Relationship between the amount of propranolol permeating through the stratum corneum of guinea pig skin after application of propranolol adhesive patches and skin irritation

Deep Eutectic Solvents Based on L-Arginine and 2-Hydroxypropyl-β-Cyclodextrin for Drug Carrier and Penetration Enhancement

By selecting L-arginine as the hydrogen bond acceptor (HBA) and 2-hydroxypropyl-β-cyclodextrin (2HPβCD) as the hydrogen bond donor (HBD), deep eutectic solvents (DESs) with various water content were prepared at the 4:1 mass ratio of L-arginine to 2HPβCD with 40 to 60% of water, and were studied for its application in transdermal drug delivery system (TDDS). The hydrogen bond networks and internal chemistry structures of the DESs were measured by attenuated total reflection Fourier transform infrared (ATR-FTIR) and 1H-nuclear magnetic resonance spectroscopy (1H-NMR), which demonstrated the successful synthesis of DESs. The viscosity of DES was decreased from 10,324.9 to 3219.6 mPa s, while glass transition temperature (Tg) of the DESs was increased from - 60.8 to - 51.4 °C, as the added water was increased from 45 to 60%. The solubility of ibuprofen, norfloxacin, and nateglinide in DES with 45% of water were increased by 79.3, 44.1, and 3.2 times higher than that in water, respectively. The vitro study of transdermal absorption of lidocaine in DESs showed that the cumulative amounts of lidocaine reached 252.4 µg/cm2, 226.1 µg/cm2, and 286.1 µg/cm2 at 8 h for DESs with 45%, 50%, and 60% of water, respectively. The permeation mechanism of DES with lower content of water (45%) was mainly by changing the fluidization of lipids, while changing the secondary structure of keratin in stratum corneum (SC) at higher water content (50% and 60%). These nonirritant and viscous fluid like DESs with good drug solubility and permeation enhancing effects have broad application prospect in the field of drug solubilization and transdermal drug delivery system.

The Study of Deep Eutectic Solvent Based on Choline Chloride and L-(+)-Tartaric Acid Diethyl Ester for Transdermal Delivery System

Deep eutectic solvents (DESs) based on choline chloride (C) and L-(+)-tartaric acid diethyl ester (L) were prepared and used in transdermal drug delivery system (TDDS). The internal chemistry structure including the formation and changes of hydrogen bonds of choline chloride and L-(+)-tartaric acid diethyl ester DES was characterized via attenuated total reflection Fourier transform infrared (ATR-FTIR) and ¹H nuclear magnetic resonance (¹H NMR) spectroscopy. The stoichiometric ratio of choline chloride to L-(+)-tartaric acid diethyl ester as well as water content affected the viscosity, glass transition temperature (T_g), and drug solubility of the DES. The viscosity and glass transition temperature of the DES (CL14) prepared at the ratio of 1:4 of choline chloride to L-(+)-tartaric acid diethyl ester were 1.19 Pa·s and - 44.01°C, respectively, and decreased to 0.10 Pa·s and - 55.31°C when 10% water (CL1410) was added. Taking diclofenac diethylamine (DDEA), the nonsteroidal anti-inflammatory drug as model, drug solubility was as high as 60 mg/ml and 250 mg/ml in CL14 and CL1410, respectively. The cumulative amount of DDEA was 4.63 ± 2.67 μg/cm² and 15.27 ± 4.63 μg/cm² for CL14 and CL1410, respectively, at 8 h. The mechanism of percutaneous permeability by the DES may be the disturbance of stratum corneum (SC) lipids as well as changes in the protein conformations. CL14 and CL1410 were also verified as low-cytotoxic and nonirritant. Therefore, the DESs studied are promising to be used in drug solubilization enhancement and transdermal drug delivery system.

