Thiolated chitosan: development and in vitro evaluation of an oral delivery system for acyclovir

CNS Viral Infections-What to Consider for Improving Drug Treatment: A Plea for Using Mathematical Modeling Approaches

Neurotropic viruses may cause meningitis, myelitis, encephalitis, or meningoencephalitis. These inflammatory conditions of the central nervous system (CNS) may have serious and devastating consequences if not treated adequately. In this review, we first summarize how neurotropic viruses can enter the CNS by (1) crossing the blood-brain barrier or blood-cerebrospinal fluid barrier; (2) invading the nose via the olfactory route; or (3) invading the peripheral nervous system. Neurotropic viruses may then enter the intracellular space of brain cells via endocytosis and/or membrane fusion. Antiviral drugs are currently used for different viral CNS infections, even though their use and dosing regimens within the CNS, with the exception of acyclovir, are minimally supported by clinical evidence. We therefore provide considerations to optimize drug treatment(s) for these neurotropic viruses. Antiviral drugs should cross the blood-brain barrier/blood cerebrospinal fluid barrier and pass the brain cellular membrane to inhibit these viruses inside the brain cells. Some antiviral drugs may also require intracellular conversion into their active metabolite(s). This illustrates the need to better understand these mechanisms because these processes dictate drug exposure within the CNS that ultimately determine the success of antiviral drugs for CNS infections. Finally, we discuss mathematical model-based approaches for optimizing antiviral treatments. Thereby emphasizing the potential of CNS physiologically based pharmacokinetic models because direct measurement of brain intracellular exposure in living humans faces ethical restrictions. Existing physiologically based pharmacokinetic models combined with in vitro pharmacokinetic/pharmacodynamic information can be used to predict drug exposure and evaluate efficacy of antiviral drugs within the CNS, to ultimately optimize the treatments of CNS viral infections.

Formulation strategies to improve the efficacy of intestinal permeation enhancers. Adv Drug Deliv Rev 2021;177:113925. [PMID: 34418495 DOI: 10.1016/j.addr.2021.113925]

The use of chemical permeation enhancers (PEs) is the most widely tested approach to improve oral absorption of low permeability active agents, as represented by peptides. Several hundred PEs increase intestinal permeability in preclinical bioassays, yet few have progressed to clinical testing and, of those, only incremental increases in oral bioavailability (BA) have been observed. Still, average BA values of ~1% were sufficient for two recent FDA approvals of semaglutide and octreotide oral formulations. PEs are typically screened in static in vitro and ex-vivo models where co-presentation of active agent and PE in high concentrations allows the PE to alter barrier integrity with sufficient contact time to promote flux across the intestinal epithelium. The capacity to maintain high concentrations of co-presented agents at the epithelium is not reached by standard oral dosage forms in the upper GI tract in vivo due to dilution, interference from luminal components, fast intestinal transit, and possible absorption of the PE per se. The PE-based formulations that have been assessed in clinical trials in either immediate-release or enteric-coated solid dosage forms produce low and variable oral BA due to these uncontrollable physiological factors. For PEs to appreciably increase intestinal permeability from oral dosage forms in vivo, strategies must facilitate co-presentation of PE and active agent at the epithelium for a sustained period at the required concentrations. Focusing on peptides as examples of a macromolecule class, we review physiological impediments to optimal luminal presentation, discuss the efficacy of current PE-based oral dosage forms, and suggest strategies that might be used to improve them.

Trends in liposomal nanocarrier strategies for the oral delivery of biologics

The number of approved macromolecular drugs such as peptides, proteins and antibodies steadily increases. Since drugs with high molecular weight are commonly not suitable for oral delivery, research on carrier strategies enabling oral administration is of vital interest. In past decades, nanocarriers, in particular liposomes, have been exhaustively investigated as oral drug-delivery platform. Despite their successful application as parenteral delivery vehicles, liposomes have up to date not succeeded for oral administration. However, a plenitude of approaches aiming to increase the oral bioavailability of macromolecular drugs administered by liposomal formulations has been published. Here, we summarize the strategies published in the last 10 years (vaccine strategies excluded) with a main focus on strategies proven efficient in animal models.

