Determination of R(+)- and S(–)-Lansoprazole Using Chiral Stationary-Phase Liquid Chromatography and Their Enantioselective Pharmacokinetics in Humans

Purpose. Stereoselective and sensitive methods employing chiral stationary phase columns for HPLC determination of enantiomers of lansoprazole in the human serum were developed and pharmacokinetic behaviors of the enantiomers were evaluated in seven subjects. Methods. Five chiral stationary phase columns: Chiralcel OD (cellulose tris(3,5-dimethyl-phenylcarbamate)), OF (cellulose tris(4-chloro-phenylcarbamate)), OG (cellulose tris(4-methylphenylcarbamate)) and OJ (cellulose tris(4-methylbenzoate)), and Chiralpak AS (amylose tris ((S)-1 -phenylethylcarbamate)) were investigated. Results. Chiralcel OD and Chiralpak AS columns gave a good resolution of R(+)- and S(–)-enantiomers from racemic lansoprazole, but Chiralcel OF, OG, and OJ did not. The mean C_max and the AUC values of R(+)-enantiomer were 3–5 times greater than those of S(–)-enantiomer following oral administration of 30 mg of racemic lansoprazole. The CL_tot values of R(+)-enantiomer were significantly smaller than those of S(–)-enantiomer. Binding of R(+)-enantiomer to human serum proteins was significantly greater than that of S(–)-enantiomer. The mean metabolic ratio (metabolites/parent compound) in human liver microsomes of S(–)-enantiomer was significantly greater than that of R(+)-enantiomer. Conclusions. The stereoselective pharmacokinetics of lansoprazole enantiomers is likely due to its Stereoselective protein binding and/ or metabolism.     

Stereoselective Systemic Disposition of Ibuprofen Enantiomers in the Dog

The pharmacokinetics of ibuprofen are complicated by the unidirectional metabolic inversion of the (–)-R- to ( + )-S-enantiomer. Chiral inversion is of therapeutic significance since the drugs pharmacologic activity has been shown to depend upon the ( + )-S-isomer. As a result, the present study was undertaken to determine if chiral inversion occurs systemically and to elucidate further the kinetics of the inversion process. Experiments were performed in the beagle dog after intravenous bolus injections of ibuprofen enantiomers separately [100 mg (–)-R, n = 4; 100 mg ( + )-S, n = 4] and as admixtures of varying proportions [100 mg (–)-R + 100 mg ( + )-S, n = 4; 100 mg (–)-R + 200 mg ( + )-S, n = 2]. Plasma samples of (–)-R-and ( + )-S-enantiomers were measured by a stereospecific HPLC assay after all drug administrations. Based on the area under the plasma concentration–time curves for ( + )-S after administration of each enantiomer alone, chiral inversion was 70 to 75%. A progressive reduction in total plasma clearance of (–)-R-ibuprofen is also observed as increasing amounts of ( + )-S-enantiomer are added to the system. The results demonstrate that chiral inversion occurs to a significant extent in the systemic circulation in dog and that R-to-S inversion of ibuprofen may be inhibited by its ( ( + )-S-enantiomer.     

Apparent Lack of Mrp1-Mediated Efflux at the Luminal Side of Mouse Blood-Brain Barrier Endothelial Cells

Purpose. The purpose of this work was to determine mrp1-mediated efflux across the luminal membrane of endothelial cells at the blood-brain barrier (BBB) in mice. Methods. The transport of radiolabeled etoposide, 17-estradiol-D-17-glucuronide (E₂17G), vincristine, and doxorubicin across the BBB of mrp1(–/–) and wild-type mice was evaluated by in situ brain perfusion. Etoposide transport was also determined in P-glycoprotein-deficient mdr1a(–/–) mice perfused with both etoposide and mrp1 inhibitors like probenecid or MK571. Cerebral vascular volume was determined by co-perfusion with labeled sucrose. Results. Sucrose perfusion indicated that the vascular space was close to normal in all the studies, indicating that the BBB remained intact. The transport of etoposide, E₂17G, vincristine, and doxorubicin into the brain was not affected by the lack of mrp1. Trans-efflux studies in mrp1-deficient mice with etoposide and E₂17G confirmed that mrp1 was not involved in the efflux of these substrates across the BBB. There was also a significant P-gp-mediated efflux of etoposide in studies with P-glycoprotein-deficient mdr1a(–/–) mice. Perfusion of mdr1a(–/–) mice etoposide plus probenecid or MK571 did not affect the brain transport of etoposide. Conclusion. Efflux mediated by mrp1 does not seem to occur across the luminal membrane of the endothelial cells forming the mouse BBB.     

