Permeation Of Acyclovir Research Articles

Effects of storage conditions on permeability and electrical impedance properties of the skin barrier

The aim of this study was to investigate the effect of various skin preservation protocols on in vitro drug permeation, epidermal-dermal drug distribution, and electrical impedance properties of skin membranes. Acyclovir (AC) and methyl salicylate (MS) were selected as model drugs due to their different physicochemical properties and skin metabolic profiles. In particular, AC is relatively hydrophilic (logP −1.8) and not expected to be affected by skin metabolism, while MS is relatively lipophilic (logP 2.5) and susceptible to metabolism, being a substrate for esterase residing in skin. Skin from pig ears was used and freshly excised into split-thickness membranes, which were divided and immediately stored at five different storage conditions: a) 4 °C overnight (fresh control), b) 4 °C for 4 days, c) and d) −20 °C for 6 weeks and one year, respectively, and e) −80 °C for 6 weeks. Based on the combined results, general trends are observed showing that fresh skin is associated with lower permeation of both model drugs and higher skin membrane electrical resistance, as compared to the other storage conditions. Interestingly, in the case of fresh skin, significantly lower amounts of MS are detected in the epidermis and dermis compartments, implying higher levels of ester hydrolysis of MS (i.e., higher esterase activity). In line with this, the concentration of salicylic acid (SA) extracted from the dermis is significantly higher for fresh skin, as compared to the other storage conditions. Nevertheless, for all storage conditions, substantial amounts of SA are detected in the receptor medium, as well as in the epidermis and dermis, implying that esterase activity is maintained to some extent in all cases. For AC, which is not expected to be affected by skin metabolism, freeze storage (protocols c-e) is observed to result in higher accumulation of AC in the epidermis, as compared to the case of fresh skin, while the AC concentration in dermis is unaffected. These observations can be rationalized primarily by the observed lower permeability of fresh skin towards this hydrophilic substance. Finally, a strong correlation between AC permeation and electrical skin resistance is shown for individual skin membranes irrespective of storage condition, while the corresponding correlation for MS is inferior. On the other hand, a strong correlation is shown for individual membranes between MS permeation and electrical skin capacitance, while a similar correlation for AC is lower. The observed correlations between drug permeability and electrical impedance open up for standardizing in vitro data for improved analysis and comparisons between permeability results obtained with skin stored at different conditions.

Enhanced Transdermal Delivery of Acyclovir via Hydrogel Microneedle Arrays

Hydrogel microneedles represent a promising approach to deliver drug molecules across skin into systemic circulation in a sustained release manner and without any polymer residue within skin. Acyclovir is an antiviral drug used for the treatment of several viral infections. However, the oral administration of acyclovir may cause gastrointestinal tract (GIT) disturbances with low bioavailability and poor patient compliance due to its requirement of five daily administrations to produce the desired effect. Therefore, it is thought that the preparation of hydrogel microneedle arrays containing acyclovir would improve the bioavailability and patient compliance by reducing the frequency of administration to once daily as well as overcome the GIT side effects associated with oral administration. A mixture of PEG 10,000 Da and PMVE/MA co-polymer 1,980,000 Da at a ratio of 1:3 (7.5%:22.5% w/w) with Na2CO3 3% w/w was found to produce the optimum hydrogel microneedle array formulation (F8) which showed suitable needle formation with an appropriate mechanical strength and excellent insertion ability, high drug content, sufficient swelling property and a sustained drug release over a period of 24 hours. The Ex vivo permeation study across human skin has demonstrated that the permeation of acyclovir from F8 hydrogel microneedle array was significantly (P≤ 0.05) increased by 39 times in comparison with microneedle-free film (control). The microneedle array has delivered 75.56% ± 4.2 of its loading dose over 24 hours, while the control film was only able to deliver 1.94% ± 0.14 of the total loading dose during the same period. Accordingly, these findings propose the potential application of hydrogel microneedle arrays for the transdermal delivery of acyclovir in a sustained release manner over 24 hours.

