Chemical Permeation Enhancers Research Articles

Estimation of Scattering Properties Modifications Caused by InVivo Human Skin Optical Clearing Using Line-Field Confocal Optical Coherence Tomography.

The image contrast and probing depth of optical methods applied to invivo skin could be improved by reducing skin scattering using the optical clearing method. The aim of this study was to quantify, from line-field confocal optical coherence tomography (LC-OCT) 3D images, the modifications of skin scattering properties invivo during optical clearing. Nine mixtures of optical clearing agents were used in combination with physical and chemical permeation enhancers on the human skin of three healthy volunteers. Scattering coefficient and anisotropy factor of the epidermis and the upper dermis were estimated from the 3D LC-OCT images of skin using an exponential decay model of the in-depth intensity profile. We were able to demonstrate a decrease in epidermal scattering (down to 33%) related to optical clearing, with the best results obtained by a mixture of polyethylene glycol, oleic acid, and propylene glycol.

Comparing effects of terpene-based deep eutectic solvent and solid microneedles on skin permeation of drugs with varying lipophilicity

Transdermal delivery of therapeutic molecules is often hindered by the properties of the skin, with the stratum corneum serving as the primary permeation barrier. To overcome this barrier, the integrity of the stratum corneum can be modified by chemical permeation enhancers, such as deep eutectic solvents (DESs), or by mechanically impairing the skin with microneedles (MNs). However, a systematic comparison between these strategies is currently lacking. Hence, this study examined the potential of DESs and MNs to promote the permeation and retention of drugs with varying lipophilicities – specifically, the hydrophilic drug metronidazole (logP ∼ 0), the moderately lipophilic drug lidocaine (logP ∼ 2.3), and the highly lipophilic drug clotrimazole (logP ∼ 5). A mixture of menthol and thymol was selected as a model terpene-based DES and delivery vehicle, while a DermaPen equipped with solid MNs was used to mechanically impair the skin. Permeation rates of model drugs applied to the skin with either DES, MNs, or both were compared to the rates determined for the drugs applied in control vehicles. Both strategies were found to compromise the skin barrier function, but their permeation-enhancing effect was dependent on the lipophilicity of tested model drug. The DES was most effective for the hydrophilic drug metronidazole, while the MNs were more effective in increasing the permeation of the highly lipophilic drug clotrimazole. For the moderately lipophilic drug lidocaine, neither the DES nor microneedles increased its permeation rate, as the drug permeated through the skin well on its own. Notably, the combination of both enhancement strategies did not result in significantly better permeation rates of the drugs compared to the individual approaches. In conclusion, both the terpene-based DES and solid MNs are effective strategies to enhance drug permeation through the skin, but our results suggest that the choice of strategy should be dictated by the drug’s lipophilicity. Moreover, from a permeation-enhancing perspective, there is no benefit in combining these two strategies.

Innovative Long-Acting Bisoprolol Patch: Synergistic Ion-Pair Skin Adsorption for Drug Delivery Control Coupled with Dynamic Modulation of Penetration Enhancers.

This study aims to develop a sustained release patch for bisoprolol (BSP) to address the issue of blood pressure fluctuations caused by traditional dosing methods, ensuring continuous drug release and efficient utilization. Long-chain saturated fatty acids (C6-C12) were chosen as counterions to precisely control BSP's permeation rate in the patch formulation, and the ion-pairing strategy's mechanism in drug delivery was thoroughly investigated. Molecular docking results revealed significant differences in the adsorption capacities of different ion pairs in the stratum corneum (SC) and epidermis, directly influencing their residence times and thereby regulating BSP's passive diffusion rate. Particularly, the BSP-C10 ion pair successfully reduced BSP's permeation rate to one-third of its baseline. To enhance drug delivery efficiency and reduce costs, chemical permeation enhancers (CPEs) are typically added to sustained release patches. In contrast to traditional static analyses based on cumulative permeation, this study utilized ATR-FTIR dynamic detection of isopropyl myristate (IPM) as a preferred enhancer, studying its disruptive effects on the skin barrier during drug delivery. The study observed that during drug delivery, the interaction between IPM and skin lipids follows a U-shaped trend: initially increasing, then decreasing, with the peak occurring at 10 h. Similarly, the drug delivery rate displays a comparable pattern. The addition of IPM as CPE increased the patch utilization rate from 39.8 ± 4.31 to 79.8 ± 7.27%. This strategy aims to rapidly reduce blood pressure in the initial phase with subsequent weakening of IPM disruption, allowing the ion-pairing strategy to dominate drug delivery control and maintain stable long-term therapeutic effects. Pharmacokinetic studies demonstrated that the newly developed BSP sustained release patch maintains stable blood drug concentrations, reduces burst release effects, increases bioavailability to 84.679%, doubles MRT0-t, halves Cmax, and significantly reduces the occurrence of blood pressure fluctuations.