Acyclovir-Loaded Solid Lipid Nanoparticles: Optimization, Characterization and Evaluation of Its Pharmacokinetic Profile

Acyclovir is an antiviral drug used for the treatment of herpes simplex virus infection. Its oral bioavailability is low; therefore, frequent and high doses are prescribed for optimum therapeutic efficacy. Moreover, the current therapeutic regimen of acyclovir is associated with unwarranted adverse effects, hence prompting the need for a suitable drug carrier to overcome these limitations. This study aimed to develop solid lipid nanoparticles (SLNs) as acyclovir carriers and evaluate their in vivo pharmacokinetic parameters to prove the study hypothesis. During the SLN development process, response surface methodology was exploited to optimize the composition of solid lipid and surfactant. Optimum combination of Biogapress Vegetal 297 ATO and Tween 80 was found essential to produce SLNs of 134 nm. The oral bioavailability study showed that acyclovir-loaded SLNs possessed superior oral bioavailability when compared with the commercial acyclovir suspension. The plasma concentration of acyclovir-loaded SLNs was four-fold higher than the commercial suspension. Thus, this investigation presented promising results that the method developed for encapsulation of acyclovir offers potential as an alternative pathway to enhance the drug’s bioavailability. In conclusion, this study exhibited the feasibility of SLNs as an oral delivery vehicle for acyclovir and therefore represents a new promising therapeutic concept of acyclovir treatment via a nanoparticulate drug delivery system.

Suitability and functional characterization of two Calu-3 cell models for prediction of drug permeability across the airway epithelial barrier

The Calu-3 cell line has been largely investigated as a physiological and pharmacological model of the airway epithelial barrier. Its suitability for prediction of drug permeability across the airway epithelia, however, has not been yet evaluated by using large enough set of model drugs. We evaluated two Calu-3 cell models (air-liquid and liquid-liquid) for drug permeability prediction based on the recent regulatory guidelines on showing suitability of in vitro permeability methods for drug permeability classification. Bidirectional permeability assays using 22 model drugs and several zero permeability markers, as well as using ABC transporter substrates were conducted. Functional activity of P-gp, but not of BCRP was revealed. The potential of the Calu-3 cells to be used as a model of the nasal epithelial barrier, despite their different anatomical origin, has been demonstrated by the obtained excellent correlation with the fully differentiated 3D human nasal epithelial model (MucilAir™) for 11 model drugs, as well as by the good correlation obtained with the human nasal epithelial cell line RPMI 2650. In addition, the permeability values determined in the two Calu-3 models correlated well with the intestinal permeability model Caco-2.

Demonstrating suitability of the Caco-2 cell model for BCS-based biowaiver according to the recent FDA and ICH harmonised guidelines

Objective

According to the regulatory guidelines, one of the critical steps in using in-vitro permeability methods for permeability classification is to demonstrate the suitability of the method. Here, suitability of the permeability method by using a monolayer of cultured epithelial cells was verified with different criteria.

Methods

Imaging with a transmission electron microscope was used for characterisation of the cells. Monolayer integrity was confirmed by transepithelial electrical resistance measurements and permeability of zero permeability marker compounds. Real-time polymerase chain reaction was employed to evaluate expression levels of 84 known transporters. Samples for bidirectional permeability determination were quantified by ultra-performance liquid chromatography.

Key findings

The Caco-2 cells grow in an intact monolayer and morphologically resemble enterocytes. Genes of 84 known transporters were expressed at different levels; furthermore, expression was time depended. Functional expression of efflux transporter P-glycoprotein was confirmed. We established a correlation between permeability coefficients of 21 tested drug substances ranging from low, moderate and high absorption with human fraction absorbed literature data (R2 = 0.84).

Conclusions

Assay standardisation assures the consistency of experimental data. Only such fully characterised model has the ability to accurately predict drug's intestinal permeability at the early stage of research or for the BCS-based biowaiver application.