Epithelia transmembrane transport of orally administered ultrafine drug particles evidenced by environment sensitive fluorophores in cellular and animal studies

Little is known about the in vivo fate of drug particles taken orally, in particular, the drug release kinetics and interaction with the gastrointestinal (GI) membrane. Lacking is analytical means that can reliably identify the integrity of drug particles under the complexity of biological environment. Herein, we explored fluorescent probes whose signals become quenched upon being released from drug carriers. Taking advantage of so-called the aggregation caused quenching (ACQ), particles may be identified by the integrated fluorophores, which are "turned off" when the particles become destructed and dyes are released. In the current study, ultrafine amorphous particles (UAPs) of cyclosporin A (CsA) were prepared with synthesized ACQ dyes physically entrapped. The fluorescence intensity of suspension of these UAPs was found correlated well with the dissolution of the particles. When given to rats orally, it was found that some of the administered UAPs could survive the animal's GI tracts for as long as 18h. Whole-body fluorescence imaging detected fluorescent signals in the liver and lungs. Particularly noticed in sections of jejunum and ileum, the detection suggested the possibility of direct absorption of UAPs through epithelial membranes. Moreover, 250nm particles were absorbed faster via transepithelia than larger ones (550nm), while the latter were preferably taken up by M cells in the follicle-associated epithelium (FAE) region of Peyer's patches. In vitro permeation studies with Caco-2 cells confirmed the transmembrane transport of the dye-integrated UAPs. Our study supports the idea of using ACQ fluorophores for imaging and characterizing the fate of intact particles in a biological environment.

Prospects of iontophoresis in cardiovascular drug delivery

Clinical benefits, industry interest, regulatory precedence, and strong market potential have made transdermal research the fastest growth area in drug delivery. As most drugs permeate poorly through skin, a major challenge is achieving the therapeutic level by enhancement of permeation rate. Iontophoresis, utilizing a minimal amount of current, is found to affect the skin permeation process drastically. Ideally suited for protein drugs, attempts have been made to utilize the technology for accelerating the low-molecular-weight drugs for chronic administration. However, because of the difficulty associated with the energy supply, commercialization was not feasible until recent times. Fortunately, the unprecedented growth of microelectronics has bridged this lacuna and brought the technology right into limelight. This article analyses the advantages of electrically assisted drug delivery in relation to passive permeation, with special reference to some cardiovascular drugs, for which there is already a demand in the market.

Topical propranolol therapy for infantile hemangiomas

The nonselective beta-adrenergic receptor antagonist propranolol is an effective therapy for infantile hemangiomas. Systemic propranolol therapy shows a rapid therapeutic effect with good drug tolerability. We report on the efficacy of local application of propranolol ointment in superficial hemangiomas of the skin. In our outpatient department, 45 children with 65 hemangiomas were treated with 1% propranolol in a hydrophilic ointment topically applied twice a day. Before start of treatment and at each visit, clinical photographs were taken. If ultrasound did not confirm occult deeper components, children were included in the study. Treatment in the proliferative phase within the first 6 months of life (including seven preterm infants) induced regression in 59% and cessation of growth in 26% of the hemangiomas. No response or proliferation of subcutaneous components was observed in 15%. Clinically, no side effects caused by the beta-receptor blocker were noticed. Treatment of two ulcerated hemangiomas of the perineal region twice using a flash lamp pulsed-dye laser and propranolol ointment in the surrounding lesion led to healing of the ulcers in 3 and 6 weeks, respectively. In six patients, topical therapy was started between the ages of 7 and 33 months. Even in these hemangiomas, improvement was obvious after 2 or 3 months. Propranolol administered topically in 1% ointment could have a beneficial effect on superficial hemangiomas of the skin. The treatment was well tolerated without side effects even in preterm infants and in children with numerous or large lesions.

