorelevant solubilization of the drug along the gastrointestinal tract (GIT), the unstirred water layer (UWL) adjacent to the GI membrane, and the overall absorption. HPßCD significantly increased danazol solubility, and decreased the drugs' permeability, in a concentration-dependent manner. These Peff results were in good correlation (R2 = 0.977) to literature rat AUC data of the same formulations. Unlike vehicle without HPßCD, formulations containing 8.5% HPßCD and above were shown to successfully dissolve the drug dose during the entire biorelevant dissolution experiment. We conclude that CD-based solubility-enabling formulations should contain the minimal amount of CD sufficient to dissolve the drug dose throughout the GIT, and not more than that; excess CD does not provide solubility gain but causes further permeability loss, and the overall absorption is then impaired. Moreover, a significant UWL effect was revealed in danazol intestinal permeability, and accounting for this effect allowed an excellent prediction of the solubility-permeability trade-off vs % HPßCD. Overall, this work assessed the contribution of each individual step of the absorption cascade to the success/failure of HPßCD-based formulation, allowing a more mechanistic development process of better solubility-enabling formulations.

Solution or suspension - Does it matter for lipid based systems? In vivo studies of chase dosing lipid vehicles with aqueous suspensions of a poorly soluble drug.

In this study, the potential of co-administering an aqueous suspension with a placebo lipid vehicle, i.e. chase dosing, was investigated in rats relative to the aqueous suspension alone or a solution of the drug in the lipid vehicle. The lipid investigated in the present study was Labrafil M2125CS and three evaluated poorly soluble model compounds, danazol, cinnarizine and halofantrine. For cinnarizine and danazol the oral bioavailability in rats after chase dosing or dosing the compound dissolved in Labrafil M21515CS was similar and significantly higher than for the aqueous suspension. For halofantrine the chase dosed group had a tendency towards a low bioavailability relative to the Labrafil M2125CS solution, but still a significant higher bioavailability relative to the aqueous suspension. This could be due to factors such as a slower dissolution rate in the intestinal phase of halofantrine or a lower solubility in the colloidal structures formed during digestion, but other mechanisms may also be involved. The study thereby supported the potential of chase dosing as a potential dosing regimen in situations where it is beneficial to have a drug in the solid state, e.g. due to chemical stability issues in the lipid vehicle.

Computational Models of the Gastrointestinal Environment. 2. Phase Behavior and Drug Solubilization Capacity of a Type I Lipid-Based Drug Formulation after Digestion.

Lipid-based drug formulations can greatly enhance the bioavailability of poorly water-soluble drugs. Following the oral administration of formulations containing tri- or diglycerides, the digestive processes occurring within the gastrointestinal (GI) tract hydrolyze the glycerides to mixtures of free fatty acids and monoglycerides that are, in turn, solubilized by bile. The behavior of drugs within the resulting colloidal mixtures is currently not well characterized. This work presents matched in vitro experimental and molecular dynamics (MD) theoretical models of the GI microenvironment containing a digested triglyceride-based (Type I) drug formulation. Both the experimental and theoretical models consist of molecular species representing bile (glycodeoxycholic acid), digested triglyceride (1:2 glyceryl-1-monooleate and oleic acid), and water. We have characterized the phase behavior of the physical system using nephelometry, dynamic light scattering, and polarizing light microscopy and compared these measurements to phase behavior observed in multiple MD simulations. Using this model microenvironment, we have investigated the dissolution of the poorly water-soluble drug danazol experimentally using LC-MS and theoretically by MD simulation. The results show how the formulation lipids alter the environment of the GI tract and improve the solubility of danazol. The MD simulations successfully reproduce the experimental results showing the utility of MD in modeling the fate of drugs after digestion of lipid-based formulations within the intestinal lumen.

A heuristic model to quantify the impact of excess cyclodextrin on oral drug absorption from aqueous solution.