P-Glycoprotein in skin contributes to transdermal absorption of topical corticosteroids

ATP binding cassette transporters, P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), are expressed in skin, but their involvement in transdermal absorption of clinically used drugs remains unknown. Here, we examined their role in transdermal absorption of corticosteroids. Skin and plasma concentrations of dexamethasone after dermal application were reduced in P-gp and BCRP triple-knockout (Mdr1a/1b/Bcrp^-/-) mice. The skin concentration in Mdr1a/1b/Bcrp^-/- mice was reduced in the dermis, but not in the epidermis, indicating that functional expression of these transporters in skin is compartmentalized. Involvement of these transporters in dermal transport of dexamethasone was also supported by the observation of a higher epidermal concentration in Mdr1a/1b/Bcrp^-/- than wild-type mice during intravenous infusion. Transdermal absorption after dermal application of prednisolone, but not methylprednisolone or ethinyl estradiol, was also lower in Mdr1a/1b/Bcrp^-/- than in wild-type mice. Transport studies in epithelial cell lines transfected with P-gp or BCRP showed that dexamethasone and prednisolone are substrates of P-gp, but are minimally transported by BCRP. Thus, our findings suggest that P-gp is involved in transdermal absorption of at least some corticosteroids in vivo. P-gp might be available as a target for inhibition in order to deliver topically applied drugs and cosmetics in a manner that minimizes systemic exposure.

Potential of amphiphilic graft copolymer α-tocopherol succinate-g-carboxymethyl chitosan in modulating the permeability and anticancer efficacy of tamoxifen

Recent studies showed an enhanced oral bioavailability of tamoxifen (TMX) by hydrophobically modified α-tocopherol succinate-g-carboxymethyl chitosan (Cmc-TS) micelles. As a continued effort, here we evaluated TMX-loaded polymeric micelles (TMX-PMs) for its enhanced permeability with increased anticancer efficacy and decreased hepatotoxicity. We employed co-solvent evaporation technique to encapsulate TMX into Cmc-TS. Apparent permeability assay of TMX-PMs was performed on Caco-2 cell line. The absorptive transport of TMX increased significantly about 3.8-fold when incorporated into Cmc-TS PMs. Cytotoxicity of Cmc-TS PMs was studied on MCF-7 cell line by MTT and; confocal microscopy was used for cellular uptake. Confocal microscopy revealed that Cmc-TS PMs could effectively accumulate in the cytosol of MCF-7 cell lines. In vitro data was further validated using N-methyl-N-nitrosourea (MNU)-induced mammary carcinogenesis model in Sprague-Dawley rats. Hepatotoxicity profiles of TMX-PMs at three different doses were also evaluated against the free drug TMX. TMX-PMs were more effective in suppressing breast tumor in MNU-induced mammary carcinoma model than free TMX with better safety profile. In addition, histological data shows that tumors are "benign" in TMX-PMs treated group compared with "malignant" tumors in free TMX treated and control groups. Overall, the results implicate that our Cmc-TS PMs may serve as a promising carrier for the intracellular delivery of anticancer drug molecules via oral route.

Development of mannose-anchored thiolated amphotericin B nanocarriers for treatment of visceral leishmaniasis

AIM

Our goal was to improve treatment outcomes for visceral leishmaniasis by designing nanocarriers that improve drug biodistribution and half-life. Thus, long-acting mannose-anchored thiolated chitosan amphotericin B nanocarrier complexes (MTC AmB) were developed and characterized.

MATERIALS & METHODS

A mannose-anchored thiolated chitosan nanocarrier was manufactured and characterized. MTC AmB was examined for cytotoxicity, biocompatibility, uptake and antimicrobial activities.

RESULTS

MTC AmB was rod shaped with a size of 362 nm. MTC AmB elicited 90% macrophage viability and 71-fold enhancement in drug uptake compared with native drug. The antileishmanial IC50 for MTC AmB was 0.02 μg/ml compared with 0.26 μg/ml for native drug.

CONCLUSION

These studies show that MTC can serve as a platform for clearance of Leishmania in macrophages.

