Extracellular vesicles from recombinant cell factories improve the activity and efficacy of enzymes defective in lysosomal storage disorders

In the present study the use of extracellular vesicles (EVs) as vehicles for therapeutic enzymes in lysosomal storage disorders was explored. EVs were isolated from mammalian cells overexpressing alpha-galactosidase A (GLA) or N-sulfoglucosamine sulfohydrolase (SGSH) enzymes, defective in Fabry and Sanfilippo A diseases, respectively. Direct purification of EVs from cell supernatants was found to be a simple and efficient method to obtain highly active GLA and SGSH proteins, even after EV lyophilization. Likewise, EVs carrying GLA (EV-GLA) were rapidly uptaken and reached the lysosomes in cellular models of Fabry disease, restoring lysosomal functionality much more efficiently than the recombinant enzyme in clinical use. In vivo, EVs were well tolerated and distributed among all main organs, including the brain. DiR-labelled EVs were localized in brain parenchyma 1 h after intra-arterial (internal carotid artery) or intravenous (tail vein) administrations. Moreover, a single intravenous administration of EV-GLA was able to reduce globotriaosylceramide (Gb3) substrate levels in clinically relevant tissues, such kidneys and brain. Overall, our results demonstrate that EVs from cells overexpressing lysosomal enzymes act as natural protein delivery systems, improving the activity and the efficacy of the recombinant proteins and facilitating their access to organs neglected by conventional enzyme replacement therapies.

Impact of different vehicles for laser-assisted drug permeation via skin: full-surface versus fractional ablation

PURPOSE

This study aimed to assess impact of different vehicles for laser-assisted skin drug delivery. We also tried to uncover the mechanisms by which different vehicles affect laser-aided skin permeation.

METHODS

Full-surface ablative (conventional) and fractional lasers were used to irradiate nude mouse skin. Imiquimod and 5-aminolevulinic acid (ALA) were used as lipophilic and hydrophilic permeants. Vehicles employed included water with 40% polyethylene glycol 400 (PEG 400), propylene glycol (PG), and ethanol. Lipid nanoparticles were also utilized as carriers.

RESULTS

In vitro permeation profiles showed improvement in imiquimod flux with conventional laser (2.5 J/cm2) producing a 12-, 9-, and 5-fold increase when loading imiquimod in 40% PEG400, PG, and ethanol, respectively, as compared with intact skin. Nanoparticulate delivery by laser produced a 6-fold enhancement in permeation. Fractional laser produced less enhancement of imiquimod delivery than conventional laser. Laser exposure increased follicular imiquimod accumulation from 0.80 to 5.81 μg/cm2. ALA permeation from aqueous buffer, PEG 400, and PG with conventional laser treatment was 641-, 445-, and 104-fold superior to passive control. In vivo skin deposition of topically applied ALA examined by confocal microscopy indicated the same trend as the in vitro experiment, with aqueous buffer showing the greatest proporphyllin IX signaling. Diffusion of cosolvent molecules into ablated skin and drug partitioning from vehicle to skin are two predominant factors controlling laser-assisted delivery. In contrast to conventional laser, lateral drug diffusion was anticipated for fractional laser.

CONCLUSIONS

Our results suggest that different drug delivery vehicles substantially influence drug penetration enhanced by lasers.

Effect of soybean-lecithin as an enhancer of buccal mucosa absorption of insulin

OBJECTIVE

Transmucosal delivery is a suitable route for insulin non-injection administration. In order to understand how insulin passes through mucosa with soybean-lecithin as an enhancing absorption.

METHODS

The penetration rate of insulin molecular through porcine buccal mucosa was investigated by measuring transbuccal fluxes in the Ussing Chambers. The imaging morphology of rabbits buccal mucosa was analyzed by using non-contact mode atomic force microscopy.

RESULTS

The permeation rate can be increased by co-administration of soybean-lecithin. Untreated buccal mucosa showed relatively smooth surface characteristics, with many small crater-like pits and indentations spread over mucosa surfaces. Buccal mucosa that had been treated with 1.0% (w/v) sodium deoxycholic acid (pH 7.4) appeared to much more indentations characteristic, which treated with 2.5% (w/v) soybean-lecithin (pH 7.4) and 2.5% (w/v) Azone or laurocapram (pH 7.4) appeared rather different, the surface mucosa treated with soybean-lecithin emulsion showed a fine, rippling effect whereas those exposed to Azone display a more coarse, undulating surface feature. As a result of that Azone could damage the surface of the buccal mucosa, but soybean-lecithin could not.

