An in vivo confocal Raman spectroscopic investigation of salicylic acid penetration: Variation with formulation parameters.

Salicylic acid (SA) is widely used in leave-on antiacne formulations, typically at a 2% level. As a ß-hydroxy acid, it is a milder active ingredient than either α-hydroxy acids or benzoyl peroxide. SA is a keratolytic agent, a bacteriocide, and a comedolytic agent. For these reasons, improving the efficiency of SA delivery is of interest. The objective of this work is to measure in vivo SA penetration from topically applied 2% SA leave-on products and to understand the penetration in terms of formulation parameters. Penetration of SA was measured in three depth zones-0-3 µm, 3-6 µm, and 6-9 µm below the surface-using in vivo confocal Raman spectroscopy. The delivery of SA from an emulsion, pH 4.0, and a hydrogel, pH 3.75, was compared and contrasted. A comparison of depth profiles reveals, e.g., significant differences in SA distribution between-treatment profiles at various time points after treatment, particularly 3℃6 µm below the surface. The hydrogel exhibited the higher normalized level of SA in the 3-6 µm depth zone. Confocal in vivo Raman spectroscopy is proving to be a valuable tool in determination of details of penetration of products into the skin. The penetration of various 2% SA anti-acne product forms will be compared and contrasted in this presentation. Delivery of SA will be discussed in terms of formulation parameters such as phase, pH, and specific ingredients and molecular-level interactions.

Liquen plano en cavidad oral: reporte de un caso clínico y revisión de la literatura / Oral lichen planus: a clinical case report and literature review

El liquen plano oral (LP) es una enfermedad mucocutánea crónica, de carácter inflamatorio, etiología desconocida y naturaleza autoinmune, en la que se produce una agresión por parte de los linfocitos T dirigida frente a las células basales del epitelio de la mucosa oral. Clínicamente se manifiesta como formas reticulares o atrófico-erosivas y potencialmente puede afectar a la piel y mucosas, siendo frecuente que las lesiones bucales precedan a las cutáneas o que sea única la localización intraoral. El diagnóstico del LPO debe basarse en la observación clínica y confirmarse con la descripción de las características histopatológicas. Hay una serie de criterios clínicos e histopatológicos importantes para sentar el diagnóstico de una manera concluyente. La etiopatogenia es desconocida, aunque hay suficientes datos que permiten suponer que los mecanismos inmunológicos son fundamentales en la iniciación y perpetuación del proceso. Hoy día se acepta que el LPO representa una respuesta inmune mediada por células en la que existe una interacción linfocito-epitelio dirigida contra antígenos de los queratinocitos basales del epitelio que culmina con la degeneración del estrato basal del epitelio. Se presenta caso clínico de paciente femenino de36 años de edad que acudió a consulta odontológica en la Facultad de Odontología de la Universidad de Cartagena por presentar descamaciones ubicadas en encía vestibular zona de de antero superiores de varios meses de evolución, sintomática. La paciente manifiesta episodios de stress constante en los últimos meses. Se le realizó biopsia incisional y se envió a patología donde se confirmó el diagnóstico de Liquen Plano

Oral lichen Planus (LP) is a chronic mucocutaneous disease, an inflammatory autoimmune nature and unknown etiology, which produces an aggression directed against T lymphocyte cells of the basal epithelium of the oral mucosa. Clinically it shows reticular or atrophic-erosive forms and can potentially affect the skin and mucous membranes, where oral lesions often precede the skin or intraoral location is unique. The diagnosis of OLP should be based on clinical observation and confirmed with the description of the histopathological changes. There are an important number of clinical and histopathological criteria important to establish the diagnosis of a conclusive manner. The pathogenesis is unknown, although there are sufficient data suggesting that immunological mechanisms are essential in the initiation and perpetuation of the process. Today it is accepted that the LPO is a cell-mediated immune response in which there is a lymphocyte interaction directed against epithelial antigens of the basal keratinocytes of the epithelium leading to the degeneration of the basal layer of the epithelium. We present clinical the case of a 36 years old female patient who visited the Dental School of Dentistry, University of Cartagena for showing a descamative lesion in the upper vestibular gingival, located in the anterior area with several months of development, with no symptoms, as.the patient referred, In addition, the patient commented to be under stressfull episodes in the latest months. Incisional biopsy was performed and sent to pathology which confirmed the diagnosis of lichen planus

An isocratic reversed-phase high-performance liquid chromatographic method for the simultaneous determination of benzoyl peroxide and the related compounds benzoic acid, benzaldehyde, ethyl benzoate, methylparaben, and propylparaben in dermal preparations.

A reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of benzoyl peroxide and the related compounds benzoic acid (BA), methylparaben, benzaldehyde, propylparaben, and ethyl benzoate. The compounds are separated on a column containing octadecyl silane chemically bonded to porous silica particles. The mobile phase is acetonitrile-buffer (45 + 55, v/v). Solutions are injected into the chromatographic system under isocratic conditions at a constant flow rate of 1.5 mL/min with UV detection at 235 nm. Analysis of stability samples showed rapid accumulation of BA by thermal degradation. A rationale has been established for the acceptable limit of BA in the formulation, which already contains BA (0.2%) as a preservative. The proposed method is efficient and determines the active compound and 5 related compounds in a run time of 20 min. The method was validated according to the guidelines of the International Conference on Harmonization and demonstrated good agreement with the validation requirements.

Influence of particle size on the quantitative determination of salicylic acid in a pharmaceutical ointment using FT-Raman spectroscopy.

A second order polynomial calibration model was developed and statistically validated for the direct and non-destructive quantitative analysis - without sample preparation - of the active pharmaceutical ingredient (API) salicylic acid in a pharmaceutical ointment using FT-Raman spectroscopy. The calibration curve was modeled by plotting the peak intensity of the vector normalized spectral band between 757 and 784cm(-1) against the known salicylic acid concentrations in standards. At this band, no spectral interferences from the ointment vehiculum (white vaseline) are observed. For the validation of the polynomial model, its fit and its predictive properties were evaluated. The validated model was used for the quantification of 25 ointments, compounded by different retail pharmacists. The same standards and samples were used, both for development and validation of a regression model and for quantitative determination by HPLC - with sample preparation - as described for the related substances of salicylic acid in the Ph. Eur. IV. The quantification results obtained by the FT-Raman method corresponded with the HPLC results (p=0.22), provided that the particle size of salicylic acid in the standards is the same as in the analyzed samples. The non-destructive FT-Raman method is a reliable alternative for the destructive HPLC method, as it is faster and does not require sample pre-treatment procedures.

A rapid HPLC method for simultaneous determination of tretinoin and isotretinoin in dermatological formulations.

A rapid method using an isocratic high-pressure liquid chromatography and UV detection for determination of both all-trans retinoic acid (tretinoin) and 13-cis retinoic acid (isotretinoin) in dermatological preparations is presented. Tretinoin and isotretinoin samples were extracted with acetonitrile by a procedure that can be completed in less than 10 min. Subsequent separation and quantification of amounts as low as 10 pmol was accomplished in less than 15 min using reversed-phase HPLC with isocratic elution with 0.01% trifluoroacetic acid (TFA)/acetonitrile (15:85, v/v). Validation experiments confirmed the precision and accuracy of the method. When applied to commercial tretinoin samples, recoveries of 104.9% for cream formulations and 107.7% for gel formulations were obtained. Application of the method for analysis of a tretinoin cream exposed to solar simulated light (SSL) demonstrated detection of the major photoisomerization product isotretinoin as well as 9-cis retinoic acid, demonstrating the utility of the method for studies of tretinoin photostability. The method should also facilitate studies of the formulation compatibility and photocompatibility of tretinoin with agents that may improve its clinical tolerability.

The effect of simulated solar UV irradiation on tretinoin in tretinoin gel microsphere 0.1% and tretinoin gel 0.025%.