Intestinal permeation enhancers for oral peptide delivery

Intestinal permeation enhancers (PEs) are one of the most widely tested strategies to improve oral delivery of therapeutic peptides. This article assesses the intestinal permeation enhancement action of over 250 PEs that have been tested in intestinal delivery models. In depth analysis of pre-clinical data is presented for PEs as components of proprietary delivery systems that have progressed to clinical trials. Given the importance of co-presentation of sufficiently high concentrations of PE and peptide at the small intestinal epithelium, there is an emphasis on studies where PEs have been formulated with poorly permeable molecules in solid dosage forms and lipoidal dispersions.

Role of ABCB1, ABCG2, ABCC2 and ABCC5 transporters in placental passage of zidovudine

Zidovudine (AZT) is one of the most frequently used antiretroviral drugs in prevention of perinatal transmission of HIV. However, safety concerns on AZT use in pregnancy still persist as severe side effects are associated with AZT exposure in children. In our study we aimed to contribute to current knowledge on AZT transplacental transport and to evaluate potential involvement of the main human drug efflux ATP-binding cassette (ABC) transporters, p-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2) and multidrug resistance-associated proteins 2 and 5 (ABCC2 and ABCC5) in the disposition of AZT between mother and fetus. In order to elucidate this issue we investigated the effect of selected ABC transporters on AZT transepithelial transport across MDCKII cell monolayers. In addition we used the in situ method of dually perfused rat term placenta to further study the role of ABC transporters in AZT transplacental transport. In vitro studies revealed significant effect of ABCB1 and ABCG2 on AZT transport which was subsequently confirmed also on organ level. Lamivudine, an antiretroviral agent commonly co-administered with AZT, did not affect ABC transporter-mediated AZT transfer.

Thiomers and their potential applications in drug delivery

INTRODUCTION

Thiomers are the product of the immobilization of sulfhydryl-bearing ligands onto the polymer backbone of a conventional polymer, which results in a significant improvement in mucoadhesion; in situ gelation and efflux inhibition compare with unchanged polymers. Because of thiol groups, thiomers have more reactivity and enhanced protection against oxidation. Since the late 1990s, extensive work has been conducted on these promising polymeric excipients in the pharmaceutical field. Areas covered: This review covers thiomers, their classification and their different properties. Various techniques for the synthesis, purification and characterization of thiomers are described in detail. This review also encompasses their various properties such as mucoadhesion, permeation enhancement, in situ gelation and efflux inhibition, as well as different formulations based on thiomers. In addition to the use of thiomers as multifunctional excipients, this review also encompasses their use as drugs. Expert opinion: The synthesis is realized by linkage of sulfhydryl-bearing ligands but reported methods give low yields. Higher degrees of modification are not necessary and would probably lead to extreme changes in properties. Nevertheless, an accurate characterization of the final product is important. The scale-up procedure for industrial manufacturing has been adapted to produce GMP materials; Lacrimera® eye drops have already entered the European market.

Curcumin-carboxymethyl chitosan (CNC) conjugate and CNC/LHR mixed polymeric micelles as new approaches to improve the oral absorption of P-gp substrate drugs

The low oral bioavailability of numerous drugs has been mostly attributed to the significant effect of P-gp-mediated efflux on intestinal drug transport. Herein, we developed mixed polymeric micelles (MPMs) comprised of curcumin-carboxymethyl chitosan (CNC) conjugate, as a potential inhibitor of P-gp-mediated efflux and gastrointestinal absorption enhancer, and low-molecular-weight heparin-all-trans-retinoid acid (LHR) conjugate, as loading material, with the aim to improve the oral absorption of P-gp substrate drugs. CNC conjugate was synthesized by chemical bonding of curcumin (Cur) and carboxymethyl chitosan (CMCS) taking advantage of the inhibition of intestinal P-gp-mediated secretion by Cur and the intestinal absorption enhancement by CMCS. The chemical structure of CNC conjugate was characterized by ¹H NMR with a degree of substitution of Cur of 4.52-10.20%. More importantly, CNC conjugate markedly improved the stability of Cur in physiological pH. Cyclosporine A-loaded CNC/LHR MPMs (CsA-CNC/LHR MPMs) were prepared by dialysis method, with high drug loading 25.45% and nanoscaled particle size (∼200 nm). In situ single-pass perfusion studies in rats showed that both CsA + CNC mixture and CsA-CNC/LHR MPMs achieved significantly higher K_a and P_eff than CsA suspension in the duodenum and jejunum segments (p <  0.01), which was comparable to verapamil coperfusion effect. Similarly, CsA + CNC mixture and CsA-CNC/LHR MPMs significantly increased the oral bioavailability of CsA as compared to CsA suspension. These results suggest that CNC conjugate might be considered as a promising gastrointestinal absorption enhancer, while CNC/LHR MPMs had the potential to improve the oral absorption of P-gp substrate drugs.

