SciCombinator

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Concept: Biopharmaceutics Classification System

168

We investigated flexible liposomes as a potential oral drug delivery system. However, enhanced membrane fluidity and structural deformability may necessitate liposomal surface modification when facing the harsh environment of the gastrointestinal tract. In the present study, silica-coated flexible liposomes loaded with curcumin (CUR-SLs) having poor water solubility as a model drug were prepared by a thin-film method with homogenization, followed by the formation of a silica shell by the sol-gel process. We systematically investigated the physical properties, drug release behavior, pharmacodynamics, and bioavailability of CUR-SLs. CUR-SLs had a mean diameter of 157 nm and a polydispersity index of 0.14, while the apparent entrapment efficiency was 90.62%. Compared with curcumin-loaded flexible liposomes (CUR-FLs) without silica-coatings, CUR-SLs had significantly higher stability against artificial gastric fluid and showed more sustained drug release in artificial intestinal fluid as determined by in vitro release assays. The bioavailability of CUR-SLs and CUR-FLs was 7.76- and 2.35-fold higher, respectively, than that of curcumin suspensions. Silica coating markedly improved the stability of flexible liposomes, and CUR-SLs exhibited a 3.31-fold increase in bioavailability compared with CUR-FLs, indicating that silica-coated flexible liposomes may be employed as a potential carrier to deliver drugs with poor water solubility via the oral route with improved bioavailability.

Concepts: Pharmacology, Sol-gel, Drugs, Membrane biology, Medicinal chemistry, Pharmacokinetics, Biopharmaceutics Classification System, Digestion

168

In this paper work, four naked nanocrystals (size range 80-700 nm) were prepared without any surfactant or polymer using the solvent/nonsolvent method. The effects of particle size on their solubility, dissolution, and oral bioavailability were investigated. Solubility and dissolution testing were performed in three types of dissolution medium, and the studies demonstrated that the equilibrium solubilities of coenzyme Q(10) nanocrystals and bulk drugs were not affected by the dissolution media but the kinetic solubilities were. Kinetic solubility curves and changes in particle size distribution were determined and well explained by the proposed solubilization model for the nanocrystals and bulk drugs. The particle size effect on dissolution was clearly influenced by the diffusion coefficients of the various dissolution media, and the dissolution velocity of coenzyme Q(10) increased as particle size decreased. The bioavailability of coenzyme Q(10) after oral administration in beagle dogs was improved by reducing the particle size. For 700 nm nanocrystals, the AUC(0-48) was 4.4-fold greater than that for the coarse suspensions, but a further decrease in particle size from 700 nm to 120 nm did not contribute to improvement in bioavailability until the particle size was reduced to 80 nm, when bioavailability was increased by 7.3-fold.

Concepts: Improve, Effect, Solubility, Affect, Particle size distribution, Biopharmaceutics Classification System, Solvation, Colloidal chemistry

31

Polymeric excipients are crucial ingredients in modern pills, increasing the therapeutic bioavailability, safety, stability, and accessibility of lifesaving products to combat diseases in developed and developing countries worldwide. Because many early-pipeline drugs are clinically intractable due to hydrophobicity and crystallinity, new solubilizing excipients can reposition successful and even failed compounds to more effective and inexpensive oral formulations. With assistance from high-throughput controlled polymerization and screening tools, we employed a strategic, molecular evolution approach to systematically modulate designer excipients based on the cyclic imide chemical groups of an important (yet relatively insoluble) drug phenytoin. In these acrylamide- and methacrylate-containing polymers, a synthon approach was employed: one monomer served as a precipitation inhibitor for phenytoin recrystallization, while the comonomer provided hydrophilicity. Systems that maintained drug supersaturation in amorphous solid dispersions were identified with molecular-level understanding of noncovalent interactions using NOESY and DOSY NMR spectroscopy. Poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (poly(NIPAm-co-DMA)) at 70 mol % NIPAm exhibited the highest drug solubilization, in which phenytoin associated with inhibiting NIPAm units only with lowered diffusivity in solution. In vitro dissolution tests of select spray-dried dispersions corroborated the screening trends between polymer chemical composition and solubilization performance, where the best NIPAm/DMA polymer elevated the mean area-under-the-dissolution-curve by 21 times its crystalline state at 10 wt % drug loading. When administered to rats for pharmacokinetic evaluation, the same leading poly(NIPAm-co-DMA) formulation tripled the oral bioavailability compared to a leading commercial excipient, HPMCAS, and translated to a remarkable 23-fold improvement over crystalline phenytoin.