Topical tretinoin is highly effective and widely used in the treatment of acne vulgaris. Tretinoin gel microsphere 0.1% (TGM)--alone or in combination with erythromycin-benzoyl peroxide (EBP) or clindamycin-benzoyl peroxide (CBP) topical gels-and tretinoin gel 0.025% (TG)--alone or, combined with EBP-were exposed to simulated solar UV irradiation to determine the degree of tretinoin photodegradation/isomerization. The investigation revealed that 94% and 84% of the initial tretinoin in the TGM formulation remained stable after 2 and 6 hours, respectively, of simulated solar UV irradiation. When combined with EBP topical gel, 89% and 81% of the initial tretinoin remained stable after 2 and 6 hours, respectively, of exposure to simulated solar UV irradiation; 86% and 80% of the tretinoin remained stable after 2 and 6 hours, respectively, when combined with CBP topical gel. In contrast, only 19% and 10% of the tretinoin remained unchanged after 2 and 6 hours, respectively, of simulated solar UV irradiation of TG. Combined with the EBP topical gel, undegraded tretinoin quantities were further reduced to 7% and 0% at 2 and 6 hours, respectively, with TG. These data suggest that the TGM formulation offers marked protection against tretinoin photodegradation compared with TG, even in the presence of a topical gel containing a potent antibiotic or a strong oxidizing agent. Although simulated solar UV irradiation is not entirely reflective of actual conditions, the results appear to be substantial.

Development of a gas chromatography method for the determination of isotretinoin and its degradation products in pharmaceuticals.

This paper describes the development of a gas chromatography (GC) method used for the assay of isotretinoin in its isolated form and in pharmaceutical formulations. Isotretinoin soft and hard gelatin capsules were prepared with various excipients. The performance of the proposed gas chromatography method was compared to that of traditional high performance liquid chromatography (HPLC) systems for this substance, and the GC parameters were established based on several preliminary tests, including thermal analysis of isotretinoin. Results showed that gas chromatography-flame ionization detector (GC-FID) exhibited a separation efficiency superior to that of HPLC, particularly for separating isotretinoin degradation products. This method was proven to be effectively applicable to stability evaluation assays of isotretinoin and isotretinoin based pharmaceuticals.

A simple rapid method of sample preparation for LC analysis of retinoyl beta-glucuronide and retinoic acid in water-based creams.

A simple method of sample preparation for LC analysis of retinoic acid (RA) and retinoyl beta-glucuronide (RAG) in creams has been developed. Water-based cream of all trans-RAG, devoid of side effects but efficacious in the treatment of acne vulgaris, was found to be hydrolyzed to RA in a temperature dependant manner. The potential benefits of water-based RAG cream stored at room temperature for the treatment of acne and wrinkle is discussed.

Investigation on the photostability of a tretinoin lotion and stabilization with additives.

Tretinoin, a drug that is used in topical preparations for the treatment of acne vulgaris, is known to be very susceptible to degradation under daylight. The objective of this work was to investigate the degradation of a tretinoin lotion placed in front of a xenon lamp. Analysis was performed with HPLC. The tretinoin lotion was degraded to about 20% of its initial concentration within 30 min. Incorporation of tretinoin in beta-cyclodextrin or in some surfactants (Brij(R)s) did not have any effect on the photodegradation of tretinoin. Neither could a UV-B sunscreen retard the photodegradation of tretinoin while a UV-A sunscreen had very little effect. Irradiation with selected wavelengths revealed that 420 nm seemed to be the most harmful wavelength for the degradation of tretinoin and not the wavelength of maximum absorption (350 nm) as expected. Then the addition of the yellow colourants chrysoin and fast yellow, absorbing in the region of 420 nm, was tested. These colourants did indeed retard the photo-degradation of tretinoin more or less depending on the concentration of the dye. Finally we only had to select a concentration that was still effective but that did not colour the skin.

Comparative anti-dandruff efficacy between a tar and a non-tar shampoo.

A randomized double-blind clinical study was conducted on two groups of 30 volunteers using either a non-tar shampoo (2% salicylic acid, 0.75% piroctone olamine and 0.5% elubiol) or a 0.5% coal tar shampoo. Subjects were diagnosed as having moderate to marked dandruff. The study consisted of a 3-week washout, followed by a 4-week treatment and a 4-week posttreatment regression phase. The clinical evaluations and subject self-assessments showed that the non-tar shampoo was as effective as the tar shampoo. Both received high approval ratings (> or =70%). Biometrological methods proved to be more sensitive than clinical evaluations to assess the efficacy of the shampoos. The non-tar shampoo yielded a significantly better reduction of Malassezia spp. counts (p<0.02) during the treatment phase and reduced the spontaneous increase in squamometry values (p< 0.01) during the posttreatment phase. It is concluded that a formulation associating salicylic acid, piroctone olamine and elubiol exhibited increased beneficial effects compared to the coal tar shampoo.

