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  • Author: Ljubica Suturkova x
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Development and validation of a bioanalytical LC-UV method with solid-phase extraction for determination of valproic acid in saliva

A bioanalytical HPLC method with UV detection for the determination of the antiepileptic drug valproic acid in human saliva has been developed and validated. Saliva represents an alternative matrix for therapeutic monitoring of antiepileptic drugs due to the increasing interest in free drug concentration. The proposed method involved solid-phase extraction for sample preparation and yielded very good mean recoveries of 99.4 % and 97.9 % for valproic acid and IS, respectively. The calibration function for valproic acid was linear over the concentration range of 1.0-50.0 μg mL-1 (R 2 = 0.9989). Within-run and between-run precision and accuracy were studied at four concentrations and RSDs were less than 7.3 and 2.2 %, while accuracy values were higher than 96.8 and 97.5 %, respectively. The described method provides sensitivity, linearity, precision, accuracy and is suitable for analyses of valproic acid in saliva samples.


The use of biological medicine has significantly increased in recent decades and has made substantial contributions to improving the effectiveness of therapies in many diseases. The expiration of patents of biological innovative medicines enables copies of those drugs called similar biological products (biosimilars) to be approved by regulatory authorities and to enter in clinical use. Biosimilars are comparable but not identical and are not a generic version of the innovator biological product. Although biosimilars undergo rigorous characterization as well as clinical studies to prove their safety and effectiveness, specific regulatory requirements for registration apply in the case of biosimilars. They are highly complex molecules and small changes in the production process can have major implications in its safety and effectiveness profile. The availability of biosimilars enhances competition, with the potential to improve patient access to biological medicines and to contribute to the financial sustainability of healthcare systems. In order to be certain that a biosimilar reaches its potential in clinical use, an intensive pharmacovigilance monitoring system must be established in order to prove the true similarity between the original biologic and its biosimilar. There is a need for further guidance and resolution of the ongoing discussions on biosimilar labelling, naming, pharmacovigilance and substitution in order to ensure effective and appropriate use of biosimilars in clinical practice.


The aim of this study was to evaluate the most common ABCB1 (MDR1, P-glycoprotein) polymorphisms in the population of R. Macedonia and compare the allele and haplotype frequencies with the global geographic data reported from different ethnic populations. The total of 107 healthy Macedonian individuals from the general population was included.

Genotypes for the ABCB1 for three polymorphisms C1236T [rs1128503], G2677A/T [rs2032582] and C3435T [rs1045642] were analyzed by Real-Time PCR. Obtained allele frequencies for these three SNPs were similar to those observed in other European Caucasians. The detected genotype frequencies were 33.6% for 1236CC, 44.9% for 1236CT and 21.5% for 1236TT in exon 12; 32.7%, 44.9% and 22.4% for 2677GG, 2677GT and 2677GT consecutively in exon 21; and 25.2% for 3435CC, 52.3% for 3435CT and 22.5% for 3435TT in exon 26. Strong LD was observed in our study among all three SNPs with the highest association confirmed for C1236T and G2677T ((D' = 0.859, r2 = 0.711). Eight different haplotypes were identified and the most prominent was the CGC haplotype (45.3%). Our study was the first to have documented the distribution of ABCB1 alleles, genotypes and haplotypes in the population of R. Macedonia. The obtained results can help in the prediction of different response to the drugs that are P-glycoprotein substrates. Additionally, in the era of individualized medicine the determination of the P-glycoprotein genotype might be a good predictive marker for determination of the subpopulations with higher risk to certain diseases.


Antipsychotic drugs are widely used in the treatment of schizophrenia and psychotic disorder. The lack of antipsychotic response and treatment-induced side-effects, such as neuroleptic syndrome, polydipsia, metabolic syndrome, weight gain, extrapyramidal symptoms, tardive dyskinesia or prolactin increase, are the two main reasons for non-compliance and increased morbidity in schizophrenic patients. During the past decades intensive research has been done in order to determine the influence of genetic variations on antipsychotics dosage, treatment efficacy and safety. The present work reviews the molecular basis of treatment response of schizophrenia. It highlights the most important findings about the impact of functional polymorphisms in genes coding the CYP450 metabolizing enzymes, ABCB1 transporter gene, dopaminergic and serotonergic drug targets (DRD2, DRD3, DRD4, 5-HT1, 5HT-2A, 5HT-2C, 5HT6) as well as genes responsible for metabolism of neurotransmitters and G signalling pathways (5-HTTLPR, BDNF, COMT, RGS4) and points their role as potential biomarkers in everyday clinical practice. Pharmacogenetic testing has predictive power in the selection of antipsychotic drugs and doses tailored according to the patient’s genetic profile. In this perception pharmacogenetics could help in the improvement of treatment response by using different medicinal approaches that would avoid potential adverse effects, reduce stabilization time and will advance the prognosis of schizophrenic patients.