Study and development of microemulsion formulations to increase the permeability of acyclovir

The purpose of this study was to improve the permeability of acyclovir (ACV) by developing a water-in-oil microemulsion, since it is an important factor that influences the oral absorption and, consequently, the oral bioavailability of drugs. Pseudoternary phase diagrams (PTPD) were constructed to identify the regions for obtaining microemulsions (ME). From the region of fluid transparent systems, five ME were chosen to evaluate the effect on ACV permeability by using two-compartment horizontal Franz diffusion cells, using a bio-mimetic artificial membrane, which simulates the typical lipophilic characteristics of the biological membranes. The characterization of ME was carried out by PTPD, conductivity determination and Nuclear Magnetic Resonance studies. The formulation that showed the higher incorporation of ACV (81.57 mg/ml) consisted of 13.3% Polysorbate 80, 13.3% ethanol, 6.6% ginger oil and 66% water. An increase in ACV permeability was observed, reaching an apparent permeability coefficient of 1.99.10−6 cm/s, corresponding to a fraction of human absorbed dose of 99.97%, according to the correlation previously established by our research group. These results indicated the ability of ME to improve the permeability of ACV, representing a system with the potential to improve the efficacy of ACV in oral administrated pharmaceutical formulation.

Preparation and characterization of 12-HSA-based organogels as injectable implants for the controlled delivery of hydrophilic and lipophilic therapeutic agents.

Organogels prepared with low molecular weight organogelators to structure liquid oils represent excellent matrices for the controlled delivery of a wide variety of drug molecules. Although studies on organogel systems are reported in the literature, relatively few investigate their potential as gels formed in situ intended for drug delivery. This study reports the development of injectable subcutaneous 12- hydroxystearic acid (12-HSA) organogels for the delivery of both lipophilic and hydrophilic drugs. The rheological characterization (flow, dynamic temperature ramp and amplitude oscillatory measurements) and physicochemical properties (syringeability, swelling and degradation studies), as well as permeability and cytotoxicity were analyzed to gain insights into the influence of the gel composition (surfactant addition, organogelator concentration) on the gelation process and organogel properties. Sol-gel phase transition temperature (Tgel) and gel-sol phase transition temperature (Tmelt) were determined by the tube-inverting method and complementary rheology studies. An increase in 12-HSA concentration led to an augmentation in gel strength and storage (G') and loss (G″) moduli values, evidencing the self-assembly of crystalline gelator structure entrapping the oil phase into a three-dimensional (3D) network. The addition of polysorbate 80 (Tween 80, T80) surfactant molecules in the system caused a weaker gel-like structure, with lower flow rate during syringeability assays, despite its lower apparent viscosity compared to those of 12-HSA organogels. In addition, the swelling studies of 12-HSA/12-HSA T80 organogels as a function of time in phosphate buffered saline (PBS) revealed that the erosion rates were modulated by the organogel compositions. The permeability of acyclovir (ACV) and clotrimazole (CTM), hydrophilic and lipophilic model drugs, respectively, loaded in 12-HSA-based organogels, was assessed in Franz diffusion cells. Organogel-loaded drugs presented lower in vitro release rates and ex vivo drug permeabilities compared to the corresponding drug solutions. Furthermore, 12-HSA T80 organogel could slow down the release of ACV by a factor of about 2.6-fold, up to 6 h, compared to CTM-loaded 12-HSA organogels. Finally, the cytotoxicity of 12-HSA-based organogels was evaluated through in vitro cell viability assays in human foreskin fibroblasts (HFF). Increased 12-HSA concentration resulted in higher cytotoxic effect, with a higher test sensitivity observed for the 3D collagen-embedded cell layer setup matrix versus 2-D cell cultures. Our results support the hypothesis that 12-HSA-based organogels are promising systems for controlled drug delivery as in situ-forming implants.

Ionic Liquid-In-Oil Microemulsions Prepared with Biocompatible Choline Carboxylic Acids for Improving the Transdermal Delivery of a Sparingly Soluble Drug.