A finasteride patch for the treatment of androgenetic alopecia: A study of promoting permeability strategy using synthetic novel O-acylmenthols combined with ion-pair

Currently, finasteride (FIN) is approved to treat androgenetic alopecia only orally, and the application of FIN in transdermal drug delivery system (TDDS) has introduced a new approach for treating the disease. This study was aimed to develop a FIN transdermal patch for the treatment of androgenetic alopecia（AGA） by combing ion-pair and O-acylmenthols (AM) as chemical permeation enhancers (CPEs). The formulation of patch was optimized though single-factor investigation and Box-Behnken design. The pharmacokinetics and androgenetic alopecia pharmacodynamics of the patch were evaluated. Additionally, the permeability enhancement mechanisms of ion-pair and AMs were explored at both the patch and skin levels. The effects of ion-pair and AMs on the patch were characterized by rheology study, FTIR, and molecular docking, and the effects on the skin were assessed through ATR-FTIR, Raman study, DSC, CLSM and molecular dynamics. The finalized formulation of FIN patches was consisted of 5 % (w/w) synthetic FIN-CA (Citric Acid), 6 % MT-C6 as CPEs, 25-AAOH as a pressure-sensitive adhesive (PSA), with a patch thickness of 80 ± 5 μm. The final Q24 h is 78.22 ± 5.18 μg/cm2. Based on the high FIN permeability, the pharmacokinetic analysis revealed that the FIN patch group exhibited a slower absorption rate (tmax = 7.3 ± 2.7 h), lower peak plasma concentration and slower metabolic rate (t1/2 = 6.2 ± 0.8 h, MRT0-t = 26.0 ± 7.8 h) compared to the oral group. Moreover, the FIN patch also demonstrated the same effect as the oral group in promoting hair growth in AGA mice. The results indicated that both FIN-CA and AMs could enhance the fluidity of the PSA and weaken the interaction between FIN-CA and PSA, thereby promoting the release of the FIN from the patch. The interaction sites on the skin for ion-pair and the four AMs were found in the stratum corneum (SC) of the skin, disrupting the tight arrangement of stratum corneum lipids. This study serves as a reference for the multi-pathway administration of FIN and the combination of ion-pair with AMs to enhance drug permeation.

Deep eutectic solvent combined with permeation enhancer strategy to convert tandospirone from oral to transdermal formulations improving drug bioavailability

Tandospirone(Tan) is a commonly used drug for anxiety treatment. However, it has a significant first-pass effect and needs to be taken three times a day. To increase the bioavailability of the drug and reduce the number of administrations, this work amid to prepare a Tan patch that can be administered once a day by using the strategy of therapeutic deep eutectic solvent(THEDES) in cooperation with chemical permeation enhancer(CPE). In this study, four organic acids and five permeation enhancers were selected, and the optimized formulation was obtained by single-factor investigation and Box-Behnken design. The optimized formulation could significantly enhance drug loading by 2.5-fold and skin permeation up to 586.6 ± 17 μg/cm2 in rats. Based on pharmacokinetic results, compared to oral administration, the drug exhibited a substantially elevated bioavailability, registering a 17-fold increase(from 3.01 % to 52.17 %), alongside a 10-fold rise in the mean residence time(MRT). Meanwhile, the patch was not irritating. The results of the mechanistic study showed that levulinic acid(LeA) acted as a bridge to increase the interaction between the Tan and the matrix and inhibited the crystallization of the drug in the patch, and THEDES together with CPE improved the matrix fluidity and skin permeability. This study provides a reference for the joint application of THEDES and CPEs in patch development.