The psychiatric and other CNS disorders are characterized with unregulated neuro-inflammatory processes and chronic microglia cell activation resulting with detrimental effect. ABCB1gene polymorphismsC1236T, G2677T/Aand C3435T are associated with P-glycoprotein expression and function andare linked with predisposition to psychiatric disorders such as schizophrenia and bipolar disorders. The relationship between mood disorders and glucocorticoids has been confirmed and ABCB1 SNPs influence the glucocorticoids access to the brain.

The aim of the study is evaluation of the influence of the three most common ABCB1SNPs on predisposition to psychiatric disorders in Macedonian population.

In the study 107 unrelated healthy Macedonians of both sexes were enrolled as a control group and patient population of 54 patients (22 to 65 years old) diagnosed with schizophrenia or bipolar disorder. ABCB1 for three polymorphisms were analyzed by Real-Time PCR in both groups.

The results have confirmed the role of the ABCB1 gene in predisposition to psychiatric disorders and increased risk of developing bipolar disorder in carriers of the heterozygotes and mutant homozygotes for polymorphic variations in 1236 and 2677 in comparison to the normal genotype carriers. Three-fold higher risk was estimated for psychiatric illness in women that are 1236 and 2677 heterozygous carrier (heterozygous and mutant homozygous) compared to healthy control (men and women) population and four-fold higher risk in comparison only to healthy women population. Mutant allele carriers for 1236 and 2677 polymorphisms that are 35 years and below in patients population have almost three-fold higher risk for development of psychiatric illness.


Atypical antipsychotic risperidone is widely used first-line monotherapy in schizophrenia and combined therapy in bipolar disorders. Therapeutic plasma concentrations of risperidone and its active moiety are directly influenced by genetic variations in metabolic CYP450 enzymes (CYP2D6 and CYP3A4/5) and transporter (ABCB1) protein and additional environmental factors. Since active metabolite 9-OH risperidone has a greater percentage of the pharmacologically active fraction and is equipotent to the parent drug risperidone, it is assumed that it contributes significantly to therapeutic and adverse effects.

Unpredictable dose/concentration ratio, narrow therapeutic index, number of interactions, along with serious adverse reactions (ADR), raises the need for individualization of risperidone treatment and establishing of good therapeutic regime using TDM.

A simple and reliable validated bioanalytical liquide-liquide extraction HPLC/UV method was applied for the simultaneous determination of risperidone and its active metabolite, 9-OH risperidone, in human plasma and urine of 52 hospitalized schizophrenia/bipolar disorder patients treated with risperidone as monotherapy and in polytherapy. All the patients were previously genotyped for CYP2D6 (EM=30, EM/IM=14, IM=4 IM/PM=1 and PM=3) and ABCB1 using Real-Time PCR methods with TaqMan SNP genotyping suitable assays according to the guidelines of the manufacturer (Life Technologies, USA).The influence of CYP2D6 phenotype on metabolic ratio MR (Ris/9-OHRis) in plasma (p=0.012) and in urine (p=0.048) was confirmed. Statistically significant correlation (R2=55.53%, Rho=0.844, p<0,0001) for MR in both plasma and urine indicates that urine may be utilized as appropriate media for initial CYP2D6 phenotype identification and selection of patients on risperidone treatment with high risk for ADR.


The relative contribution of CYP2C9 allelic variants to the pharmacokinetics (PK) of ibuprofen (IBP) enantiomers has been studied extensively, but the potential clinical benefit of pharmacogenetically guided IBP treatment is not evident yet. The role of AKR1D1*36C>T (rs 1872930) allelic variant in interindividual variability of CYP450 mediated drug metabolism was recently elucidated. A total of 27 healthy male subjects, volunteers in IBP single-dose two-way cross-over bioequivalence studies were genotyped for CYP2C9*2, CYP2C9*3 and AKR1D1*36 polymorphisms. The correlation between CYP2C9 and AKR1D1 genetic profile and the PK parameters for S-(+) and R-(−)-IBP was evaluated. Remarkable changes in the PK values pointing to reduced CYP2C9 enzyme activity were detected only in the CYP2C9*2 allelic variant carriers. Statistically significant association between the AKR1D1*36 allele and the increased IBP metabolism (low AUC 0-t and 0–∞, high Cl tot and short t max values for both enantiomers) was observed in subjects carrying the CYP2C9 *1/*3 or CYP2C9*1/*1 genotype. The clinical value of concomitant CYP2C9 and AKR1D1 genotyping has to be further verified.