The intestinal drug solubilising capacity (Dtot(SC)) of a drug formulated as an aqueous cyclodextrin solution is a recently proposed quantity to predict the cyclodextrin concentration needed to fully solubilise the drug in the intestinal lumen. According to this concept, the cyclodextrin concentration in the drug product must be higher than the amount needed to solubilise the compound, due to the displacement of the drug from the cyclodextrin cavity by bile salts in the intestinal lumen. On the other hand, dosing cyclodextrin at >Dtot(SC) is expected to result in decreased free intestinal drug concentrations and thus potentially a lower fraction absorbed. In this study, data from three previous in vivo studies in rats with fixed concentrations of three compounds (danazol, cinnarizine and benzo[A]pyrene) and various cyclodextrin concentrations >Dtot(SC) were analysed. The model was developed for danazol and applied to the two other compounds. Absorption, as quantified from the area under the plasma concentration-time profile, was predicted by the model to decrease at elevated concentrations of co-administered cyclodextrin in accordance with the in vivo data. In addition, at high cyclodextrin concentrations a delay in Tmax and a decrease in Cmax were predicted, again in accordance with the experimental observations. These observations were rationalised in terms of the free intestinal drug concentration by a chemical equilibrium model for Dtot(SC). This model depends on the quantity termed the dimensionless dose concentration, Dtot(∗)=Do/Pn, given as the fraction of the permeation number (Pn) and dose number (Do). The model provides the formulation scientist with a critical quality attribute for assessing the implication of having excess cyclodextrin in an oral solution.

Characterization of Supersaturated Danazol Solutions - Impact of Polymers on Solution Properties and Phase Transitions.

PURPOSE: Excipients are essential for solubility enhancing formulations. Hence it is important to understand how additives impact key solution properties, particularly when supersaturated solutions are generated by dissolution of the solubility enhancing formulation. Herein, the impact of different concentrations of dissolved polymers on the thermodynamic and kinetic properties of supersaturated solutions of danazol were investigated. METHODS: A variety of experimental techniques was used, including nanoparticle tracking analysis, fluorescence and ultraviolet spectroscopy and flux measurements to characterize the solution phase behavior. RESULTS: Neither the crystalline nor amorphous solubility of danazol was impacted by common amorphous solid dispersion polymers, polyvinylpyrrolidone, hydroxypropylmethyl cellulose (HPMC) or HPMC-acetate succinate. Consequently, the maximum membrane transport rate was limited only by the amorphous solubility, and not by the presence of the polymers. The polymers were able to inhibit crystallization to some extent at concentrations as low as 1 µg/mL, with the maximum effectiveness being reached at 10 µg/mL. Aqueous danazol solutions formed a drug-rich phase with a mean size of 250 nm when the concentration exceeded the amorphous solubility, and the polymers modified the surface properties of this drug-rich phase. CONCLUSIONS: The phase behavior of supersaturated solutions is complex and the kinetics of phase transformations can be substantially modified by polymeric additives present at low concentrations. However, fortunately, these additives do not appear to impact the bulk thermodynamic properties of the solution, thus enabling supersaturated solutions, which provide enhanced membrane transport relative to saturated solutions to be generated.

Effect of cyclodextrin concentration on the oral bioavailability of danazol and cinnarizine in rats.

Cyclodextrins (CDs) are frequently used as an excipient to enhance the intestinal drug absorption of compounds with a low aqueous solubility. However, there exists an intricate interplay between opposing effects that determine the optimal dosing criterion. These opposing effects are the benefits of circumventing the dissolution time required to dissolve the non-absorbable drug particles in the intestine versus the disadvantage of decreasing the concentration of the drug available to permeate the intestinal membrane if excessive CD concentrations are used. This study investigated whether there is a potential risk of overdosing CDs in aqueous formulations resulting in suboptimal bioavailability. This was done by measuring the in vivo pharmacokinetics of danazol, which has a high affinity for hydroxypropyl-ßCD, and cinnarizine, which has a pH-dependent low to medium affinity. Pharmacokinetic studies of danazol in rats showed a significant longer Tmax and decreased Cmax resulting in decreased bioavailability when the CD concentration was increased. No significant difference was seen for any of the pharmacokinetic parameters for cinnarizine as a function of CD dose. The present study thus demonstrates that surplus CD concentrations can have a major effect on the pharmacokinetic profile of one compound and a minor effect on the pharmacokinetic profile of another. This suggests that there are some compounds where the CD excipient should be used with care and others where it can be used without major concerns.

