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A series of novel dermal penetration enhancers, esters and amides of clofibric acid, was synthesized. The permeation parameters and skin retention of two steroids (hydrocortisone-21-acetate and betamethasone-17-valerate) in propylene glycol were studied with athymic nude mouse skin by in vitro diffusion cell techniques in the presence of the novel enhancer compounds. Isopropyl myristate, dimethyl lauramide, and 1-dodecylazacycloheptan-2-one (laurocapram, Azone) were used as control enhancers. The most satisfactory enhancement of both the ester and amide series was observed with clofibric acid octyl amide; coadministration increased skin retention of hydrocortisone acetate after 24 h by 3.5-fold and that of betamethasone valerate by 2.9-fold. Diffusion cell receptor concentrations increased 51.6- and 10.3-fold, respectively, during the same time period. However, the enhancer compound in this case was applied to the skin 1 h prior to each of the steroids. The amide analogues were more effective than the equivalent ester compounds of the same carbon chain length. The best enhancer compounds (2c, 3d, 3e, and 3f) were nonirritating to athymic mouse skin in vivo.

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Synopsis A series of clofibric acid amides has been synthesized and previously reported by the authors as possessing enhancer activity in vitro in athymic nude mouse skin against model drugs, hydrocortisone-21-acetate and beta-methasone-17-valerate. An assay was required for each of these enhancers however, which would be specific for each compound and would also separate model drugs and their metabolite peaks. This study reports reverse phase high performance liquid chromatography assays for clofibric acid amide and seven derivatives (Ia-Ig). All enhancers showed maximum absorption at 232 nm, betamethasone (BM) and its valerate (BMV) at 238 nm, and hydrocortisone (HC) and its acetate (HCA) at 242 nm. Practical units of detection for the amides were 0.46-2.8 mug ml(-1) and peaks were sharp and well-separated from steroid peaks in three vehicles - methanol alone. Franz diffusion cell receptor phase samples (isotonic phosphate buffer), and full-thickness athymic nude mouse skin extracts in methanol. Mobile phases consisted of various proportions of acetonitrile and water, some with 2-propanol. The octyl amide for example, with mobile phase CH(3)CN: H(2)O (85:15) at 1 ml min(-1) had a retention time (t(R)) of 7.9 mins. Under the same conditions, retention times for the steroids were HC, t(R)= 3.3 mins; HCA, t(R)= 4.3 mins; BM, t(R)= 3.4 mins; BMV, t(R)= 4.6 mins. Résumé Les auteurs avaient démontré dans un article précédent le pouvoir accélérateur de pénétration dermique in vitro d'une gamme d'amides d'acide clofibrique sur la peau de souris sans poils, et sans thymus avec des médicaments types tels que l'acetate 21 d'hydrocortisone et le valerate 17 de beta-metasone. Il a cependant été requis, pour chacun de ces accélérateurs, un test spécifique pour chaque composition, permettant de séparer chaque médicament et les pics des métabolites. Cette étude décrit des tests par chromatographie liquide à haute performance en phase inverse pour l'acide chlofibrique et 7 dérivés (Ia-Ig). Tous les accélérateurs ont montré une absorption maximale à 232 nm, la beta-metasone (BM) et son valerate (BMV) à 238 nm, l'hydrocortisone (HC) et son acetate (HCA) à 242 nm. Les unités de détection s'élevaient à 0.46-2.8 mug ml(-1) pour les amides et les pics étaient aigus et distincts des pics stéroïdes et se composaient de 3 véhicules - le méthanol seul, des échantillons du récepteur de cellule de diffusion Franz (tampon du phosphate isotonique) et des extraits de peau de souris sans thymus dans du méthanol. Les phases mobiles étaient constituées de différentes proportions d'acetonitrile et d'eau, certaines avec du propanol-2. L'amide octyl par exemple, avec une phase mobile CH(3)CN: H(2)O (85:15) à 1 ml min(-1) avait un temps de rétention (t(R)) de 7.9 min. Dans des conditions identiques, les temps de rétention pour les stéroïdes étaient les suivants: pour HC, t(R)= 3.3 mins; pour HCA, t(R)= 4.3 mins; pour BM: t(R)= 3.4 mins; pour BMV: t(R)= 4.6 mins.

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Specific, sensitive, reverse-phase high-performance liquid chromatographic (HPLC) assays of 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) have been devised with analytical sensitivities as low as 2.7 ng/ml of plasma for MDMA and 1.6 ng/ml for MDA, using spectrophotometric detection at 280 nm. The assays were used to determine some properties of MDMA and MDA. Both drugs were stable in aqueous 1 M HCl, and 1 M NaOH solutions at room temperature. The half-life for MDMA was 6.6 h and for MDA was 7.1 h under the extreme conditions of 90 degrees C and 6 M HCl. MDMA and MDA were highly stable for 28 h in plasma at 25 degrees and 39 degrees C. The concentrations of the drugs were unchanged in frozen plasma after 47 days. The apparent red blood cell-plasma partition coefficient determined from assayed concentrations of the drugs in plasma and erythrocytes was 1.45 for both MDMA and MDA. An equation is presented to correct drug concentration in erythrocytes for the trapped equilibrated plasma/buffer in the packed red blood cells. The fraction of MDMA and MDA bound to dog plasma proteins was determined by several methods and it is 0.34-0.40 for both drugs. The extent of protein binding was independent of the drugs' concentration.

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Specific, sensitive, reverse-phase high-performance liquid chromatographic (HPLC) assays of cocaine (I) and its hydrolysis products, benzoylecgonine (II) and benzoic acid (III), have been devised with analytical sensitivities as low as 15 ng/ml of plasma for I using spectrophotometric detection at 232 nm. Cocaine can be separated from its hydrolysis products by extraction at pH 7.5 with haloalkanes. Benzoylecgonine and benzoic acid can be extracted at pH 3.0 with 1-butanol. The evaporated residues were reconstituted in acetonitrile-water for HPLC assay. The assay was used to determine the stabilities of I and II in aqueous solutions, to establish log k-pH profiles at various temperatures, and to evaluate Arrhenius' parameters. Hydrolyses were by specific acid-base catalysis. Cocaine showed hydrogen and hydroxyl ion attack on protonated I with 40 and 90% proceeding through the benzoylecgonine route, respectively, as well as hydroxyl ion attack on neutral cocaine, with only 6% proceeding through the benzoylecgonine route. Cocaine is relatively unstable in the neutral pH range with a half-life of 5 hr in buffer at pH 7.25 and 40 degrees. Similar half-lives were observed in fresh dog plasma at 300 and 30 micrograms/ml, although one study at 0.5 microgram/ml indicated a doubling of the rate.

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