Razvoj in uporaba tehnike suhe lise plazme za kvantitativno določevanje topiramata v študijah farmakokinetike in bioekvivalence : doktorska disertacija
Development and use of dried plasma spots technique for quantitative determination of topiramate in pharmacokinetics and bioequivalence studies : doctoral dissertation

slovenian

doktorska dela

2013

Univerza v Mariboru, Fakulteta za kemijo in kemijsko tehnologijo

As a part of my doctoral studies I have developed and evaluated dried plasma spot technique for determining topiramate in pharmacokinetic and bioequivalence studies. Dried plasma spot technique derives from dried blood spot technique. In the last two years the latter was rediscovered by bioanalysts and pharmacokineticians and introduced in pharmacokinetic and bioequivalence studies as an alternative for traditional sampling and determination of substances from liquid human plasma. The collection of whole blood samples on paper, known as the dried blood spot technique (DBS), dates back to the early 1960s, when it was used for detecting metabolic problems in newborns. Today DBS offers a number of advantages over conventional whole blood in pharmacokinetic and bioequivalence studies. These advantages are related to ethical, practical, and cost aspects. DBS provides the ethical benefits of reduced blood volume (less than 100 ŽL compared to more than 1.0 mL blood, which is usually obtained during the conventional blood sample collection) and less invasive sampling (finger or heel prick rather than conventional venous cannula). Furthermore, it provides easier transfer and simpler and cheaper storage (no need for dry ice or freezers). When DBS technique was being reintroduced, the questions from the perspective of its practical advantages, technical improvements and possible analysis problems were considered. It was only until later that the technique got attention fromthe viewpoint of pharmacokinetics and bioanalysis. At that point it was discovered that blood matrix and consequently DBS technique is not useful for determining active substances in all kinds of studies. Therefore, DBS technique hasn't been regulatory acknowledged as an independent method for quantitative determination of active substances when it comes to the registration of human and veterinary drugs. In pharmacokinetic studies, liquidplasma is usually used as biological matrix for the determination of active substances. The aforementioned dried plasma spot technique (from now onDPS - Dried Plasma Spot) offers the same advantages as DBS technique alongside with the advantage of plasma being already acknowledged matrix for the majority of active substances. As a result of that, a question whether DPStechnique can completely replace the method of determining active substances from the basic matrix, liquid plasma, emerged in my mind. The answer to that question was sought in the molecule of topiramate. Topiramate is an anti-epileptic drug that is used for the treatment of various forms of epilepsy in adults and children and for the prevention of frequently recurringmigraines in adults as well as for treatment of Lennox-Gastaut syndrome. Topiramate enhances the action of inhibitory neurotransmitters (GABA), blocks voltage-sensitive sodium channels and mildly inhibits carbonic anhydrase (CA) isoenzymes. Binding to CA, which is highly concentrated in erythrocytes, may affect drug pharmacokinetics. Topiramate's tendency to bind to CA in erythrocytes implies that blood concentration-time profile may be different from plasma profile and the blood-to-plasma ratio might be greater than 1. The purpose of the research was to determine which is the most appropriate dried matrix for the quantitative determination of topiramate in biological samples of pharmacokinetic and bioequivalence studies, on the basisof literature and DBS and DPS samples from the monitoring research on thetherapeutic effect. The doctoral dissertation consists of three parts of experimental work. In the first part, the method for quantitative determination of topiramate from dried plasma spot was developed and validated. In the second and third part of experimental work, the method for quantitative determination of topiramate from liquid human plasma and the method for quantitative determination of topiramate from dried blood spot weredeveloped and validated.

07.08.2023