Simultaneous Determination of Phenobarbital, Phenytoin, Carbamazepine and Carbamazepine-10,11-epoxide in Plasma of Epileptic Patients

Abstract

IntroductionAntiepileptic drugs (AEDs) are a group of drugs used to treat neurological disorder such as epilepsy, neuropathic pain, and migraine. Epilepsy is a common and diverse set of chronic neurological disorders. It is characterized by seizures affecting about 1% of the population. 1,2 The pharmacotherapy with AEDs is the first choice for the treatment of epilepsy as it controls the occurrence of unpredictable epileptic seizures on approximately two thirds of the patients. 3 Approximately 30-40% of patients do not achieve seizure control with a single AED and rational polytherapy with the goal of finding combinations of AEDs that have favorable characteristics, has become of greater importance. 4 Before that one should ensure that the drug has reached its therapeutic range and there is no possibility to increase its daily dose. The first generation AEDs (phenobarbital (PB), phenytoin (PHT) and carbamazepine (CBZ)) have been widely used to treat epilepsy. Because of their narrow therapeutic range in adults (10-40 µg mL -1 , 5-20 µg mL -1 and 2-12 µg mL -1 , respectively for PB, PHT and CBZ) 5 and their complex pharmacokinetic properties, their blood levels should be monitored. Therapeutic ranges of PB, PHT and CBZ in children are 20-60 µg mL -1 , 3 6-11 µg mL -1 6 and 4-12 µg mL -1 , 7 respectively. Lethal concentrations of PB and PHT are 50 µg mL -1 for both drugs 5 and fatalities could be observed in CBZ serum concentrations of >20 µg mL -1 5 or >39 µg mL -1 . 8 CBZ is metabolized to its metabolite, i.e. carbamazepine-10, 11epoxide (CBZE), or simply the "epoxide" metabolite. The presence of this metabolite can have clinically significant implications in therapeutic drug monitoring (TDM) of CBZ. In addition, toxic symptoms may occur when plasma concentration of CBZE is >3.2 µg mL -1 . Thus CBZE quantification is importance in patients where CBZ has been ingested. 9,10 When each one of these three drugs fails to control seizures, a combination of the two most effective among them can be used. If the combination of CBZ and PHT fails, a combination of PB with CBZ or PHT would then become a consideration. 11 Drug A B S T R A C TBackground: Quantitative analyses of antiepileptic drugs are required in clinic and to rational dosage adjustment, the clinician needs the blood levels of these drugs. A highperformance liquid chromatography with spectrophotometric detection has been developed and validated for simultaneous determination of some antiepileptic drugs in plasma of patients with epilepsy. Methods: A simple procedure based on deproteinization by acetonitrile was used for pretreatment of plasma samples. Liquid chromatographic analysis was carried out on a Nova-Pak® C18 analytical column, using a ternary mixture of potassium dihydrogen phosphate buffer (pH 6.0)-acetonitrile-2-propanol (63:22:15, v/v/v) as the mobile phase, at a flow rate of 1.0 mL min -1 . Results: Calibration curves were linear over a range of 1-40 µg mL -1 for phenobarbital, 1-30 µg mL -1 for phenytoin, 0.3-15 µg mL -1 for carbamazepine and 0....

Electropolymerization of Metallo-Octaethylporphyrins: A Study to Explore Their Sensing Capabilities

“…In general, the method described presents a much faster analysis time, a higher precision and similar accuracy to the chromatographic methods found in the literature. However, chromatographic methods generally present better LoDs [ 29 , 30 ].…”

New Methods Used in Pharmacokinetics and Therapeutic Monitoring of the First and Newer Generations of Antiepileptic Drugs (AEDs)

“…There are different methods (GC, LC, HPLC, High Performance Thin Layer Chromatography (HPTLC), LC-MS/MS, UHPLC-MS/MS, SFC-ESI-MS/MS) to measure the level of CBZ and its major metabolite in biological samples of epilepsy patients treated with this AED in monotherapy or polytherapy. The presented methods use biological samples such as: Plasma [47][48][49][50][51][52][53][54][55], serum [53,[56][57][58], urine [47,59], saliva [60], dried saliva [61] and respiratory condensate [62,63], dried blood spot [20,64,65]. In TDM of CBZ, plasma, serum, and urine are the most commonly used.…”

“…Saliva is particularly useful in children, and the correlation between blood and saliva CBZ and its metabolite concentration was confirmed [60]. The described methods differ in the sample preparation technique including liquid-liquid extraction (LLE) [53,55,56,61], ultrasound-assisted emulsification microextraction (SAEME) [47,50], microextraction by packed sorbent (MEPS) [55,66] and deproteinization [48,49,57,58]. The most frequently used analytical method is RP-HPLC with a C18 column.…”

“…HPLC-MS/MS, compared to other techniques, is an important tool in TDM and clinical laboratory routine due to its high sensitivity and specificity. The mobile phase is usually polar and simple and consists of a mixture of water and an organic solvent (methanol, ethanol, 2-propanol, isopropyl alcohol, n-hexane or acetonitrile) [48][49][50]52,53,57,58,61,66]. In some methods, acid modifiers (acetic acid, formic acid, phosphoric acid,) are added [50,57,58].…”