Neuronal Differentiation of Induced Pluripotent Stem Cells on Surfactant Templated Chitosan Hydrogels

The development of effective tissue engineering materials requires careful consideration of several properties beyond biocompatibility, including permeability and mechanical stiffness. While surfactant templating has been used for over a decade to control the physical properties of photopolymer materials, the potential benefit of this technique with regard to biomaterials has yet to be fully explored. Herein we demonstrate that surfactant templating can be used to tune the water uptake and compressive modulus of photo-cross-linked chitosan hydrogels. Interestingly, templating with quaternary ammonium surfactants also hedges against property fluctuations that occur with changing pH. Further, we demonstrate that, after adequate surfactant removal, these materials are nontoxic, support the attachment of induced pluripotent stem cells and facilitate stem cell differentiation to neuronal phenotypes. These results demonstrate the utility of surfactant templating for optimizing the properties of biomaterials intended for a variety of applications, including retinal regeneration.

The Interesting Case of Acyclovir Delivered Using Chitosan in Humans: Is it a Drug Issue or Formulation Issue?

PURPOSE

Attempts to formulate acyclovir to improve its bioavailability and reduce the frequency of dosing from the present q4h have not materialized.

DISCUSSION

It was thought that an approach using permeability enhancer such as chitosan may impart improved absorption profile to acyclovir; however, the recently published pharmacokinetic data suggested otherwise. The lack of promise of chitosan formulation was attributed to the muco-adhesive properties of chitosan to hold off acyclovir and preventing its transport across the gastrointestinal tract. However, the above hypothesis was refuted by another published human pharmacokinetic study of fexofenadine formulated with chitosan formulation - in this work it was unambiguously shown that chitosan helped in enhanced absorption of fexofenadine which is a well-known Pgp substrate. If one examines the pharmacokinetic disposition of acyclovir, it is clear that renal elimination is so rapid necessitating frequent dosing of acyclovir. In summary, the ability of chitosan based formulations to aid in the oral absorption of drugs may be drug dependent as enumerated by data obtained from acyclovir and fexofenadine. While chitosan favourably improved the pharmacokinetics of fexofenadine, acyclovir may not be ideal for chitosan type of formulation.

CONCLUSION

The choice of the drug and the formulation type intended to deliver the drug need to be made in a diligent and pragmatic fashion.

The Influence of Chitosan on the Oral Bioavailability of Acyclovir--a Comparative Bioavailability Study in Humans

PURPOSE

The effects of chitosan hydrochloride on the oral absorption of acyclovir in humans were studied to confirm the absorption enhancing effects reported for in vitro and rat studies, respectively.

METHODS

A controlled, open-label, randomized, 3-phase study was conducted in 12 healthy human volunteers. Zovirax 200 mg dispersible tablets co-administered with doses of 400 and 1000 mg chitosan HCl were compared with Zovirax only.

RESULTS

The expected increased absorption of acyclovir was not observed. On the contrary, mean area under the plasma concentration-time curve (AUC0-12 h) and maximal plasma concentration (Cmax) decreased following concomitant chitosan intake (1402 versus 1017 and 982.0 ng ∙ h/ml and 373 versus 208 and 235 ng/ml, respectively). In addition, Tmax increased significantly in presence of 1000 mg of chitosan from 1 to 2 h.

CONCLUSIONS

The results of this study in human volunteers did not confirm an absorption enhancing effect of chitosan. Reference values were comparable to literature data, whereas addition of chitosan resulted in significant opposite effects on Cmax, Tmax and AUC. Additional studies are needed to investigate the cause of the discrepancy. The observed variability and complex potential interactions may complicate the use of chitosan HCl in oral pharmaceutical formulations.