In vitro assessment of skin permeation properties of enzymatically derived oil-based fatty acid esters of vitamin C.

Current topical formulations containing vitamin C face limitations in therapeutic effectiveness due to the skin's selective properties that impede drug deposition. Consequently, the widespread use of toxic and irritating chemical permeation enhancers is common. Hereby, we investigated enzymatically derived fatty acid ascorbyl esters (FAAEs) obtained using natural oils for their skin permeation properties using the Strat-M® skin model in a Franz cell diffusion study. By evaluating various cosmetic formulations without added enhancers, we found that emulgel is most suitable for enhancing the cutaneous and transdermal delivery of FAAEs. Furthermore, medium-chain coconut oil-derived FAAEs exhibited faster diffusion rates compared to sunflower oil-based FAAEs with long-side acyl residues, including the commonly applied ascorbyl palmitate. Experimental data were successfully fitted using the Peppas and Sahlin model, which accounted for a lag phase and the combined effect of Fickian diffusion and polymer relaxation. In the case of long-chain esters, the lag phase was prolonged, and the calculated effective diffusion coefficients (Deff) were lower compared to medium-chain FAAEs. Accordingly, the highest Deff value was observed for ascorbyl caprylate, being even 60 times higher than for ascorbyl palmitate. These results suggest the emerging potential of emulgel with incorporated coconut oil-derived FAAEs for efficiently delivering vitamin C into the skin.

Effects and Action Mode of Oleic Acid and Azone on Release and Penetration Process of Levothyroxine Sodium Patches.

In recent years, there has been a significant increase in the prevalence of thyroid diseases, particularly hypothyroidism. In this study, we investigated the impact and mechanisms of Chemical permeation enhancement(CPE) on transdermal permeation of levothyroxine sodium (L-T4) patches.We found that the combination of oleic acid (OA) and Azone (NZ) yielded the best transdermal permeation effect for L-T4.Subsequently, we also investigated the relevant propermeability mechanism.The results demonstrate that the combined application of OA and NZ significantly enhances the transdermal permeation of L-T4 compared to individual applications,it is attributed to two mechanisms: firstly, OA improves drug release by increasing the flowability of the pressure-sensitive adhesive (PSA) matrix; secondly, both OA and NZ act on the stratum corneum, especially facilitating L-T4 permeation through the hair follicle pathway. No skin irritation or cytotoxicity is observed with these final patches, which exhibit a remarkable therapeutic effect on hypothyroidism. this study contributes to the development of transdermal formulations of L-T4.

Contribution of chemical permeation enhancers to the process of transdermal drug delivery: Adsorption, microscopic interactions, and mechanism

Transdermal drug delivery (TDD) has attracted widespread attention because of the advantage of its non-invasive nature, easy self-administration, and low side effects. The key to this pathway of drug delivery is how to overcome the barrier of the lipid matrix in the stratum corneum (SC). In this work, molecular dynamics (MD) were employed to investigate the adsorption of thyrotropin-releasing hormone (TRH) on the SC, and the effects of three different chemical permeation enhancers (ethanol (ETOH), carveol (CAV), and borneol (BOR)) on the SC were analyzed. The results showed that ETOH hardly altered the order of lipids in the SC, while CAV and BOR disrupted the morphology of the SC. The primary target of CAV was the CHOL in SC, which not only disrupted the ordered arrangement of CHOL, but also “extracted” CHOL from SC. The thickness distribution of SC became more inhomogeneous in the presence of CAV and BOR, which facilitated the penetration of drug molecules. Compared to no chemical permeation enhancers, the free energy of permeation in the presence of chemical permeation enhancers was less than 4–10 kcal mol−1, which suggested that chemical permeation enhancers were more favorable for the permeation of drugs from viewpoints of thermodynamics. All the results provided theoretical insights into the effect of chemical permeation enhancers on the transdermal permeation of drugs.

Ionic liquids: Emerging chemical permeation enhancers

Ionic liquids: Emerging chemical permeation enhancers

A Pseudo-Surfactant Chemical Permeation Enhancer to Treat Otitis Media via Sustained Transtympanic Delivery of Antibiotics.

