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A Marzo

Publications and source records attributed to A Marzo.

At least 55 records · Page 3Linked to original sources
PubMed1994

Incoming guidelines on chirality. A challenge for pharmacokinetics in drug development.

Even though scientific interest regarding enantiomeric purity of chiral drugs is continuously increasing, the availability of enantioselective assays has not developed to a level to resolve all the problems, especially those related to pharmacokinetics of chiral drugs active at low or very low plasma concentrations. Enantioselective assay in pharmacokinetics of chiral drugs is required in the case of a drug developed as a racemate in order to study the different disposition of individual stereoisomers and could be also needed in the case of the development of an individual enantiomer to ascertain whether an unidirectional enzyme mediated conversion occurs in the body. A strenuous effort is required from pharmacokinetic investigators to study enantioselective pharmacokinetics of chiral drugs, mainly for setting up adequate analytical assays. Incoming guidelines on chirality from European, USA and Japan authorities should take into account these difficulties in order to allow the investigators to select the most appropriate design, case by case.

Chemical Phenomena↗
PubMed1993

High-performance liquid chromatographic assay for N2-[5-(hypoxanthin-9-yl)pentyloxycarbonyl]-L-arginine (ST 789) in plasma by cyclization with benzoin and fluorimetric detection.

This paper describes a new highly sensitive assay for N2-[5-(hypoxanthin-9-yl)pentyloxycarbonyl]-L-arginine, an immunomodulatory agent, required for clinical pharmacokinetic investigation. A pre-column derivatization by cyclization with benzoin in aqueous medium produces the fluorescent 2-substituted amino-4,5-diphenylimidazole fluorescing at 450 nm (excitation wavelength 310 nm). L-Arginine-acetyl-L-carnitinamide chloride (ST 857, II), another arginine derivative, was used as an internal standard. A C18 DB column (5 microns, 250 mm x 4.6 mm I.D.) and a 45:55 (v/v) mixture of 0.05 M ammonium phosphate at pH 7.2 and methanol as mobile phase were used. Linearity was ascertained in the range 5-100 ng. Extraction recovery from plasma proved to be higher than 90% in the range 5-50 ng/ml. Intra-day precision, expressed as coefficient of variation, was in the range 4.7-6.0%. The limit of quantification proved to be 5 ng/ml and the limit of detection 2 ng/ml at a signal-to-noise ratio of 5. The method is specific.

Adjuvants, Immunologic↗
PubMed1993

How incoming guidelines on chiral drugs could impact on the international scenery of drug development.IUPAC.

In this review incoming guidelines on chiral drugs are examined for their impact on drug development. Problems related to synthesis, enantiomeric resolution, analytics, pharmacokinetics, preclinical and clinical studies are discussed throughout the paper. Problems related to the validation of an enantioselective assay in pharmacokinetics are certainly the most difficult, mainly for chiral drugs active at low or very low plasma concentrations. The compliance with incoming guidelines on chirality will require new approaches and new technologies and will produce an increased cost of the drug development.

Drug Industry↗
PubMed1993

Effect of acetyl-L-carnitine treatment on the levels of levocarnitine and its derivatives in streptozotocin-diabetic rats.

The effect of diabetes induced by streptozotocin and that of acetyl-L-carnitine (ALC) hydrochloride (CAS 5080-50-2) treatment on the homeostasis of the levocarnitine (L-carnitine) moiety was investigated in Sprague-Dawley rats. The diabetic status was ascertained by measuring blood glucose. L-carnitine (LC), total acid soluble L-carnitine (TC) and ALC were measured in serum, tissues and urine by radioenzymatic methods. Short-chain L-carnitine esters (SCLCE) were obtained by subtracting LC from TC. Serum concentration of L-carnitine moiety was decreased in diabetic when compared to normal rats; whereas ALC oral treatment (50 and 150 mg/kg p.o. for 4 weeks) in diabetic rats increased, dose-dependently, all the components of L-carnitine moiety, SCLCE and ALC being completely restored. In the liver of diabetic rats all the analytes proved to be higher than in normal rats, mainly LC and TC. A similar trend was observed in skeletal muscle, at least with LC and TC, whereas SCLCE and ALC were not affected. The treatment with ALC increased the liver concentration of all the analytes in a dose-related way whereas in skeletal muscle only LC and TC showed an increase with the highest dose of ALC. Myocardium and kidneys showed a decrease of all the analytes in diabetes; the treatment with ALC normalized the situation in kidneys, in a dose-related way, but not in the myocardium. Urinary excretion and renal clearance of L-carnitine moiety increased in diabetes; an additional dose-related increase was observed with the ALC treatment.

