Long-acting transdermal drug delivery formulations: Current developments and innovative pharmaceutical approaches.

Transdermal administration remains an active research and development area as an alternative route for long-acting drug delivery. It avoids major drawbacks of conventional oral (gastrointestinal side effects, low drug bioavailability, and need for multiple dosing) or parenteral routes (invasiveness, pain, and psychological stress and bio-hazardous waste generated from needles), thereby increasing patient appeal and compliance. This review focuses on the current state of long-acting transdermal drug delivery, including adhesive patches, microneedles, and molecularly imprinted polymeric systems. Each subsection describes an approach including key considerations in formulation development, design, and process parameters with schematics. An overview of commercially available conventional (adhesive) patches for long-acting drug delivery (longer than 24 h), the reservoir- and matrix-type systems under preclinical evaluation, as well as the advanced transdermal formulations, such as the core-shell, nanoformulations-incorporated and stimuli-responsive microneedles, and 3D-printed and molecularly imprinted polymers that are in development, is also provided. Finally, we elaborated on translational aspects, challenges in patch formulation development, and future directions for the clinical advancement of new long-acting transdermal products.

Comparative evaluation of physical and chemical enhancement techniques for transdermal delivery of linagliptin.

Linagliptin is a dipeptidyl peptidase-4 inhibitor used for the management of type-2 diabetes. US FDA-approved products are available exclusively as oral tablets. The inherent drawbacks of the oral administration route necessitate exploring delivery strategies via other routes. In this study, we investigated the feasibility of transdermal administration of linagliptin through various approaches. We compared chemical penetration enhancers (oleic acid, oleyl alcohol, and isopropyl myristate) and physical enhancement techniques (iontophoresis, sonophoresis, microneedles, laser, and microdermabrasion) to understand their potential to improve transdermal delivery of linagliptin. To our knowledge, this is the first reported comparison of chemical and physical enhancement techniques for the transdermal delivery of a moderately lipophilic molecule. All physical enhancement techniques caused a significant reduction in the transepithelial electrical resistance of the skin samples. Disruption of the skin's structure post-treatment with physical enhancement techniques was further confirmed using characterization techniques such as dye binding, histology, and confocal microscopy. In vitro permeation testing (IVPT) demonstrated that the passive delivery of linagliptin across the skin was < 5 µg/sq.cm. Two penetration enhancers - oleic acid (93.39 ± 8.34 µg/sq.cm.) and oleyl alcohol (424.73 ± 42.86 µg/sq.cm.), and three physical techniques - iontophoresis (53.05 ± 0.79 µg/sq.cm.), sonophoresis (141.13 ± 34.22 µg/sq.cm.), and laser (555.11 ± 78.97 µg/sq.cm.) exceeded the desired target delivery for therapeutic effect. This study established that linagliptin is an excellent candidate for transdermal delivery and thoroughly compared chemical penetration and physical transdermal delivery strategies.

Transdermal delivery of naloxone hydrochloride using minimally invasive physical ablation techniques.

NAL's hydrophilicity and the inherent lipophilic properties of the stratum corneum hinders its capacity for immediate delivery through skin in opioid rescue cases. In this study, we had sought to investigate the feasibility of using minimally invasive physical ablative techniques including sonophoresis, laser, dermaplaning, microneedles, and microdermabrasion for systemically delivering NAL via the skin. These techniques reduced lag time to NAL delivery to about 3-12 min from 71.22 ± 9.62 min seen for passive delivery. Also, they all significantly enhanced the amount of NAL delivered in 1 h and over 24 h period of evaluation as compared to the passive group (p < 0.05). Sonophoresis and laser showed the greatest delivery in 1 h, followed by dermaplaning. The cumulative amount of drug delivered by these approaches in 1 h were 1277.95 ± 387.06, 83.33 ± 11.11, 30.66 ± 5.67 µg/cm2, respectively. Though the most remarkable, inconsistencies in in vitro permeation profile of NAL were observed with the 1 MHz ultrasound frequency used. With proper optimization of the conditions of use and design, the different approaches explored in this study can be potentially applied for the systemic delivery of naloxone in opioid overdose emergencies and opioid disaccustoming purposes.

Menthol based hydrophobic deep eutectic solvent for extraction and purification of ergosterol using response surface methodology.

Vitamin D deficiency has been linked to various diseases, but could be rectified via fortified food stuffs or supplementation. In this study 39 different hydrophobic deep eutectic solvents were evaluated for green extraction of ergosterol from mushroom. Extraction parameters (e.g. time, solvent volume) were optimized using response surface methodology (RSM) and a maximum extraction yield of 6995.00 µg ergosterol/g dry weight mushroom was attained with menthol: pyruvic acid. The extracted ergosterol was purified using a novel methodology and the extraction solvent was reused for six cycles, while retaining extraction efficiency (up to 28%). The ergosterol was exposed to ultra-violet radiation for conversion to ergocalciferol (vitamin D2) resulting in a yield of ergocalciferol that was equivalent to 2142.01 µg/g dry weight mushroom.