Diketopiperazine Formation,Hydrolysis, and Epimerization of the New Dipeptide Angiotensin-Converting Enzyme Inhibitor RS-10085

The degradation kinetics, products, and mechanisms of RS-10085(1), 2-[2-(l-ethoxycarbonyl)-3-phenylpropyl]amino-l-oxopropyl]-6,7-dimethoxy-l,2,3,4-tetrahydroisoquinoline-3-carboxylic acid(S,S,S), in aqueous solution were investigated at 40, 60, and 80°C from pH 1 to pH 13. Pseudo-first-order kinetics were observed throughout the pH range studied and the log(rate)–pH profiles reflected four kinetic processes (k _o, k_o, k_o, and k _OH) as well as the two pKa's of 1. Excellent (>98%) mass balance was obtained through products 2–5. At pH 4 or below, intramolecular cyclization leading to diketopiperazine 5 accounted for greater than 93% of the observed neutral- or water-catalyzed processes (k _o and k_o). At pH levels greater than 5, hydrolysis giving 2 predominated and was responsible for the observed neutral- or water-catalyzed (k_o) and specific base-catalyzed (k _OH) kinetic processes. Some epimerization leading to the S,S,R drug isomer (4) was also observed at pH levels greater than 7. The relative acidity of the protons at the three chiral centers of 1 was qualitatively compared and was used to explain the observed specificity in epimerization.     

柱前衍生化RP-HPLC法分离苯乙醇胺类化合物对映体

目的以2,3,4,6-四-O-乙酰基-β-D-葡萄糖异硫氰酸酯(GITC)为手性衍生化试剂,建立苯乙醇胺类化合物对映体RP-HPLC分离分析方法。方法采用RP-HPLC法。考察了衍生化反应中碱化试剂和衍生化试剂的浓度等反应条件对衍生化产率的影响,并考察流动相的组成和pH值等因素对生成的非对映异构体分离的影响。讨论了化合物的分子结构对手性衍生化及衍生后的非对映异构体色谱分离的影响。结果在三乙胺和GITC的浓度分别为10和5 mmol.L-1的乙腈溶液中,室温下反应20 min后,有5个苯乙醇胺化合物转化成相应的非对映异构体的硫脲衍生物。在色谱条件为:Diamonsil C18色谱柱(150 mm×4.6 mm,5μm),30 mmol.L-1醋酸铵(pH6.0)-乙腈(体积比为50∶50)为流动相,检测波长254 nm,流速1.0 mL.min-1,室温下,5个苯乙醇胺化合物对映体衍生化后非对映异构体的分离度达到4以上。结论该方法可作为苯乙醇胺类化合物对映体分离的方法之一。     

The Measurement of Warfarin Enantiomers in Serum Using Coupled Achiral/Chiral,High-Performance Liquid Chromatography (HPLC)

An assay for the serum concentration of the enantiomers of warfarin, R-warfarin and S-warfarin, has been developed using a bovine serum albumin chiral stationary phase (BSA-CSP) coupled to a Pinkerton internal-surface reverse-phase (ISRP) achiral column. The ISRP column is used to separate R,S-warfarin from the serum components and warfarin metabolites and to quantitate the total R,S-warfarin concentration. The eluent containing R,S-warfarin is then selectively transferred to the BSA-CSP, where the enantiomers are stereochemically resolved ( = 1.19) and the enantiomeric composition is determined. This system is sensitive and accurate, does not require extensive precolumn manipulations, and can be automated for use in large-scale clinical studies.     