Ball-milled solid dispersions of BCS Class IV drugs: Impact on the dissolution rate and intestinal permeability of acyclovir

Acyclovir, an analog of 2'-deoxyguanosine, is one of the most important drugs in the current approved antiviral treatment. However, it's biopharmaceutical properties, contribute to acyclovir's poor oral bioavailability, which restricts the clinical use of the drug. In this view, the aim of this work was to improve the dissolution rate and intestinal permeability of acyclovir through the development of ball milling solid dispersions with the hydrophilic carriers Pluronic F68®, hydroxypropylmethyl cellulose K100M® and chitosan. Solid dispersions were obtained and completely characterized through different solid state techniques. The solid state data demonstrated a decrease in the crystallinity (amorphous phase and defects) and the presence of hydrogen bonds for SD HPMC and SD CTS. The enhancement of dissolution rates was observed for all SDs developed. In addition, no detrimental effects over the in vitro antiviral activity were detected. The solid dispersions with Pluronic F68® significantly improved the intestinal permeability of acyclovir across Caco-2 cells. In summary, the SDs developed in this study could be considered as potential systems for solid dosage forms containing acyclovir with superior biopharmaceutical properties.

Thiomers--from bench to market

Thiolated polymers or designated thiomers are obtained by immobilization of sulhydryl bearing ligands on the polymeric backbone of well-established polymers such as poly(acrylates) or chitosans. This functionalization leads to significantly improved mucoadhesive properties compared to the corresponding unmodified polymers, as disulfide bonds between thiol groups of thiomers and cysteine-rich glycoproteins of the mucus gel layer are formed. Furthermore, enzyme- and efflux-pump inhibiting as well as improved permeation-enhancing properties are advantages of thiolization. By the covalent attachment of mercaptonicotinamide substructures via disulfide bonds to thiolated polymers these properties are even substantially further improved and stability towards oxidation even in aqueous media can be provided. Meanwhile, more than 50 research groups worldwide are working on thiolated polymers. For certain thiomers the scale up process for industrial production has already been done and GMP material is available. Furthermore, safety of thiolated poly(acrylic acid), thiolated chitosan and thiolated hyaluronic acid could be demonstrated via orientating studies in human volunteers and via various clinical trials. The first product (Lacrimera® eye drops, Croma-Pharma) containing a chitosan-N-acetylcysteine conjugate for treatment of dry eye syndrome will enter the European market this year. It is the only product providing a sustained protective effect on the ocular surface due to its comparatively much more prolonged residence time worldwide. Various further products utilizing, for instance, thiolated hyaluronic acid in ocular surgery are in the pipeline.

Insights into and relative effect of chitosan-H, chitosan-H-propolis, chitosan-H-propolis-nystatin and chitosan-H-nystatin on dentine bond strength

OBJECTIVE

The purpose of the study was to design and evaluate novel functional chitosan hydrogels (chitosan-H-propolis, chitosan-H-propolis-nystatin and chitosan-H-nystatin) by using the chitosan-H polymer as "dual function restorative materials".

MATERIALS AND METHODS

The nystatin/antioxidant carrier gel was prepared by dispersion of the corresponding component in glycerol and 3% acetic acid with 5% chitosan gelling agent was then added to the dispersion with continuous mixing. The natural bio-adhesive functionalized chitosan hydrogels were combined with built in drug delivery system and bio-actives such as propolis in order to increase the dentin bond strength capacity and maintain therapeutic properties of the alternative drug delivery system. The surface morphology, release behaviors (physiological pH and also in acidic conditions), stability of nystatin:antioxidant:chitosan and the effect of the hydrogels on the shear bond strength of dentin were also evaluated.

STATISTICAL ANALYSIS USED

Non-parametric ANOVA test was used to asses significance of higher shear bond values than dentine treated or not treated with phosphoric acid.

RESULTS

The release of both nystatin and propolis confer the added benefit of dual action of a functional therapeutic delivery when comparing the newly designed chitosan-based hydrogel restorative materials to commercially available nystatin alone. Neither the release of nystatin nor the antioxidant stability was affected by storage. Chitosan-H, chitosan-propolis, chitosan-nystatin and chitosan-nystatin-propolis treated dentine gives significantly (P < 0.05) higher shear bond values (P < 0.05) than dentine treated or not treated with phosphoric acid.

