Sustained oral mucosal delivery in human volunteers of buprenorphine from a thin non-eroding mucoadhesive polymeric disk

In vivo, ex vivo and in vitro assessment of buccal permeation of drugs from delivery systems

Introduction: Buccal mucosa has been described as an attractive site for local and systemic drug delivery, owing its accessibility, safety, and excellent blood supply. The absorption of drugs through buccal mucosa has been assessed by in vivo, ex vivo and in vitro permeability studies, using animal and cell-based models with close resemblance to the human buccal mucosa.Areas covered: This paper focuses on the current in vivo, ex vivo and in vitro permeability studies to analyze the absorption of compounds of interest through buccal mucosa, as well as their advantages and limitations in the preclinical studies of the drugs absorption profiles. The techniques for preparation and preservation of the animal buccal tissue are also discussed to evaluate their interference in the integrity and permeability of the tissues.Expert opinion: Overall, the permeability studies have been useful to evaluate the drugs absorption and to clarify the mechanism of transport of drugs across human buccal mucosa, as well as to explain the enhancement of permeability provided by certain dosage forms. Currently, several researchers have demonstrated particular interest in ex vivo permeability studies, due to their effectiveness in the evaluation of drug absorption and low costs in the acquisition of buccal mucosa samples.

Recent trends in oral transmucosal drug delivery systems: an emphasis on the soft palatal route

INTRODUCTION

The oral mucosa is an appropriate route for drug delivery systems, as it evades first-pass metabolism, enhances drug bioavailability and provides the means for rapid drug transport to the systematic circulation. This delivery system offers a more comfortable and convenient delivery route compared with the intravenous route. Although numerous drugs have been evaluated for oral mucosal delivery, few of them are available commercially. This is due to limitations such as the high costs associated with developing such drug delivery systems.

AREAS COVERED

The present review covers recent developments and applications of oral transmucosal drug delivery systems. More specifically, the review focuses on the suitability of the oral soft palatal site as a new route for drug delivery systems.

EXPERT OPINION

The novelistic oral soft palatal platform is a promising mucoadhesive site for delivering active pharmaceuticals, both systemically and locally, and it can also serve as a smart route for the targeting of drugs to the brain.

Manufacture and characterization of mucoadhesive buccal films

The buccal route of administration has a number of advantages including bypassing the gastrointestinal tract and the hepatic first pass effect. Mucoadhesive films are retentive dosage forms and release drug directly into a biological substrate. Furthermore, films have improved patient compliance due to their small size and reduced thickness, compared for example to lozenges and tablets. The development of mucoadhesive buccal films has increased dramatically over the past decade because it is a promising delivery alternative to various therapeutic classes including peptides, vaccines, and nanoparticles. The "film casting process" involves casting of aqueous solutions and/or organic solvents to yield films suitable for this administration route. Over the last decade, hot-melt extrusion has been explored as an alternative manufacturing process and has yielded promising results. Characterization of critical properties such as the mucoadhesive strength, drug content uniformity, and permeation rate represent the major research areas in the design of buccal films. This review will consider the literature that describes the manufacture and characterization of mucoadhesive buccal films.

Development of mucoadhesive dosage forms of buprenorphine for sublingual drug delivery

The development of mucoadhesive formulations of buprenorphine for intended sublingual usage in the treatment of drug addiction is described. The formulations include mucoadhesive polymer films, with or without plasticizers, and mucoadhesive polymer tablets, with or without excipients that enhance drug release and/or improve tablet compaction properties. The mucoadhesive polymers studied include carbomers such as Carbopol 934P, Carbopol 974P, and the polycarbophil Noveon AA-1, with excipients chosen from pregelatinized starch, lactose, glycerol, propylene glycol, and various molecular weights of polyethylene glycol. The development of plasticizer-containing mucoadhesive polymer films was feasible; however, these films failed to release their entire drug content within a reasonable period. Thus, they were not determined suitable for sublingual usage because of possible loss by ingestion during routine meal intakes. The mucoadhesive strength of tablet formulations containing Noveon AA-1 appears to be slightly superior to the Carbopol-containing tablets. However, the Carbopol 974P formulations exhibited superior drug dissolution profiles while providing adequate mucoadhesive strength. The tablet formulations containing Carbopol 974P as mucoadhesive polymer, lactose as drug release enhancer, and PEG 3350 as compaction enhancer exhibited the best results. Overall, the mucoadhesive tablet formulations exhibited superior results compared with the mucoadhesive film formulations.

Development of polymer film dosage forms of lidocaine for buccal administration: II. Comparison of preparation methods

In previous studies, we prepared film dosage forms of lidocaine (LC) with hydroxypropylcellulose (HPC) as a film base using the solvent evaporation (SE) method. However, from the viewpoint of environmental issues, a reduction in organic solvent use in pharmaceutical and other industries is required. In this study, we prepared the LC films by direct compression of the physical mixture (DCPM method) and direct compression of the spray dried powder (DCSD method). Magnesium stearate, which was required as a lubricant for direct compression, showed no effect on the LC release rate. The LC release rate (%/h) was independent of the compression pressure, but a higher pressure was preferable to easily remove the film from the punches. An increase in the film weight decreased the LC release rate expressed in %/h, whereas no significant effect of film weight was observed on the LC release rate from unit surface area expressed in mg/h/cm(2). The LC release rate (%/h) was independent of the LC content, suggesting that the LC release rate (mg/h) can be quantitatively controlled by changing the LC content in the formulation. The LC release rate and penetration rate were affected by the preparation method; that is, DCPM method < DCSD method < SE method. The LC penetration rates through excised hamster oral mucosa were linearly correlated to the release rate of un-ionized LC, which was estimated by the LC release rate multiplied by the un-ionized fraction of LC for the HPC film dosage form.

