Topically applied KTTKS: a review.

Skin ageing is an irreversible process that is caused by both intrinsic and extrinsic factors. The possibility of arresting or delaying skin ageing represents a large research area and has a big potential in the cosmetics sector. Recently, the polypeptide lysine-threonine-threonine-lysine-serine (KTTKS) has attracted a lot of attention and it features in numerous up-market cosmetic products where it has become erroneously associated with the term 'pentapeptide'. In this study, we review in detail KTTKS and its major derivatives, in terms of the limited information in the literature and an appraisal of its physicochemical and theoretical skin permeation properties. There appears to be a sound in vitro basis for its action on fibroblasts due to its stimulatory effect on extracellular matrix synthesis, where the stimulatory effect of KTTKS is specific to collagen types I and III and fibronectin expression. However, there is a surprising absence of in vitro skin penetration data in the literature, and there are relatively few clinical studies using these materials.

Pre-treatment with Aloe vera juice does not enhance the in vitro permeation of ketoprofen across skin.

BACKGROUND/AIMS: The potential of pre-treating skin with Aloe vera juice as a penetration enhancer was evaluated in vitro using ketoprofen as model permeant. METHODS: To excised porcine skin mounted in Franz diffusion cells was applied either: (1) commercial Aloe vera; (2) commercial Aloe vera followed by massaging; (3) previously boiled commercial Aloe vera; (4) water (negative control); (5) tea tree oil (positive control). After 1 h, the pre-treatment was removed and the skin dosed with a saturated solution of ketoprofen in polyethylene glycol 400; the appearance of drug in the receptor phase was then monitored by HPLC. RESULTS: No statistically significant differences in the transdermal delivery of ketoprofen were observed between water and all the Aloe vera pre-treatments (p > 0.05). The tea tree oil pre-treatment was significantly different to all others (p < 0.05). CONCLUSION: Aloe vera appears to have no value as a penetration enhancer when used as a pre-treatment, although the data indirectly support the mechanism of action proposed previously, work when used 'within-vehicle'. Handling household products containing Aloe vera appears not to leave the user at elevated risk of subsequent absorption of exogenous chemicals.

Control of microbial contamination of Franz diffusion cell receptor phase in the development of transcutaneous breast cancer therapeutics.

AIMS: To determine the micro-organism contamination of excised porcine (pig) ear, and evaluate the use of Cyclopore track-etched membranes (CTEM) for preventing ingress into Franz-type diffusion cells. METHODS: Swabs were taken from four locations and used to inoculate Tryptone Soya Agar (TSA) and Sabouraud Dextrose Agar (SDA) plates. Diffusion cells were assembled to include porcine skin with and without CTEM, and the receptor phase sampled periodically and spread onto plates. RESULTS: Five distinct colony types were isolated after incubation of all swabs on TSA plates at 37 degrees C; on SDA plates, one fungal colony was found at 30 degrees C and one at 37 degrees C. The SDA agar plate incubated at 30 degrees C resulted in the growth of a large diffused white fungal colony. No regional differences were observed. Without the CTEM, the receptor phase became contaminated within 6 h. With the CTEM present, microbial ingress was substantially retarded with visible presumptive fungal growth occurring at 24 h and detectable contamination on both microbiological media at 48 h. CONCLUSIONS: As expected, the native porcine ears were considerably contaminated. The ingress of contamination into the diffusion cell receptor phases can be largely, but not entirely, eliminated using CTEM. The addition of antimicrobial agents was necessary to eliminate micro-organisms that were observed at later time points. SIGNIFICANCE AND IMPACT OF THE STUDY: This article, while highlighting the presence of a high number of micro-organisms on native porcine skin, presents a practical means to reduce the risk of microbial contamination in transdermal/transcutaneous permeation studies, particularly in the study of cell cultures grown within Franz diffusion cell receptor compartments.

Scope and limitations of the co-drug approach to topical drug delivery.

