Browsing by Author "Kovačević, Sandra Vezmar (57204567668)"

The choice of an antiepileptic drug (AED) is usually based upon the epileptic seizure type. However, pharmacokinetic (PK) characteristics of AEDs may be valuable support in choosing the optimal therapeutic option for the individual patient. The novel (second and third generation) AEDs include: eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin, and zonisamide. Although, these drugs belong to the same group, their individual PK characteristics differ. Gabapentin, unlike other new AEDs, is characterised by dose-dependent absorption, which is presumably caused by saturable L-amino acid transport system, and therefore its bioavailability ranges from 35-60%. Furthermore, gabapentin, pregabalin and vigabatrin are eliminated completely, while levetiracetam and topiramate are eliminated predominantly through the renal system. Therefore, PK variability of these individual drugs is less pronounced and more predictable in comparison to older AEDs. Their potential for drug interactions is minor, and consequently they have major clinical importance for patients with impaired hepatic function. On the other hand, felbamate, lamotrigine, oxcarbazepine, tiagabine and zonisamide are eliminated via metabolic pathways, either cytochrome P (CYP) 450, or conjugation dependent transformation. Oxcarbazepine is a prodrug, and its active metabolite is licarbazepine. These drugs interact with other drugs, and disease conditions, which alter the activity of metabolic enzymes; thus these changes in PK commonly have clinical implications. Gabapentin, levetiracetam and tiagabine do not induce or inhibit hepatic metabolism enzymes. Felbamate demonstrated an inducing effect on CYP 3A4 isoenzyme, and inhibition effect on CYP 2C19 and on β-oxidation of valproic acid. Lamotrigine induces its own metabolism, and some reports imply a decrease of valproic acid levels during concomitant treatment with lamotrigine. Oxcarbazepine induces CYP 3A4, 3A5, and uridine diphosphate glucuronyl transfereases (UGT), and inhibits the metabolism of phenytoin via CYP 2C19 isoenzyme. Similar induction and inhibition characteristics are attributed to topiramate, while some studies indicate that zonisamide may have inhibition potential on phenytoin metabolism. In general, novel AEDs have linear PK, low plasma protein binding, and renal elimination, so their PK is more favorable in comparison with carbamazepine, phenobarbitone and valproic acid. This chapter gives a review of PK parameters of novel AEDs and its' variability based on age, comorbidities, concomitant therapy, and highlights the need of therapeutic drug monitoring. © 2012 Nova Science Publishers, Inc. All rights reserved.

The choice of an antiepileptic drug (AED) is usually based upon the epileptic seizure type. However, pharmacokinetic (PK) characteristics of AEDs may be valuable support in choosing the optimal therapeutic option for the individual patient. The novel (second and third generation) AEDs include: eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin, and zonisamide. Although, these drugs belong to the same group, their individual PK characteristics differ. Gabapentin, unlike other new AEDs, is characterised by dose-dependent absorption, which is presumably caused by saturable L-amino acid transport system, and therefore its bioavailability ranges from 35-60%. Furthermore, gabapentin, pregabalin and vigabatrin are eliminated completely, while levetiracetam and topiramate are eliminated predominantly through the renal system. Therefore, PK variability of these individual drugs is less pronounced and more predictable in comparison to older AEDs. Their potential for drug interactions is minor, and consequently they have major clinical importance for patients with impaired hepatic function. On the other hand, felbamate, lamotrigine, oxcarbazepine, tiagabine and zonisamide are eliminated via metabolic pathways, either cytochrome P (CYP) 450, or conjugation dependent transformation. Oxcarbazepine is a prodrug, and its active metabolite is licarbazepine. These drugs interact with other drugs, and disease conditions, which alter the activity of metabolic enzymes; thus these changes in PK commonly have clinical implications. Gabapentin, levetiracetam and tiagabine do not induce or inhibit hepatic metabolism enzymes. Felbamate demonstrated an inducing effect on CYP 3A4 isoenzyme, and inhibition effect on CYP 2C19 and on β-oxidation of valproic acid. Lamotrigine induces its own metabolism, and some reports imply a decrease of valproic acid levels during concomitant treatment with lamotrigine. Oxcarbazepine induces CYP 3A4, 3A5, and uridine diphosphate glucuronyl transfereases (UGT), and inhibits the metabolism of phenytoin via CYP 2C19 isoenzyme. Similar induction and inhibition characteristics are attributed to topiramate, while some studies indicate that zonisamide may have inhibition potential on phenytoin metabolism. In general, novel AEDs have linear PK, low plasma protein binding, and renal elimination, so their PK is more favorable in comparison with carbamazepine, phenobarbitone and valproic acid. This chapter gives a review of PK parameters of novel AEDs and its' variability based on age, comorbidities, concomitant therapy, and highlights the need of therapeutic drug monitoring. © 2012 Nova Science Publishers, Inc. All rights reserved.