Acetylcarnitine↗
PubMed1992

Effect of prolonged treatment with propionyl-L-carnitine on erucic acid-induced myocardial dysfunction in rats.

The aim of this study was to evaluate the ability of propionyl-L-carnitine to prevent cardiac damage induced by erucic acid. Rats were fed for 10 days with normal or 10% erucic acid-enriched diets with or without propionyl-L-carnitine intraperitoneally injected, (1 mM/kg daily, for 10 days). The erucic acid diet produced increases in triglycerides (from 5.6 to 12.4 mg/gww, P less than 0.01), and free fatty acids (from 2.0 to 5.1 mg/gww, P less than 0.01), but no changes in phospholipids. When the hearts were perfused aerobically with an isovolumic preparation there was no difference in mechanical activity. On the contrary, when pressure-volume curves were determined, the pressure developed by hearts from the erucic acid-treated rats were reduced. Independent of diet, propionyl-L-carnitine treatment always produced positive inotropy. This was concomitant with improved mitochondrial respiration (RCI 5.1 vs 9.3, P less than 0.01), higher tissue ATP content (10.3 vs 18.4 mumol/gdw P less than 0.01) and reduction of triglycerides (12.4 vs 8.0 mg/gww, P less than 0.01). These data suggest that propionyl-L-carnitine, when given chronically, is able to prevent erucic acid-induced cardiotoxicity, probably by reducing triglyceride accumulation and improving energy metabolism.

Adenosine Triphosphate↗
PubMed1992

Determination of pentoxifylline and its metabolites in human plasma by high-performance liquid chromatography with solid-phase extraction.

A simple and reliable method for the determination of pentoxifylline and its main metabolites in human plasma has been developed using high-performance liquid chromatography. After selective solid-phase extraction, pentoxifylline, its metabolites and an internal standard, 7-(2'-chloroethyl)theophylline, were separated on a 5-micron LiChrospher 100 RP-18 column using water-dioxan-acetonitrile (87:6.5:6.5, v/v/v) acidified with acetic acid (0.5%, v/v) as the mobile phase. The analytes were detected at 275 nm. The lowest detectable concentration for all analytes was 25 ng/ml; the recovery was 85%. The assay has been successfully applied to analysis of these compounds in human plasma after administration of an oral dose of 400 mg of pentoxifylline to healthy volunteers.

Administration, Oral↗
PubMed1992

Enzymes in stereoselective pharmacokinetics of endogenous substances.

The use of enzymes to assay individual components of the L-carnitine family in pharmaceuticals, foodstuffs, and biological fluids with various forms of detection is reviewed. The most useful enzyme in the assay of compounds of the L-carnitine family is carnitine acetyl transferase (CAT), which catalyses the reversible interconversion of L-carnitine and its short-chain acyl esters. CAT can be used in one or more coupled reactions combined with U.V., or radiolabelled detection, or combined with HPLC, allowing, enantioselective, structurally specific, and, in the case of radiolabelled tracing, highly sensitive assays to be carried out. When compared with chromatographic separation of enantiomers or diastereoisomers, enantioselective enzyme mediated assays may be cheaper, more sensitive, and simpler, but they do not allow the nonpreferred isomer to be assayed. Consequently, they are appropriate for the specific assay of endogenous enantiomeric substrates of the enzyme concerned, in biological samples. The analysis of the other enantiomer in raw materials or in pharmaceuticals must be more properly approached by enantioselective chromatographic methods.

Carnitine↗
PubMed1992

Pharmacokinetics of 2-(alpha-thenoylthio)-propionylglycine (TTPG) in healthy volunteers--an oral dose-proportionality investigation.