Microbial transformation of danazol with Cunninghamella blakesleeana and anti-cancer activity of danazol and its transformed products.

Biotransformation of danazol (1) (17ß-hydroxy-17α-pregna-2,4-dien-20-yno-[2,3-d]-isoxazole) with Cunninghamella blakesleeana yielded three new metabolites 2-4 and a known metabolite 5. These metabolites were identified as 14ß,17ß-dihydroxy-2-(hydroxymethyl)-17α-pregn-4-en-20-yn-3-one (2), 1α,17ß-dihydroxy-17α-pregna-2,4-dien-20-yno-[2,3-d]-isoxazole (3), 6ß,17ß-dihydroxy-17α-pregna-2,4-dien-20-yno-[2,3-d]-isoxazole (4), and 17ß-hydroxy-2-(hydroxymethyl)-17α-pregn-1,4-dien-20-yn-3-one (5). Danazol (1) and its derivatives were evaluated against cervical cancer cell line (HeLa). Compound 1 showed a potent cytotoxicity with IC50=0.283±0.013 µM, as compared to doxorubicin (IC50=0.506±0.015 µM), where compound 3 was also found to be significantly active with IC50=13.427±0.819 µM.

Dissolution of Danazol Amorphous Solid Dispersions: Supersaturation and Phase Behavior as a Function of Drug Loading and Polymer Type.

Amorphous solid dispersions (ASDs) are of great interest as enabling formulations because of their ability to increase the bioavailability of poorly soluble drugs. However, the dissolution of these formulations under nonsink dissolution conditions results in highly supersaturated drug solutions that can undergo different types of phase transitions. The purpose of this study was to characterize the phase behavior of solutions resulting from the dissolution of model ASDs as well as the degree of supersaturation attained. Danazol was chosen as a poorly water-soluble model drug, and three polymers were used to form the dispersions: polyvinylpyrrolidone (PVP), hydroxypropylmethyl cellulose (HPMC), and hydroxypropylmethyl cellulose acetate succinate (HPMCAS). Dissolution studies were carried out under nonsink conditions, and solution phase behavior was characterized using several orthogonal techniques. It was found that liquid-liquid phase separation (LLPS) occurred following dissolution and prior to crystallization for most of the dispersions. Using flux measurements, it was further observed that the maximum attainable supersaturation following dissolution was equivalent to the amorphous solubility. The dissolution of the ASDs led to sustained supersaturation, the duration of which varied depending on the drug loading and the type of polymer used in the formulation. The overall supersaturation profile observed thus depended on a complex interplay between dissolution rate, polymer type, drug loading, and the kinetics of crystallization.

High-Throughput Raman Spectroscopy Screening of Excipients for the Stabilization of Amorphous Drugs.

Low aqueous solubility of active pharmaceutical ingredients (APIs) is an enduring problem in pharmaceutical development, and it is becoming increasingly prevalent among new drug candidates. It is estimated that about 40% of drugs in the development pipeline and approximately 60% of the drugs coming directly from discovery suffer from poor aqueous solubility and slow dissolution, thereby reducing their bioavailability and efficacy and thus preventing their commercialization. It is well known that utilizing the amorphous form of a drug can be a useful approach to improve the dissolution rate and solubility of poorly water-soluble APIs. Amorphous compounds are thermodynamically unstable, but they can be stabilized by combining them with a carrier polymer (excipient) to form a solid dispersion. High-throughput Raman spectroscopy was used in this study to identify excipients that promote formation and stabilization of the amorphous drug form in solid dispersions. Four model APIs were used as poorly soluble drug candidates: ketoprofen, danazol, griseofulvin, and probucol. The Raman signals of excipients were generally negligible, and therefore Raman bands from the drugs were used with minimal spectral pre-processing. By comparing Raman spectra collected from the APIs in the crystalline and molten state, appropriate spectral features and regions were identified for the development of semi-quantitative methods to determine the amorphous content for each API. It is demonstrated that methods based on peak intensity ratio, peak width, peak distance, and classical least squares can all be effective methods for the screening of excipients. Interesting excipient-dependent phase transformation behavior was also observed for probucol.

