Acyclovir delivery systems

Green Synthesis of Polycyclodextrin/Drug Inclusion Complex Nanofibrous Hydrogels: pH-Dependent Release of Acyclovir

The development of an approach or a material for wound healing treatments has drawn a lot of attention for decades and has been an important portion of the research in the medical industry. Especially, there is growing interest and demand for the generation of wound care products using eco-friendly conditions. Electrospinning is one of these methods that enables the production of nanofibrous materials with attractive properties for wound healing under mild conditions and by using sustainable sources. In this study, starch-derived cyclodextrin (hydroxypropyl-β-cyclodextrin (HPβCD)) was used both for forming an inclusion complex (IC) with acyclovir, a well-known antiviral drug, and for electrospinning of free-standing nanofibers. The nanofibers were produced in an aqueous system, without using a carrier polymer matrix and toxic solvent/chemical. The ultimate HPβCD/acyclovir-IC nanofibers were thermally cross-linked by using citric acid, listed in the generally regarded as safe (GRAS) category by the US Food and Drug Administration (FDA). The cross-linked HPβCD/acyclovir-IC nanofibers displayed stability in aqueous medium. The hydrogel-forming feature of nanofibers was confirmed with their high swelling profile in water in the range of ∼610-810%. Cellulose acetate (CA)/acyclovir nanofibers were also produced as the control sample. Due to inclusion complexation with HPβCD, the solubility of acyclovir was improved, so cross-linked HPβCD/acyclovir-IC nanofibrous hydrogels displayed a better release performance compared to CA/acyclovir nanofibers. Here, a pH-dependent release profile was obtained (pH 5.4 and pH 7.4) besides their attractive swelling features. Therefore, the cross-linked HPβCD/acyclovir-IC nanofibrous hydrogel can be a promising candidate as a wound healing dressing for the administration of antiviral drugs by holding the unique properties of CD and electrospun nanofibers.

Layer-by-Layer Vaginal Films for Acyclovir Controlled Release to Prevent Genital Herpes

Genital herpes is one of the most common sexually transmitted infections worldwide. It mainly affects women, as the rate of sexual transmission from male-to-female is higher than from female-to-male. The application of vaginal antivirals drugs could reduce the prevalence of genital herpes and prevent future infections. Layer-by-layer vaginal films were prepared by the solvent evaporation method using iota-carrageenan, hydroxypropyl methylcellulose and the polymethacrylates Eudragit® RS PO and Eudragit® S100, for the controlled release of acyclovir. The films were characterized by texture analysis and Raman spectroscopy. Swelling, mucoadhesion, and drug release studies were conducted in simulated vaginal fluid. The results show that Layer-by-Layer films exhibited adequate mechanical properties. The structuring of the layer-by-layer films allowed the controlled release of acyclovir and produced a prolonged mucoadhesion residence time of up to 192h. The films formed in layer 2 by the combination of Eudragit® RS PO and S100 showed a controlled release of acyclovir for eight days, and adequate mechanical properties. These promising formulations for the prevention of genital herpes deserve further evaluation.

Feasibility of Enhancing Skin Permeability of Acyclovir through Sterile Topical Lyophilized Wafer on Self-Dissolving Microneedle-Treated Skin

Acyclovir is an antiviral drug that is frequently prescribed for the herpes virus. However, the drug requires frequent dosing due to limited bioavailability (10–26.7%). The rationale of the present study was to develop a self-dissolving microneedle system for local and systemic delivery of acyclovir using a topical lyophilized wafer on microneedle-treated skin to provide the drug at the site of infection. The microneedles prepared with hydroxypropyl methylcellulose (HPMC) (8% w/w) or HPMC (8% w/w)-polyvinyl pyrrolidone (PVP) (30% w/w) penetrated excised rat skin, showing sufficient mechanical strength and rapid polymer dissolution. The topical wafer was prepared with acyclovir (40% w/w; equivalent to 200 mg of drug), gelatin (10% w/w), mannitol (5% w/w), and sodium chloride (5% w/w). The uniform distribution of acyclovir within the wafer in an amorphous form was confirmed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). No polymer–drug interaction was evident in the lyophilized wafer as per Fourier transform infrared spectroscopy (FTIR) analysis. The wafer showed a sufficiently porous structure for rapid hydration as per scanning electron microscopy (SEM) analysis. During ex-vivo analysis, the skin was pre-treated with a self-dissolving microneedle array for 5 minutes, and the wafer was placed on this microporated-skin. Topical wafer provided ∼7–11 times higher skin concentration than the ID₉₉ reported with a lower lag-time. Based on in-vivo testing, ∼2.58 µg/ml of Cmax was achieved in rabbit plasma during 24 hours’ study. Our findings suggest that the self-dissolving microneedle-assisted topical wafer, proposed for the first time, would be efficacious against the infection residing in the skin layer and for systemic therapy.

