Design and mechanism of on-off pulsed drug release using nonenteric polymeric systems via pH modulation

Development of an enhanced formulation to minimize pharmacokinetic variabilities of a weakly basic drug compound

Formulating poorly water soluble, weakly basic drugs with consistent exposure is often a challenge due to pH dependent solubility. When the oral formulation is exposed to different pH ranges in the gastrointestinal (GI) tract, drug precipitation or incomplete dissolution may occur resulting in decreased drug absorption and higher intra-and inter-patient pharmacokinetic variabilities.In the present study, a series of enhanced formulations containing organic acids and/or surfactants were developed and compared with conventional formulations with respect to their in vitro dissolution performance. The formulation containing 5% citric acid and 1% sodium lauryl sulfate (SLS) showed much less variations in dissolution performance at different pH conditions than a conventional formulation. The combination of citric acid and SLS demonstrated a synergistic effect as compared to use of citric acid alone or in combination with PEG4000 as a precipitation inhibitor.When compared with a conventional formulation and a spray-dried amorphous solid dispersion (ASD) formulation in a dog pharmacokinetics study, the enhanced formulation demonstrated the least AUC and C_max variability between the two gastric pH-controlled groups. In conclusion, an enhanced formulation using a combination of organic acid and surfactant is recommended for weakly basic drug compounds to minimize drug pharmacokinetic variabilities in clinical studies.

Release kinetics of hydroxypropyl methylcellulose governing drug release and hydrodynamic changes of matrix tablet

BACKGROUND

Hydrophilic hydroxypropyl methylcellulose (HPMC) matrix tablets are the standard role model of the oral controlled-release formulation. Nevertheless, the HPMC kinetics for the mechanistic understanding of drug release and hydrodynamic behaviors are rarely investigated. This study aims to investigate the release behaviors of both HPMC and paracetamol (model drug) from the hydrophilic matrix tablet.

METHODS

Two different viscosity grades of HPMC were used (Low viscosity: 6 cps, High viscosity: 4,000 cps). Three different ratios of drug/HPMC (H:38.08%, M:22.85%, and L:15.23% (w/w) of HPMC amounts in total weight) matrix tablets were prepared by wet granulation technique. The release profiles of the drug and HPMC in a matrix tablet were quantitatively analyzed by HPLC and 1H-nuclear magnetic resonance (NMR) spectroscopy. The hydrodynamic changes of HPMC were determined by the gravimetric behaviors such as swelling and erosion rates, gel layer thickness, front movement data,and distributive near-infrared (NIR) chemical imaging of HPMC in a matrix tablet during the dissolution process.

RESULTS

High viscosity HPMC tablets showed slower release of HPMC than the release rate of drug, suggesting that drug release preceded polymer release.Different hydration phenomenon was qualitatively identified and corresponded to the release profiles. The release behaviors of HPMC and drug in the tablet could be distinguished with the significant difference with fitted dissolution kinetics model (Low viscosity HPMC 6cps; Korsmeyer-Peppas model, High viscosity HPMC 4000cps; Hopfenberg model, Paracetamol; Weibull model) according to the weight of ingredients and types of HPMC.

CONCLUSION

The determination of HPMC polymer release correlating with drug release, hydrodynamic behavior, and NIR chemical imaging of HPMC can provide new insights into the drug release-modulating mechanism in the hydrophilic matrix system.

The Use of Natural Materials in Film Coating for Controlled Oral Drug Release

BACKGROUND

Although synthetic materials have been used in film coating processes for drug delivery for many years, substantial studies on natural materials have also been conducted because of their biodegradable and unique properties.

METHODS

Because of the ability to form and modify films for controlled oral drug delivery, increasing attention has been shown to these materials in the design of film coating systems in recent research.

RESULTS

This review aims to provide an overview of natural materials focusing on film coating for oral delivery, specifically in terms of their classification and their combinations in film coating formulations for adjusting the desired properties for controlled drug delivery.

CONCLUSIONS

Discussing natural materials and their potential applications in film coating would benefit the optimization of processes and strategies for future utilization.

Drug stabilization in the gastrointestinal tract and potential applications in the colonic delivery of oral zein-based formulations

In recent years, various oral dosage forms using biomaterials have been developed to deliver drugs to the colon for therapy due to the advantages of local treatment and its ideal location for drug delivery. To achieve site-specific delivery, the complete drug should be released in the colon, while the drug must be protected or their delivery minimized in the stomach and small intestine. The use of natural or synthetic polymers has been reported for these purposes. The roles of zein in drug delivery have been identified with various types of formulations for improving bioavailability, controlled drug release and targeted delivery. Although zein has been demonstrated as a potential material for pharmaceutical applications, a review of zein in the gastrointestinal tract for stabilizing drug- and colon-specific delivery is still missing. In the present review, we aim to provide typical strategies for using zein in formulations to minimize drug release/ensure drug protection in the upper part of the gastrointestinal tract. Furthermore, effective fabrications or modifications for drug release in the colon will be highlighted. This primary resource of related methods of using zein in the gastrointestinal tract will advance technologies for using it as a natural polymer for drug delivery.

Controlled Release Film Forming Systems in Drug Delivery: The Potential for Efficient Drug Delivery

Despite many available approaches for transdermal drug delivery, patient compliance and drug targeting at the desired concentration are still concerns for effective therapies. Precise and efficient film-forming systems provide great potential for controlling drug delivery through the skin with the combined advantages of films and hydrogels. The associated disadvantages of both systems (films and hydrogels) will be overcome in film-forming systems. Different strategies have been designed to control drug release through the skin, including changes to film-forming polymers, plasticizers, additives or even model drugs in formulations. In the current review, we aim to discuss the recent advances in film-forming systems to provide the principles and review the methods of these systems as applied to controlled drug release. Advances in the design of film-forming systems open a new generation of these systems.

On-off pulsed oral drug-delivery systems: a possible tool for drug delivery in chronotherapy

Circadian rhythms regulate most body functions and are important factors to consider when administering drugs. The existence of circadian rhythms in nature and their influences on human biological systems have given rise to the concept of chronotherapy, which is the science of delivering drugs in a synchronized manner with the rhythm-dependent circadian variation inherent in the human body. The safety and efficacy of a drug can be improved by matching the peak plasma concentration during a 24 h period of the rhythms. An on-off pulsed (pulsatile or time-controlled) release drug-delivery system offers rapid and transient release; stepwise release; and the sustained release of a certain amount of drug within a short time period after a predetermined off-release period according to the circadian rhythm of disease states. These systems deliver the drug at the right time and at an appropriate dosage and are the best approach for chronotherapy. These systems show promise for the optimal therapy of chronic diseases such as asthma, hypertension, myocardial infarction and arthritis, which show a circadian dependency. Various technologies have been adopted to mimic circadian rhythms in physiological functions and diseases. This review focuses on the basic concept of circadian rhythm, chronotherapy and recent advances in the development of on-off pulsed oral drug-delivery systems for optimal therapy.