Development of a high-throughput in vitro intestinal lipolysis model for rapid screening of lipid-based drug delivery systems.

PURPOSE: To develop a high-throughput in vitro intestinal lipolysis (HTP) model, without any means of pH-stat-titration, to enable a fast evaluation of lipid-based drug delivery systems (LbDDS). MATERIAL AND METHOD: The HTP model was compared to the traditionally used dynamic in vitro lipolysis (DIVL) model with regard to the extent of lipid digestion and drug distribution of two poorly soluble model drugs (cinnarizine and danazol), during digestion of three LbDDS (LbDDS I-III). RESULT: The HTP model was able to maintain pH around 6.5 during digestion, without the addition of NaOH to neutralize the free fatty acids (FFAs), due to an increased buffer capacity. Cinnarizine was primarily located in the aqueous phase during digestion of all three LbDDS and did not differ significantly between the two models. The distribution of danazol varied from formulation to formulation, but no significant difference between the models was observed. The triacylglycerides (TAG) in LbDDS III were digested to the same extent in both models, whereas the TAG present in LbDDS II was digested slightly less in the HTP model. No TAG was present in LbDDS I and digestion was therefore not analyzed. CONCLUSION: The HTP model is able to predict drug distribution during digestion of LbDDS containing poorly water soluble drugs in the same manner as the DIVL model. Thus the HTP model might prove applicable for high-throughput evaluation of LbDDS in e.g. 96 well plates or small scale dissolution equipment.

Optimization of PEGylated nanoemulsions for improved pharmacokinetics of BCS class II compounds.

The objective of the study was the optimization of nanoemulsion formulations to prevent their rapid systemic clearance after intravenous administration. An amphiphilic PEG derivative DSPE-PEG (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy-poly(polyethylene glycol) with different chain lengths and concentration was used as a nanoemulsion droplet surface modifier. The danazol loading in all nanoemulsions was kept on the same level of ∼2 mg/mL. In the present investigation, PEGylated and non-PEGylated nanoemulsions were compared in vitro phagocytosis by incubating with lung macrophages and in vivo after intravenous administration in rats. Danazol-containing nanoemulsions (NE) modified with various PEG chain lengths (2000-10 000) and concentrations (3-12 mg/mL) were prepared and characterized. Nanoemulsion droplets were reproducibly obtained in the size range of 213-340 nm. The non-PEGylated NE had the surface charge of -25.4 mV. This absolute charge value decreased with increasing chain length and concentration. With increase in chain length and density the macrophage uptake decreased which could be due to decrease in surface charge and hydrophilicity of droplets. The greatest shielding of the NE droplets was reached with DSPE-PEG5000 at the concentration of 6 mg/mL where the surface charge changed to -1.27 mV. Following intravenous administration a maximum danazol exposure (401 ± 68.2 h ng/mL) was observed with the lowest clearance rate (5.06 ± 0.95 L/h/kg) from 6 mg/mL DSPE-PEG5000 nanoemulsion. PEG5000 and PEG10000 altered the pharmacokinetic of danazol by decreasing clearance and volume of distribution which is likely explained by the presence of hydrophilic shields around the droplets that prevent their rapid systemic clearance and tissue partitioning.

Impact of solidification on the performance of lipid-based colloidal carriers: oil-based versus self-emulsifying systems.