The transdermal delivery of sparingly soluble drugs is challenging due to of the need for a drug carrier. In the past few decades, ionic liquid (IL)-in-oil microemulsions (IL/O MEs) have been developed as potential carriers. By focusing on biocompatibility, we report on an IL/O ME that is designed to enhance the solubility and transdermal delivery of the sparingly soluble drug, acyclovir. The prepared MEs were composed of a hydrophilic IL (choline formate, choline lactate, or choline propionate) as the non-aqueous polar phase and a surface-active IL (choline oleate) as the surfactant in combination with sorbitan laurate in a continuous oil phase. The selected ILs were all biologically active ions. Optimized pseudo ternary phase diagrams indicated the MEs formed thermodynamically stable, spherically shaped, and nano-sized (<100 nm) droplets. An in vitro drug permeation study, using pig skin, showed the significantly enhanced permeation of acyclovir using the ME. A Fourier transform infrared spectroscopy study showed a reduction of the skin barrier function with the ME. Finally, a skin irritation study showed a high cell survival rate (>90%) with the ME compared with Dulbecco’s phosphate-buffered saline, indicates the biocompatibility of the ME. Therefore, we conclude that IL/O ME may be a promising nano-carrier for the transdermal delivery of sparingly soluble drugs.

Different BRIJ97 colloid systems as potential enhancers of acyclovir skin permeation and depot.

The low efficacy of Acyclovir topical therapy is due to its physicochemical properties that limit the permeation across the stratum corneum. The goal of this research was to evaluate the ability of biodegradable surfactant, Brij97, to self-assembly in different types of colloid systems which can improve the Acyclovir permeation and accumulation at the target site (the basal epidermis). New Acyclovir formulation based on Brij97 have been analyzed in order to investigate the effect of drug encapsulation on the structure. After that, the in vitro percutaneous permeation of Acyclovir has been compared with that one of the commercial specialty Zovirax® 5%. To estimate the potential of the new formulations proposed as topical delivery, it has been essential to quantify the Acyclovir in the skin layers. The results confirmed that the self-assembly of the surfactant in different nanosized structures improved the amount of permeated Acyclovir and the formation of intracutaneous drug reservoir. Furthermore, the different lipophilicity and structural organization of carriers based on Brij97 showed different influence on the promotion of permeation. The experimental data suggest that the designed carriers could be a valid alternative to improve the efficacy of the current antiviral therapy.

FORMULATION AND EVALUATION OF ACYCLOVIR LOADED NOVEL NANO-EMULSION GEL FOR TOPICAL TREATMENT OF HERPES SIMPLEX VIRAL INFECTIONS

Acyclovir has low bioavailability mainly due to low solubility. This study aimed to formulate an optimized acyclovir (ACV) nanoemulsion gel for the slow, variable and incomplete oral drug absorption in patient suffering from herpes simplex viral infection. The dispersion solubility of acyclovir was studied in various oils, surfactants and co-surfactants and by constructing pseudo phase ternary diagram nanoemulsion area was identified. The optimized formulations of nanoemulsions were subjected to thermodynamic stability tests. After stability study, stable formulation was characterized for droplet size, pH determination, centrifugation, % drug content in nanoemulsion, Zeta Potential and Vesicle size measurement and than nanoemulsion gel were prepared and characterized for spreadability, measurement of viscosity, drug content, In-vitro diffusion, in-vitro release data. Span 40 was selected as surfactant, PEG 400 as co surfactant and castor oil as oil component based on solubility study. The in vitro drug release from acyclovir nanoemulsion gel was found to be considerably higher in comparison to that of the pure drug. The in-vitro diffusion of nanoemulsion gel was significantly good. Based on this study, it can be concluded the solubility and permeability of acyclovir can be increased by formulating into nanoemulsion gel.&#x0D; Keywords: Acyclovir, Nanoemulsion, In-vitro diffusion, Zeta potential, Stability

Development and evaluation of transdermal gel of acyclovir using Nerolidol as penetration enhancer