Chemical permeation enhancers (CPEs) represent a prevalent and safe strategy to enable noninvasive drug delivery across skin-like biological barriers such as the tympanic membrane (TM). While most existing CPEs interact strongly with the lipid bilayers in the stratum corneum to create defects as diffusion paths, their interactions with the delivery system, such as polymers forming a hydrogel, can compromise gelation, formulation stability, and drug diffusion. To overcome thischallenge, differing interactions between CPEs and the hydrogel system are explored, especially those with sodium dodecyl sulfate (SDS), an ionic surfactant and a common CPE, and those with methyl laurate (ML), a nonionic counterpart with a similar length alkyl chain. Notably, the use of ML effectively decouples permeation enhancement from gelation, enabling sustained delivery across TMs to treat acute otitis media (AOM),which is not possible with the use of SDS. Ciprofloxacin and ML are shown to form a pseudo-surfactant that significantly boosts transtympanic permeation. The middle ear ciprofloxacin concentration is increased by 70-fold in vivo in a chinchilla AOM model, yielding superior efficacy and biocompatibility than the previous highest-performing formulation. Beyond improved efficacy and biocompatibility, this single-CPE formulation significantly accelerates its progression toward clinical deployment.

Enhanced Skin Permeation of 5-Fluorouracil through Drug-in-Adhesive Topical Patches.

5-fluorouracil (5-FU), commercially available as a topical product, is approved for non-melanoma skin cancer (NMSC) treatment with several clinical limitations. This work aimed to develop 5-FU-loaded topical patches as a potential alternative to overcome such drawbacks. The patches offer accurate dosing, controlled drug release and improved patient compliance. Our study highlights the development of Eudragit® E (EuE)-based drug-in-adhesive (DIA) patches containing a clinically significant high level of 5-FU (approximately 450 µg/cm2) formulated with various chemical permeation enhancers. The patches containing Transcutol® (Patch-TRAN) or oleic acid (Patch-OA) demonstrated significantly higher skin penetration ex vivo than their control counterpart, reaching 5-FU concentrations of 76.39 ± 27.7 µg/cm2 and 82.56 ± 8.2 µg/cm2, respectively. Furthermore, the findings from in vitro permeation studies also validated the superior skin permeation of 5-FU achieved by Patch-OA and Patch-TRAN over 72 h. Moreover, the EuE-based DIA patch platform demonstrated suitable adhesive and mechanical properties with an excellent safety profile evaluated through an inaugural in vivo human study involving 11 healthy volunteers. In conclusion, the DIA patches could be a novel alternative option for NMSC as the patches effectively deliver 5-FU into the dermis layer and receptor compartment ex vivo for an extended period with excellent mechanical and safety profiles.

A Comprehensive Review on Potential Chemical and Herbal Permeation Enhancers Used in Transdermal Drug Delivery Systems.

Using skin patches to deliver drugs is dependable and doesn't have the same issues as permeation enhancers, which help drugs get through the skin but struggle because of the skin's natural barrier. Strategies are required to increase topical bioavailability to enhance drug absorption. Natural compounds offer a promising solution by temporarily reducing skin barrier resistance and improving drug absorption. Natural substances allow a wider variety of medications to be distributed through the stratum corneum, offering a dependable approach to enhancing transdermal drug delivery. Natural substances have distinct advantages as permeability enhancers. They are pharmacologically effective and safe, inactive, non-allergenic, and non-irritating. These characteristics ensure their suitability for use without causing adverse effects. Natural compounds are readily available and well tolerated by the body. Studies investigating the structure-activity relationship of natural chemicals have demonstrated significant enhancer effects. By understanding the connection between chemical composition and enhancer activity, researchers can identify effective natural compounds for improving drug penetration. In conclusion, current research focuses on utilizing natural compounds as permeability enhancers in transdermal therapy systems. These substances offer safety, non-toxicity, pharmacological inactivity, and non-irritation. Through structure-activity relationship investigations, promising advancements have been made in enhancing drug delivery. Using natural compounds holds enormous potential for improving the penetration of trans-dermally delivered medications.

Efficiency of NZ2114 on Superficial Pyoderma Infected with Staphylococcus pseudintermedius.