Elastic liposomes mediated transdermal delivery of an anti-hypertensive agent: propranolol hydrochloride

One major problem encountered in transdermal drug delivery is the low permeability of drugs through the skin barrier. In the present investigation ultradeformable lipid vesicles, that is, elastic liposomes were prepared incorporating propranolol hydrochloride for enhanced transdermal delivery. Elastic liposomes bearing propranolol hydrochloride were prepared by conventional rotary evaporation method and characterized for various parameters including vesicles shape and surface morphology, size and size distribution, entrapment efficiency, elasticity, turbidity, and in vitro drug release. In vitro flux, enhancement ratio (ER), and release pattern of propranolol hydrochloride were calculated for transdermal delivery. In vivo study conducted on male albino rats (Sprague Dawley) was also taken as a measure of performance of elastic liposomal, liposomal, and plain drug solution. The better permeation through the skin was confirmed by confocal laser scanning microscopy (CLSM). Results indicate that the elastic liposomal formulation for transdermal delivery of propranolol hydrochloride provides better transdermal flux, higher entrapment efficiency, ability as a self-penetration enhancer and effectiveness for transdermal delivery as compared to liposomes.

Transdermal delivery of beta-blockers

Beta-adrenoceptor blocking drugs (beta-blockers) are one of the most frequently used class of cardiovascular drugs that are mainly used in conventional dosage forms., which have their own limitations including hepatic first-pass metabolism, high incidence of adverse effects due to variable absorption profiles, higher frequency of administration and poor patient compliance. Essentially, attempts have been made to develop novel drug delivery systems for beta-blockers, including transdermal delivery systems, to circumvent the drawbacks of conventional drug delivery. However, so far none of the beta-blocker drugs have been marketed as transdermal delivery systems. Nevertheless, there have been noteworthy research endeavours worldwide at the laboratory level to investigate the skin permeation and to develop transdermal formulations of beta-blockers including: propranolol, metoprolol, atenolol, timolol, levobunolol, bupranolol, bopindolol, mepindolol, sotalol, labetolol, pindolol, acebutolol and oxprenolol. Innovative research exploiting penetration-enhancing strategies, such as iontophoresis, electroporation, microneedles and sonophoresis, holds promise for the successful use of these drugs as consumer-friendly transdermal dosage forms in clinical practice. This paper presents an overview of the transdermal research on this important class of drugs.

Effects of Ethylcellulose and 2-Octyldodecanol Additives on Skin Permeation and Irritation with Ethylene-Vinyl Acetate Copolymer Matrix Patches Containing Formoterol Fumarate

Skin permeation of formoterol fumarate (FF) and irritation with ethylene-vinyl acetate (EVA) copolymer matrix patches was investigated using rat and human skin in vitro and different species of experimental animal, respectively. Skin permeation of FF increased remarkably without addition of ethylcellulose (EC) and was remarkably enhanced by incorporation of 2-octyldodecanol (OD) instead of hydrogenated rosin glycerol ester (Ester Gum H). Effects on skin permeation of FF with EVA matrix patches were similar in rat and human skin, but rat skin was 1000 times more permeable than human skin after 24 h. The primary irritation indices for matrix patches without EC and with EC (OD-0), EC and 0.5 mg OD per square centimeter (OD-0.5), and EC and 1.0 mg OD per square centimeter (OD-1) were 1.46, 1.13,1.29 and 1.38. The results suggested that the irritation induced by these patches was rather mild, but significantly greater than the 0.21 observed with the control. No significant effects were noted for either EC or OD alone. Skin irritation intensity with EVA matrix patches was observed to be in the order of rabbits, guinea pigs, rats and miniature swine.