Investigation of the chemical stability of an erythromycin-tretinoin lotion by the use of an optimization system.

A combination of 2% erythromycin and 0.05% tretinoin in an alcohol-isopropanol lotion was prepared. Two parameters were investigated for their influence on the stability of erythromycin and/or tretinoin, namely pH and the concentration of butylhydroxytoluene (BHT) as antioxidant. To investigate these two parameters, an optimization technique was used with two factors (pH and concentration of BHT) at two levels. Accelerated stability analysis was performed at 45 degrees C in the dark to exclude isomerization of tretinoin. To analyse erythromycin and tretinoin in the combination preparation, a TLC method, previously developed in the laboratory, was used. The degradation of erythromycin seemed to be much faster than the tretinoin degradation. Optimal stability is shown in the pH range of 8.2-8.6 for erythromycin and 7.2-8.2 for tretinoin while the concentration of BHT had no significant influence.

In vivo microdialysis for the investigation of drug levels in the dermis and the effect of barrier perturbation on cutaneous drug penetration. Studies in hairless rats and human subjects.

The thesis opens with review chapters concerning theoretical and practical aspects of the investigation of drug contents in the skin. A discussion of the advantages and limitations of the established methods as well as the relatively new sampling method of microdialysis, which is employed in the experimental section, is given. Factors influencing the barrier function of the normal human skin are described as are the alterations in skin barrier function found in diseased and experimentally barrier perturbed skin. The microdialysis technique consists of introducing an ultra thin, semipermeable tube, a so-called probe, in the dermis. The tube is connected to a precision pump, which provides a steady flow of a tissue-compatible fluid through the probe at a very low flow. Smaller molecules in the tissue, among them the non-protein bound fraction of the drug content in the extracellular fluid, will passively diffuse across the surface of the membrane and thus enter the flow of the perfusate, which is sampled at regular intervals and analysed. Microdialysis is used for the determination of drug levels in the skin after topical as well as systemic drug delivery in the experimental part of the thesis. The method is not applicable to the investigation of all drugs or compounds, as we have shown that it is not feasible to sample highly protein-bound drugs or very lipophilic drugs by microdialysis without further development of the method. The investigation of topical drug administration consists of 2 studies of cutaneous penetration of a model drug, salicylic acid, initially investigated in hairless rats and subsequently in human volunteers. In both studies, barrier perturbation of the skin was undertaken by physical (removal of the stratum corneum by repeated tape stripping) or chemical (treatment with acetone) methods or by provocation of irritative dermatitis (by application of sodium lauryl sulphate, a detergent). Prior to the penetration experiment, the barrier damage inflicted was quantified by non-invasive measurements of transepidermal, water loss and erythema. The penetration of salicylic acid, applied in an ethanol solution in chambers glued to the skin in the barrier perturbed areas, was measured by microdialysis sampling of the drug level in the underlying dermis. At the end of the experiment, probe depth in the dermis and skin thickness were measured by ultrasound scanning. In humans and hairless rats alike, the cutaneous drug penetration was highly increased in tape stripped skin (157- and 170-fold increased, respectively, in comparison to the penetration in unmodified skin) and in skin with irritative dermatitis (46- and 80-fold increased). Delipidization by acetone led to a doubling of the penetration in humans but had no effect on penetration in hairless rats. In both studies a close correlation between the measurements of barrier perturbation by non-invasive methods and the cutaneous drug penetration in the same area was found. In the human study, the barrier perturbation in the acetone treated area was not measurable by non-invasive methods, whereas drug penetration, measured by microdialysis sampling, was significantly increased, indicating that the microdialysis method possesses high sensitivity in the detection and quantification of perturbed skin barrier function. In the human study, a dose-response relationship between the concentration of detergent used for the induction of irritant dermatitis and the ensuing increase in drug penetration across the skin could be demonstrated. In the hairless rat study a correlation between probe depth in the dermis and drug penetration was found, demonstrating that the more superficially a probe was placed, the earlier it would be reached by the influx of drug across the skin. Systemic drug distribution was studied in healthy volunteers following oral administration of 2 g acetylsalicylic acid. (ABSTRACT TRUNCATED)

Densitometric thin layer chromatographic analysis of tretinoin and erythromycin in lotions for topical use in acne treatment.