Concepts: Pharmacology, Polymer, Polymer chemistry, Solubility, Monomer, Solid, Biopharmaceutics Classification System, Polymerization

28

Rhizoma paridis steroidal saponins (RPS) have been prepared and identified as the active compounds for antitumor activity in our previous study. However, the low oral bioavailability of the steroidal saponins restricted its using. In the present research, solid dispersion (SD) and phytosome (PHY) formulation of RPS were prepared, and the physicochemical parameters as well as the intestinal absorption in rat everted gut sac model were investigated. Seven agents were selected as the carriers of SD, and poloxamer 407 (P 407) was the most suitable one. SD reduced the particle size of saponins in the water solution, enhanced the solubility of the saponins by about 3.5 folds, and significantly improved the absorption transport of saponins from 48 to 104μg in everted gut sac of the rat system. PHY significantly enhanced the hydrophilic of saponins but showed little effect on the absorption in small intestine. Jejunum and ileum part absorbed more absolute contents of total saponins than duodenum parts. Six saponins, the main contents of RPS, used as the index of comparing the three forms, were also further investigated in the physico-chemical properties and the absorption tests. n-Octanol/water partition coefficients of the six saponins ordered in RPS, SD and PHY were Chonglouoside H>Dioscin>Polyphyllin D>Gracillin>Paris-VII>Formosanin C. All the saponins possessed the higher absorptive characteristics in SD formulation. The absorption rate of diosgenyl saponins in intestine was more than the pennogenyl saponins.

Concepts: Digestive system, Solubility, Intestine, Small intestine, Pharmacokinetics, Biopharmaceutics Classification System, Digestion, Duodenum

28

Abstract 1. Doxorubicin exhibited dose-independent pharmacokinetics after intravenous (5-20 mg/kg) and oral (20-100 mg/kg) administration to rats. Nearly all (82.1-99.7%) of the orally administered doxorubicin remained unabsorbed, and the hepatic first-pass extraction ratio and oral bioavailability of doxorubicin were approximately 0.5% and 1%, respectively. Based on these results, it is likely that the primary factor responsible for the low oral bioavailability of doxorubicin is the limited intestinal absorption, rather than the CYP3A4-mediated first-pass metabolism. 2. Moreover, the in vitro transport and cellular uptake studies using Caco-2 cell monolayers have revealed that doxorubicin crosses the intestinal epithelium primarily via the paracellular pathway (accounting for 85.6% of the overall absorptive transport) probably due to its physicochemical properties (hydrophilic cation; pK(a) = 9.67, log P = -0.5). These results suggest that P-glycoprotein (P-gp)-mediated efflux activity does not play a significant role in limiting the intestinal absorption of doxorubicin, attenuating the absorptive transport by only 5.56-13.2%. 3. Taken together, the present study demonstrated that the limited and paracellular intestinal absorption of doxorubicin was a major factor responsible for its low oral bioavailability, restricting the role of CYP3A4-mediated first-pass metabolism and P-gp-mediated efflux.

Concepts: Epithelium, Small intestine, Physical chemistry, Medicinal chemistry, Pharmacokinetics, Biopharmaceutics Classification System, Bioavailability

28

Introduction: Many active pharmaceutical ingredients (APIs), in development and already on the market, show a limited and variable bioavailability mainly associated to inadequate biopharmaceutical properties such as aqueous solubility and dissolution rate. The latter is the main factor responsible for the limited, and sometimes inadequate, efficacy of many orally administered drugs, belonging to class II and IV of the Biopharmaceutics Classification System (BCS). Moreover, because of their low solubility, such drugs require high doses to be administered in order to obtain their pharmacological effect, increasing the side effect incidence. Areas covered: The present review reports the most common technological approaches intended to improve solubility and dissolution rate of BCS class II and IV drugs such as nanocrystals, solid dispersions, cyclodextrins and solid lipid nanoparticles. Particular attention will be focused on the use of inorganic matrices (lamellar anionic clays and mesoporous materials) as host for the delivery of poor soluble APIs (guest). Expert opinion: The employment of inorganic matrices for the realization of host-guest composites is a suitable strategy for the biopharmaceutical properties enhancement. This objective can be achieved without any modification of API chemical structure.

Concepts: Pharmacology, Drug, Solubility, Pharmaceutical drug, Biopharmaceutics Classification System, Bioavailability, Active ingredient, Solvation

