Quantification of permanent positively charged compounds in plasma using one-step dilution to reduce matrix effect in MS.

BACKGROUND: Bioanalysis of conventional methods for compounds with permanent positive charge leads to peak tailing in separation and matrix effects in MS. This study describes a novel, rapid and sensitive method for quinolinium-containing compounds quantification. Results & methodology: A charged surface hybrid chromatography-tandem MS/MS using one-step protein precipitation dilution technique has been developed for determining analytes in plasma. We found symmetric peak and high recoveries for the analytes without matrix effect. All calibration curves had good linearity (r 0.991). The intra- and inter-assay precision was within 15% and the accuracy ranged from 88 to 103%. The method has been successfully applied to the PK study. CONCLUSION: The proposed method was sensitive, reproducible and applicable to other permanent positively charged compounds.

Small Quaternary Inhibitors K298 and K524: Cholinesterases Inhibition, Absorption, Brain Distribution, and Toxicity.

UNLABELLED: Inhibitors of acetylcholinesterase (AChE) may be used in the treatment of various cholinergic deficits, among them being myasthenia gravis (MG). This paper describes the first in vivo data for promising small quaternary inhibitors (K298 and K524): acute toxicity study, cholinesterase inhibition, absorption, and blood-brain barrier penetration. The newly prepared AChE inhibitors (bis-quinolinium and quinolinium compounds) possess a positive charge in the molecule which ensures that anti-AChE action is restricted to peripheral effect. HPLC-MS was used for determination of real plasma and brain concentration in the pharmacokinetic part of the study, and standard non-compartmental analysis was performed. The maximum plasma concentrations were attained at 30 min (K298; 928.76 ± 115.20 ng/ml) and 39 min (K524; 812.40 ± 54.96 ng/ml) after i.m. APPLICATION: Both compounds are in fact able to target the central nervous system. It seems that the difference in the CNS distribution profile depends on an active efflux system. The K524 brain concentration was actively decreased to below an effective level; in contrast, K298 progressively accumulated in brain tissue. Peripheral AChE inhibitors are still first-line treatment in the mild forms of MG. Commonly prescribed carbamates have many severe side effects related to AChE carbamylation. The search for new treatment strategies is still important. Unlike carbamates, these new compounds target AChE via apparent π-π or π-cationic interaction aside at the AChE catalytic site.

Determination of the trypanocidal drugs homidium, isometamidium and quinapyramine in bovine serum or plasma using HPLC.

Sensitive HPLC analytical methods for trypanocidal drugs in serum or plasma have been developed. The methods are suitable for the analysis of drugs that are widely used against animal trypanosomiasis at present, including Homidium bromide (Ethidium, Boots Company Ltd.), Homidium chloride (Novidium, May and Baker Ltd.), Isometamidium chloride (Samorin, May and Baker Ltd.), Quinapyramine chloride (Antrycide, ICI) and Quinapyramine sulphate (Trypacide, May and Baker Ltd.). The detection limits for various drugs range between 3 and 20 ng per ml of serum, when serum volumes up to 10 ml have been processed. These methods provide a significant improvement of sensitivity for Isometamidium over existing analytical procedures and represent new methods for analysis of Homidium and Quinapyramine.

Quinuronium levels in ovine plasma as determined by an in vitro/in vivo system with Babesia rodhaini.

Quinuronium was shown to have a babesicidal activity in vitro. In vitro/in vivo system with Babesia rodhaini gave an in vitro EC50 for 13.5 ng/ml. Quinuronium levels in ovine plasma increased to a maximum mean of approximately 27 ng/ml at 2 hours with a gradual decay from 8 hours up to almost no detectable levels at 48 hours following administration of therapeutic dose (1 mg/kg s.c.). This study supports previous reports of the use of Babesia rodhaini as an organism in screening antibabesials. The in vitro/in vivo model can be used to monitor quinuronium levels in ovine plasma. Second treatment with quinuronium may be administered after 24 to 48 hours whenever clinically indicated.