The study aims to develop and optimise lipid-based colloidal carriers (LBCC) for enhancing solubilisation and reducing fed/fasted variation for the poorly water-soluble danazol (DAN). Oil-based and self-microemulsifying delivery systems (SMEDDS) were developed, and the effect of solidification was investigated. Liquid SMEDDS (L-SMEDDS, Capmul MCM:Tween 80:Transcutol HP 1:2:1, w/w) and emulsion (Capmul MCM:soya lecithin 100:0.6, w/w) were developed. Solid-state formulations were prepared via (i) physical adsorption of L-SMEDDS (P-SMEDDS) or (ii) spray drying of emulsion (silica-lipid hybrid, SLH) and L-SMEDDS (spray-dried SMEDDS, S-SMEDDS) using Aerosil 380 silica nanoparticles as the solid carrier. In vitro lipid digestion and drug solubilisation under simulated intestinal conditions in both fasted and fed states were investigated. Solubilisation of unformulated DAN under both fasted and fed conditions was low, and a large fed/fasted variation was observed, i.e. 6.6-fold difference. All LBCC formulations provided enhanced drug solubilisation and significantly reduced the fed/fasted variation. For self-emulsifying LBCC, the fasted state drug solubilisation was ranked as L-SMEDDS > PSMEDDS > S-SMEDDS, suggesting that solidification reduced the capability of SMEDDS in presenting DAN to the aqueous phase. However, in the case of oil-based LBCC, improved drug solubility was observed with the solid form SLH under both fasted and fed state in comparison to that of the equivalent liquid form. Overall, the SLH, which provided the highest drug solubilisation in the fasted state (i.e. 10-fold higher than the pure DAN) and the smallest fed/fasted variation, was considered an optimised solid LBCC to enhance the solubilisation of DAN and reduce the fed/fasted variation.

Formulation and performance of danazol nano-crystalline suspensions and spray dried powders.

PURPOSE: This study focuses on the formulation optimization, in vitro and in vivo performance of differently sized nano-crystalline liquid suspensions and spray-dried powders of a poorly soluble BCS class II compound i.e. Danazol. METHODS: A DoE approach was utilized to optimize stabilizer concentration and formulate danazol (BCS class II) nano-crystalline suspensions and dry powders via wet milling followed by spray drying. Solubility studies were performed to select best stabilizers. Particle size, PXRD, contact angle measurement and in vitro dissolution were utilized in characterization of the liquid and spray-dried powder formulations. RESULTS: The liquid nano-crystalline suspensions followed particle size-dependent dissolution rates i.e. faster dissolution for smaller crystals. The spray-dried nano-crystal powders did not show fast dissolution profiles compared to the liquid nano-crystalline suspension. The poor dissolution of the spray-dried powder correlated to its high LogP value (i.e. LogP 4.53) and poor wetting (or polar surface-area). In vivo bioavailability studies showed superior performance of the liquid nano-crystalline suspensions compared to other milled and un-milled formulations. CONCLUSION: Wet-milling and spray-drying optimization for danazol nano-crystalline suspension was performed. This study indicates that drug candidates with high LogP values and low polar surface area may not be suitable for formulation as dry nano-crystals.

Toward the establishment of standardized in vitro tests for lipid-based formulations, part 6: effects of varying pancreatin and calcium levels.

The impact of pancreatin and calcium addition on a wide array of lipid-based formulations (LBFs) during in vitro lipolysis, with regard to digestion rates and distribution of the model drug danazol, was investigated. Pancreatin primarily affected the extent of digestion, leaving drug distribution somewhat unaffected. Calcium only affected the extent of digestion slightly but had a major influence on drug distribution, with more drug precipitating at higher calcium levels. This is likely to be caused by a combination of removal of lipolysis products from solution by the formation of calcium soaps and calcium precipitating with bile acids, events known to reduce the solubilizing capacity of LBFs dispersed in biorelevant media. Further, during the digestion of hydrophilic LBFs, like IIIA-LC, the un-ionized-ionized ratio of free fatty acids (FFA) remained unchanged at physiological calcium levels. This makes the titration curves at pH 6.5 representable for digestion. However, caution should be taken when interpreting lipolysis curves of lipophilic LBFs, like I-LC, at pH 6.5, at physiological levels of calcium (1.4 mM); un-ionized-ionized ratio of FFA might change during digestion, rendering the lipolysis curve at pH 6.5 non-representable for the total digestion. The ratio of un-ionized-ionized FFAs can be maintained during digestion by applying non-physiological levels of calcium, resulting in a modified drug distribution with increased drug precipitation. However, as the main objective of the in vitro digestion model is to evaluate drug distribution, which is believed to have an impact on bioavailability in vivo, a physiological level (1.4 mM) of calcium is preferred.