Measurement of Underivatized Propranolol Enantiomers in Serum Using a Cellulose –Tris(3,5 -Dimethylphenylcarbamate) High-Performance Liquid Chromatographic (HPLC) Chiral Stationary Phase

A commercially available high-performance liquid chromatographic (HPLC) chiral stationary phase (HPLC-CSP) has been used to measure serum levels of d- and l-propranolol. The HPLC-CSP is based upon cellulose–tris(3,5-dimethylcarbamate) and is able to stereochemically resolve d- and l-propranolol without precolumn derivatization using a mobile phase composed of hexane:2-propranol:N,N-dimethyloctylamine (92:8:0.01, v/v/v). Under these conditions the observed stereochemical resolution () of the two enantiomers was = 2.2. A subject's concentration–time curve of the two isomers was determined following the ingestion of 160 mg racemic propranolol.     

Effects of Hyperlipidemia on the Pharmacokinetics of Nifedipine in the Rat

Purpose. The effect of hyperlipidemia on nifedipine pharmacokinetics was studied. The mechanisms by which hyperlipidemia affects pharmacokinetics of drugs are mainly undetermined. Hyperlipidemia may decrease the fraction of unbound drug in plasma and/or decrease intrinsic ability of the cytochrome P-450 systems due to excess membrane cholesterol. Hyperlipidemia is a primary risk factor for coronary artery disease leading to hypertension and ischemic heart disease, for which nifedipine, a calcium channel blocker, is used. Methods. Poloxamer 407 (P407)-induced hyperlipidemic rat model was used to study the effects of hyperlipidemia on the pharmacokinetics of nifedipine (6 mg kg^–1 given iv, ip and po). Total plasma cholesterol levels increased from 0.82–2.02 to 5.27–11.05 mmol L^–1 48 h post P407 administration (Ig kg^–1, ip). Protein binding studies were conducted by an ultrafiltration method. Results. Hyperlipidemia significantly decreased CL_TB by 38% and CL_TB/F by 45 and 42% following po and ip doses, respectively, thereby increasing AUC_0–, C_max and half-life. Absolute bioavailability and Vd_ss remained unchanged. AUC_0– was affected to the same extent in each route of administration, therefore, the effect was mainly systemic rather than presystemic. Hyperlipidemia significantly lowered the fraction unbound in plasma by approximately 31%. Conclusions. The altered pharmacokinetics of nifedipine by P407-induced HYPERLIPIDEMIA may be, at least in part, due to the decrease in fraction unbound in plasma. A decrease in intrinsic clearance, however, cannot be ruled out.     

Stability of Prostacyclin Analogues: An Unusual Lack of Reactivity in Acid-Catalyzed Alkene Hydration

Prostacyclin analogue 5 undergoes specific acid-catalyzed hydration (k _H+ = 1.9 × 10^–7 M ^–l sec^–1 at 25°C) and a pH-independent oxidation reaction (k ₀ = 1.2 × 10^–10 sec^–1 at 25°C) above pH5. The hydration reaction for 5 is much slower than for other structurally similar exocyclic alkenes, even though the rate-determining step is proton transfer. This slowness of reaction and an analysis of the pH–rate profile show that 5 does not exhibit significant intramolecular general acid catalysis, as does prostacyclin.     

The Stereospecific Determination of Fluoxetine and Norfluoxetine Enantiomers in Human Plasma by High-Pressure Liquid Chromatography (HPLC) with Fluorescence Detection

A quantitative method for the simultaneous HPLC resolution and detection of the enantiomers of (R,S) fluoxetine (F) and their metabolites (R,S) norfluoxetine (N) in human plasma has been developed. F is a serotonin uptake inhibitor used in the treatment of depression and is administered as a racemate. After liquid–liquid extraction and derivatization with (R) napthyl ethyl isocyanate (NEI), the separation and detection of the resultant diasteriomers were achieved using normal phase HPLC and fluorescence. The four NEI diastereomers and the internal standard [(–)-N-methyl--(2-methylphenoxy) benzenepropanamine hydrochloride], representing the enantiomers S-F, R-F, S-N, and R-N were resolved within 15 min. The assay for each analyte was linear using two concentration ranges of 1–10 and 10–500 ng/ml of human plasma. The precision and accuracy are reported as the coefficient of variation (%CV) and relative error (%RE). The sum of the chiral HPLC results from plasma samples were compared to the achiral gas chromatographic/electron capture (GC/EC) results. The correlation between these two methods, for total F and N, resulted in r ² values of 0.98 and 0.89, respectively. The chiral HPLC method is currently being applied to clinical studies for the evaluation of the enantiomeric disposition of F.     