The dose linearity of 2-(alpha-thenoylthio)-propionylglycine (TTPG) pharmacokinetics after a single oral administration at three different TTPG doses (180, 540 and 1080 mg) was evaluated in 12 healthy volunteers according to an open, randomized, cross-over study with a 1-week wash-out period between each administration. The duration of the study, for each subject, was 4 weeks. Plasma concentration and urinary excretion of TTPG and its two systemic metabolites, namely propionylglycine (tiopronin) and thiophenecarboxylic acid (TCA) were assayed by a previously well validated HPLC method. Due to differences in the physical and chemical properties of these compounds, two assays were needed, one to measure TTPG and TCA as such, and one to measure derivatized tiopronin. Both used UV detection. TTPG, tiopronin and TCA were quickly detected in plasma, suggesting that the drug administered is rapidly absorbed and biotransformed, in part, in the systemic circulation into the two metabolites noted above. Time-to-peak for all three analytes showed a trend to increase with increasing doses of TTPG, being: 0.42, 0.40 and 0.67 h (P < 0.01) with TTPG; 0.53, 0.47 and 0.73 h (P < 0.05) with TCA; and 1.33, 2.13 and 2.58 h (P < 0.01) with tiopronin. Cmax showed the opposite behaviour with values (ng ml-1) normalized to the dose of 540 mg: 1235, 905 and 513 (P < 0.001) with TTPG; 888, 547 and 383 (P < 0.001) with TCA; and 7290, 6950 and 5170 (P < 0.01) with tiopronin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

L-carnitine deficiency in AIDS patients.

OBJECTIVE: To evaluate carnitine (3-hydroxy-4-N-trimethyl-ammoniobutanoate) deficiency in AIDS patients by measuring serum total, free and short-chain carnitine concentrations. DESIGN: We conducted an open study. SETTING: All patients were seen at the Infectious Diseases Clinic, Università 'La Sapienza', Rome, Italy. PATIENTS, PARTICIPANTS: Twenty-nine AIDS patients, aged 27-41 years, with a previous history of drug use; and 14 healthy age- and sex-matched controls were studied. INTERVENTIONS: Study subjects were administered 500-800 mg zidovudine daily for 2 to 28 months (8 +/- 6 months). MAIN OUTCOME MEASURES: Carnitine deficiency was suspected in study participants prior to data collection because of previously reported cardiac symptoms, muscle weakness, hypometabolism and/or cachexia. RESULTS: A marked decrease in total and free carnitine was observed in 21 (72%) subjects. Nine of these patients also had low levels of short-chain carnitine. CONCLUSIONS: AIDS patients may become carnitine-depleted and therefore at risk for alterations in fatty-acid oxidation and energy supply.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Pharmacokinetics of endogenous substances.

The paper deals with the most relevant aspects related to the pharmacokinetics of the endogenous substances. Homeostatic equilibrium maintaining basal concentration of these substances, renal clearance and its role in preserving such equilibrium, the most appropriate pharmacokinetic analysis, the pharmacokinetic-pharmacodynamic relationships and the lack of specific regulatory aspects are the main items focused on.

Animals↗
PubMed1992

Metabolism of drugs: a reappraisal.

The paper deals with an up-to-date reappraisal of the most relevant aspects connected to the investigation of drug metabolism including the most appropriate methods used in preclinical and clinical field. Renal and biotransformation clearance is considered with several specific references. Reversible metabolism, active metabolites of drugs, various kinds of first pass effect, genetic polymorphism in drug metabolizing enzymes, the most appropriate pharmacokinetic analysis and regulatory aspects are the main aspects focused on.

Animals↗
PubMed1992

Pharmacokinetic investigation of ST 789 in rats and mice.