CONCLUSION

This study demonstrated that soybean-lecithin is a better and safer enhancer for insulin transmucosal delivery.

Dissecting drug and vehicle metabolic effects in rats by a metabonomic approach

A combined application of high resolution (1)H NMR spectroscopy and multivariate statistical techniques focused on establishing a consistent statistical approach to metabonomic studies was tested. The data reduction, which is preliminary to the application of multivariate analysis to NMR spectra, was carried out by means of two complementary methods: pure Pattern Recognition (PR) and Assigned Signal Analysis (ASA). The simultaneous use of both approaches allowed us to obtain additional information in the analysis of metabonomic data, compared to the use of PR alone. This additional information consists in the possibility of a biochemical interpretation of the effects induced by treatment with xenobiotics, such as drugs or drug vehicles, on the metabolic networks of the systems under investigation. This approach allowed us to ascertain that a single-dose treatment with ST1959 vehicled by Sesame oil affects the production of hepatic glucose associated to an increment of the amino acid ketogenic process.

Anginex-Conjugated Liposomes for Targeting of Angiogenic Endothelial Cells

Identification of a tumor angiogenesis specific ligand would allow targeting of tumor vasculature. Lipidic vehicles can be used to deliver therapeutic agents for treatment of disease or contrast agents for molecular imaging. A targeting ligand would allow specific delivery of such formulations to angiogenic sites, thereby reducing side effects and gaining efficiency. Anginex, a synthetic 33-mer angiostatic peptide, has been described to home angiogenically activated endothelium, suggesting an ideal candidate as targeting ligand. To investigate this application of anginex, fluorescently labeled paramagnetic liposomes were conjugated with anginex. Using phase contrast and fluorescence microscopy as well as magnetic resonance imaging (MRI), we demonstrate that anginex-conjugated liposomes bind specifically to activated endothelial cells, suggesting application as an angiogenesis targeting agent for molecular targeting and molecular imaging of angiogenesis-dependent disease.

Alginate-whey protein granular microspheres as oral delivery vehicles for bioactive compounds

Alginate (AL)-whey protein isolate (WPI) microspheres of varied WPI/AL ratio, particle diameter and concentration of polymer bead forming solution (C(AL+WPI)) were prepared in order to develop a biocompatible vehicle for oral administration of bioactive compounds. Microscopy revealed a special matrix/granular structure for microspheres with a WPI/AL ratio of 8:2, 100 microm diameter and C(AL+WPI) of 5% (AL-WPI A2), featuring WPI granules 3-10 microm in diameter homogeneously distributed within an AL spherical matrix. The compound release properties of these microspheres were investigated in simulated gastric and intestinal fluids (SGF and SIF). They demonstrated the desirable property of retarding riboflavin release in SGF and underwent alginate matrix erosion together with liberation of WPI granules in SIF, followed by complete release of the riboflavin. Riboflavin release in SGF and in SIF without pancreatin followed the Higuchi diffusion model while release in SIF in the presence of pancreatin was attributed to WPI granule degradation.

The importance of valency in enhancing the import and cell routing potential of protein transduction domain-containing molecules

Protein transduction domains (PTDs) are peptides that afford the internalization of cargo macromolecules (including plasmid DNA, proteins, liposomes, and nanoparticles). In the case of polycationic peptides, the efficiency of PTDs to promote cellular uptake is directly related to their molecular mass or their polyvalent presentation. Similarly, the efficiency of routing to the nucleus increases with the number of nuclear localization signals (NLS) associated with a cargo. The quantitative enhancement, however, depends on the identity of the PTD sequence as well as the targeted cell type. Thus the choice and multivalent presentation of PTD and NLS sequences are important criteria guiding the design of macromolecules intended for specific intracellular localization. This review outlines synthetic and recombinant strategies whereby PTDs and signal sequences can be assembled into multivalent peptide dendrimers and promote the uptake and routing of their cargoes. In particular, the tetramerization domain of the tumour suppressor p53 (p53tet) is emerging as a useful scaffold to present multiple routing and targeting moieties. Short cationic peptides fused to the 31-residue long p53tet sequence resulted in tetramers displaying a significant enhancement (up to 1000 fold) in terms of their ability to be imported into cells and delivered to the cell nucleus in relation to their monomeric analogues. The design of future polycationic peptide dendrimers as effective delivering vehicles will need to incorporate selective cell targeting functions and provide solutions to the issue of endosomal entrapment.