Many currently available drugs show unfavourable physicochemical properties for delivery into or across the skin and temporary chemical modulation of the penetrant is one option to achieve improved delivery properties. Pro-drugs are chemical derivatives of an active drug which is covalently bonded to an inactive pro-moiety in order to overcome pharmaceutical and pharmacokinetic barriers. A pro-drug relies upon conversion within the body to release the parent active drug (and pro-moiety) to elicit its pharmacological effect. The main drawback of this approach is that the pro-moiety is essentially an unwanted ballast which, when released, can lead to adverse effects. The term 'co-drug' refers to two or more therapeutic compounds active against the same disease bonded via a covalent chemical linkage and it is this approach which is reviewed for the first time in the current article. For topically applied co-drugs, each moiety is liberated in situ, either chemically or enzymatically, once the stratum corneum barrier has been overcome by the co-drug. Advantages include synergistic modulation of the disease process, enhancement of drug delivery and pharmacokinetic properties and the potential to enhance stability by masking of labile functional groups. The amount of published work on co-drugs is limited but the available data suggest the co-drug concept could provide a significant therapeutic improvement in dermatological diseases. However, the applicability of the co-drug approach is subject to strict limitations pertaining mainly to the availability of compatible moieties and physicochemical properties of the overall molecule.

Topical delivery of retinyl ascorbate co-drug. 5. In vitro degradation studies.

Chemical and enzymatic hydrolysis of the co-drug of retinoic acid (vitamin A) and ascorbic acid (vitamin C) - retinyl ascorbate (RA-AsA)--have been studied. Firstly, the amount of protein and ester hydrolysis activity was determined in crude cellular extracts from freshly excised porcine ear skin (<3 h) and stored porcine ear skin (frozen >6 months) using ethyl butyrate as model substrate. The stability of RA-AsA was then determined in the crude cell extracts with and without additional antioxidants. Lastly, the enzymatic hydrolysis of RA-AsA and retinyl-2-carboxy-2-hydroxy-ethanoate were determined by incubating with porcine liver esterase - retinol palmitate and ascorbyl palmitate were included for comparison. Freshly excised skin contained higher amounts of active proteins than previously frozen skin. RA-AsA underwent hydrolytic reduction causing the AsA moiety to disintegrate due to the presence of free radicals in the media. An intermediate was produced that seemed to be cleaved by enzymes. Addition of ascorbic acid, as antioxidant, to the media of crude protein extracts decelerated the hydrolysis rate. This was supported when RA-AsA and retinyl-2-carboxy-2-hydroxy-ethanoate were incubated separately with pure esterase. There was approximately 5-fold more soluble protein per ml of cytosol in the fresh skin compared to the stored skin. Therefore, the amount of protein present within approximately 1.5 cm(2) of skin (average diffusion area in the Franz cells used in our skin penetration studies) was 0.06 mg cm(-2) and 0.01 mg cm(-2) for fresh and stored extracts, respectively.

Topical delivery of retinyl ascorbate co-drug: 6. Determination of toxic dose and antioxidant activity in cultured human epidermal keratinocytes.

The maximum effective dose of retinyl ascorbate and its potential therapeutic benefits against induced oxidative damage were assessed in vitro using cultured human epidermal keratinocytes. RA-AsA exhibited toxic effects at concentrations >6 microM. The findings indicate to the potency of RA-AsA as free radical scavenger and cell proliferation regulator.

Solvent content and macroviscosity effects on the in vitro transcutaneous delivery and skin distribution of ketoprofen from simple gel formulations.

The effects of decreasing solvent content and macroviscosity of simple topical gel formulations on the transcutaneous delivery and distribution of ketoprofen through skin were studied. Simple topical gels, based on ketoprofen, PEG 400 and either Cabosil M-5 or hydroxypropylcellulose were formulated and applied to freshly excised pig ear skin in vitro. Receptor phase samples were taken to determine permeation and depth profiles of ketoprofen were constructed, following tape stripping and membrane separation. Reduction of solvent from the Cabosil-thickened gels resulted in a rank order reduction in the permeation and distribution of ketoprofen. Reduced amounts of ketoprofen were distributed through the skin, particularly the dermis, with decreasing solvent. Two gels sharing the same macroviscosity exhibited significantly different skin permeation and distribution characteristics. The rank order reduction in both permeation and distribution of ketoprofen was attributed to the physiochemical properties of the formulation and how they may change after application, in particular the increased adsorptivity of ketoprofen to the Cabosil relative to the amount of solvent present in the system. This effect appeared to be predominant over any interactions occurring between the formulation and the skin. The data provided further evidence that adsorption to the thickener, rather than changes in viscosity, were primarily responsible for reduced permeation and distribution in the system examined.

