Micro- and nanoemulsions are potential drug solubilizers and penetration enhancers through the high surfactant/co-surfactant content. This study aimed to evaluate the influence of minoxidil (MXD) solubilized in the microemulsions (MEs) on drug release by in vitro/ex vivo diffusion through the semi-permeable membrane Spectra/Por® (Spectrum Laboratory, Gardena, CA, USA) and porcine ear skin. Moreover, a residual amount of drug in the skin after ex vivo diffusion was evaluated. The reference MER, lecithin-containing MEL, and gelatin-containing MEG were characterized in terms of their size, polydispersity index, density, viscosity, electrical conductivity and surface tension. Based on the in vitro diffusion, it can be argued that MEL slowed down the drug release, while MER and MEG have no significant effect compared to the sample, in which propylene glycol (PG) was used as a solubilizer. Determination of the residual drug amount in the skin after 6 h of the ex vivo permeation was demonstrated as the most valuable method to evaluate the effectiveness of the ME’s application. The results indicate that the most optimal MXD permeation enhancers in alginate gel were the natural surfactants containing MEs. MXD solubilization in MEG and MEL had caused more than 5% of the drug remaining in the skin, which is almost a 1.5-fold higher amount compared to the reference gel.

The objective of this research is to outline the liberation of indomethacin from different chitosan gels containing O/W microemulsion. The influence of surfactant, sodium lauryl sulfate, in two concentrations (0.5% and 0.75%, w/w) was determined in dissolution medium on the release of indomethacin, which was used as poor water-soluble model drug. Chitosan gels were prepared in four different concentrations of chitosan-1%, 1.5%, 2%, and 3% (w/w). Microemulsion enhanced the liberation of the indomethacin from chitosan gels into all dissolution mediums. Adding the surfactant into phosphate-buffered saline decreased the amount of liberated indomethacin from microemulsion, gel mixture, but increased the drug liberation from pure chitosan gels. It was detected that with the increased concentration of chitosan in the samples, the amount of indomethacin liberated (p < 0.05) also increased. A conclusion was drawn that the liberation of indomethacin from chitosan gels was influenced by increased pH of the samples. The high viscosity induced a higher release of indomethacin from 3% (w/w) chitosan hydrogel at pH 5.8 as compared with 3% (w/w) chitosan hydrogel at pH 3.8. The highest percentage of released indomethacin was determined when a mixture of microemulsion gel with higher chitosan content was used.

The paper is focused on liberation of indomethacin from gels and the influence of microemulsion´s presence in the system. Liberation of drug was performed in vitro through a semipermeable membrane and drug quantity was determined spectrophotometrically. Our results pointed out that the influence of microemulsion system on drug liberation depends on the gel selection. The presence of o/w microemulsion in the lipophilic gel (aerosil in liquid paraffin) increased the released amount of the drug approximately 50%. The liberation profile of indomethacin is better when the hydrophilic gel (carbopol) was used. Drug was released in higher amounts from hydrophilic gel comparised to the commercial gel. The presence of microemulsion in carbopol gel did not have any significant influence.

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This study aimed to prepare and evaluate pellets containing acyclovir as a model drug. Pellets were prepared by the extrusion–spheronization process. Aqueous solutions of natural marine polymers (sodium alginate, chitosan) were compared to semi-synthetic hydroxypropyl methylcellulose (HPMC) in the role of binders. The study focused on the characterization of the pellet properties that are crucial for the formulation of the final dosage form, such as in multi-unit pellet system (MUPS) tablets or hard gelatin capsules filled with the pellets. Finally, the mentioned dosage forms were tested for drug dissolution. The morphology of pellets observed by scanning electron microscopy correlated with the shape evaluation performed by dynamic image analysis. Sodium alginate pellets exhibited the lowest value of sphericity (0.93), and many elongated rods and dumbbells were observed in this batch. Chitosan pellets had the highest value of sphericity (0.97) and were also less rough on the surface. The pellets maintained a constant surface geometry during the dissolution studies; they only reduced in size. The most significant reduction in size and weight was assessed after 2 h of dissolution testing. This fact was in line with the drug release from pellets in capsules or MUPS tablets, which was massive during the first hour, in both cases. The dissolution profiles of all of the batches were comparable.

Background: Tretinoin (TRE) is, for its anti-comedogenic and comedolytic activity, widely used in the topical treatment of acne vulgaris. The effect lies in the regulation of sebum production and collagen synthesis. The study is devoted to the formulation of dermal gels containing TRE using microemulsion as the drug solubilizer. Methods: The aim was to evaluate the effect of the reference microemulsion (ME) and lecithin-containing microemulsion (MEL) on the release of TRE through the synthetic membrane (in vitro) and the pig’s ear skin (ex vivo) through the Franz cell diffusion method. Subsequently, after an ex vivo study, the amount of the drug in the skin influenced by the applied formulation was determined. In addition, the impact of ME on the microscopic structure, texture, and rheological properties of gels was evaluated. Results: On the basis of the analysis of texture, rheological properties, and drug release studies, Carbopol formulations appear to be more appropriate and stable. Considering the synthetic membrane as a stratum corneum, the Carbopol gel penetrated about 2.5-higher amounts of TRE compared to the Xanthan gel. In turn, ex vivo studies suggest that MEL slows the drug transfer to the dissolution medium, simulating absorption into the blood, which is a desirable effect in local treatment. The drug retention study proved the highest amounts of TRE in the skin to which microemulsion-Carbopol formulations were applied. Conclusion: The results confirm the benefit of TRE solubilization in ME due to its bioavailability from the tested dermal formulations.

Rectal administration is a suitable route of administration for drugs that are either very irritating to the intestine (e.g., indomethacin) or are more effective when the first-pass effect in the liver is circumvented. Microemulsions are a tool for the improvement of penetration of sparingly soluble drugs. They are mainly used in topical and transdermal drug delivery. However, they find application also in other routes of administration, mainly due to their ability to solubilize sparingly soluble drugs. The selection of a suppository base depends on the physical properties of the drug. The study focused on evaluating the effect of the microemulsion as the solubilizer of sparingly soluble indomethacin in hydrophilic and lipophilic suppository bases compared with Polysorbate 80 as the excipient contained in the microemulsion. The reference suppositories were prepared by the traditional moulding technique from Adeps solidus or Macrogol suppository base without the previous drug solubilization. The microemulsion-based suppositories were prepared after the initial solubilization of the drug in the microemulsion or Polysorbate 80, followed by the addition of suppository base to maintain the same drug/solubilizer ratio. The suppositories were tested for softening time, hardness, and uniformity of mass. The dissolution test was performed using the dialysis tubing method in the basket apparatus. The amount of indomethacin released into the dissolution medium was determined spectrophotometrically at 320 nm. The results indicate that solubilization of indomethacin in the microemulsion had a positive effect on in vitro drug release but not as significant as in the case of Polysorbate 80 used alone. The enhancement ratio for Polysorbate 80 in Adeps suppositories was 2.9, for the microemulsion in Adeps suppositories was 1.1, and for Polysorbate 80 in Macrogol suppositories was 7.4 after 3 hours. The test of uniformity of mass had shown that all suppositories (reference, solubilizer-containing) are within the permitted limits. The softening time was reduced by adding the solubilizer to each type of suppository base.