Rice as a vehicle for dietary fluoride uptake

The objective of this study was to analyze aspects of the metabolism and bio-availability of fluoride after consumption of a sample of polished white rice containing 5.6 ppm fluoride ion. Up to 400 g of fluoridated rice was consumed by three volunteer adult subjects over specific time periods on two separate occasions. Saliva concentrations were elevated immediately and remained so 90 minutes following ingestion, among other indications. It was concluded that polished rice has the potential to be a useful vehicle for dietary fluoride transport.

Polylysine as a vehicle for extracellular matrix-targeted local drug delivery, providing high accumulation and long-term retention within the vascular wall

We present the first steps in the elaboration of an approach of extracellular matrix-targeted local drug delivery (ECM-LDD), designed to provide a high concentration, ubiquitous distribution, and long-term retention of a drug within the vessel wall after local intravascular delivery. The approach is based on the concept of a bifunctional drug comprising a "therapeutic effector" and an "affinity vehicle," which should bind to an abundant component of the vessel wall. The aim of the present study was to select molecules suitable for the role of affinity vehicles for ECM-LDD and to study their intravascular delivery and retention ex vivo and in an animal model. By use of fluorescence microscopy, the following molecules were selected on the basis of strong binding to cross sections of human vessels: protamine, polylysine, polyarginine, a glycosaminoglycan-binding peptide from vitronectin, and a synthetic dendrimer. With polylysine as a prototypic affinity vehicle, we showed that after intravascular delivery, polylysine was concentrated throughout a luminal layer of the vascular wall to an extremely high concentration of 20 g/L and was retained therein for at least 72 hours of perfusion without noticeable losses. Low molecular weight (fluorescein) and high molecular weight (hirudin) compounds could be chemically conjugated to polylysine and were retained in the vessel wall after intravascular delivery of the conjugates. In conclusion, by use of the ECM-LDD method, an extremely high concentration and long-term retention of locally delivered drug can be reached. Polycationic molecules can be considered as potential affinity vehicles for ECM-LDD.

Peptide-based intracellular shuttle able to facilitate gene transfer in mammalian cells

Loligomers are peptide-based intracellular vehicles able to penetrate cells and self-localize into distinct cellular compartments. Loligomers can be rapidly assembled by automated solid-phase approaches and were designed to act as nonviral, nonlipophilic intracellular shuttles. One nucleus-directed loligomer, termed loligomer 4, was evaluated for its ability to function as a transfection agent. Loligomer 4 readily associates with plasmids to form noncovalent complexes. The migration of loligomer 4-plasmid complexes into cells was monitored by flow cytometry and fluorescence microscopy. Populations of plasmids labeled with 7-AAD exist either free or in association with loligomer 4 inside cells and are visible throughout the cytosol and nucleus of chinese hamster ovary (CHO) cells. Loligomer 4-plasmid complexes were not cytotoxic to cells and were readily imported by most cells (>70%). CHO cells were transfected with complexes of loligomer 4 and plasmids harboring luciferase, green fluorescent protein or beta-galactosidase reporter genes. The transfection efficiency of loligomer 4-plasmid DNA complexes was greater when cells were maintained as suspensions instead of monolayers. Transfections could be performed with cells suspended in serum-containing medium. The observed levels of transfection, however, were modest with 5-10% of CHO cells expressing either a green fluorescent protein or the enzyme beta-galactosidase. Loligomers have recently been observed in vesicular compartments [Singh, D., Kiarash, R., Kawamura, K, LaCasse, E. C., and Gariépy, J. (1998) Biochemistry 37, 5798-5809] and differences between levels of cellular import and transfection efficiency may well reflect the need to optimize the release of loligomers and their complexes from these compartments in future designs. In summary, loligomer 4 behaves as a stable, soluble and effective transfection agent. These results demonstrate the feasibility of designing loligomers able to act as intracellular guided agents aimed at gene transfer applications.

Screening of urine by one-dimensional and pulsed-field gradient two-dimensional 1H NMR spectroscopy: intoxication by propylene glycol in an infant patient

1H NMR spectroscopy is a promising method for the analysis of physiological fluids in clinical medicine. In the course of screening the urine of patients by 1D- and pulsed-field gradient 2D 1H NMR spectroscopy at 500 MHz, we encountered a case with a very high excretion of propylene glycol compared to others who received similar doses of the medication. In this case, the propylene glycol was scarcely metabolized by the patient. Propylene glycol is widely used as a safety material which is transformed into pyruvate and lactate in the healthy body. In this paper, we discuss how NMR spectroscopy can be a useful method for screening a patient intoxicated with propylene glycol.

