Preparation and in vitro-in vivo evaluation of acyclovir floating tablets

Enhanced gastric residence time of acyclovir by floating raft formulation using box-behnken design

This research paper reports enhancing Acyclovir's gastric residence time by implementing a raft-forming drug delivery system. Because acyclovir is a narrow absorption window drug, it has a poor bioavailability of 10-20 % and a short half-life (t1/2) of 2.5 h. The guar gum and GMS-based floating raft formulation retain the drug in the stomach for an extended period by enhancing GRT. The Box-Behnken design is used to optimize the amount of guar gum, glyceryl monostearate, and calcium carbonate and to study how they affect the in vitro gelation time, viscosity, and in vitro drug release. The ratio of drug and excipients in guar gum (1:0.5), GMS (1:1.25) based FRF suspension containing sodium citrate (0.25 %), carbopol (0.1 %), and calcium carbonate (1:1.5). Seventeen runs were developed through the Box-Behnken design to study all the optimal interactions between variables and responses through a polynomial equation. The optimized formulation is then characterized using various physicochemical tests such as rheological analysis, in vitro drug release, kinetic drug release, and in vitro permeation studies. The in vitro gelation time, viscosity, and in vitro drug release time of optimized FRF are 12 s, 1090 cps, and 88 % at 24 h, respectively. The flux and permeability coefficient of the optimized batch have a higher value indicating higher permeability of acyclovir. The FRF follows non-fickian diffusion as a drug release mechanism. The results show that the raft-forming drug delivery system significantly enhances the absorption of Acyclovir by prolonging drug release and also improving its gastric residence time in the stomach. This research contributes to the field of drug delivery systems by providing a novel approach for improving the therapeutic efficacy of acyclovir and potentially other drugs with similar characteristics.

Formulation and evaluation of taste-masked oral disintegrating tablet containing tolterodine-loaded montmorillonite

Background and purpose

The present study aimed to obtain a taste-masked oral disintegrating tablet (ODT) containing tolterodine tartrate (TT) intercalated into montmorillonite (MMT).

Experimental approach

The TT-MMT hybrid was prepared by ion exchange reaction. The effect of the initial concentration of TT, MMT, temperature, and pH on the encapsulation efficiency (EE) % of the drug in MMT was evaluated. The selected TT-MMT hybrid was characterized by X-ray diffraction (XRD), Fourier transforms infrared (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Then, the optimized TT-MMT hybrid was incorporated in the ODT prepared by direct compression method and taste-masking assessment performed by a human test panel.

Findings/Results

The EE% of TT was in the range of 22.67 to 71.06% in different formulations. It was found that increases in MMT concentration significantly increased EE%. DSC and XRD studies indicated that the TT was intercalated in the MMT interlayer space in an amorphous or molecular state. In-vitro release studies at pH 6.8 showed that the amount of the drug released from the TT-MMT hybrid was negligible for the first 3 min. The post-compression of ODT also showed satisfactory results in terms of friability, hardness, disintegration time, and taste.

Conclusion and implications

MMT-ODT could be a suitable vehicle for the taste masking of TT, with the potential for use in patients with swallowing problems.

Polymeric Excipients in the Technology of Floating Drug Delivery Systems

The combination of targeted transport and improvement of the release profile of the active pharmaceutical ingredient (API) is a current trend in the development of oral medicinal products (MP). A well-known way to implement this concept is to obtain floating gastroretentive delivery systems that provide a long stay of the dosage form (DF) on the surface of the stomach contents. The nomenclature of excipients (Es) of a polymeric nature used in the technology of obtaining floating drug delivery systems (FDDS) is discussed. Based on the data presented in research papers, the most widely used groups of polymers, their properties, and their purpose in various technological approaches to achieving buoyancy have been determined. In addition, ways to modify the release of APIs in these systems and the Es used for this are described. The current trends in the use of polymers in the technology of floating dosage forms (FDF) and generalized conclusions about the prospects of this direction are outlined.

Preparation of Acyclovir-Containing Solid Foam by Ultrasonic Batch Technology

In recent years, the application of solid foams has become widespread. Solid foams are not only used in the aerospace field but also in everyday life. Although foams are promising dosage forms in the pharmaceutical industry, their usage is not prevalent due to decreased stability of the solid foam structure. These special dosage forms can result in increased bioavailability of drugs. Low-density floating formulations can also increase the gastric residence time of drugs; therefore, drug release will be sustained. Our aim was to produce a stable floating formula by foaming. Matrix components, PEG 4000 and stearic acid type 50, were selected with the criteria of low gastric irritation, a melting range below 70 °C, and well-known use in oral drug formulations. This matrix was melted at 54 °C in order to produce a dispersion of active substance and was foamed by different gases at atmospheric pressure using an ultrasonic homogenizer. The density of the molded solid foam was studied by the pycnometer method, and its structure was investigated by SEM and micro-CT. The prolonged drug release and mucoadhesive properties were proved in a pH 1.2 buffer. According to our experiments, a stable foam could be produced by rapid homogenization (less than 1 min) without any surfactant material.