Incidence, patterns, risk factors and clinical outcomes of intravenous acyclovir induced nephrotoxicity

Objectives

Acyclovir is approved to treat herpes simplex virus (HSV) type 1, type 2 and varicella-zoster virus. It is mainly eliminated via the kidneys, for which drug crystals accumulation might lead to nephrotoxicity. This study aimed to determine the incidence, risk factors, preventive measures, and clinical outcomes of acyclovir induced-nephrotoxicity.

Methods

This is a retrospective cohort study of patients >12 years of age at Sultan Qaboos University Hospital (SQUH) receiving IV acyclovir therapy between January 2016 and December 2020.

Results

Out of 191 included patients, 40 (20.1%) developed acyclovir induced-nephrotoxicity. Age (per year older: OR 1.04, 95 %CI 1.01–1.07), total duration of treatment (per day OR1.19, 95 %CI 1.06–1.33), and concomitant use of vancomycin (OR 5.96, 95 %CI 1.87–19.01) were significant independent risk factors for acyclovir induced-nephrotoxicity development. Nine patients (4.5%) died during the same hospitalization, including those three patients who required renal replacement therapy (1.5%).

Conclusion

Frequent monitoring of kidney function for older patients with concurrent use of vancomycin and IV hydration is essential to prevent IV acyclovir induced-nephrotoxicity. Antimicrobial stewardship is a crucial method to reduce the duration of treatment with IV acyclovir as appropriate.

Pluronic F127-tailored lecithin organogel of acyclovir: preclinical evidence of antiviral activity using BALB/c murine model of cutaneous HSV-1 infection

Herpes is a well-known contagious infection equally affecting both sexes. Among many antiviral drugs employed for its treatment, acyclovir (ACY) is the drug of choice. The currently available therapies of ACY suffer from limitations like poor oral bioavailability (10-15%) and high-dose requirement. The present scientific study aims to explore pluronic lecithin organogel (PLO) as a novel drug delivery platform for ACY to bring an improvement in its delivery through topical route. The properties of organogel like biocompatibility and amphiphilic nature which facilitates dissolution of various drugs of different solubility characteristics along with enhancing the permeation potential of active molecules make it a favorable drug delivery platform for the management of topical diseases. The developed PLO formulations were characterized for micromeritic characteristics, viz., zeta potential, percentage drug content, organogel morphology, skin permeation, retention, and stability studies. The selected topical formulation was further compared with the marketed one for its therapeutic efficacy by inducing cutaneous Herpes simplex virus type 1 infection followed by confirmation of viral load by immunofluorescence and PCR analyses. The developed formulation showed significant improvement over the marketed product as reflected in lesion scoring index and PCR analysis. Further, it proved better to the marketed formulation in t.i.d. treatment regimen in comparison to control. The improvement in overall performance leading to enhanced bioavailability and safety is attributed to the synergism between excipient properties and formulation characteristics. The drug ACY in this micro environment not only finds an improved delivery vehicle but it also offers enhanced drug-target interactions.

Poloxamer Modified Chitosan Nanoparticles for Vaginal Delivery of Acyclovir

OBJECTIVE

The aim of the present study was to design a surface modified chitosan nanoparticle system for vaginal delivery of acyclovir for effective drug uptake into vaginal mucosa.

METHODS

Acyclovir-loaded chitosan nanoparticles, with and without modification by poloxamer 407, were prepared by ionic gelation method. The effects of two independent variables, chitosan to sodium tripolyphosphate mass ratio (X1) and acyclovir concentration (X2), on drug entrapment in nanoparticles were studied using 32 full factorial design. The surface response and counterplots were drawn to facilitate an understanding of the contribution of the variables and their interaction. The nanoparticles were evaluated for drug entrapment, size with zeta potential, morphological analysis by TEM, solid-state characterization by FTIR, DSC, XRD, in vitro dissolution, in vitro cell uptake using HeLa cell line and in vivo vaginal irritation test in Wistar rats.

