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At least 307 records · Page 17Linked to original sources
PubMed1990

Topical ultraviolet light-absorbing chromophore protects against experimental photokeratitis.

Ultraviolet radiation may play a causative role in a number of human ocular and dermatologic conditions; reduction of environmental UV light exposure may decrease their incidence. We investigated the effects of two different UV light-absorbing chromophores, octyl methoxycinnamate (Parsol-MCX) and butyl methoxydibenzoylmethane (Parsol-1798) on corneal UV light transmittance, and evaluated topically applied Parsol-MCX for its protective effect against experimental UV light-induced keratitis in New Zealand white rabbits. Both Parsol-1789 (UV-A light absorber) and Parsol-MCX (UV-B light absorber) are well tolerated by New Zealand white rabbit eyes. Pretreatment with a single drop of Parsol-MCX reproducibly protected against UV light-induced keratitis, apparently by absorbing greater than 75% of UV-B (peak wavelength, 308 nm) irradiation.

Administration, Topical↗
PubMed1988

Bupropion in depression. I. Biochemical effects and clinical response.

We studied the biochemical effects of bupropion hydrochloride, a unicyclic antidepressant, in 11 depressed patients. Plasma homovanillic acid level increased significantly in patients who had poor responses to treatment but not in patients who obtained good clinical responses. Although bupropion is characterized preclinically as a weak dopamine reuptake inhibitor without appreciable effects on norepinephrine (NE) reuptake, it reduced whole-body NE turnover without altering plasma NE levels at rest and following orthostatic challenge. There was a trend toward a reduction in cerebrospinal fluid 3-methoxy-4-hydroxyphenylglycol and homovanillic acid concentrations following bupropion treatment, although these changes did not achieve statistical significance. Reduction in whole-body NE turnover has now been described for six disparate antidepressant treatments. Poor clinical outcome following treatment with bupropion may be related to perturbations in dopaminergic systems.

Adult↗
PubMed1988

Bupropion in depression. II. The role of metabolites in clinical outcome.

We studied the steady-state pharmacokinetics of bupropion hydrochloride, a unicyclic aminoketone antidepressant, in depressed patients. The metabolites hydroxybupropion (HB), threohydrobupropion, and erythrohydrobupropion predominated over the parent compound in plasma and cerebrospinal fluid at steady state. Plasma concentrations of each metabolite correlated with cerebrospinal fluid concentrations. Higher plasma metabolite concentrations were associated with poor clinical outcome. This relationship was most striking with HB; plasma HB levels were greater than 1250 ng/mL in all five nonresponders and less than 1200 ng/mL in all seven responders. Plasma HB levels correlated with postreatment plasma homovanillic acid levels. High levels of bupropion metabolites may be associated with poor clinical outcome due to toxic effects involving dopaminergic systems. Alternatively, a curvilinear dose-response relationship may exist for bupropion metabolites. Future studies should explore the clinical utility of plasma metabolite measurements in enhancing the efficacy of treatment with bupropion.

Adult↗
PubMed1988

Antidepressants reduce whole-body norepinephrine turnover while enhancing 6-hydroxymelatonin output.

The effects of antidepressant treatment on noradrenergic function were studied in 27 patients with a major affective disorder. Twenty-four-hour urinary excretion of 6-hydroxymelatonin and "whole-body norepinephrine (NE) turnover," ie, 24-hour urinary output of NE and its major metabolites 3-methoxy-4-hydroxyphenylglycol, vanillylmandelic acid, and normetanephrine, were measured before and after treatment with the tricyclic desipramine hydrochloride, the aminoketone bupropion hydrochloride, the nonselective monoamine oxidase (MAO) inhibitor tranylcypromine sulfate, and the specific MAO type A inhibitor clorgiline. 6-Hydroxymelatonin excretion increased following antidepressant treatment, while at the same time whole-body NE turnover was reduced. These findings support the hypothesis that antidepressant therapy increases noradrenergic "efficiency," in that functional output, as measured by 6-hydroxymelatonin, is maintained while total NE production is decreased.

Adult↗
PubMedDate not supplied

Determination of the new MDR-modifier PFP 6 and its metabolites in human liver microsomes by high-performance liquid chromatography.

A specific and sensitive method for the determination of PFP 6, a new compound for reverting multidrug resistance, and its two main metabolites in human liver microsomes has been developed. Samples were almost quantitatively isolated by solid phase extraction and further analysed by HPLC. Separation was achieved on an endcapped reversed phase C-18 column with triethylamine as an organic modifier in the mobile phase. The method exhibits high recovery and a good sensitivity for analyses of small sample volumes. The application of the method for screening the metabolism of this new drug in human liver microsomes is presented.