Central Composite Design for Formulation and Optimization of Solid Lipid Nanoparticles to Enhance Oral Bioavailability of Acyclovir

Treatment of herpes simplex infection requires high and frequent doses of oral acyclovir to attain its maximum therapeutic effect. The current therapeutic regimen of acyclovir is known to cause unwarranted dose-related adverse effects, including acute kidney injury. For this reason, a suitable delivery system for acyclovir was developed to improve the pharmacokinetic limitations and ultimately administer the drug at a lower dose and/or less frequently. In this study, solid lipid nanoparticles were designed to improve the oral bioavailability of acyclovir. The central composite design was applied to investigate the influence of the materials on the physicochemical properties of the solid lipid nanoparticles, and the optimized formulation was further characterized. Solid lipid nanoparticles formulated from Compritol 888 ATO resulted in a particle size of 108.67 ± 1.03 nm with an entrapment efficiency of 91.05 ± 0.75%. The analyses showed that the optimum combination of surfactant and solid lipid produced solid lipid nanoparticles of good quality with controlled release property and was stable at refrigerated and room temperature for at least 3 months. A five-fold increase in oral bioavailability of acyclovir-loaded solid lipid nanoparticles was observed in rats compared to commercial acyclovir suspension. This study has presented promising results that solid lipid nanoparticles could potentially be used as an oral drug delivery vehicle for acyclovir due to their excellent properties.

Novel Swellable/Expandable Gastroretentive Floating Films of Gliclazide Folded in Capsule Shell for the Effective Management of Diabetes Mellitus: Formulation Development, Optimization and In Vitro Evaluation

Background:

Gliclazide (GLZ) belongs to the second-generation of sulphonylureas; it is a drug of choice for the management of type II DM. It belongs to BCS Class II. The major site of drug absorption for GLZ is the stomach; it displays variation in the drug absorption rate and bioavailability due to the shorter gastric retention time. The floating mechanism gets affected when the gastric fluid level is not sufficiently higher, which ultimately obstructs the floating behavior, which is the major limitation of reported formulations. This limitation can be overcome by folding the film into the capsule shell dissolved in the gastric fluid and the film swells/expands to dimensions higher than pylorus sphincter (12mm), thus preventing its evacuation.

Objective:

The study aims to explore the floating mechanism in the design of films along with a tendency to expand by swelling and unfolding by utilizing a mixture of hydrophilic and hydrophobic polymer to achieve the controlled drug delivery and prolonged gastric retention of drug.

Methods:

The gastroretentive floating films were formulated by the solvent casting technique using 32 full factorial designs and subjected to in vitro evaluation parameters, drug-excipient compatibility, Xray diffraction and accelerated stability study.

Results:

The pre-formulation study established the purity and identification of a drug. FTIR study confirmed no drug excipient interaction. F3, F6, and F9 were optimized based on in vitro floating characteristics, swelling/expanding ability, and unfolding time. All developed formulations were unfolded within 14-22 min after capsule disintegration. The F3 was selected as the final formulation as its ability to control the release of the drug for 24 hrs followed by zero-order kinetics having super case 2 transport. XRD confirmed the amorphousness of the drug within the formulation. The stability study results revealed that the formulation was quite stable at extreme storage conditions.

Conclusion:

The developed novel formulation has good potential for the effective management and treatment of diabetes mellitus.

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.

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.

Development of a gastroretentive delivery system for acyclovir by 3D printing technology and its in vivo pharmacokinetic evaluation in Beagle dogs

Gastroretentive (GR) systems are designed to prolong gastric residence time to allow sustained absorption and improve the oral bioavailability of drugs with a narrow absorption window in the upper part of the gastrointestinal tract. The present study aimed to develop a GR system for acyclovir using 3D printing technology and evaluate its in vivo pharmacokinetics after oral administration in Beagle dogs. The system consisted of a gastro-floating device, which can float in the gastric fluid, prepared by a fused deposition modeling 3D printer and conventional acyclovir sustained-release (SR) tablet. The acyclovir SR tablet was inserted to the floating device to allow sustained release of the drug in the stomach. The buoyancy and sustained-release property of the developed GR system were determined using an in vitro dissolution test, in vivo pharmacokinetic study, and abdominal X-ray imaging in Beagle dogs. The in vivo dissolution profiles of the GR system were also predicted based on the in vivo pharmacokinetic data using a population pharmacokinetic (POP-PK) model. In the dissolution test, the sustained-release characteristic of the GR system was identified with a time corresponding to 80% dissolution (T₈₀) of 2.52 h. Following oral administration of the GR system, the time to reach the maximum concentration (T_max) of acyclovir was significantly prolonged, whereas the maximum concentration (C_max) decreased and the area under the curve increased compared with those obtained after the administration of immediate-release and SR tablets, indicating prolonged absorption. By X-ray imaging, we showed that the developed GR system stayed in the stomach for more than 12 h. The POP-PK model successfully described the observed plasma concentration-time data and predicted the in vivo biphasic dissolution profiles of the GR system, which was significantly different from the in vitro dissolution. The developed GR system could be applied to various drugs and had great prospects in the design and development of novel controlled-release formulations.