RESULTS

Chitosan nanoparticle formulation with chitosan to sodium tripolyphosphate mass ratio of 2:1 and acyclovir concentration of 2 mg/mL resulted in the highest entrapment efficiency. The resulting nanoparticles revealed spherical morphology with a particle size of 191.2 nm. The surface modification of nanoparticles with poloxamer resulted in higher drug entrapment (74.3±1.5%), higher particle size (391.1 nm) as a result of dense surface coating, lower zeta potential and sustained drug release compared to unmodified nanoparticles. The change in the crystallinity of the drug during nanoparticle formulation was observed in DSC and XRD study. Cellular uptake of poloxamer-modified chitosan nanoparticles was found to be higher than chitosan nanoparticles in HeLa cells. Safety of nanoparticle formulations by vaginal route was evident when tested in female rats.

CONCLUSION

Conclusively, poloxamer-modified CH NP could serve as a promising and safe delivery system with enhanced cellular drug uptake.

Development of nanoparticle-delivery systems for antiviral agents: A review

The COVID-19 pandemic has resulted in unprecedented increases in sickness, death, economic disruption, and social disturbances globally. However, the virus (SARS-CoV-2) that caused this pandemic is only one of many viruses threatening public health. Consequently, it is important to have effective means of preventing viral transmission and reducing its devastating effects on human and animal health. Although many antivirals are already available, their efficacy is often limited because of factors such as poor solubility, low permeability, poor bioavailability, un-targeted release, adverse side effects, and antiviral resistance. Many of these problems can be overcome using advanced antiviral delivery systems constructed using nanotechnology principles. These delivery systems consist of antivirals loaded into nanoparticles, which may be fabricated from either synthetic or natural materials. Nevertheless, there is increasing emphasis on the development of antiviral delivery systems from natural substances, such as lipids, phospholipids, surfactants, proteins, and polysaccharides, due to health and environmental issues. The composition, morphology, dimensions, and interfacial characteristics of nanoparticles can be manipulated to improve the handling, stability, and potency of antivirals. This article outlines the major classes of antivirals, summarizes the challenges currently limiting their efficacy, and highlights how nanoparticles can be used to overcome these challenges. Recent studies on the application of antiviral nanoparticle-based delivery systems are reviewed and future directions are described.

Acyclovir in the Treatment of Herpes Viruses – A Review

Background:

Herpes Simplex (HSV) viruses are widely spread, highly contagious human pathogens. The statistics indicate that 50-90% of adults worldwide are seropositive for these viruses, mainly HSV-1 and HSV-2. The primary infection results in the appearance of watery blisters (cold sores) on the skin, lips, tongue, buccal mucosa or genitals. The ocular infection is the major cause of corneal blindness in the Western World. Once the HSV virus enters human body, it cannot be completely eradicated because HSV viruses are able to change into their latent form which can survive the treatment. The viron resides in trigeminal ganglia of the host, who becomes vulnerable to the reoccurrence of the disease during the whole lifespan. The neurotropic and neuro-invasive properties of HSV are responsible for neurodegenerative illnesses, such as Alzheimer's disease. Acyclovir and its analogues, being the inhibitors of the viral DNA replication, are the only approved medicines for HSV infection therapies.

Objective:

The current paper presents the up-to-date overview of the important pharmacological features of acyclovir, its analogues and their delivery systems including the mechanism of action, routes of administration, absorption and metabolism, as well as side effects of the therapy.

Conclusion:

Acyclovir remains the gold standard in the treatment of herpes virus infections, mainly due to the emerging of the new delivery systems improving considerably its bioavailability. The analogues of acyclovir, especially their esters, characterized by significantly higher bioavailability and safety, may gradually replace acyclovir in selected applications.

Volatile Acid-Solvent Evaporation (VASE): Molecularly Homogeneous Distribution of Acyclovir in a Bioerodable Polymer Matrix for Long-Term Treatment of Herpes Simplex Virus-1 Infections