The aim of this study was to investigate the effect of Nerolidol on the penetration of Acyclovir in the form of transdermal gel formulation. Different formulations were prepared containing different concentrations of Nerolidol (0-5%) using Aloe vera gel as a base. Formulations evaluated for pH, Viscosity, Percent drug content, Spreadability, Diffusion study and In-vitro permeation study. Rheological study showed that viscosity is inversely proportional to the rate of shear and thus the system shows pseudoplastic behaviour. pH of all the formulations was found to be around 6 which is skin compatible. The percent drug content was found to be within the range of 98 to 101% for all the formulations. Spreadability of formulations is found to be in the range of 11.25 to 12.66 gm.cm/sec. Stability studies showed that the formulation is stable at 40oC at 75% RH for a period of one month. It was evident that the permeation of Acyclovir was enhanced, across freshly excised hairless rat abdominal skin, in presence of Nerolidol which can be attributed toincreased lipid disruption in the stratum corneum. Comparison of F5with marketed formulation (Acivir, Cipla) for permeation of Acyclovir across hairless rat abdominal skin, showed greater flux 12.89 mg/cm2. as compared to flux 4.74 mg/cm2.hr of marketed formulation. F0 (without Nerolidol) showed better flux of 6.59 mg/cm2.hr than the marketed product, this can be attributed to the use of Aloe vera gel as an absorption base which consists of lignins, that intensify penetrative properties.

Acyclovir lipid nanocapsules gel for oromucosal delivery: A preclinical evidence of efficacy in the chicken pouch membrane model

The study aimed to develop a patient-friendly acyclovir gel with improved efficacy in viral mouth infections, in response to patients' need for an intraoral acyclovir product. Acyclovir was loaded in lipid nanocapsules in gel form, and formulae were evaluated for oromucosal delivery. Lipid nanocapsules were prepared by the phase inversion method. Formulae were optimized to achieve maximum acyclovir entrapment and minimum acyclovir precipitation. Colloidal properties, and pharmaceutical performance indicators were assessed. Drug-loaded lipid nanocapsules were in the nanorange (39–120 nm), PdI (0.03–0.2), negative zeta potential, and entrapment efficiency (33–64%). Acyclovir (0.3% w/w) lipid nanocapsules gels were prepared using hydroxyethylcellulose (3% w/w). Resulting gel attributes were considered suitable.Lipid nanocapsules gels (0.3% w/w) showed enhanced Ex vivo acyclovir permeation across, and comparable retention in chicken pouch membrane compared to the 5% marketed cream despite lower drug content. The data provides basis for future exploration of lipid nanocapsules as carrier for transmucosal delivery of acyclovir; the enhanced acyclovir retention in chicken pouch membrane, compared to controls, suggests suitability of lipid nanocapsules for drug delivery to the viral lesion within the buccal membrane.

Investigation of permeation of acyclovir through skin using alaptide

The investigation deals with the affection of the permeation of acyclovir through full-thickness pig ear skin using a Franz diffusion cell from the donor vehicles of phosphate buffer (pH 7.4) and propylene glycol–water (1:1) using synthesised (S)-8-methyl-6,9-diazaspiro[4.5]decane-7,10-dione, alaptide as a transdermal permeation enhancer. Alaptide was applied in ratio 1:10 (w/w) relative to the amount of acyclovir. At the first hour after application, the permeated amount of acyclovir from propylene glycol–water system, simulating semisolid dosage forms, was ca. four-fold higher than from the formulation without alaptide. Despite that the enhancement ratio of alaptide in a steady state was 1.7, the pseudo-enhancement ratio of alaptide in the time range of first to third hour was 2.3. Both enhancement ratios indicate that alaptide modifies skin structure, while the short-term application of the alaptide formulation seems to be more advantageous.