Aim. To identify potential risk factors for the development of subclinical hypothyroidism following long-term valproic acid monotherapy in children with epilepsy. Methods. Serumlevels of thyroid-stimulating hormone, free thyroxine, free triiodothyronine, thyreoglobulin antibodies, and thyroid peroxidase antibodies were determined in 41 patients and in 41 sex- And age-matched healthy children. Results. Meanvalproic acid treatment durationwas 2.80?}1.96 years. The valproic acid group had higher serum thyroid-stimulating hormone (p<0.001) and free triiodothyronine (p<0.05) levels compared to the control group. Serum thyroid-stimulating hormone and free triiodothyronine were above the upper limit for healthy controls in 34% and 32% of patients, respectively, and no clinical features of thyroid dysfunction were observed. Duration of valproic acid monotherapy for less than four years was a risk factor for elevated thyroid-stimulating hormone levels. Conclusion. One third of children with normal range serum valproic acid levels may have elevated serum thyroid-stimulating hormone and free triiodothyronine levels, especially in the first four years of treatment.

Aim. To identify potential risk factors for the development of subclinical hypothyroidism following long-term valproic acid monotherapy in children with epilepsy. Methods. Serumlevels of thyroid-stimulating hormone, free thyroxine, free triiodothyronine, thyreoglobulin antibodies, and thyroid peroxidase antibodies were determined in 41 patients and in 41 sex- And age-matched healthy children. Results. Meanvalproic acid treatment durationwas 2.80?}1.96 years. The valproic acid group had higher serum thyroid-stimulating hormone (p<0.001) and free triiodothyronine (p<0.05) levels compared to the control group. Serum thyroid-stimulating hormone and free triiodothyronine were above the upper limit for healthy controls in 34% and 32% of patients, respectively, and no clinical features of thyroid dysfunction were observed. Duration of valproic acid monotherapy for less than four years was a risk factor for elevated thyroid-stimulating hormone levels. Conclusion. One third of children with normal range serum valproic acid levels may have elevated serum thyroid-stimulating hormone and free triiodothyronine levels, especially in the first four years of treatment.

Background: Aspirin-induced chronic rhinosinusitis (CRS) is a severe progressive persistent disease, usually associated with nasal polyps (NPs). Aim/objective: To compare effect of hypertonic (2.3% NaCl) sea water and isotonic 0.9% NaCl on symptoms and endoscopic findings in those patients in the period of 1 month after endoscopic sinus surgery (ESS). Material and methods: This prospective, randomized study included 30 patients with aspirin-induced CRS undergoing ESS. Patients were divided into two groups of 15 subjects and one of the two nasal irrigation solutions was administered in each group. Intensity of 5 symptoms (nasal obstruction, nasal discharge/postnasal drip, facial pain/pressure, headache and trouble sleeping) and endoscopic findings were assessed during the 1st, 7th, 14th, 21st and 28th days after the nasal packs removal. Results: We found significantly lower total symptom score (TSS) during the 7th (p =.009), 14th (p =.003), 21st (p <.001) and the 28th day (p =.001), lower total endoscopic score (TES) on the 21st (p =.002) and 28th day (p =.001), lower nasal obstruction, facial pain/pressure, headache and trouble sleeping, and lower nasal mucosal edema, nasal secretion and nasal crusting in patients treated by hypertonic sea water. Conclusion and significance: Hypertonic sea water should be recommended douching solution in the early postoperative care of patients with aspirin-induced CRS. © 2019, © 2019 Acta Oto-Laryngologica AB (Ltd).

Due to wide intra-and inter-individual pharmacokinetic variability and narrow therapeutic index of sirolimus, the therapeutic drug monitoring (TDM) of sirolimus with detailed biochemical and clinical monitoring is necessary for dose individualization in kidney transplant patients. The purpose of the study was to explore and identify factors that contribute to pharmacokinetic variability by developing and validating a population model using routine TDM data and routinely monitored biochemical and clinical parameters. The data obtained by routine monitoring of 38 patients over a period of one year from the sirolimus treatment initiation, were collected from patients' records. Population analysis was performed using the software NONMEM®. The validity of the model was tested by the internal and external validation techniques. The pharmacokinetic variability was partially explained with patient's age and liver function. CL/F was found to decrease with age. According to the developed model, sirolimus CL/F decreases by, in average, 37% in patients with aspartate aminotransferase (AST) greater than 37 IU/L. The internal and external validation confirmed the satisfactory prediction of the developed model. The population modeling of routinely monitored data allowed quantification of the age and liver function influence on sirolimus CL/F. According to the final model, patients with compromised liver function expressed via AST values require careful monitoring and dosing adjustments. Proven good predictive performance makes this model a useful tool in everyday clinical practice. © 2019 Bojana Golubović, Katarina Vučićević, Dragana Radivojević, Sandra Vezmar Kovačević, Milica Prostran, Branislava Miljković.