Drug delivery across the skin

Since the introduction of the first through the skin (TTS) therapeutic in 1980, a total of 34 TTS products have been marketed and numerous drugs have been tested by more than 50 commercial organisations for their suitability for TTS delivery. Most of the agents which have been tested have had low molecular weights, due to the impermeability of the skin barrier. This barrier resides in the outermost skin layer, the stratum corneum. It is mechanical, anatomical, as well as chemical in nature; laterally overlapping cell multi-layers are sealed by tightly packed, intercellular, lipid multi-lamellae. Chemical skin permeation enhancers increase the transport across the barrier by partly solubilising or extracting the skin lipids and by creating hydrophobic pores. This is often irritating and not always well-tolerated. The TTS approach allows drugs (< 400 kDa in size) to permeate through the resulting pores in the skin, with a short lag-time and subsequent steady-state period. Drug bioavailability for TTS delivery is typically below 50%, avoiding the first pass effect. Wider, hydrophilic channels can be generated by skin poration, with the aid of a small electrical current (> 0.4 mA/cm2) across the skin (iontophoresis) or therapeutic ultrasound (few W/cm2; sonoporation). High-voltage (> 150 V, electroporation) widens the pores even more and often irreversibly. These standard poration methods require experience and equipment and are therefore, not practical; at best, charged/small molecules (< or = 4000 kDa in size) can be delivered efficiently across the skin. In spite of the potential harm of gadget-driven skin poration, this method is used to deliver molecules which conventional TTS patches are unable to deliver, especially polypeptides. Lipid-based drug carriers (liposomes, niosomes, nanoparticle microemulsions, etc.) were proposed as alternative, low-risk delivery vehicles. Such suspensions provide an improved drug reservoir on the skin, but the aggregates remain confined to the surface. Conventional carrier suspensions increase skin hydration and/or behave as skin permeation enhancers. The recently developed carriers; Transferomes, comprise pharmaceutically-acceptable, established compounds and are thought to penetrate the skin barrier along the naturally occurring transcutaneous moisture gradient. Transfersomes are believed to penetrate the hydrophilic (virtual) channels in the skin and widen the former after non-occlusive administration. Both small and large hydrophobic and hydrophilic molecules are deliverable across the stratum after conjugation with Transfersomes. Drug distribution after transdermal delivery probably proceeds via the lymph. This results in quasi-zero order kinetics with significant systemic drug levels reached after a lag-time of up to a few hours. The relative efficiency of TTS drug delivery with Transfersomes is typically above 50 %; with the added possibility of regional drug targeting.

Iontophoretic in vivo transdermal delivery of beta-blockers in hairless rats and reduced skin irritation by liposomal formulation

PURPOSE

To demonstrate the in vivo transdermal delivery and establish the comparative pharmacokinetics of five beta-blockers in hairless rat.

METHODS

Intravenous dosing was initially done via jugular cannula. For iontophoretic delivery, current (0.1 mA/cm2) was applied for 2 h through a drug reservoir patch containing the beta-blocker (10 mg/ml). Blood samples were collected and analyzed by stereoselective HPLC assays. Any irritation resulting from patch application was quantified by a chromameter. Multilamellar liposomal formulation was prepared by the thin-film hydration method and converted to unilamellar liposomes by extrusion.

RESULTS

With transdermal iontophoresis, therapeutically relevant amounts of propranolol (83.78 +/- 7.4 ng/ml) were delivered within an hour and lasted for up to 4 h. Cmax (185.1 +/- 56.8 ng/ml) was reached at hour 3. A significantly higher amount (p < 0.05) of sotalol HCl was delivered compared to other beta-blockers. There was no significant difference in the S/R ratio of AUC0-t for enantiomers after both intravenous and transdermal delivery. Skin irritation was significantly reduced (p < 0.05) when a liposomal formulation of the propranolol base was used rather than the base itself.

CONCLUSIONS

The comparative pharmacokinetics of intravenous and transdermal iontophoretic delivery of five beta-blockers in hairless rats was established. It was shown that there is no stereoselective permeation.

Liquid crystalline pharmacogel based enhanced transdermal delivery of propranolol hydrochloride