In Vitro and In Situ Permeability of a 'Second Generation' Hydroxypyridinone Oral Iron Chelator: Correlation with Physico-Chemical Properties and Oral Activity

Purpose. The in vitro and in situ transport of CGP 65015 ((+)-3-hydroxy-1-(2-hydroxyethyl) -2-hydroxyphenyl-methyl-1 H-pyridin-4-one), a novel oral iron chelator, is described. The predictive power of these data in assessing intestinal absorption in man is described. Methods. Caco-2 epithelial monolayer and in situ rat jejunum perfusion intestinal permeability models were utilized. In vivo iron excretion and preliminary animal pharmacokinetic experiments were described, lonization constants and octanol/aqueous partition coefficients were measured potentiometrically. Solubilities and intrinsic dissolution rates were determined using standard procedures. Results. Caco-2 cell (P_app 0.25 X 10^–6 cm.s^–1) and rat jejunum (P_w 0.4) permeabilities of CGP 65015 were determined. The log D(pH 7.4) of CGP 65015 was 0.58 and its aqueous solubility was > 0.5 mg.ml^–1 (pH 3–9). The intrinsic dissolution rate of CGP 65015 in USP simulated intestinal fluid was 0.012 mg.min^–1.cm^–2. CGP 65015 promotes iron excretion effectively and dose dependently in animals. Conclusions. Caco-2 and rat intestinal permeabilities predict incomplete oral absorption of CGP 65015 in man. Preliminary rat pharmacokinetics support this. Physico-chemical data are, also, in line and suggest that CGP 65015 may, in addition, be solubility/dissolution rate limited in vivo. Nevertheless, early animal pharmacological data demonstrate that CGP 65015 is a viable oral iron chelator candidate.     

The Effect of Cetylpyridinium Chloride (CPC) on the Cell Surface Hydrophobicity and Adherence of Candida albicansto Human Buccal Epithelial Cells in Vitro

Purpose. This study examined the effects of cetylpyridinium chloride (CPC) on cell surface hydrophobicity (CSH) and adherence of blastospores of Candida albicans(MEN strain) to human buccal epithelial cells (EEC) in vitro. Methods. The effect of CPC treatment of either C. albicans blastospores or BEC on their subsequent adherence was determined using ³⁵SO₄ labelled blastospores in association with a Percoll gradient. The effects of CPC treatment of blastospores on their CSH was determined using Hydrophobic Interaction Chromatography. Results. Treatment of exponential and stationary phase blastospores with CPC (50 µg mL^–1) for 0.5–30 minutes, or with CPC (0.5–50 µg mL^–1) for 15 minutes resulted in significant reductions in both blastospore CSH and adherence to BEC in vitro. No correlation was apparent (r < 0.8) between reduced CSH and reduced blastospore adherence following treatment with CPC (0.5–50 µg mL^–1). Significantly reduced adherence of C. albicans (stationary or exponential growth phases) to human EEC was also observed following treatment of BEC with CPC (50 µg mL^–1) for 0.5–30 minutes or with CPC (0.5–50 µg mL^–1) for 15 minutes. Antiadherence effects were observed at both sub and super-minimum inhibitory concentrations of CPC. Conclusions. It is suggested that, whilst the ability of CPC to reduce the CSH of C. albicans may contribute to its reduced adherence to human BEC in vitro, reduced CSH is only one of several possible factors that contribute to the observed antiadherence effects.     

Chiral Amines Derived from 2-Arylpropionic Acids: Novel Reagents for the Liquid Chromatographic (LC) Fluorescence Assay of Optically Active Carboxylic Acid Xenobiotics

For the enantiospecific analysis of optically active carboxylic acids, the availability of readily detectable coupling components is desirable, but highly fluorescent chiral amines are rare. From activated enantiomers of fluorescent 2-arylpropionic acids fluorescent chiral amines were synthesized via Curtius degradation, i.e., under formation of the acyl azide, the isocyanate, and finally, the amine. The formation of isocyanates and of amine hydrochlorides led to an inversion of the direction of rotation of polarized light. Amines derived from R- and S-flunoxaprofen, R- and S-naproxen, and R/S-benoxaprofen were characterized. The amines were found to be applicable for the chiral separation of carboxylic acids (such as 2-arylpropionic acids) as diastereomeric derivatives via high-performance liquid-chromatographic (normal and reversed-phase) and thin-layer chromatographic techniques.     

