Assessment of tear concentrations on therapeutic drug monitoring. II. Pharmacokinetic analysis of valproic acid in guinea pig serum, cerebrospinal fluid, and tears

Slug-Flow Microextraction Mass Spectrometry for Enhanced Detection of Analytes in Human Tear Fluids using Noninvasive Microsampling and Nanoelectrospray Ionization via a Capillary

In vivo noninvasive sampling and sensitive analysis of human tear fluids at the microliter level is an important but challenging task in investigating eye health. In this work, capillary microsampling coupled with slug-flow microextraction mass spectrometry (SFME-MS) was developed for enhanced detection of analytes in human tear fluids. As low as 1.0 μL of human tear fluid could be directly sampled using a capillary, and extraction/spray solvent was then loaded into the capillary to perform slug-flow microextraction and direct nanoelectrospray ionization (nESI) of analytes. All analytical procedures, including tear microsampling, microextraction, and ionization of analytes, were performed using a capillary. Enhanced detection of therapeutic drugs and disease biomarkers in human tear fluids was successfully demonstrated. Acceptable analytical performances including sensitivity, reproducibility, and quantitation were obtained. It is found that the use of SFME could improve the nESI-MS detection of trace analytes over 100-fold that depends on the chemical properties of analytes. Overall, this study showed that SFME-nESI-MS is a highly effective method for enhanced detection of trace analytes in tear fluids and is expected to be a potentially powerful tool in significant biological and clinical applications.

Polymeric and Composite Carriers of Protein and Non-Protein Biomolecules for Application in Bone Tissue Engineering

Conventional intake of drugs and active substances is most often based on oral intake of an appropriate dose to achieve the desired effect in the affected area or source of pain. In this case, controlling their distribution in the body is difficult, as the substance also reaches other tissues. This phenomenon results in the occurrence of side effects and the need to increase the concentration of the therapeutic substance to ensure it has the desired effect. The scientific field of tissue engineering proposes a solution to this problem, which creates the possibility of designing intelligent systems for delivering active substances precisely to the site of disease conversion. The following review discusses significant current research strategies as well as examples of polymeric and composite carriers for protein and non-protein biomolecules designed for bone tissue regeneration.

Schirmer Paper Noninvasive Microsampling for Direct Mass Spectrometry Analysis of Human Tears

Rapid and sensitive detection of metabolites and chemical residues in human tears is highly beneficial for understanding eye health. In this study, Schirmer paper was used for noninvasive microsampling of human tears, and then paper spray mass spectrometry (PSMS) was performed for direct analysis of human tears. Schirmer PSMS was successfully used for rapid diagnosis of dry-eye syndrome by detecting the volume and metabolites of human tears. Drugs of abuse, therapeutic drugs, and pharmacodynamics in human tears were also investigated by Schirmer PSMS. Furthermore, specific markers of environmental exposures in the air to human eyes, including volatile organic compounds, aerosol, and smoke, were unambiguously sampled and detected in human tears using Schirmer PSMS. Excellent analytical performances were achieved, including single-use, low-sample consumption (1.0 μL), rapid analysis (the whole analytical procedure completed within 3 min), high sensitivity (absolute limit of detection less than or equal to 0.5 pg, signal-to-noise ratio greater than or equal to 3), good reproducibility (relative standard deviation less than 10%, n = 3), and accurate quantitation (average deviation less than 3%, n = 3). Overall, our results showed that Schirmer PSMS is a highly effective method for direct tear analysis and is expected to be a convenient tool for human tear analysis in significant clinical applications.

Pharmacokinetics of Theophylline in Guinea Pig Tears

It is well recognized that the theophylline (TP) concentration in human tears correlates well with the free TP concentration in human plasma. However this correlation was found only in a very narrow range of concentrations of TP, and pharmacokinetic analysis of TP in tears has not been carried out for a wide range of concentrations of TP. The aims of this investigation were to develop a simple kinetic model for TP in guinea pig plasma (total [Cf+b] and free [Cf]), cerebrospinal fluid (CSF) [C](CSF) and tears [C](T), and to examine whether [Cf], [Cf+b] and [C](CSF) can be predicted from [C](T) using the resulting kinetic parameters. [Cf+b], [Cf], [C](CSF) and [C](T) were determined by GC/EI-SIM following bolus i.v. injection of TP in doses of 10, 50 and 100 mg/kg into guinea pigs. The wide range of concentrations of [Cf+b] could be quantitatively described by a two-compartment model with non-linear elimination kinetics and individual volume distribution of TP at each dose. [C](T) and [C](CSF) were analyzed using passive diffusion models with and without the pH-partition theory, respectively. The value of [Cf] could be predicted from the value of [C](T). Thus, the measurement of [C](T) which can be collected non-invasively would be a useful method for the therapeutic drug monitoring of TP.

