Angelo Mancinelli

Determination of l-carnitine, acetyl-l-carnitine and propionyl-l-carnitine in human plasma by high-performance liquid chromatography after pre-column derivatization with 1-aminoanthracene

A new sensitive high-performance liquid chromatographic procedure for the determination of L-carnitine (LC), acetyl-L-carnitine (ALC) and propionyl-L-carnitine (PLC) in human plasma has been developed. Precolumn derivatization with 1-aminoanthracene (1AA), performed in phosphate buffer in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) as catalyst, is involved. The fluorescent derivatives were isocratically separated on a reversed-phase column (C18). The eluate was monitored with a fluorimetric detector set at 248 nm (excitation wavelength) and 418 nm (emission wavelength). Because of the presence of endogenous carnitines, the validation was performed using dialyzed plasma. The identity of the derivatized compounds was assessed by mass spectrometry and the purity of the chromatographic peaks was confirmed by HPLC-tandem mass spectrometry. The limits of quantitation were 5 nmol/ml for LC, 1 nmol/ml for ALC and 0.25 nmol/ml for PLC. The recovery of the extraction procedure was in the range 82.6%-95.4% for all 3 compounds. Good linearity (R approximately 0.99) was observed within the calibration ranges studied: 5-160 nmol/ml for LC, 1-32 nmol/ml for ALC and 0.25-8 nmol/ml for PLC. Precision was in the range 0.3-16.8% and accuracy was always lower than 10.6%.

CARNITINE REPLACEMENT IN END-STAGE RENAL DISEASE AND HEMODIALYSIS

Abstract: In patients with chronic renal failure, not yet undergoing hemodialysis (HD), plasma acylcarnitines accumulate in part due to a decreased renal clearance of esterified carnitine moieties. In these patients, a high acylcarnitine/free‐carnitine ratio is usually found in plasma. Patients undergoing maintenance HD, usually present with plasma carnitine insufficiency, due to accumulation of metabolic intermediates combined with impaired carnitine biosynthesis, reduced protein intake and increased removal via HD. Plasma carnitine concentrations rapidly decrease to 40% of baseline level during the dialysis session, with a slow restoration of the carnitine concentration during the interdialytic period, mainly from organs of storage (skeletal muscle). Dietary intake also plays an important role in carnitine homeostasis of HD patients since the prevalence of malnutrition ranges from 18% to 75% of these cases. This could differentially affect various body compartments, with clinical consequences such as impaired muscle function, decreased wound healing, altered ventilatory response, and abnormal immune function. Repeated hemodialytic treatments are associated with decreased carnitine stores in skeletal muscle. The administration of intravenous l‐carnitine (LC) postdialysis replenishes the free carnitine removed from the blood and contributes to replenishment of muscle carnitine content. LC supplementation in selected uremic patients may yield clinical benefits by ameliorating several conditions, such as erythropoietin‐resistant anemia, decreased cardiac performance, intradialytic hypotension, muscle symptoms, as well as impaired exercise and functional capacities. Furthermore, LC may positively influence the nutritional status of HD patients by promoting a positive protein balance, and by reducing insulin resistance and chronic inflammation, possibly through an effect on leptin resistance.

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.

NaF and two other esterase inhibitors unaffect acetyl salicylic acid enzyme hydrolysis

Prevention of chemical or enzyme hydrolysis of drugs such as esters, amides and carbamates during analytical manipulation is a mandatory need in pharmacokinetics (Stella 1990). This hydrolysis occurs through the action of non-specific esterases which are present in blood, plasma and tissues, and it is common to add NaF or other esterase inhibitors to plasma during extraction procedures (Mays et a1 1984). We have investigated the enzyme hydrolysis of acetyl salicylic acid as a model for evaluating the inhibitory effect of sodium fluoride (NaF), diisopropyl-fluorophosphate (DFP) and 1,5 bis(4-ally1 dimethyl ammonium phenyl)-pentan-3-one dibromide (ADAPP).

Pharmacokinetics of 5-Ht6 Receptor Ligands

Publisher Summary This chapter describes the role of adsorption, distribution, metabolism, and excretion (ADME) (i.e., pharmacokinetics) in the research and development of CNS therapeutics. The chapter provides information on physicochemical properties and ADME results of preclinical and clinical studies available on 5-HT 6 receptor compounds. During the research and development of novel therapeutic agents, all the compounds that have shown high-activity in vitro biological screening are submitted to pharmacokinetic and metabolic evaluation to optimize pharmacokinetic and pharmacological properties. The inclusion of ADME investigation at the earlier stages of drug development has been shown to reduce failure because of poor pharmacokinetic features at the clinical stage from 40% to 10%. An enormous effort in the design of 5-HT 6 receptor ligands has resulted in the synthesis of potential therapeutic agents with activity in CNS and obesity disorders.