The 5-HT1A receptor selective ligands, (R)-8-OH-DPAT and (S)-UH-301, differentially affect the activity of midbrain dopamine neurons

Summary The effects of the selective 5-HT_1A receptor agonist (R)-8-hydroxy-2(di-n-propylamino)tetralin [(R)-8-OH-DPAT] and the novel 5-HT_1A antagonist (S)-5-fluoro-8-hydroxy-2-(dipropylamino)-tetralin [(S)-UH-301] were studied with regard to the firing pattern of single mesencephalic dopamine (DA) neurons with extracellular recording techniques in chloral hydrate anesthetized male rats. Neuronal activity was studied with respect to firing rate, burst firing and regularity of firing. In the ventral tegmental area (VTA) low doses of (R)-8-OH-DPAT (2–32 g/kg i.v.) caused an increase in all three parameters. The effect on firing rate of DA neurons was more pronounced in the parabrachial pigmentosus nucleus than in the paranigral nucleus, the two major subdivisions of VTA. In the substantia nigra zona compacta (SN-ZC), (R)-8-OH-DPAT (2–256 g/kg i.v.) had no effect on firing rate and regularity of firing and only slightly increased burst firing. High doses of (R)-8-OH-DPAT (512–1024 g/kg i.v.) decreased the activity of DA cells in both areas, an effect that was prevented by pretreatment with the selective DA D₂ receptor antagonist raclopride. (S)-UH-301 (100–800 g/kg i.v.) decreased both firing rate and burst firing without affecting regularity of DA neurons in the VTA. In the SN-ZC, (S)-UH-301 decreased the firing rate but failed to affect burst firing and regularity of firing. These effects of (S)-UH-301 were blocked by raclopride pretreatment. Local application by pneumatic ejection of 8-OH-DPAT excited the DA cells in both the VTA and the SN-ZC, whereas (S)-UH-301 inhibited these cells when given locally. These results show that 5-HT_1A receptor related compounds differentially affect the electrophysiological activity of central DA neurons. The DA receptor agonistic properties of these compound appear to contribute to the inhibitory effects of high doses of (R)-8-OH-DPAT and (S)-UH-301 on DA neuronal activity. Given the potential use of 5-HT_1A receptor selective compounds in the treatment of anxiety and depression their effects on central DA systems involved in mood regulation and reward related processes are of considerable importance.Correspondence to T. H. Svensson at the above address     

Stereoselective disposition of carvedilol in man after intravenous and oral administration of the racemic compound

The racemic compound carvedilol is a multiple-action oral antihypertensive drug that exhibits both vasodilator and non-selective beta-adrenergic blocking activities. The effects of the levorotatoryS-enantiomer [S( – )-CARV] are vasodilatation and beta-blockade. TheR (+)-enantiomer [R (+)-CARV] is a pure vasodilating agent. Quantitative determination of the enantiomers in human plasma by HPLC was carried out after formation of diastereoisomers with the chiral reagent 2,3,4,6-tetraO-acetyl--d-glucopyranosyl isothiocyanate (GITC). The pharmacokinetics of the enantiomers were studied following i. v. (12.5 mg in 1 h) and p. o. (50 mg) administration of racemic carvedilol in ten healthy male subjects according to a randomized crossover design. The AUCs ofS (–)-CARV were significantly lower than those ofR (+)-CARV after both i. v. and p. o. administration. The systemic clearance of the two enantiomers was significantly different, whereas half-lives and apparent distribution volumes were comparable. Following p. o. administration, the absolute bioavailability (31.1% and 15.1%, respectively) and maximal plasma concentrations ofR (+ )-CARV were twice those ofS (–)-CARV A similar difference was found in the half-lives. A close correlation existed between enantiomeric ratios after i.v. and after p. o. administration, demonstrating slight intraindividual variability. The preferential systemic clearance of theS ( – )-enantiomer suggests stereoselective hepatic metabolism of carvedilol, becoming especially apparent after p. o. administration. The small intrasubject variability in enantiomer ratios indicates a relatively constant relation of beta-blockade to vasodilation during chronic treatment.     