Inter- and intralaboratory variation of in vitro diffusion cell measurements: an international multicenter study using quasi-standardized methods and materials.

In vitro measurements of skin absorption are an increasingly important aspect of regulatory studies, product support claims, and formulation screening. However, such measurements are significantly affected by skin variability. The purpose of this study was to determine inter- and intralaboratory variation in diffusion cell measurements caused by factors other than skin. This was attained through the use of an artificial (silicone rubber) rate-limiting membrane and the provision of materials including a standard penetrant, methyl paraben (MP), and a minimally prescriptive protocol to each of the 18 participating laboratories. "Standardized" calculations of MP flux were determined from the data submitted by each laboratory by applying a predefined mathematical model. This was deemed necessary to eliminate any interlaboratory variation caused by different methods of flux calculations. Average fluxes of MP calculated and reported by each laboratory (60 +/- 27 microg cm(-2) h(-1), n = 25, range 27-101) were in agreement with the standardized calculations of MP flux (60 +/- 21 microg cm(-2) h(-1), range 19-120). The coefficient of variation between laboratories was approximately 35% and was manifest as a fourfold difference between the lowest and highest average flux values and a sixfold difference between the lowest and highest individual flux values. Intralaboratory variation was lower, averaging 10% for five individuals using the same equipment within a single laboratory. Further studies should be performed to clarify the exact components responsible for nonskin-related variability in diffusion cell measurements. It is clear that further developments of in vitro methodologies for measuring skin absorption are required.

Topical delivery of retinyl ascorbate co-drug. 2. Comparative skin tissue and keratin binding studies.

Retinyl ascorbate (RA-AsA), an ester co-drug of vitamins A (RA) and C (AsA), is proposed as a topical antioxidant/cell division regulator for reducing UV-induced generation of free radicals and disrupted dermal cell growth. The efficacy of dermatological agents is influenced by their retention within the skin, which is increased by the interaction with skin components. Keratin is the major protein (approximately 95%) in the skin, and this paper reports the binding of RA-AsA, RA, AsA, retinol, ascorbic acid palmitate and retinol palmitate to three tissues-human callus, pig ear skin and bovine horn keratin. Tissue samples were incubated with solutions of compounds and the uptake measured as the ratio of bound/free compound at equilibrium. Binding to keratin was assessed using delipidised tissue, and was much higher for the polar compounds, suggesting dipolar/H-bonding interaction. Binding strength was ranked as human > porcine > bovine, but there was no distinction for highly lipophilic compounds. The binding characteristic of native tissues was complicated by lipid content of the tissues. There seemed to be a dual effect. The binding of very lipophilic materials increased with lipid content, implying that a substantial amount is dissolved in the lipid matrix. For highly polar AsA, lipid content decreased the binding, suggesting that the lipid reduced the strong polar interactions with skin protein/keratin.

Binding of primaquine to epidermal membranes and keratin.

The localisation of primaquine was studied within epidermal membranes following the application of a topical dose. A depth profile was constructed by tape-stripping human epidermis following permeation of a 70 mgml(-1) solution of primaquine in Miglyol 840. Comparative binding studies of primaquine were carried out on isolated human stratum corneum and whole epidermis, using normal and delipidised tissue. An additional study was undertaken using bovine keratin powder as a model of human keratin. The depth profile showed that primaquine decreased with depth and decreasing keratin content, and the total primaquine recovered (15.5 mgcm(-2)) was 300 x the amount of extractable lipid. Binding to delipidised skin was saturable, whereas binding to normal skin was unsaturable, reflecting the high miscibility of drug in the lipid domains as opposed to a finite, but large number of binding sites on the corneocytes. Binding was greater for stratum corneum than stratum corneum plus viable epidermis, probably due to greater accessibility of corneocytes keratin. Binding was dose dependent, although binding to delipidised skin was far greater than to normal skin, demonstrating that primaquine had an affinity for lipoidal regions and an even higher affinity for the proteinaceous domains of the stratum corneum. This was supported by high saturable levels of primaquine binding to bovine horn keratin. The results indicated extensive binding to corneocyte keratin has a significant effect on reservoir formation and the permeability of primaquine across human skin. It is speculated that the large amount of keratin presented at the skin surface may be an evolutionary protective process for the sequestration of ingressing molecules.