Due to wide intra-and inter-individual pharmacokinetic variability and narrow therapeutic index of sirolimus, the therapeutic drug monitoring (TDM) of sirolimus with detailed biochemical and clinical monitoring is necessary for dose individualization in kidney transplant patients. The purpose of the study was to explore and identify factors that contribute to pharmacokinetic variability by developing and validating a population model using routine TDM data and routinely monitored biochemical and clinical parameters. The data obtained by routine monitoring of 38 patients over a period of one year from the sirolimus treatment initiation, were collected from patients' records. Population analysis was performed using the software NONMEM®. The validity of the model was tested by the internal and external validation techniques. The pharmacokinetic variability was partially explained with patient's age and liver function. CL/F was found to decrease with age. According to the developed model, sirolimus CL/F decreases by, in average, 37% in patients with aspartate aminotransferase (AST) greater than 37 IU/L. The internal and external validation confirmed the satisfactory prediction of the developed model. The population modeling of routinely monitored data allowed quantification of the age and liver function influence on sirolimus CL/F. According to the final model, patients with compromised liver function expressed via AST values require careful monitoring and dosing adjustments. Proven good predictive performance makes this model a useful tool in everyday clinical practice. © 2019 Bojana Golubović, Katarina Vučićević, Dragana Radivojević, Sandra Vezmar Kovačević, Milica Prostran, Branislava Miljković.

Purpose: The purpose of the study was to examine and describe adjunctive lamotrigine (LTG) pharmacokinetics in paediatric and young adult patients using a nonlinear mixed effects modelling (NONMEM) approach. Methods: The study included 53 patients (age range 3-35 years) who were concomitantly treated with carbamazepine (CBZ) and/or valproic acid (VPA). A total of 70 blood samples corresponding to trough levels were available for analysis. Data were modelled, and the final model was evaluated using NONMEM and auxiliary software tools. Results: The final LTG population model included the effects of concomitant drugs and patient's weight (WT) which stratified the population into three groups: ≤25 kg, >25 to <60 kg and ≥60 kg. Based on the final model, the estimated LTG oral clearance (CL/F) for a typical patient weighing ≤25 kg, >25 to <60 kg or ≥60 kg who was concomitantly treated with CBZ was estimated to be 3.28, 4.23, or 7.15 l/h, respectively. If a patient was concomitantly treated with CBZ + VPA, the CL/F decreased on average by 69.5 % relative to LTG + CBZ co-therapy. VPA was found to decrease the LTG CL/F by 87.6 % compared to co-therapy with only CBZ. Conclusion: The LTG population pharmacokinetic model developed in this study may be a reliable method for individualising the LTG dosing regimen in paediatric and young adult patients on combination therapy during therapeutic drug monitoring. © 2013 Springer-Verlag Berlin Heidelberg.

Purpose: The purpose of the study was to examine and describe adjunctive lamotrigine (LTG) pharmacokinetics in paediatric and young adult patients using a nonlinear mixed effects modelling (NONMEM) approach. Methods: The study included 53 patients (age range 3-35 years) who were concomitantly treated with carbamazepine (CBZ) and/or valproic acid (VPA). A total of 70 blood samples corresponding to trough levels were available for analysis. Data were modelled, and the final model was evaluated using NONMEM and auxiliary software tools. Results: The final LTG population model included the effects of concomitant drugs and patient's weight (WT) which stratified the population into three groups: ≤25 kg, >25 to <60 kg and ≥60 kg. Based on the final model, the estimated LTG oral clearance (CL/F) for a typical patient weighing ≤25 kg, >25 to <60 kg or ≥60 kg who was concomitantly treated with CBZ was estimated to be 3.28, 4.23, or 7.15 l/h, respectively. If a patient was concomitantly treated with CBZ + VPA, the CL/F decreased on average by 69.5 % relative to LTG + CBZ co-therapy. VPA was found to decrease the LTG CL/F by 87.6 % compared to co-therapy with only CBZ. Conclusion: The LTG population pharmacokinetic model developed in this study may be a reliable method for individualising the LTG dosing regimen in paediatric and young adult patients on combination therapy during therapeutic drug monitoring. © 2013 Springer-Verlag Berlin Heidelberg.