Influence of solubility and permeant size on absorption and metabolism of xenobiotics in rabbit skin

1 In order to obtain an understanding of the risks associated with dermal uptake of xenobiotics it is necessary to investigate the principles governing percutaneous absorption and metabolism. The single-pass perfused rabbit ear served as a convenient model for the simultaneous study of absorption and metabolism of a variety of substances. We found: 2 When substances are applied in a lipophilic vehicle the permeation coefficient Kr is notably decreased when the distribution coefficient (n-octanol/perfusion buffer (pH 7.4)) Poct. exceeds 2000, Kr also decreases with increasing molecular weight. 3 Substances which are in the ionized state at pH 7.4 may have a higher permeation coefficient than would be expected from Poct. or by molecular weight. 4 The partition of a drug from the stratum corneum to the epidermal enzymes controls the extent of its metabolism. However, substances with increased solubility at physiological pH are metabolized to a lesser extent than expected from their absorption rate. 5 The decrease in percutaneous absorption and metabolism of a substance with a Poct. exceeding 2000 is consistent with the assumption that high lipophilicity hinders partition of the substance from the stratum corneum to the viable metabolizing tissue.

Physiological effect of polyethylene glycol conjugation on stroma-free bovine hemoglobin in the conscious dog after partial exchange transfusion

This study was designed to determine the effect of polyethylene glycol (PEG) conjugation on stroma-free bovine hemoglobin. This was accomplished by examining the effects of unmodified stroma-free bovine hemoglobin (bovine Hb), PEG modified bovine hemoglobin (PEG-Hb) and dextran 70 on heart rate (HR), mean arterial pressure (MAP), gross renal morphology, blood chemistry, and hemoglobinuria development in conscious beagle dogs following a 30% exchange transfusion. Dogs were implanted with telemetric blood pressure probes and after 2 weeks underwent an isovolumic 30% blood volume exchange transfusion. Dogs treated with bovine Hb displayed a significant increase in MAP for 2 h following the exchange transfusion with no effect on HR. These animals exhibited significant levels of hemoglobinuria (> 20% of infused dose) within 24 h. Histopathologically, all bovine Hb infused dogs displayed renal tubular vacuolization, with 2 dogs showing regions of tubular casts and tubular cell regeneration. PEG-Hb was shown to have a circulatory half-life of 58.3 +/- 2.4 h and caused no significant changes in MAP or HR throughout the study period. Dogs excreted less than 0.1% of infused PEG-Hb within 24 h and displayed only renal tubular epithelial cell vacuolization. Dextran 70 caused a slight but insignificant decrease in MAP, elevated the HR, and exhibited only slight renal vacuole formation. Blood chemistry remained essentially stable following exchange transfusion with all the test articles. The conjugation of PEG to hemoglobin greatly increased the parent protein's vascular retention while attenuating some of its less favorable attributes.

Kinetic investigations with inhibitors that mimic the posthomolysis intermediate in the reactions of coenzyme-B12-dependent glycerol dehydratase and diol dehydratase

Kinetic investigations were performed on the coenzyme-B12-dependent glycerol dehydratase and diol dehydratase reactions using 1,2-propanediol as substrate and [omega-(adenosin-5'-O-yl)alkyl]cobalamins as mimics of the posthomolysis intermediate state of the coenzyme. All the coenzyme-B12 analogues with oligomethylene chains (C3-C7) inserted between the central Co atom and the 5' O of the adenosine moiety were competitive inhibitors with respect to coenzyme B12. The apparent inhibition constants (Ki) of the shorter-chain inhibitors, especially the C5 inhibitor, were smaller for both enzymes than those of the longer-chain (C6, C7) compounds. These results are in agreement with the expected (0.6-0.9 nm) distance between the Co and 5'-methylene paramagnetic centers in the posthomolysis intermediate state of coenzyme B12 in these reactions.