Reversed-phase liquid chromatographic separation of enantiomeric and diastereomeric bases related to chloramphenicol and thiamphenicol

The important antimicrobial agents chloramphenicol and thiamphenicol are N-acylated amines whose chemical structures include two chiral centers. Each drug is the single enantiomer of R,R configuration. The N-deacylated bases of the drugs are important intermediates in their synthesis and optical resolution. In this report, reversed-phase HPLC methods are described for the separation of enantiomeric and diastereomeric bases of the two drugs and of two closely related bases used in some syntheses of the drugs. The stereoisomeric bases were derivatized with a homochiral isothiocyanate and the resulting diastereomeric thioureas were separated on C18 columns with methanol:water mixtures as mobile phases and detection at 254 nm. The four stereoisomeric bases of chloramphenicol and those of its unnitrated analogue were thus separable after derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate. This reagent also allowed the separation of the D-threo isomer of the p-mercaptomethyl analogue of thiamphenicol base from its stereoisomers. The stereoisomers of thiamphenicol base were similarly separated with (R)-alpha-methylbenzyl isothiocyanate as the derivatizing agent. The diastereomers of chloramphenicol base and of thiamphenicol base were chromatographically separable after derivatization with the nonchiral reagent benzyl isothiocyanate. The procedures developed may be useful in the determination of the stereoisomeric composition of the drugs in research and in quality control, and may be applicable to other similar agents whose chemistry and pharmacology are receiving considerable attention.     

Biotransformation of Estradiol in the Human Keratinocyte Cell Line HaCaT: Metabolism Kinetics and the Inhibitory Effect of Ethanol

Purpose. The aim of our study was to investigate the kinetics of -estradiol (E₂) metabolism in the human keratinocyte cell line HaCaT and to estimate the effect of the potential inhibitor ethanol on the biotransformation reaction. Methods. The formation rates of estrone (E₁) in dependence on substrate concentrations were determined in HaCaT cells using tritium labelled E₂. Experiments were conducted with and without addition of dehydroepiandrosterone (DHEA) and ethanol. Possible toxic effects on the cells due to ethanol were investigated by cytotoxicity tests. Results. The metabolism of E₂ in HaCaT cells exhibited Michaelis-Menten kinetics with K_m and V_max values of 3.5 M and 216 pmol × mg^–1 protein × h^–1, respectively. The reaction was inhibited by DHEA and ethanol. The alcohol showed a reversible competitive inhibition mechanism for concentrations of 4 to 8% (v/v). Lower ethanol concentrations had no effect, whereas levels 10% significantly decreased cell viability leading to a different inhibition mechanism. Conclusions. The HaCaT cell line seems to be a suitable model for studying enzyme kinetics equivalent to the human skin. The concentration dependent inhibitory effect of ethanol observed in this cell line may be relevant for the transdermal E₂ application in patients.     

Snake F(ab′)2 Antivenom from Hyperimmunized Horse: Pharmacokinetics Following Intravenous and Intramuscular Administrations in Rabbits

Purpose. The pharmacokinetics of a currently available horse F(ab)₂ antivenoms to Vipera aspis, V. ammodytes, and V. berus (Ipser Europe) and a new more purified and pasteurized preparation (SAV) was investigated in the rabbit. Methods. An immunoradiometric assay using an affinity-purified goat IgG horse F(ab)₂ specific and the same IgG labelled with iodine 125 as a tracer was developed. The limit of quantification in plasma was 0.032 µg/ml. Specificity study showed that mouse F(ab)₂ and Fab did not cross-react. Results. Pharmacokinetic analysis showed that the plasma F(ab)₂ concentration followed a biexponential decline after intravenous bolus administration with distribution and elimination half-lives of 2.66 ± 0.18 hrs and 49.69 ± 4.13 hrs, respectively. The total volume of distribution (Vdss or Vd) was between 209 and 265 ml.kg^–1 and was similar to the volume of the extracellular fluid in the rabbit (300 ml.kg^–1). Total body clearance ranged from 3.33 to 3.96 ml. h^–1 · kg^–1. After intramuscular administration which was only investigated with SAV, Tmax was 48 hrs and the absolute bioavailability was 42%. Conclusions. No difference in pharmacokinetics was observed between the two antivenom preparations following the intravenous administration. In contrast, a reduced rate and extent of absorption was shown following intramuscular administration.     