Access of HTB, main metabolite of triflusal, to cerebrospinal fluid in healthy volunteers

OBJECTIVE

Triflusal has been shown to exert neuroprotective effects by downregulating molecules considered responsible for the development of Alzheimer's disease (AD). The aim of this study was to develop a population pharmacokinetic model to characterize plasma and cerebrospinal fluid (CSF) pharmacokinetics of the main active metabolite of triflusal-HTB (2-hydroxy-4-trifluoro-methylbenzoic acid)-in healthy volunteers.

METHODS

Data from two studies were combined. Study A: subjects received single oral doses of triflusal 900 mg. Triflusal and HTB plasma concentrations were extensively measured. Study B: triflusal 600 mg once daily was administered orally for 14 days. HTB plasma and CSF concentrations were determined in healthy volunteers. Population pharmacokinetic modeling was performed using NONMEM.

RESULTS

A one-compartmental model with rapid first-order absorption for triflusal and first-order formation of HTB best described plasma concentrations. Triflusal elimination rate constant was 50 times faster than that estimated for the metabolite. CSF concentrations of HTB ranged between 0.011 microg/ml and 0.341 microg/ml. A CSF-plasma partition coefficient of 0.002 and a k(e0) value of 0.059 h(-1) were estimated by means of population modeling.

CONCLUSION

In the present study in healthy volunteers, HTB penetrated into the CSF in a range of concentrations experimentally proven to have protective effects in AD. These concentrations suggest that triflusal could be used in the treatment of central nervous system diseases in doses similar to those used in cardiovascular diseases. Access to the CSF compartment was characterized by a slow equilibrium rate constant and a low CSF-plasma partition coefficient.

Valproate: past, present, and future

Preclinical studies have been carried out during the past four decades to investigate the different mechanisms of action of valproate (VPA). The mechanisms of VPA which seem to be of clinical importance include increased GABAergic activity, reduction in excitatory neurotransmission, and modification of monoamines. These mechanisms are discussed in relation to the various clinical uses of the drug. VPA is widely used as an antiepileptic drug with a broad spectrum of activity. In patients, VPA possesses efficacy in the treatment of various epileptic seizures such as absence, myoclonic, and generalized tonic-clonic seizures. It is also effective in the treatment of partial seizures with or without secondary generalization and acutely in status epilepticus. The pharmacokinetic aspects of VPA and the frequent drug interactions between VPA and other drugs are discussed. The available methods for the determination of VPA in body fluids are briefly evaluated. At present, investigations and clinical trials are carried out and evaluated to explore the new indications for VPA in other conditions such as in psychiatric disorders, migraine and neuropathic pain. Furthermore, the toxicity of VPA, both regarding commonly occurring side effects and potential idiosyncratic reactions are described. Derivatives of VPA with improved efficacy and tolerability are in development.

Assessment of Tear Concentrations on Therapeutic Drug Monitoring. III. Determination of Theophylline in Tears by Gas Chromatography/Mass Spectrometry with Electron Ionization Mode

A simple and sensitive method for the quantitation of theophylline (TP) in tears and plasma developed using gas chromatography/electron-impact ionization/mass spectrometry. Tears were collected by non-invasive Schirmer method. Plasma was pipetted on a Schirmer tear test strip (cutting to 5 mm x 5 mm). Then, TP was converted directly into its pentafluorobenzoyl amide derivative without the need to perform any extraction from the biological fluid absorbed on Schiemer test paper and was quantified by gas chromatography-selected ion recordings with electron ionization mode. The concentrations in tears [C]t correlated very well with those of the free form in the plasma [Cf]p and those of the total form in the plasma [Cb+f]p. The ratios between TP concentrations in tears and plasma (free and total form) were as follows: [C]t/[Cb+f]p=0.53+/-0.20; [C]t/[Cf]p=1.21+/-0.19; [Cf]p/[Cb+f]p=0.44+/-0.14. The ratios of [C]t/[Cb+f]p, [C]t/[Cf]p and [Cf]p/[Cb+f]p were in good agreement with the previously published data.