Improvement of the rectal bioavailability of latamoxef sodium by adjuvants following administration of a suppository

The absorption of an antibiotic, latamoxef sodium (LMOX), following the rectal administration of a suppository containing adjuvants was investigated. A lipophilic base (Witepsol H15) was used. The rectal absorption of LMOX following the administration of a suppository without adjuvants was very low. Diclofenac sodium (DF) was used as an absorption promoter; it enhances rectal membrane permeability. The blood level of LMOX following the addition of DF(10 mg) to the base was increased only about 1.3-fold compared with that achieved with LMOX alone (difference not significant); even with a higher dose of DF, the absorption of LMOX was not sufficient. The release rate of LMOX from the base was slow. When Tween 80, a non-ionic surfactant, was added to improve the release rate of LMOX, the rate was sufficiently increased. The rectal absorption of LMOX on the addition of both Tween 80 and DF was markedly increased compared to that achieved with LMOX alone or with DF. These results indicate that the rectal absorption of LMOX after administration by a suppository was sufficiently improved by enhancing both the release rate from the base and the membrane permeability of the rectum. Lymphatic uptake and blood levels of LMOX were also investigated after the rectal administration of the LMOX preparation containing both Tween 80 and DF; the lymphatic uptake of LMOX was significantly enhanced compared with the LMOX preparation in which only DF was used as an adjuvant. The mechanism whereby adjuvants lead to the absorption of a non-absorbable drug, and the subsequent drug transportation routes through the membrane are discussed.

Mucoadhesive ophthalmic vehicles: evaluation of polymeric low-viscosity formulations

A series of polyanionic natural or semi-synthetic polymers (polygalacturonic acid, hyaluronic acid, carboxymethylamylose, carboxymethylchitin, chondroitin sulfate, heparan sulfate and mesoglycan) were evaluated as potential mucoadhesive carriers for ophthalmic drugs. Solutions containing cyclopentolate (CY) or pilocarpine (PI) as salts (or polyanionic complexes) with the acidic polymers, all showing a low viscosity, were tested for miotic (resp. mydriatic) activity in albino rabbits. In the case of some polymeric complexes, small but significant increases of the areas under the activity vs. time curves (AUC) over reference cyclopentolate hydrochloride (CYHC1) or pilocarpine nitrate (PINO3) vehicles, and significant AUC decreases after removal of precorneal mucin by treatment with N-acetylcysteine were observed. A correlation was found between these data, considered indicative of the occurrence of a mucoadhesive interaction "in vivo", and "in vitro" viscometric data expressing the polymers-mucin force of interaction. The advantages and limitations of the mucoadhesive non-viscous approach in the formulation of ophthalmic vehicles are presented and discussed.

The role of propylene glycol metabolism in lactatemia in the rabbit

Propylene glycol (1,2-propanediol PD) has been reported to significantly alter the blood parameters when administered as a drug vehicle. In this study, experiments were performed to estimate the pH, levels of PD, and its metabolites to determine the acute effect of PD in blood. PD was administered to rabbits orally in a single dose of 1 ml 28.4% aqueous solution per 100 g body weight equivalent to 38.66 mmol/kg. Whole blood pH and the levels of PD and metabolites were estimated at fast (O.O h, before feeding PD) and at 0.25, 1, and 3 h after the dose. PD elevated the concentrations of blood PD to its maximum (41.04 +/- 9.98 mmol/liter, n = 4) at 1 h; whereas blood PD is normally absent during fasting. PD significantly increased (P less than 0.01) the concentration of L-lactate in blood, which reached its plateau (2.55 +/- 0.62 mmol/liter, n = 4) at 0.25 h and was 2.45-fold higher than the observed fasted values (1.04 +/- 0.22 mmol/liter, n = 4). Production of D-lactate in blood was similarly increased significantly from 5.1 +/- 5.0 mumols/liter at fast to 150.0 +/- 30.4 mumols/liter at 3 h after oral PD (P less than 0.001, n = 4). As was observed in the fasted blood of PD treated rabbits, D-lactate levels at fast and after saline ingestion in the control animals was found either absent or too low. Despite this increase in lactate, blood pH did not alter significantly when appropriate anticoagulant, i.e., heparin + 4-methylpyrazole, was employed.(ABSTRACT TRUNCATED AT 250 WORDS)

The tissue distribution of clodronate (dichloromethylene bisphosphonate) in mice. The effects of vehicle and the route of administration