CONCLUSION

The added benefits of their unique functionality involve increased dentin adhesive bond strengths (after 24 h and after 6 months) and positive influence on the nystatin release. Nystatin was a model therapeutic agent, evaluating the concept of using functional materials as carriers for pro-drugs as well as displaying a certain degree of defence mechanism for free radical damage of the novel functional drug delivery. Overall, there was an insignificant relapse in the shear bond strength after 6 months.

Mechanisms of chitosan-coated poly(lactic-co-glycolic acid) nanoparticles for improving oral absorption of 7-ethyl-10-hydroxycamptothecin

Chitosan-modified poly(lactic-co-glycolic acid) nanoparticles (CHI/PLGA NPs) loaded with 7-ethyl-10-hydroxycamptothecin (SN-38), named CHI/PLGA/SN-38 NPs, were successfully prepared using an oil-in-water (O/W) solvent evaporation method. The physicochemical properties of the novel NPs were characterized by DLS, Zeta potential, SEM, DSC, XRD, and FTIR. The encapsulation efficiency and drug loading content were 71.83 (±2.77)% and 6.79 (±0.26)%, respectively. In vitro drug release in the simulated gastric juice was lower than that in the intestinal juice. In situ single-pass intestinal perfusion (SPIP) studies indicated a dramatic improvement of drug absorption as a result of the synergistic effect between CHI and PLGA on P-glycoprotein (Pgp) inhibition. CHI/PLGA NPs showed high cellular uptake and low efflux for drugs in Caco-2 cells. The cytotoxicity studies revealed that CHI/PLGA NPs had a transient effect on the membrane integrity, but did not have an influence on cell viability. Based on the in vitro release studies, SPIP, and intracellular drug accumulation and transport investigations, we speculate rationally that CHI/PLGA NPs were mainly internalized in the form of intact NPs, thus escaping the recognition of enterocyte Pgp and avoiding efflux into the apical part of the enterocytes. After partial release of drugs inside the enterocytes, CHI/PLGA interfered with the microenvironment of Pgp and further weakened the Pgp-mediated efflux. Then, the drug-loaded NPs exited via the exocytose effect from the basal part of the enterocytes and entered the blood circulation. These results showed that CHI/PLGA NPs would be smart oral delivery carriers for antineoplastic agents that are also Pgp substrates.

Sulfobutylether-β-cyclodextrin/chitosan nanoparticles enhance the oral permeability and bioavailability of docetaxel

The aim of this research is to develop novel chitosan nanoparticles including cyclodextrins complexes for docetaxel (DTX), evaluate the performance of nanoparticles which could enhance the oral permeability and bioavailability of DTX in vitro and in vivo. DTX/sulfobutylether-β-cyclodextrin inclusion complexes were made and it was the main ingredient to prepare the DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles due to their promising physicochemical properties. DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles were prepared by the ionic gelation of chitosan with tripolyphosphate in the presence of cyclodextrins. Results indicated that DTX/sulfobutylether-β-cyclodextrin inclusion complexes and docetaxel/sulfobutylether-β-cyclodextrin/chitosan nanoparticles both had good performances in the studies of release and the rat small intestinal absorption in vitro. DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles showed preferable capability in improving the small intestinal absorption and inhibiting the efflux of DTX. In pharmacokinetics study, the DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles increased the AUC0→t and decreased the clearance significantly, and the oral relative bioavailability of the DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles was as high as 1447.53% compared to the pure DTX formulation. The DTX/sulfobutylether-β-cyclodextrin/chitosan nanoparticles prepared in this study have a good prospect for oral administration as an alternative of current DTX formulations.

Acyclovir achieves a lower concentration in African HIV-seronegative, herpes simplex virus 2-seropositive women than in non-African populations

Acyclovir pharmacokinetics was evaluated in 68 HIV-seronegative, herpes simplex virus 2 (HSV-2)-seropositive African women, who received a single oral 400-mg dose of acyclovir, with plasma acyclovir concentrations measured over 8 h. Geometric mean peak concentration and area under the concentration-time curve were 0.31 μg/ml and 1.59 h · μg/ml, respectively, 54% and 52% lower than values from non-Africans. Lower acyclovir concentrations may partly explain the reduced acyclovir suppression of HSV-2 genital ulcer recurrence in HPTN 039 African women participants.