Development of polymer film dosage forms of lidocaine for buccal administration. I. Penetration rate and release rate

We examined the penetration rate of lidocaine (LC) through excised oral mucosa from hamster cheek pouch and the in vitro release rate of LC from film dosage forms with hydroxypropylcellulose (HPC) as a film base. Addition of glycyrrhizic acid (GL) to the HPC films increased the LC release rate almost GL-content-dependently, while an optimum GL content was observed for the LC penetration rate. No LC penetration was observed from an acidic aqueous solution (pH 3.4) of LC, suggesting only unionized LC can substantially penetrate through the mucosa. A significant relationship between the penetration rate of LC and the release rate of unionized LC was found, suggesting that the in vitro dissolution study is a useful tool to predict the penetration rate taking the unionized drug fraction into consideration.

Electrically-assisted transdermal delivery of buprenorphine

The objective of this study was to explore the electrically assisted transdermal delivery of buprenorphine. Oral delivery of buprenorphine, a synthetic opiate analgesic, is less efficient due to low absorption and large first-pass metabolism. While transdermal delivery of buprenorphine is expected to avoid the first-pass effect and thereby be more bioavailable, use of electrical enhancement techniques (iontophoresis and/or electroporation) could provide better programmability. Another use of buprenorphine is for opiate addiction therapy. However, a patch type device is subject to potential abuse as it could be removed by the addict. This abuse can be prevented if drug particles are embedded in the skin. The feasibility of doing so was investigated by electro-incorporation. Buprenorphine HCl (1 mg/ml) in citrate buffer (pH 4.0) was delivered in vitro across human epidermis via iontophoresis using a current density of 0.5 mA/cm(2) and silver-silver chloride electrodes. Electroporation pulses were also applied in some experiments. For electro-incorporation, drug microspheres or particles were driven into full thickness human skin by electroporation. It was observed that the passive transdermal flux of buprenorphine HCl was significantly enhanced by iontophoresis under anodic polarity. The effectiveness of electro-incorporation seemed inconclusive, with pressure also playing a potential role. Delivery was observed with electro-incorporation, but the results were statistically not different from the corresponding controls.

Mucoadhesive buccal disks for novel nalbuphine prodrug controlled delivery: effect of formulation variables on drug release and mucoadhesive performance

The objective of this work was to assess the effects of drug solubility and loading percent, as well as Carbopol 934/hydroxypropylcellulose (CP/HPC) ratio, on drug release and mucoadhesive performance of the nalbuphine prodrug loaded buccal disks. Drug release rates for the disks were found to be a function of drug solubility, with higher drug release rates for disks loaded with more hydrophilic prodrugs and an increased amount of beta-cyclodextrin. The drug release rates increased with loading percents for nalbuphine hydrochloride, whereas an opposite drug release trend was observed for disks loaded with nalbuphine enanthate, which can be explained by the diffusional drug release mechanism. The CP/HPC ratio affected release rates of nalbuphine enanthate, whereas the ratio had no impact on the release of nalbuphine hydrochloride. Within the 2 days of experiment time, all formulations attached well to the porcine buccal tissues, indicating those formulation variables had no influence on the mucoadhesive performance of CP/HPC-based buccal disks.

Transmucosal, oral controlled-release, and transdermal drug administration in human subjects: a crossover study with melatonin

The effect of oral controlled-release (CR), oral transmucosal (buccal; TMD) and transdermal (TDD) drug delivery systems on plasma concentrations of melatonin (MT) and its principal metabolite in human subjects using a crossover, single dose design was evaluated. Twelve adult male volunteers participated in the study and received all three dosage forms on three separate occasions. All patch dosage forms were removed after 10 h of wear. Plasma concentrations of the parent drug and its metabolite, 6-sulfatoxymelatonin (MT6s) were measured by radioimmunoassay. Between-subject plasma concentrations of MT were very variable following both oral CR and TDD. Use of the oral CR system gave plasma MT profiles in some subjects that were initially similar to physiological levels, but then differed substantially from physiological in the rate of MT offset; in a few subjects, plasma MT levels remained consistently much below normal nocturnal physiological levels. Also, the ratio of metabolite to parent drug by the oral CR route was many times greater than physiological. TDD resulted in a significant delay in systemic drug levels and a gradual decline in drug delivery after patch removal, possibly due to deposition of melatonin in the skin. TDD failed to simulate the physiological plasma profile of MT (rapid achievement of steady-state blood levels and rapid decline after removal of the patch; i.e., so-called "square-wave" profile). TMD provided prompt systemic drug levels with less variability than oral CR or TDD delivery. Also, plasma MT levels fell promptly and rapidly after removal of the patch. No indication of mucosal deposition was observed. TMD was able to mimic the physiological plasma profiles of both MT and its principal metabolite.