28

One of the problems of praziquantel (PZQ) is its very low aqueous solubility. Moreover, its dissolution rate is considered the limiting factor for its bioavailability. This work correlates the physical properties and the dissolution behavior of PZQ-polyvinylpyrrolidone (PVP) solid dispersion (SD) at the ratios of 1:1 and 3:7 with its oral bioavailability and its in vivo efficacy against Schistosoma mansoni (S. mansoni). The PZQ and PZQ-PVP SD were characterized by infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy (SEM) and solubility test. Results showed a decrease in crystallinity, possible interaction between PZQ and PVP, greater increase in dissolution rate and appreciable reduction in particle size. S. mansoni-infected mice treated orally with either pure PZQ or PZQ-PVP at a single dose of 500 mg/kg showed a higher increase in AUC((0-8h)), C (max), K (a) and t (1/2e) with a significant decrease in k (el) versus the corresponding uninfected mice. Moreover, uninfected and infected mice treated with PZQ-PVP SD showed 2.3-, 1.6- and 1.3-, 1.25-fold increase, respectively, in AUC((0-8h)) and C (max), with a decrease in k (el) and increase in t (1/2e) by twofold versus the corresponding pure PZQ-treated groups. Percentage worm reduction at all administered doses (62.5, 125, 250, 500 and 1,000 mg/kg) was significantly higher (1- to 1.5-fold) in mice treated with PZQ-PVP SD (ED(50) = 40.92) versus those treated with pure PZQ (ED(50) = 99.29). In addition, a significant reduction in total tissue egg load concomitant with a significant decrease in total immature and mature eggs and an increase in dead eggs in PZQ-PVP SD-treated groups versus their corresponding pure PZQ-treated groups was recorded. Solid dispersion of PZQ with PVP could lead to a further improvement in the effectiveness of PZQ therapy especially with the appearance of some PZQ-tolerant S. mansoni isolates.

Concepts: Schistosomiasis, Schistosoma mansoni, Schistosoma, Digenea, Differential scanning calorimetry, Scanning electron microscope, Biopharmaceutics Classification System, Solvation

28

A series of novel tylophorine-derived dibenzoquinolines has been synthesized and their biological activity evaluated. Three assays were conducted: inhibition of cancer cell proliferation, inhibition of TGEV replication for anti-coronavirus activity, and suppression of nitric oxide production in RAW264.7 cells (a measure of anti-inflammation). The most potent compound from these assays, dibenzoquinoline 33b, showed improved solubility compared to tylophorine 9a; in vivo efficacies in a lung A549 xenografted tumor mouse model and a murine paw edema model; good bioavailability; and no significant neurotoxicity (as tested by a rota-rod test for motor coordination). This is the first study to explore in detail the role of the tylophorine E ring on biological activity, and very strongly suggests that tylophorine-derived dibenzoquinolines merit further development into orally active agents.

Concepts: Gene, Cancer, Lung cancer, Cell division, Motor control, DNA replication, Nitric oxide, Biopharmaceutics Classification System

27

Cannabidiol is the nonpsychoactive natural component of C. sativa that has been shown to be neuroprotective in multiple animal models. Our interest is to advance a therapeutic candidate for the orphan indication hepatic encephalopathy (HE). HE is a serious neurological disorder that occurs in patients with cirrhosis or liver failure. Although cannabidiol is effective in models of HE, it has limitations in terms of safety and oral bioavailability. Herein, we describe a series of side chain modified resorcinols that were designed for greater hydrophilicity and “drug likeness”, while varying hydrogen bond donors, acceptors, architecture, basicity, neutrality, acidity, and polar surface area within the pendent group. Our primary screen evaluated the ability of the test agents to prevent damage to hippocampal neurons induced by ammonium acetate and ethanol at clinically relevant concentrations. Notably, KLS-13019 was 50-fold more potent and >400-fold safer than cannabidiol and exhibited an in vitro profile consistent with improved oral bioavailability.

Concepts: Oxygen, Ammonia, Hydrogen, Cirrhosis, Liver, Neurology, Biopharmaceutics Classification System, Hepatic encephalopathy

27

Selective phosphodiesterase 2 (PDE2) inhibitors are shown to have efficacy in a rat model of osteoarthritis (OA) pain. We identified potent, selective PDE2 inhibitors by optimizing residual PDE2 activity in a series of phosphodiesterase 4 (PDE4) inhibitors, while minimizing PDE4 inhibitory activity. These newly designed PDE2 inhibitors bind to the PDE2 enzyme in a cGMP-like binding mode orthogonal to the cAMP-like binding mode found in PDE4. Extensive structure activity relationship studies ultimately led to identification of pyrazolodiazepinone, 22, which was >1000-fold selective for PDE2 over recombinant, full length PDEs 1B, 3A, 3B, 4A, 4B, 4C, 7A, 7B, 8A, 8B, 9, 10 and 11. Compound 22 also retained excellent PDE2 selectivity (241-fold to 419-fold) over the remaining recombinant, full length PDEs, 1A, 4D, 5, and 6. Compound 22 exhibited good pharmacokinetic properties and excellent oral bioavailability (F=78%, rat). In an in vivo rat model of OA pain, compound 22 had significant analgesic activity 1 and 3h after a single, 10mg/kg, subcutaneous dose.

Concepts: Pharmacology, Signal transduction, Agonist, Pharmacokinetics, Biopharmaceutics Classification System, Bioavailability, Phosphodiesterase, PDE2