Clodronate (dichloromethylene bisphosphonate) accumulates extensively in bone by binding to hydroxyapatite crystals. In an hypo-osmotic vehicle, it accumulates also in the spleen and, to a lesser extent, in the liver of mice and rats. In the present study, the effects of parenteral routes of administration (intravenous, intraperitoneal, and subcutaneous), drug dose, and injection vehicle on the distribution of [14C]-clodronate were studied in mice. The route of drug injection had no effect on the deposition of clodronate in bone. Either deionized water or iso-osmotic saline used as vehicles for intravenous administration of the drug caused equal and dose-dependent accumulation in bone. In iso-osmotic glucose, however, the osseous deposition of the drug was 2.2-2.5 times lower than in the other vehicles (water, saline, choline chloride). Clodronate accumulated in spleen and liver only after intravenous injection when the drug was in hypo-osmotic vehicle, and the process was saturable at high doses. The hypotonic vehicle probably causes a local hemolysis, and clodronate forms complexes with erythrocyte iron, which is a prerequisite for ingestion of the drug by splenic and hepatic macrophages.

Role of the carrier solution in cyclosporine pharmacokinetics in the baboon

Although numerous investigational models have demonstrated the potent immunosuppressive properties of cyclosporine, the effectiveness of any given dosage may vary with the metabolism of the animal, the route of administration, and the carrier solution of the drug. We investigated the pharmacokinetics of intramuscular cyclosporine administration in the baboon using three carriers: polyoxethylated castor oil (Cremophor), a mixture of octanoic and decanoic acids (Miglyol), and olive oil. Cyclosporine prepared in Cremophor, Miglyol, or olive oil was injected intramuscularly into the hindlegs of baboons. Specimens for cyclosporine assay were obtained 2, 4, 6, 12, 18, and 24 hours after single intramuscular injection of 10 mg/kg or 15 mg/kg. In addition, weekly, then monthly, levels were obtained on animals receiving daily intramuscular injections following heterotopic heart xenografts. Attempts at oral administration proved unreliable and were discontinued. Cyclosporine assay was performed on stored serum using the RIA-KIT (Sandoz Pharmaceuticals Corporation, East Hanover, N.J.). Cremophor provides a more bioavailable form of cyclosporine than Miglyol when administered intramuscularly. (Area under curve = 7776 +/- 1437 for Cremophor 15 mg/kg vs 1837 +/- 726 for Miglyol 15 mg/kg; 2579 +/- 694 for Cremophor 10 vs 1123 +/- 393 for Miglyol 10.) Long-term daily intramuscular administration of Cremophor provides a sustained drug serum trough level with wide variability between individual animals (80 to 825 ng/ml). Toxicity was limited to injection site inflammation. There was no biochemical evidence of renal toxicity; however, some animals did demonstrate early histologic changes of cyclosporine effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Solubility of fatty acids and other hydrophobic molecules in liquid trioleoylglycerol

The fat solubilities of some long chain fatty acids, alcohols, alkanes, and triacyglycerols, and of some aromatic, chlorinated aromatic, and chlorinated aliphatic hydrocarbons were measured in trioleoylglycerol. Above their melting temperature, all test compounds are theoretically miscible with liquid fat. Below their melting temperature the solubility of all test compounds can be estimated by the equation: log (mole fraction solubility) = (Formula: see text) where delta Sf, the entropy of fusion, can be estimated from chemical structure according to Yalkowsky and Valvani (J. Pharm. Sci. 1980. 69:912-922), and the melting point (Tm) is either known or experimentally determined. For long chain compounds, solubility in trioleoylglycerol dropped precipitously with an increase in melting point. For the aromatic and chlorinated compounds, the drop was more gradual. Since the entropy of fusion of rigid aromatic compounds is approximately 13.5 e.u. at room temperature, their solubility in triacylglycerol is a linear function of melting point.

Percutaneous absorption of hydrocortisone increases with long-term administration. In vivo studies in the rhesus monkey

This study compares percutaneous absorption of hydrocortisone after short and long-term administration. The experimental design was to first apply 14C-hydrocortisone. This was followed by long-term administration of nonradioactive hydrocortisone. Then 14C-hydrocortisone was applied again when urinary excretion of radioactivity from the first application reached minimum detectable levels. Short- (first 14C-hydrocortisone application) and long-term (second 14C-hydrocortisone application) penetrations were compared. The level of absorption of hydrocortisone significantly increased during long-term administration, whether applied in an acetone vehicle or in a 0.9% emulsion ointment base (Eucerin). A placebo study in which only an acetone vehicle was applied for a long period followed by 14C-hydrocortisone application showed no enhanced penetration. It is suggested that long-term application of hydrocortisone alters the penetration barrier, resulting in enhanced penetration. The relevance of this long-term corticosteroid use in man is possibly of great importance.