Direct enantiomeric resolution of some cardiovascular agents using synthetic polymers imprinted with (-)-S-timolol as chiral stationary phase by thin layer chromatography.

Molecular imprinted polymers (MIPs) of S-timolol were prepared as chiral stationary phases (CSPs) in thin layer chromatography (TLC). The resolution of the enantiomers of some cardiovascular drugs, including propranolol, atenolol, timolol, nadolol, nifedipine and verapamil were investigated on these CSPs. A mobile phase system of either methanol or acetonitrile was used and the effects of acetic acid content of the mobile phases were also investigated. The best resolution was achieved for enantioseparation of propranolol, timolol and atenolol on plates based on MIP of (-)-S-timolol using methacrylic acid as functional monomer (alpha = 1.52, 1.6, 1.59) respectively, using acetonitrile containing 5% acetic acid and (alpha = 1.47, 1.52, 1.5) in methanol containing 1% acetic acid as mobile phases. The results obtained show that TLC based on MIPs could be applied in the direct separation of several beta-adrenergic drugs. As the side chains on beta-blockers are similar, it is possible that this method could also be used for the resolution of other racemates in this family of drugs. Racemic drugs structurally related to print molecule, were completely resolved into two spots with the MIP plates. In general the retention of (+)-R-isomers was greater than that of (-)-S-isomers, indicating lower stereoselectivity of the MIPs to the dextrorotatory isomers. The method offers a rapid, sensitive and reliable method for quality control for these drugs.

Use of a physiologic scoring system during interhospital transport of pediatric patients.

OBJECTIVE: To determine the incidence of physiologic deterioration in critically ill and injured pediatric patients during interhospital transport with air and ground ambulance DESIGN: Prospective, descriptive study SETTING: All children were treated in regional hospitals and then transported to a pediatric tertiary care center. PATIENTS: Children (n = 100) with a median age of 1.4 years (range 1 week to 18 years) MAIN RESULTS: Three sets of physiologic scores were calculated: at the time of referral, on departure from the referring hospital, and arrival at the tertiary care center. The incidence of significant physiologic deterioration based on the calculated physiologic scores was 5.6% (n = 4) during ground and 3.4% (n = 1) during air ambulance transports. Critical events occurred in 15% of ground and 31% of air ambulance transports. CONCLUSION: No difference existed in the incidence of adverse events or physiologic deterioration when air ambulance transports were compared with ground ambulance transports for critically ill children by our team. The physiologic scoring system we chose is simple and easy to use for quality assurance.

Anaesthetic technique for transoesophageal echocardiography in children.

OBJECTIVE: To document the safety and efficacy of an anaesthetic technique in paediatric patients undergoing transoesophageal echocardiography (TOE). METHODS: Prospective descriptive study performed in a children's hospital with all patients undergoing TOE. Topical analgesia of the pharynx was achieved with lidocaine. Anaesthesia was induced with midazolam (25 microg.kg-1), fentanyl (1 microg.kg-1), and propofol (0.5-1 mg.kg-1), followed by a continuous infusion of propofol (5-10 mg.kg-1.h-1). RESULTS: Thirty patients are reported. The mean age was 11.4 +/- 5.1 years (range 1-22) and weight 40.5 +/- 22.1 kg (range 10-110). All the patients tolerated the procedure well. Two patients experienced brief oxygen desaturations during induction, 10 patients coughed during the procedure, and six patients had significant muscle activity requiring supplemental doses of propofol. None of the patients experienced nausea or vomiting. CONCLUSION: We conclude that our anaesthetic technique in spontaneously breathing paediatric patients during TOE is effective and appears to be safe in children with heart disease.

Pharmaceutical applications for molecularly imprinted polymers.