Mucoadhesive Film Embedded with Acyclovir Loaded Biopolymeric Nanoparticles: In vitro Studies

Objective: The efficiency of acyclovir, a potent antiviral agent, is mainly limited by its low permeability.The purpose of this investigation was to formulate and assess nanoparticle impregnated buccal films to improve acyclovir permeability and thereby enhance bioavailability. Methods : Acyclovir was incorporated into the polymeric materials and formulated as nanoparticles. The prepared nanoparticles were then loaded into various films (F5-F7) prepared with varying quantities of hydroxyethyl cellulose and Eudragit RL 100. The prepared films were evaluated for physico-mechanical characters, mucoadhesion, swelling, in vitro acyclovir release and ex vivo diffusion. Results : The films so prepared showed adequate mucoadhesive strength and excellent physico-mechanical properties. Rapid hydration of films (>35%) were observed in 15 min, followed by a relatively slower phase of hydration which continued till 60 min. In vitro release profile exhibited biphasic pattern, while the rate of acyclovir release was higher with film F7. Prepared films exhibited either first order (F5, control) or Higuchi model (F6, F7) kinetics. The enhancement in acyclovir permeation in F5, F6 and F7 loaded films were 2.2, 4.1 and 6.7 folds, respectively, when compared to control. Conclusion: This study concludes that the drug loaded nanoparticles impregnated buccal film could be an alternative approach to enhance the oral bioavailability of acyclovir, and need to be proved in vivo . Key words: Acyclovir, Buccal, film, Nanoparticles, Permeation, Release studies

Acyclovir Entrapped N-Trimethyl Chitosan Nanoparticles for Oral Bioavailability Enhancement

Objective: The aim of the study was to evaluate a nanoparticulate system composed of Ntrimethyl chitosan (TMC) for improving the oral bioavailability of Acyclovir (ACV). Methods: TMC was prepared by methylation of chitosan and characterized by H-NMR spectroscopy. The ionic gelation method was used to prepare ACV loaded TMC nanoparticles. Non-everted sac technique was used to assess ex vivo permeation in rats. A pharmacokinetic study of the optimized formulation was carried out in male Wistar rats in comparison with ACV alone. Results: Ex vivo studies exhibited a significant rise in the permeation of ACV from the rat intestinal membrane when formulated as nanoparticles. The results showed an increase in plasma concentration of ACV from the nanoformulation and significant difference (p < 0.05) in pharmacokinetic parameters as compared to pure drug, ACV. Conclusion: The results suggest that higher oral delivery of ACV can be achieved by combining the benefits of both TMC and nanoparticles.

Feasibility Investigation of Cellulose Polymers for Mucoadhesive Nasal Drug Delivery Applications.

The feasibility of various cellulose polymer derivatives, including methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), sodium-carboxymethylcellulose (sodium-CMC), and cationic-hydroxyethylcellulose (cationic-HEC), for use as an excipient to enhance drug delivery in nasal spray formulations was investigated. Three main parameters for evaluating the polymers in nasal drug delivery applications include rheology, ciliary beat frequency (CBF), and permeation across nasal tissue. Reversible thermally induced viscosity enhancement was observed at near nasal physiological temperature when cellulose derivatives were combined with an additional excipient, poly(vinyl caprolactam)-poly(vinyl acetate)-poly(ethylene glycol) graft copolymer (PVCL-PVA-PEG). Cationic-HEC was shown to enhance acyclovir permeation across the nasal mucosa. None of the tested cellulosic polymers caused any adverse effects on porcine nasal tissues and cells, as assessed by alterations in CBF. Upon an increase in polymer concentration, a reduction in CBF was observed when ciliated cells were immersed in the polymer solution, and this decrease returned to baseline when the polymer was removed. While each cellulose derivative exhibited unique advantages for nasal drug delivery applications, none stood out on their own to improve more than one of the performance characteristics examined. Hence, these data may be useful for the development of new cellulose derivatives in nasal drug formulations.