Absorption of Sunscreens and Other Compounds Through Human Skin in Vivo: Derivation of a Method to Predict Maximum Fluxes

Purpose. The goal of this study was to quantify the transdermally absorbed amounts of the sunscreens octyl dimethyl p-aminobenzoic acid, oxybenzone, 4-isopropyl-dibenzoylmethane, 3-(4-methylben-zylidene)-camphor, isoamyl-4-methoxycinnamate, the repellent and plasticizer dibutyl phthalate, the antioxidant 3.5-di-t-butyl-4-hydroxyanisol, and the antimicrobial compounds butyl-4-hydroxybenzoate, biphenyl-2-ol, and 2,4,4-tri-chlor-2-hydroxydiphenylether (tri-closane). Permeabilities P _B and maximum fluxes J _max should be correlated with relevant physicochemical properties. Methods. Saturated solutions of the above-mentioned compounds in a propylene glycol/water mixture were applied to the skin using glass chambers which were fixed to the upper arms of volunteers. Maximum fluxes were calculated from concentration decreases in the vehicle. Results. A linear relationship between the logarithms of permeabilities P _B of the penetrants (0.02–0.28 cm h^–l) and the corresponding octanol/vehicle partition coefficients PC _Oct/v (166–186,208) was found. Consequently, the influence of aqueous boundary layers could be neglected. However, the slope of the resulting straight line of 0.38 is considerably smaller than unity indicating that PC _Oct/v does not represent the lipophilicity of the stratum corneum adequately. Maximum fluxes range from 0.5 to 130 µg cm^–2 h^–1. A general equation for the calculation of J _max was derived based on experimental data taking into account the PC _Oct/v and the solubilities c _sV of the respective penetrants in the vehicle.     

Neuropharmacological reassessment of the discriminative stimulus properties ofd-lysergic acid diethylamide (LSD)

The neuropharmacological mechanisms underlying the behavioral effects ofd-lysergic acid diethylamide (LSD) were assessed by comparing the discriminative stimulus properties of LSD with those of agonists and antagonists that act selectively at putative serotonin (5-hydroxytryptamine; 5-HT) receptor subtypes (5-HT₁ and 5-HT₂). Male Sprague-Dawley rats (N=23) were trained to discriminate LSD (0.08 mg/kg) from saline and given substitution tests with the following agents: 8-hydroxy-2(di-n-propylamino) tetralin (8-OHDPAT; 0.02–0.64 mg/kg), Ru 24969 (0.2–3.2 mg/kg),m-chlorophenylpiperazine (MCPP; 0.1–1.6 mg/kg), 1-(m-trifluoromethylphenyl)piperazine (TFMPP; 0.1–1.6 mg/kg), and quipazine (0.2–3.2 mg/kg). Only quipazine mimicked LSD. In combination tests, BC 105 (0.2–3.2 mg/kg), 2-bromolysergic acid diethylamide (BOL; 0.1–1.6 mg/kg), Ly 53857 (0.4–3.2 mg/kg), metergoline (0.05–0.8 mg/kg), ketanserin (0.2–3.2 mg/kg), and pipenperone (0.0025–0.08 mg/kg), all of which act as 5-HT₂ antagonists, blocked the LSD cue; only spiperone (0.02–0.32 mg/kg) was without effect. Although commonalities may exist among 5-HT agonists, the present results demonstrate that such agonists are not identical. Since putative 5-HT₁ agonists do not mimic LSD and the LSD cue is potently blocked by 5-HT₂ antagonists, it appears that 5-HT₂ neuronal systems are of greater importance than 5-HT₁ systems in mediating the discriminative stimulus and, perhaps, other effects of LSD.