Disposition kinetics of a dipeptide ester prodrug of acyclovir and its metabolites following intravenous and oral administrations in rat

The objective of this work was to study the disposition kinetics of valine-valine-acyclovir (VVACV), a dipeptide ester prodrug of acyclovir following intravenous and oral administrations in rat. A validated LC-MS/MS analytical method was developed for the analysis VVACV, Valine-Acyclovir (VACV), and Acyclovir (ACV) using a linear Ion Trap Quadrupole. ACV was administered orally for comparison purpose. In the VVACV group, both blood and urine samples and in the ACV group only blood samples were collected. All the samples were analyzed using LC-MS/MS. The LLOQ for ACV, VACV, and VVACV were 10, 10, and 50 ng/ml, respectively. Relevant pharmacokinetic parameters were obtained by non-compartmental analyses of data with WinNonlin. Following i.v. administration of VVACV, AUC(0-inf) (min*µM) values for VVACV, VACV, and ACV were 55.06, 106, and 466.96, respectively. The AUC obtained after oral administration of ACV was 178.8. However, following oral administration of VVACV, AUC(0-inf) values for VACV and ACV were 89.28 and 810.77, respectively. Thus the exposure of ACV obtained following oral administration of VVACV was almost 6-fold higher than ACV. This preclinical pharmacokinetic data revealed that VVACV has certainly improved the oral bioavailability of ACV and is an effective prodrug for oral delivery of ACV.

Acyclovir delivery systems

Herpes viruses (herpes simplex, varicella zoster, cytomegalovirus) are the main cause of a wide variety of human infections. Although the development of successful antiviral agents against infections caused by herpes viruses had been slow until the last decade, the production of delivery systems for acyclovir are a promising alternative. The present review summarizes the principal advances made in developing carriers for the delivery of acyclovir by different routes of administration.

MDR1 genotypes do not influence the absorption of a single oral dose of 600 mg valacyclovir in healthy Chinese Han ethnic males

AIMS

To investigate the influence of three single nucleotide polymorphisms (SNPs) in exon 12 (C1236T), exon 21 (G2677T/A) and exon 26 (C3435T) of MDR1 gene on the absorption of valacyclovir after a single oral administration in the Chinese Han ethnic population.

METHODS

Two hundred healthy Chinese subjects were genotyped for the SNPs of C1236T, G2677T/A and C3435T in the MDR1 gene using allele-specific polymerase chain reaction. Linkage disequilibrium (LD) was analysed. Twenty-four subjects derived from a large random sample (n = 200) received a single oral dose of 600 mg valacyclovir. Plasma concentrations of acyclovir were determined up to 14 h after administration to obtain a pharmacokinetic profile.

RESULTS

LD existed between G2677T/A in exon 21 and C3435T in exon 26 (P < 0.001), between C1236T in exon 12 and C3435T (P < 0.001), but not between C1236T and G2677T/A (P > 0.05). C(max), AUC(0-1.5 h) and AUC(0-infinity) were used as indices of valacyclovir absorption. AUC(0-infinity) for the 2677TA genotype was 17.45 +/- 2.40 microg x h/ml, which was much higher compared with the 2677GG, GA and TT genotypes of 10.44 +/- 1.00, 11.84 +/- 2.83, 11.34 +/- 2.32 microg x h/ml, respectively (P < 0.05). Similarly, a statistically significant difference of AUC(0-infinity) was also observed for different linked genotypes at position 2677 vs. 3435, and 1236 vs. 3435 (P < 0.05). However, there was no significant difference in valacyclovir absorptive pharmacokinetics between carriers and noncarriers of different haplotypes (P > 0.05).

CONCLUSIONS

Three SNPs of MDR1 gene did not influence the absorption of a single oral dose of 600 mg valacyclovir in healthy Chinese Han ethnic subjects.