A TLC-method was developed to analyse tretinoin and erythromycin in a lotion in the presence of several excipients. Erythromycin was separated on a silica gel plate and a mobile phase with dichloromethane, methanol and ammonia 25% (60:6:1 (v/v/v)), tretinoin on a C(18) RP plate with acetonitrile and water (50:25 (v/v)) as mobile phase, adding 1 ml acetic acid for the separation of the excipients and erythromycin. The derivatization for both was done with a dipping reagent, consisting of anisaldehyde, sulphuric acid and acetic acid (respectively 1, 2 and 10% (v/v/v)) and dissolved in chloroform/alcohol 94% v/v (60:30 (v/v)) for erythromycin and alcohol 94%/water (50:40 (v/v)) for tretinoin. These TLC-systems were quantitatively evaluated in terms of stability of the colour, precision, accuracy and calibration, proving the utility in the analysis of the lotion.

[The stability of all-trans retinoic acid in "retinoid solutions" of "Di Bella's Cure"]. / Stabilità dell'acido all-trans retinoico nella "soluzione ai retinoidi" della "cura Di Bella".

Recently all-trans retinoic acid, an oxidation product of retinol, has become famous, since it is a component of "retinoids solution" of "Di Bella's therapy". Since all-trans retinoic acid is rapidly destroyed in the presence of light and oxidants, we verified its stability in samples of "retinoids solution" stored in conditions believed optimal (under stream of nitrogen) and we compare the obtained results with those observed in other "retinoids solution" samples daily open and close again, simulating the intake from the patient. All samples showed a decrease of all-trans retinoic acid recovery at the end of the study, with a more rapid decline in samples daily open. From our observations, we decided to indicate an expiration date of one months from the date of "solution" preparation. The patient's manipulation brings out a change in the final composition of "retinoids solution".

Clinical pharmacokinetics of tretinoin.

Recent reports of the dramatic antitumour effect of tretinoin (all-trans retinoic acid) in patients with acute promyelocytic leukaemia (APL) have generated a great deal of interest in the use of this drug as a chemopreventive and therapeutic agent. However, the biological efficacy of tretinoin is greatly impaired by (presumably) an induced hypercatabolism of the drug leading to reduced tretinoin sensitivity and resistance. Several pharmacokinetic studies have shown that plasma drug exposure [as measured by the plasma area under the concentration-time curve (AUC infinity)] declines substantially and rapidly when the drug is administered in a long term daily tretinoin regimen. These observations led to the hypothesis that the rapid development of acquired clinical resistance to tretinoin may have a pharmacological basis and result from an inability to present an effective drug concentration to the leukaemic cells during continuous treatment. The principal mechanisms proposed to explain the increased disappearance of tretinoin from plasma include: (i) decreased intestinal absorption; (ii) enhanced enzymatic catabolism; and (iii) the induction of cytoplasmic retinoic acid binding proteins (CRABP), which leads to increased drug sequestration. The most favoured explanation is that continuous tretinoin treatment acts to induce drug catabolism by cytochrome P450 (CYP) enzymes. Several strategies aimed at preventing or overcoming induced tretinoin resistance have been, and are being, planned. These strategies include intermittent dose administration, administration of pharmacological inhibitors of CYP oxidative enzymes, combination with interferon-alpha and intravenous administration of liposome-encapsulated tretinoin. As these strategies are now under investigation and the number of patients enrolled is small, further studies are needed to determine the efficacy and toxicity of these new schedules of drug administration. In this article we provide an overview of the relevant aspects of tretinoin physiology and pharmacokinetics, and summarise the current status of knowledge to help in the better optimisation of tretinoin administration.