Treatment for herpes simplex virus-1 and -2 (HSV-1 and -2) patients who suffer from recurrent outbreaks consists of multiple daily doses of the antiviral drugs acyclovir (ACV), penciclovir, or their more orally bioavailable derivatives valacyclovir or famciclovir. Drug troughs caused by missed doses may result in viral replication, which can generate drug-resistant mutants along with clinical sequelae. We developed a molecularly homogeneous mixture of ACV with the bioerodable polymer polycaprolactone. Through scanning electron microscopy, infrared spectroscopy, gel permeation chromatography, 1H NMR, and differential scanning calorimetry, our method of combining drug and polymer, termed Volatile Acid-Solvent Evaporation (VASE), does not compromise the integrity of polymer or drug. Furthermore, VASE creates materials that deliver therapeutic amounts of drug consistently for approximately two months. Devices with high enough drug loads diminish primary infection of HSV-1 in Vero cells to the same level as seen with a single dose of ACV. Our data will lead to further experiments in animal models, demonstrating efficacy in preventing reactivation of these viruses with a single intervention, and with other antiviral drugs amenable to such manipulation. Additionally, this type of treatment would leave no trace after its useful lifetime, as drug is released and polymer matrix is degraded in vivo.

Niosomes: a review of their structure, properties, methods of preparation, and medical applications

Target-specific drug-delivery systems for the administration of pharmaceutical compounds enable the localization of drugs to diseased sites. Various types of drug-delivery systems utilize carriers, such as immunoglobulins, serum proteins, synthetic polymers, liposomes, and microspheres. The vesicular system of niosomes, with their bilayer structure assembled by nonionic surfactants, is able to enhance the bioavailability of a drug to a predetermined area for a period. The amphiphilic nature of niosomes promotes their efficiency in encapsulating lipophilic or hydrophilic drugs. Other additives, such as cholesterol, can be used to maintain the rigidity of the niosomes’ structure. This narrative review describes fundamental aspects of niosomes, including their structural components, methods of preparation, limitations, and current applications to various diseases.

Acyclovir-Polyethylene Glycol 6000 Binary Dispersions: Mechanistic Insights

The dissolution and subsequent oral bioavailability of acyclovir (ACY) is limited by its poor aqueous solubility. An attempt has been made in this work to provide mechanistic insights into the solubility enhancement and dissolution of ACY by using the water-soluble carrier polyethylene glycol 6000 (PEG6000). Solid dispersions with varying ratios of the drug (ACY) and carrier (PEG6000) were prepared and evaluated by phase solubility, in vitro release studies, kinetic analysis, in situ perfusion, and in vitro permeation studies. Solid state characterization was done by powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) analysis, and surface morphology was assessed by polarizing microscopic image analysis, scanning electron microscopy, atomic force microscopy, and nuclear magnetic resonance analysis. Thermodynamic parameters indicated the solubilization effect of the carrier. The aqueous solubility and dissolution of ACY was found to be higher in all samples. The findings of XRD, DSC, FTIR and NMR analysis confirmed the formation of solid solution, crystallinity reduction, and the absence of interaction between the drug and carrier. SEM and AFM analysis reports ratified the particle size reduction and change in the surface morphology in samples. The permeation coefficient and amount of ACY diffused were higher in samples in comparison to pure ACY. Stability was found to be higher in dispersions. The results suggest that the study findings provided clear mechanical insights into the solubility and dissolution enhancement of ACY in PEG6000, and such findings could lay the platform for resolving the poor aqueous solubility issues in formulation development.

Lipid nanoparticles (SLN, NLC): Overcoming the anatomical and physiological barriers of the eye - Part II - Ocular drug-loaded lipid nanoparticles

In the recent decades, various controlled delivery systems have been introduced with the aim to improve solubility, stability and bioavailability of poorly absorbed drugs. Among all, lipid nanoparticles gather interesting properties as drug or gene delivery carriers. These systems, composed either of solid lipids (SLN) or of solid and liquid lipids (NLC) stabilized with surfactants, combine the advantages of other colloidal particles such as polymeric nanoparticles, fat emulsions and liposomes avoiding their main disadvantages. Lipid nanoparticles represent an interesting approach for eye drug delivery as they can improve the corneal absorption of drugs enhancing their bioavailability. The Generally Recognized as Safe status of formulation excipients, the scaling-up facilities and the possibility of sterilization, make them suitable for industrial production. In this review, the latest findings, potential applications, and challenges related to the use of lipid nanoparticles for ocular drug delivery are comprehensively discussed.

Quantification of uptake and clearance of acyclovir in skin layers

BACKGROUND

Quantification of drug uptake and clearance in the skin layers could provide better insight into the skin kinetics of dermatological formulations aimed for deeper skin tissues. This study assessed the skin kinetics of acyclovir in different skin layers following topical application on the abdominal region of Wistar rats.

METHODS

In vivo skin pharmacokinetics parameters were determined by two different protocols such as post drug load assessment and subsequent drug load assessment following topical application of 500 mg of cream formulation containing 5% (w/w) of acyclovir.