Planar Microdevices for Enhanced In Vivo Retention and Oral Bioavailability of Poorly Permeable Drugs

The development of novel oral drug delivery platforms for administering therapeutics in a safe and effective manner through the harsh gastrointestinal environment is of great importance. Here, the use of engineered thin planar poly(methyl methacrylate) (PMMA) microdevices is tested to enhance oral bioavailability of acyclovir, a poorly permeable drug. Acyclovir is loaded into the unidirectional drug releasing microdevice reservoirs using a drug entrapping photocross-linkable hydrogel matrix. An increase in acyclovir permeation across in vitro caco-2 monolayer is seen in the presence of microdevices as compared with acyclovir-entrapped hydrogels or free acyclovir solution. Cell proliferation studies show that microdevices are relatively nontoxic in nature for use in in vivo studies. Enhanced in vivo retention of microdevices is observed as their thin side walls experience minimal peristaltic shear stress as compared with spherical microparticles. Unidirectional acyclovir release and enhanced retention of microdevices achieve a 4.5-fold increase in bioavailability in vivo as compared with an oral gavage of acyclovir solution with the same drug mass. The enhanced oral bioavailability results suggest that thin, planar, bioadhesive, and unidirectional drug releasing microdevices will significantly improve the systemic and localized delivery of a broad range of oral therapeutics in the near future.

Improved Permeability of Acyclovir: Optimization of Mucoadhesive Liposomes Using the Phospholipid Vesicle-Based Permeation Assay

The antiviral drug acyclovir (ACV) suffers from poor solubility both in lipophilic and hydrophilic environment, leading to low and highly variable bioavailability. To overcome these limitations, this study aimed at designing mucoadhesive ACV-containing liposomes to improve its permeability. Liposomes were prepared from egg phosphatidylcholine (E-PC) and E-PC/egg phosphatidylglycerol (E-PC/E-PG) and their surfaces coated with Carbopol. All liposomal formulations were fully characterized and for the first time the phospholipid vesicle-based permeation assay (PVPA) was used for testing in vitro permeability of drug from mucoadhesive liposome formulations. The negatively charged E-PC/E-PG liposomes could encapsulate more ACV than neutral E-PC liposomes. Coating with Carbopol increased the entrapment in the neutral E-PC liposomes. The incorporation of ACV into liposomes exhibited significant increase in its in vitro permeability, compared with its aqueous solution. The neutral E-PC liposomal formulations exhibited higher ACV permeability values compared with charged E-PC/E-PG formulations. Coating with Carbopol significantly enhanced the permeability from the E-PC/E-PG liposomes, as well as sonicated E-PC liposomes, which showed the highest permeability of all tested formulations. The increased permeability was according to the formulations' mucoadhesive properties. This indicates that the PVPA is suitable to distinguish between permeability of ACV from different mucoadhesive liposome formulations developed for various routes of administration.

Simultaneously enhancing the solubility and permeability of acyclovir by crystal engineering approach

Three acyclovir complexes including one salt with maleic acid, and two cocrystals with fumaric acid and glutaric acid, were prepared. The results of powder dissolution and in vitro skin permeation experiments revealed that both solubility and permeability of acyclovir were enhanced after the formation of cocrystals.

Effect of Age on the Gastrointestinal Absorption of Acyclovir in Rats

Drug elimination from the body after intravenous administration of acyclovir (20 mg kg-1) was delayed in 1-week-old rats but the pharmacokinetic data for 2.5-week-old rats were the same as those for 8-week-old rats. The areas under the plasma concentration-time curves at 0-infinity h (AUC) after oral administration of acyclovir (20 mg kg-1) decreased with increasing age. The absolute bioavailabilities for 1-, 2.5-, 3- and 8-week-old rats were 77.59, 51.52, 14.61 and 7.30%, respectively. The gastrointestinal absorption of poorly absorbed acyclovir was good for rats younger than 2.5 weeks but dropped abruptly between 2.5 and 3 weeks of age. The intestinal membrane permeability of acyclovir was studied using the everted sac method. The rate of transfer of an initial concentration of 10 microM acyclovir from the mucosal to the serosal side was constant until 60 min in rats of different ages while the rate in 2.5-week-old rats was significantly greater than that in 3-, 4- and 8-week-old rats. Abrupt in-vivo and in-vitro changes were observed in the experimental results between 2.5- and 3-week-old rats; this period coincided with the weaning period of the rat. The membrane transport mechanism of acyclovir in 2.5- and 8-week-old rats was also studied. Cumulative transferred amounts of acyclovir were linear (r = 0.99) over the range 5 microM-1 mM and dose-independent. The influence of metabolic inhibitors (sodium azide, 2,4-dinitrophenol, ouabain), purine and pyrimidine analogues (2-deoxyguanosine, guanine, adenine, uridine) and temperature on the permeation of acyclovir was studied. The permeation of acyclovir was inhibited only by 2-deoxyguanosine and guanine in 2.5-week-old rats. These results suggest that throughout the maturation period, the gastrointestinal absorption mechanism of acyclovir is predominantly via passive diffusion with little or no active or facilitated transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Iontophoresis and Permeation Enhancers on the Permeation of an Acyclovir Gel