Molecular imprinting is a means of introducing sites of specific molecular arrangement into an otherwise uniform polymeric matrix. This is achieved by formation of a pre-polymerisation complex between complementary monomers and the template molecule. Subsequent polymerisation in the presence of a crosslinker, in a porogenic environment, results in the production of a macroporous polymer capable of specific molecular recognition. This paper considers potential roles for molecularly imprinted polymers within a pharmaceutical remit. Applications including controlled release, drug monitoring devices and biological receptor mimetics are discussed. Histamine and ephedrine molecularly imprinted polymers (MIPs) were studied as potential biological receptor mimics whilst a propranolol MIP was investigated for its use as a rate attenuating selective excipient in a transdermal controlled release device. Preliminary studies concerning the preparation of a theophylline selective transcutaneous monitoring device, using a theophylline MIP, are also described.

Successful lysis of an obstructive aortic and renal artery thrombus in a neonate on extracorporeal membrane oxygenation.

We describe a neonate on venoarterial extracorporeal membrane oxygenation (ECMO) with acute renal failure associated with extensive aortic and bilateral renal artery thrombosis. Concurrent anticoagulation and continuous systemic thrombolytic therapy with tissue plasminogen activator (t-PA) resulted in complete thrombolysis as evaluated by Doppler flow. The relative risk and benefits of thrombolytic therapy in heparinized patients undergoing ECMO needs to be further studied.

Application of thin-layer chromatography in enantiomeric chiral analysis-an overview.

Several chiral drugs are produced and administered as pure enantiomers, whereas many others, especially of synthetic origin, are used mainly in the form of racemates. The biological and pharmacological activity of chiral compounds depends on their configuration. The racemic drugs may exhibit quite different activity from the optically pure drugs. Often only one of the enantiomers is pharmacologically active and/or even can be toxic. Since numerous enantiomers have been shown to behave differently from at least one point of view, whether pharmacokinetic, pharmacodynamic, toxicological or interaction, there seems to be hardly any exception to the general rule that a racemate cannot be considered as a single drug entity. A variety of chromatographic methods have been developed for optical resolution recently. Usually direct separation of the enantiomers is carried out on HPTLC chiral precoated plates or on plates impregnated with chiral substances. TLC techniques are a developing branch of separation and quantitation of drugs, both in pharmaceutical dosage forms and in biological material. This review presents an overview of the current successful enantioseparations of drugs by TLC and their potential in the analysis of the drug racemates.

In vitro dermal and transdermal delivery of doxycycline from ethanol/migliol 840 vehicles.

This work investigated the feasibility of dermal and transdermal delivery of doxycycline from vehicles containing Migliol 840 (M840) and ethanol. Delivery of the drug via the skin would provide a useful alternative to oral delivery, which has many undesirable side-effects, such as oesophageal ulceration and disturbance of the normal gut flora. Potential applications include malaria prophylaxis, and the treatment of acne vulgaris, Lyme disease and Reiter syndrome. Experiments were performed to determine the permeation of doxycycline across excised full-thickness human skin and heat-separated epidermal membranes from saturated solutions in ethanol, 1:1 and 2:1 ethanol/M840. Unusual burst behaviour was observed using an ethanol vehicle, possibly as a result of the formation of dimers at saturation. Doxycycline permeated to a higher degree from ethanolic vehicles when M840 is present, suggesting that M840 is capable of enhancing the permeation of doxycycline. The flux across full-thickness skin was highest from a 2:1 ethanol:M840 vehicle (2.41 microg cm(-2) h(-1)), sufficient to deliver 282 microg l(-1) using an area of application of 30 cm(2). The data also produced unexpected results in that permeability across heat separated skin was an order of magnitude greater than across full-thickness skin (28.75 microg cm(-2) h(-1) for the 2:1 ethanol:M840 vehicle). Depth profiling indicated that the drug distributed quite evenly throughout the epidermis. The mean amount of doxycycline recovered from the epidermis at the end of a permeation experiment was 458.4 microg ml(-1). This was far higher than the volume of extractable lipid present in the same unit area, approximately 52.3 microg ml(-1) and indicated that a large proportion of the drug must have been located within the proteinaceous domain. The data therefore suggest (1) significant amounts of doxycycline can be administered into and across the skin; (2) M840 is a potentially useful enhancing vehicle; and (3) the transcellular route was of significance.