Staphylococcus pseudintermedius (S. pseudintermedius) is the main pathogen causing pyoderma of canines. With the emergence of drug-resistant bacteria, traditional antibiotic treatments are limited. As a potential antibacterial agent, NZ2114 was effective against S. pseudintermedius, including drug-resistant strains. Its bactericidal efficacy was superior to mupiroxacin, ofloxacin and lincomycin. To facilitate the transcutaneous delivery of NZ2114 for the treatment of superficial pyoderma, chemical permeation enhancers were added since water-soluble NZ2114 does not easily penetrate the skin lipid layer. Two different NZ2114 sprays were prepared by combining 1% Azone + 10% propylene glycol (PG) or 5% N-methylpyrrolidone (NMP) + 10% PG with NZ2114 after screening. The cumulative permeability of NZ2114 sprays were 244.149 and 405.245 μg/cm2 at 24 h with an in vitro percutaneous assay of mice skin, which showed a 244% and 405% increase in skin permeability than NZ2114, respectively. In addition, the efficacy of NZ2114 sprays in reducing skin bacteria colonisation was demonstrated in a mouse model of superficial pyoderma (24 mice, 3 mice/group) induced by S. pseudintermedius, and the 5% NMP + 10% PG + NZ2114 group had the best therapeutic effect compared to the other groups. This preparation did not cause any skin irritation, laying the foundation for the development of an effective and non-toxic topical product.

Understanding Drug Skin Permeation Enhancers Using Molecular Dynamics Simulations.

Our skin constitutes an effective permeability barrier that protects the body from exogenous substances but concomitantly severely limits the number of pharmaceutical drugs that can be delivered transdermally. In topical formulation design, chemical permeation enhancers (PEs) are used to increase drug skin permeability. In vitro skin permeability experiments can measure net effects of PEs on transdermal drug transport, but they cannot explain the molecular mechanisms of interactions between drugs, permeation enhancers, and skin structure, which limits the possibility to rationally design better new drug formulations. Here we investigate the effect of the PEs water, lauric acid, geraniol, stearic acid, thymol, ethanol, oleic acid, and eucalyptol on the transdermal transport of metronidazole, caffeine, and naproxen. We use atomistic molecular dynamics (MD) simulations in combination with developed molecular models to calculate the free energy difference between 11 PE-containing formulations and the skin's barrier structure. We then utilize the results to calculate the final concentration of PEs in skin. We obtain an RMSE of 0.58 log units for calculated partition coefficients from water into the barrier structure. We then use the modified PE-containing barrier structure to calculate the PEs' permeability enhancement ratios (ERs) on transdermal metronidazole, caffeine, and naproxen transport and compare with the results obtained from in vitro experiments. We show that MD simulations are able to reproduce rankings based on ERs. However, strict quantitative correlation with experimental data needs further refinement, which is complicated by significant deviations between different measurements. Finally, we propose a model for how to use calculations of the potential of mean force of drugs across the skin's barrier structure in a topical formulation design.

Enhancement of polymer thermoresponsiveness and drug delivery across biological barriers by addition of small molecules

Thermoresponsive polymers that undergo sol–gel transitions in the physiological temperature range have been widely used in biomedical applications. However, some commercially and clinically available thermoresponsive materials, particularly poloxamer 407 (P407), have the significant drawback of insufficient gel strength, which limit their performance. Furthermore, co-delivery with some small molecules, including chemical permeation enhancers (CPEs) can further impair the physical properties of P407. Here, we have developed a thermoresponsive platform by combination of CPEs with the poloxamer P188 to enable gelation at physiological temperatures and enhance gel strength. P188 gels at 60 °C, which is far above the physiological range. In combination with limonene (LIM) and sodium dodecyl sulfate (SDS), P188 gels at ∼25 °C, a temperature that in useful for biomedical applications. Gelation behavior was studied by small angle neutron scattering (SANS) experiments, which identified micelle-to-cubic mesophase transitions with increasing temperature. Analysis of the SANS intensities revealed that P188 micelles became larger as LIM or SDS molecules were incorporated, making it easier to form a micellar gel structure. P188-3CPE (i.e., 2% LIM, 1% SDS and 0.5% bupivacaine (BUP)) had low viscosity at room temperature, facilitating administration, but rapidly gelled at body temperature. P188-3CPE enabled the flux of the antibiotic ciprofloxacin across the TM and completely eradicated otitis media from nontypable Haemophilus influenzae (NTHi) in chinchillas after a single administration.