Anti-Arrhythmia Agents↗
PubMed2000

Relationship between the crystallization rates of amorphous nifedipine, phenobarbital, and flopropione, and their molecular mobility as measured by their enthalpy relaxation and (1)H NMR relaxation times.

Isothermal crystallization of amorphous nifedipine, phenobarbital, and flopropione was studied at temperatures above and below their glass transition temperatures (T(g)). A sharp decrease in the crystallization rate with decreasing temperature was observed for phenobarbital and flopropione, such that no crystallization was observed at temperatures 20-30 degrees C lower than their T(g) within ordinary experimental time periods. In contrast, the crystallization rate of nifedipine decreased moderately with decreasing temperature, and considerable crystallization was observed at 40 degrees C below its T(g) within 4 months. The molecular mobility of these amorphous drugs was assessed by enthalpy relaxation and (1)H-NMR relaxation measurements. The enthalpy relaxation time of nifedipine was smaller than that of phenobarbital or flopropinone at the same T - T(g) values, suggesting higher molecular mobility of nifedipine. The spin-lattice relaxation time in the rotating frame (T(1rho)) decreased markedly at temperature above T(g). The slope of the Arrhenius type plot of the T(1rho) for nifedipine protons changed at about 10 degrees C below the T(g), whereas the slope for phenobarbital protons became discontinuous at about 10 degrees C above the T(g). Even at temperatures below its T(g), the spin-spin relaxation process of nifedipine could be described by the sum of its Gaussian relaxation, which is characteristic of solid protons, and its Lorentzian relaxation, which is characteristic of protons with higher mobility. In contrast, no Lorentzian relaxation was observed for phenobarbital or flopropione at temperatures below their T(g). These results also suggest that nifedipine has higher molecular mobility than phenobarbital and flopropione at temperatures below T(g). The faster crystallization of nifedipine than that of phenobarbital or flopropione observed at temperatures below its T(g) may be partly ascribed to its higher molecular mobility at these temperatures.

Crystallization↗
PubMed2000

Stereochemical study of tolperisone, a muscle relaxant agent, by circular dichroism and ultraviolet spectroscopy.

The stereochemistry of tolperisone, a chiral aryl-alkyl basic ketone was investigated by means of circular dichroism (CD) and ultraviolet (UV) spectroscopy. The unusually high optical activity of tolperisone hydrochloride in the n-->pi* region is interpreted by the presence of a chiral conformer in solution. For stereochemical reasons, the C = O group and the aromatic moiety lack coplanarity by forming an inherently dissymetric chromophore, of M helicity. Similar helicity prevails in the crystal phase, according to the solid-state CD spectrum of (-)-tolperisone HCl salt. The chirality rule proposed by Snatzke for nonplanar benzoyl chromophores predicts the absolute configuration of (-)-tolperisone hydrochloride to be R, in agreement with other alpha-methyl-beta-amino-ketones.

Circular Dichroism↗
PubMed2000

On-chip chiral and achiral separation of amphetamine and related compounds labeled with 4-fluoro-7-nitrobenzofurazane.

Amphetamine and analogous compounds have been labeled with 4-fluoro-7-nitrobenzofurazane and analyzed on a microfabricated chip. Separation of norephedrine, ephedrine, cathinone, pseudoephedrine, methcathinone, amphetamine and methamphetamine is demonstrated using micellar electrokinetic capillary chromatography (MEKC) and laser-induced fluorescence (LIF) detection. Chiral separations of individual drugs were studied using neutral and negatively charged cyclodextrins (CDs) with and without the addition of an organic modifier and/or sodium dodecyl sulfate (SDS). The best results were obtained using a highly sulfated gamma-CD (HS-gamm-CD) in combination with a low concentration of SDS. To obtain complete separation of a mixture of (+/-)-norephedrine, (+/-)ephedrine, (+/-)-pseudoephedrine, (+/-)-methcathinone, (+/-)-amphetamine and (+/-)-methamphetamine it was necessary to add a small amount (1.5 mM) of SDS to the separation buffer. Optimized chiral separation was achieved within 7 min using an S-folded separation channel, a separation voltage of 8 kV and a buffer consisting of 50 mM phosphate (pH 7.35), 10 mM HS-gamma-CD and 1.5 mM SDS.

4-Chloro-7-nitrobenzofurazan↗