A novel pharmacogel was developed for the enhanced transdermal delivery of propranolol hydrochloride (PH). The synthesized prodrugs, propranolol palmitate hydrochloride (PPH) and propranolol stearate hydrochloride (PSH) self-assembled to form gel simply upon mixing alcoholic solution of prodrug with an aqueous solution in a specified ratio. By varying the ratio of prodrug, alcohol and water, three-component phase diagram was constructed which revealed isotropic-gel-vesicular dispersion regions, respectively concomitant to increasing the ratio of water. The gel phase is termed 'Pharmacogel' and exhibits birefringence under plane-polarized light corroborating the presence of lamellar liquid crystals. The pharmacogel by virtue of high chemical potential gradient and improved physicochemical properties showed the enhanced in-vitro skin permeation flux of 51.5+/-3.7 and 42.5+/-3.1 microg/cm(2)/h from PPH and PSH gel, respectively, as compared to 1.9+/-0.1 microg/cm(2)/h for control; and decrease in lag time (1.8 and 2.8 h for PPH and PSH gel, respectively) compared to control (7.6 h) was observed. The admixing of egg lecithin (EL) in increasing ratio concomitantly decreased the flux values to 31.7+/-2.1 microg/cm(2)/h (at a mole ratio of 50:50 PPH:EL) and increased the lag time. In the gel containing 50% EL, the addition of span 40 and cholesterol slightly reduced the permeation while sodium deoxycholate and Tween-80 improved it. The plasma drug levels following transdermal application of control were low (C(max)=23 ng/ml) while in PPH gel, it increased with time reaching C(max) of 94 ng/ml at 8 h post-application of PPH gel (C(max) of 75 ng/ml at 12 h post application of PL5 gel) and maintained for longer times. The AUC(0-32 h) for PPH gel was much higher (1968 ng h/ml) than control (AUC(0-18 h) was 239 ng h/ml), while EL mixed gel also showed better absorption (AUC(0-32 h) was 1707 ng h/ml). The gel formulations also caused less irritation than control, while mixed gel showed least irritation. This novel self-assembled pharmacogel providing high transdermal permeation with many variables to regulate the delivery is therefore having a great potential in percutaneous delivery.

Design and in vitro evaluation of adhesive matrix for transdermal delivery of propranolol

Propranolol hydrochloride, a water-soluble drug, was incorporated in three transdermal delivery systems using three polymers (hydroxypropylmethylcellulose, polyisobutylene and Ucecryl MC808). The influence of different factors (polymeric material, matrix thickness, drug content, thickness of the adhesive layer and presence of a dissolution enhancer) was investigated. Microscopic observations and DSC thermograms have permitted to demonstrate that propranolol was essentially dissolved in the HPMC matrix and dispersed in the two other matrix types. In vitro dissolution study was carried out according to European Pharmacopoeia. Release from HPMC matrices without adhesive coating was fast. Release from these matrices became more regular (reduction of the burst effect) and slow when they are coated with a 12 microm thick Ucecryl layer. Release from different PIB matrices was too slow to be suitable as TDDS for propranolol. The best release modulation was obtained from Ucecryl matrices. In all matrices types, propylene glycol accelerated propranolol release rate. The kinetic of drug release from most matrix types was more closely described by the square-root model (Higuchi).

A study on the in-vitro percutaneous absorption of propranolol from disperse systems

Transdermal administration of propranolol can be used to avoid hepatic first-pass metabolism of the drug. The effect of polysorbate 80 concentration on the permeation of propranolol incorporated into micelles of polysorbate 80 in water, oil-in-water microemulsions of isopropyl myristate-polysorbate 80-sorbitol-water and oil-in-water emulsions of isopropyl myristate-polysorbate 80-sorbitan monooleate-water has been investigated by use of an artificial double-layer membrane, composed of a barrier foil and a lipid barrier, in Franz-type diffusion cells. Reversed-phase high-performance liquid chromatography, with celiprolol as internal standard, was used to determine the concentration of propranolol in the receptor compartment and a logarithmic equation was used to estimate the apparent permeability coefficient of propranolol from disperse systems. For each disperse system the apparent permeability coefficient of propranolol decreased with increasing polysorbate 80 concentration. Moreover, for a given polysorbate 80 concentration the apparent permeability coefficient of propranolol increased when the disperse system was changed from emulsion to microemulsion and then to solubilized system, because of the increasing interfacial area of total disperse phase. The results show that transdermal permeation of propranolol is greater when it is diffused from solubilized systems rather than from microemulsions or emulsions.