In vivo skin optical clearing efficacy quantification of clinically compatible agents using line-field confocal optical coherence tomography.

The clinical use of optical methods for in vivo skin imaging is limited by skin strong scattering properties, which reduce image contrast and probing depth. The efficiency of optical methods can be improved by optical clearing (OC). However, for the use of OC agents (OCAs) in a clinical setting, compliance with acceptable non-toxic concentrations is required. OC of in vivo human skin, combined with physical and chemical methods to enhance skin permeability to OCAs, was performed to determine the clearing-effectiveness of biocompatible OCAs using line-field confocal optical coherence tomography (LC-OCT) imaging. Nine types of OCAs mixtures were used in association with dermabrasion and sonophoresis for OC protocol on three volunteers hand skin. From 3D images obtained every 5min for 40min, the intensity and contrast parameters were extracted to assess their changes during the clearing process and evaluate each OCAs mixture's clearing efficacy. The LC-OCT images average intensity and contrast increased over the entire skin depth with all OCAs. The best image contrast and intensity improvement was observed using the polyethylene glycol, oleic acid, and propylene glycol mixture. Complex OCAs featuring reduced component concentrations that meet drug regulation-established biocompatibility requirements were developed and proved to induce significant skin tissues clearing. By allowing deeper observations and higher contrast, such OCAs in combination with physical and chemical permeation enhancers may improve LC-OCT diagnostic efficacy.

Transnasal targeted delivery of therapeutics in central nervous system diseases: a narrative review.

Currently, neurointervention, surgery, medication, and central nervous system (CNS) stimulation are the main treatments used in CNS diseases. These approaches are used to overcome the blood brain barrier (BBB), but they have limitations that necessitate the development of targeted delivery methods. Thus, recent research has focused on spatiotemporally direct and indirect targeted delivery methods because they decrease the effect on nontarget cells, thus minimizing side effects and increasing the patient's quality of life. Methods that enable therapeutics to be directly passed through the BBB to facilitate delivery to target cells include the use of nanomedicine (nanoparticles and extracellular vesicles), and magnetic field-mediated delivery. Nanoparticles are divided into organic, inorganic types depending on their outer shell composition. Extracellular vesicles consist of apoptotic bodies, microvesicles, and exosomes. Magnetic field-mediated delivery methods include magnetic field-mediated passive/actively-assisted navigation, magnetotactic bacteria, magnetic resonance navigation, and magnetic nanobots-in developmental chronological order of when they were developed. Indirect methods increase the BBB permeability, allowing therapeutics to reach the CNS, and include chemical delivery and mechanical delivery (focused ultrasound and LASER therapy). Chemical methods (chemical permeation enhancers) include mannitol, a prevalent BBB permeabilizer, and other chemicals-bradykinin and 1-O-pentylglycerol-to resolve the limitations of mannitol. Focused ultrasound is in either high intensity or low intensity. LASER therapies includes three types: laser interstitial therapy, photodynamic therapy, and photobiomodulation therapy. The combination of direct and indirect methods is not as common as their individual use but represents an area for further research in the field. This review aims to analyze the advantages and disadvantages of these methods, describe the combined use of direct and indirect deliveries, and provide the future prospects of each targeted delivery method. We conclude that the most promising method is the nose-to-CNS delivery of hybrid nanomedicine, multiple combination of organic, inorganic nanoparticles and exosomes, via magnetic resonance navigation following preconditioning treatment with photobiomodulation therapy or focused ultrasound in low intensity as a strategy for differentiating this review from others on targeted CNS delivery; however, additional studies are needed to demonstrate the application of this approach in more complex in vivo pathways.