Pharmacokinetics of ST 789 were investigated in rats and mice after oral, intravenous, subcutaneous and intramuscular routes. A HPLC method validated for pharmacokinetic studies allowed the Authors to assay ST 789 concentration in plasma, urine and tissues. ST 789 interacted poorly with albumin and plasma proteins. Blood-to-plasma concentration ratio proved to range on average from 1.3 to 2.0 in both in vivo and in vitro studies. Plasma concentration-time behaviour after i.v. injection fitted according to the open three-compartment model; after subcutaneous and intramuscular routes two phases were observed and after oral route the absorption and one elimination phases were detected. Pharmacokinetics of ST 789 proved to vary linearly with the dose administered. Cumulative urinary excretion after parenteral administration ranged on average 60-80% and cumulative biliary excretion was 9.47% of the dose given. Oral administration allowed only 2.5% of the drug given to be excreted in urine, this leading to conclude that this drug is poorly absorbed through the intestine wall. After oral administration ST 789 produced relatively high concentration in lungs and lymphatic tissues, this leading to hypothesize a lymphatic component in its enteral absorption.

Adjuvants, Immunologic↗
PubMed1991

High-performance liquid chromatographic evaluation of Med 15 and its metabolites Med 5 and tolmetin in rat plasma.

A simple and reliable high-performance liquid chromatographic method is described for the quantitative analysis of the new non-steroidal anti-inflammatory agent Med 15 and its metabolites Med 5 and tolmetin in rat plasma. After selective extraction the three analytes and an internal standard (p-phenyl-phenol) were separated on a reversed-phase Ultrasphere 5 micron column using potassium dihydrogenphosphate (0.05 M)-acetonitrile (52:48) (pH 4.7) as the mobile phase. The analytes were detected at 313 nm; the sensitivity of the method proved to be 0.05 microgram/ml for all three compounds. The method has been applied to investigate Med 15 pharmacokinetics in rats.

Animals↗
PubMed1991

High-performance liquid chromatographic evaluation of 2-(alpha-thenoylthio)propionylglycine and its two metabolites in biological fluids.

A high-performance liquid chromatographic (HPLC) method for determining 2-(alpha-thenoylthio)propionylglycine (TTPG) and its two main metabolites, thiophenecarboxylic acid and thiopronine, in biological samples was developed. TTPG and its metabolites were extracted by solvent partition and then determined by reversed-phase HPLC with UV detection at 245, 295 and 360 nm. This procedure was validated in order to allow the assay of these compounds in plasma and urine samples with sufficiently low detection limits (50 ng/ml for TTPG and TCA and 100 ng/ml for thiopronine) and with good linearity within the concentration range investigated. It was applied to a comprehensive pharmacokinetic investigation of TTPG in healthy volunteers.

Chromatography, High Pressure Liquid↗
PubMed1991

Effect of propionyl-L-carnitine on mechanical function of isolated rabbit heart.

We studied the acute and chronic effects of propionyl-L-carnitine (PLC) on mechanical function of isolated rabbit heart. Propionyl-L-carnitine was either directly delivered in the perfusate (10(-9) to 10(-3) M) or intraperitoneally injected (250 mg/kg) for 10 days to the animals. When added acutely, propionyl-L-carnitine had no effect on inotropism, heart rate, or coronary perfusion pressure. When added chronically, propionyl-L-carnitine induced a positive inotropic effect, with no changes in heart rate or in coronary perfusion pressure, and it ameliorated the pressure-volume relationship. This effect of propionyl-L-carnitine was independent of the calcium concentration of the perfusion medium, but it was correlated with an increase in the myocardial content of propionyl-L-carnitine. The effect was not apparent after 5 days of treatment, although the tissue content of propionyl-L-carnitine remained unchanged. These data suggest that propionyl-L-carnitine, when given chronically, exerts a positive inotropic effect.

Acetylcarnitine↗
PubMed1991

L-carnitine and carnitine ester transport in the rat small intestine.

L-carnitine and its esters (acetyl-L-carnitine and propionyl-L-carnitine) at pharmacological doses (1, 5 and 10 mM) are absorbed by the rat jejunum by simple diffusion. Partition coefficients of carnitine esters determined in lipophilic media (diethyl ether/water and olive oil/water) are greater than that of L-carnitine. It would therefore seem that esters diffuse more easily through the lipid component of the intestinal barrier. The transport of acetyl- and propionyl-L-carnitine at pharmacological doses seems to be linearly and positively correlated with K+ transport but not with Na+ transport.

Acetylcarnitine↗