RESULTS

Topical application of acyclovir exhibited concentration gradient between the skin layers (stratum corneum > viable epidermis > dermis) which were inconsistent over the time-course of the study. The rate and extent of drug reaching target site (basal epidermis) was relatively low. The drug uptake and clearance profiles were found to be distinct in all the three skin layers suggesting no drug concentration correlation (P<0.05) between skin layers. Drug concentration in the viable epidermis continued to increase even after termination of therapy (Tmax=4 h) and then declined rapidly. The availability of acyclovir in the target was comparatively low (approximately 0.4% of the applied dose) although an order of magnitude higher percentage was determined in the stratum corneum.

CONCLUSIONS

The data observed in this study demonstrates low skin uptake and rapid clearance of acyclovir in the target site. Further, the methodology employed can be useful for studying other topical antiviral agents as well as for optimizing formulations for drugs (such as acyclovir) that may enhance their efficacy.

Enhanced oral bioavailability of acyclovir by inclusion complex using hydroxypropyl-β-cyclodextrin

The therapeutic potential of acyclovir is limited by the low oral bioavailability owing to its limited aqueous solubility and low permeability. The present study was a systematic investigation on the development and evaluation of inclusion complex using hydroxypropyl-β-cyclodextrin for the enhancement of oral bioavailability of acyclovir. The inclusion complex of acyclovir was prepared by kneading method using drug: hydroxypropyl-β-cyclodextrin (1:1 mole). The prepared inclusion complex was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, NMR spectroscopy and evaluated in vitro by dissolution studies. In vivo bioavailability of acyclovir was compared for inclusion complex and physical mixture in rat model. Phase solubility studies indicate the formation of acyclovir-hydroxypropyl-β-cyclodextrin complex with higher stability constant and linear enhancement in drug solubility with increase in hydroxypropyl-β-cyclodextrin concentration. Characterization of the prepared formulation confirms the formation of acyclovir-hydroxypropyl-β-cyclodextrin inclusion complex. Dissolution profile of inclusion complex demonstrated rapid and complete release of acyclovir in 30 min with greater dissolution efficiency (90.05 ± 2.94%). In vivo pharmacokinetic data signify increased rate and extent of acyclovir absorption (relative bioavailability ∼160%; p < 0.0001) from inclusion complex, compared to physical mixture. Given the promising results in the in vivo studies, it can be concluded that the inclusion complex of acyclovir could be an effective and promising approach for successful oral therapy of acyclovir in the treatment of herpes viruses.

Ocular sustained release nanoparticles containing stereoisomeric dipeptide prodrugs of acyclovir

PURPOSE

The objective of this study was to develop and characterize polymeric nanoparticles of appropriate stereoisomeric dipeptide prodrugs of acyclovir (L-valine-L-valine-ACV, L-valine-D-valine-ACV, D-valine-L-valine-ACV, and D-valine-D-valine-ACV) for the treatment of ocular herpes keratitis.

METHODS

Stereoisomeric dipeptide prodrugs of acyclovir (ACV) were screened for bioreversion in various ocular tissues, cell proliferation, and uptake across the rabbit primary corneal epithelial cell line. Docking studies were carried out to examine the affinity of prodrugs to the peptide transporter protein. Prodrugs with optimum characteristics were selected for the preparation of nanoparticles using various grades of poly (lactic-co-glycolic acid) (PLGA). Nanoparticles were characterized for the entrapment efficiency, surface morphology, size distribution, and in vitro release. Further, the effect of thermosensitive gels on the release of prodrugs from nanoparticles was also studied.

RESULTS

L-valine-L-valine-ACV and L-valine-D-valine-ACV were considered to be optimum in terms of enzymatic stability, uptake, and cytotoxicity. Docking results indicated that L-valine in the terminal position increases the affinity of the prodrugs to the peptide transporter protein. Entrapment efficiency values of L-valine-L-valine-ACV and L-valine-D-valine-ACV were found to be optimal with PLGA 75:25 and PLGA 65:35 polymers, respectively. In vitro release of prodrugs from nanoparticles exhibited a biphasic release behavior with initial burst phase followed by sustained release. Dispersion of nanoparticles in thermosensitive gels completely eliminated the burst release phase.

CONCLUSION

Novel nanoparticulate systems of dipeptide prodrugs of ACV suspended in thermosensitive gels may provide sustained delivery after topical administration.