TRANSFERSOMES AS NOVEL DRUG DELIVERY SYSTEM

Transdermal drug delivery appears to be most vital drug delivery system because of its merit over conventional systems. Transferosomes & the fundamental concept of transfersomes were launched by Gregor Cevc in the year 1991. The name means carrying body and is derived from the Latin word transferre, meaning to carry across and the Greek word soma, meaning a body. Novel drug delivery system aims to deliver the drug at a rate directed by need of body during the period of treatment and channel the active entity to the site of action. Transferosome is one of the novel vesicular drug delivery system which consists of phospholipids, surfactant and water for enhanced transdermal delivery. Transferosomes are able to reach intact deeper regions of the skin after topical drug administration while delivering higher concentrations of active substances making them a successful carrier for transdermal applications. These vesicular systems can deliver low as well as high molecular weight compounds. Targeted and controlled release formulations can also be prepared by transferosomes as it can accommodate drug molecules with wide range of solubility. Various strategies can be used to augment the transdermal delivery which includes iontophoresis, electrophoresis, sonophoresis, chemical permeation enhancers, microneedles, & vesicular system (liposomes, niosomes, elastic liposomes such as ethosomes & transfersomes). It exists as an ultra-deformable complex having a hydrated core surrounded by a complex layer of lipid. It penetrates the stratum corneum by either intracellular route or the transcellular route by the generation of osmotic gradient. Advantages of Transferosomes are wide range of solubilities, better penetration, biocompatible and biodegradable etc. Disadvantages of Transferosomes are oxidative degradation, expensive, etc. The transfersomes were formulated by the conventional rotary evaporation sonication method. Transferosomes can be applied in controlled release, transportation of large molecular weight compounds, target delivery to peripheral subcutaneous tissues, transdermal immunization etc.

Benzonatate as a local anesthetic.

Benzonatate is an FDA-approved antitussive agent that resembles tetracaine, procaine, and cocaine in its chemical structure. Based on structural similarities to known local anesthetics and recent findings of benzonatate exerting local anesthetic-like effects on voltage-gated sodium channels in vitro, we hypothesized that benzonatate will act as a local anesthetic to yield peripheral nerve blockade. Benzonatate was injected at the sciatic nerve of Sprague-Dawley rats. Sensory and motor blockade were assessed using a modified hot plate test and a weight-bearing test, respectively. Additionally, the effect of co-injection with tetrodotoxin and Tween 80 (a chemical permeation enhancer) was examined. Myotoxicity of benzonatate was assessed in vivo by histological analysis. Benzonatate produced a concentration-dependent sensory and motor nerve blockade with no appreciable systemic effects. Co-injection with tetrodotoxin or Tween 80 produced prolongation of sensory nerve blockade. Histologic assessment showed significant inflammation and myotoxicity from benzonatate injection, even at low concentrations. This study demonstrates that benzonatate does act as a local anesthetic at the peripheral nerve, with sensory and motor nerve blockade. Benzonatate interacts with tetrodotoxin and Tween 80 to prolong nerve blockade. However, benzonatate causes significant myotoxicity, even at subtherapeutic concentrations.

Thermosensitive biomaterial gels with chemical permeation enhancers for enhanced microneedle delivery of naltrexone for managing opioid and alcohol dependency.

Naltrexone (NTX) can be transdermally delivered using microneedles (MN) to treat opioid and alcohol misuse disorders, but delivery is blunted by rapid in vivo micropore closure. Poloxamer (P407), a thermosensitive biocompatible hydrogel, sustains NTX delivery through MN-treated skin by generating a drug depot within the micropores. Optimizing P407 formulations could maintain sustained delivery after micropore closure while reducing required patch sizes, which would be more discreet and preferred by most patients. Here we developed NTX-loaded P407 gels with chemical permeation enhancers (CPEs) and used these novel formulations alongside MN treatment to enhance NTX permeation, utilizing parallel micropore and intact skin transport pathways. We analyzed physicochemical and rheological properties of CPE-loaded P407 formulations and selected formulations with DMSO and benzyl alcohol for further study. In vitro permeation tests demonstrated more consistent and sustained NTX delivery through MN-treated porcine skin from 16% P407 formulations vs. aqueous solutions. P407 with 1% benzyl alcohol and 10% DMSO significantly, P < 0.05, increased flux through MN-treated skin vs. formulations with benzyl alcohol alone. This formulation would require a smaller size patch than previously used to deliver NTX in humans, with half the NTX concentration. This is the first time poloxamer biomaterials have been used in combination with CPEs to improve MN-assisted transdermal delivery of an opioid antagonist. Here we have demonstrated that P407 in combination with CPEs effectively sustains NTX delivery in MN-treated skin while requiring less NTX than previously needed to meet clinical goals.