The purpose of the present study was to explore the combined effect of chemical enhancers and iontophoresis on the in vitro permeation of acyclovir gel across porcine skin. Acyclovir gel was formulated using carbopol 940 and hydroxypropyl methylcellulose K4M (HPMC K4M). Effect of drug concentration on the delivery of acyclovir was examined. Increasing drug concentration of acyclovir enhanced its flux across the skin. Incorporation of permeation enhancers (menthol, n-methyl-2-pyrrolidone and polyethylene glycol 400) into the gel resulted in enhanced acyclovir permeation when combined with iontophoresis. Menthol showed the highest drug permeation and when combined with iontophoresis it significantly increased the acyclovir skin permeation.

Polycationic Polymers and Drugs: Investigations into Interactions between Acyclovir and Polymers

Interactions between pharmaceutical ingredients play an important role in the development of drug formulations. It was the aim of our present studies to investigate drug-polymer interactions. Interaction of the antiviral drug acyclovir with polyethylenimines, polyvinylamines and the non-ionic PVP was investigated using a modified equilibrium dialysis. The membrane was only permeable to free acyclovir, while polymers and acyclovir-polymer-associates did not pass through. Significant amounts of acyclovir were bound with the polyethylenimines. The formation of associates consisting of acyclovir and either PVP or polyvinylamine could not be demonstrated. In solutions of acyclovir and polyethylenimine (Mr=25,000) the amount of bound drug is increased with increasing concentration of acyclovir. Between 7.9 µg and 31.7 µg take part in the formation of associates. Differences in the osmotic pressure of the solutions do not play an important role in the permeation of acyclovir. In solutions containing acyclovir and high molecular weight polyethylenimine (Mr=750,000) the bound amount of drug increases with increasing acyclovir concentration up to c(0)=400 µg/100 ml. Further addition of free drug to the solution does not change the amount of bound drug significantly, due to possible limitations in the binding capacity. Molecular modeling investigations were performed. According to the calculations, about 85% of the interactions can be attributed to electrostatic interactions.

Effect of chitosan glutamate, carbomer 974P, and EDTA on the in vitro Caco-2 permeability and oral pharmacokinetic profile of acyclovir in rats

Background: Chitosan glutamate and polyacrylic acid (e.g., carbomer 974P) are known to modulate the tight junctions in the intestinal wall and increase permeability and blood exposure of drugs absorbed orally by the paracellular route. Aim: To assess the impact of chitosan glutamate and carbomer 974P on the absorption of paracellularly absorbed model drug, acyclovir, in vitro and in rat in vivo. Methods: The influence of chitosan glutamate and carbomer 974P (alone and in combination with EDTA–Na2) on the in vitro Caco-2 permeability and oral pharmacokinetic profile in the rat of acyclovir was investigated. Results: In the presence of chitosan glutamate, the apparent permeability of acyclovir across Caco2 monolayer increased 4.1 times relative to control. This increase was accompanied by a significant (∼60%) decrease in transepithelial electrical resistance values indicating opening of the tight junctions in the cell monolayer. In rat, chitosan glutamate doubled oral bioavailability of acyclovir and tripled the amount of acyclovir excreted unchanged into urine. In contrast, the effect of carbomer 974P was not statistically significant at 5% level. Conclusions: In conclusion, chitosan glutamate (1–3%) and chitosan glutamate (1%)/EDTA–Na2 (0.01%) are effective excipients to increase permeability of acyclovir across Caco-2 cell monolayers and the oral absorption in the rat in vivo.