The influence of genes’ polymorphism of CYP3A5, CYP2C8 and CYP1A2 metabolising enzymes on efficacy and safety of carbamazepine therapy in children

Primena karbamazepina u terapiji epilepsija praćena je značajnom inter- individualnom varijabilnošću u efikasnosti i bezbednosti, zbog koje je ishod terapije kod jednog dela pacijenata neizvestan. Biotransformacija karbamazepina zavisi od aktivnosti niza CYP enzima, uključujući CYP3A5, CYP2C8 i CYP1A2. Cilj ovog ispitivanja bio je da utvrdi učestalost nekih od funkcionalno značajnih varijacija gena CYP3A5, CYP2C8 i CYP1A2 u srpskoj pedijatrijskoj populaciji, kao i da proceni njihov uticaj na farmakokinetiku, efikasnost i bezbednost karbamazepina. Studija je uključila 40 pacijenata sa epilepsijom lečenih karbamazepinom. Genotipizacija je obuhvatila CYP3A5*2 (g.27289C>A, rs28365083), CYP3A5*3 (g.6986A>G, rs776746), CYP2C8*3 (g.416G>A, rs11572080), CYP2C8*5 (g.475delA, rs72558196), CYP1A2*1F (g.-163C>A, rs762551) i CYP1A2*1C (g.-3860G>A, rs2069514) varijacije, a sprovedena je metodom lančanog umnožavanja DNK (engl. polymerase chain reaction, PCR) i njenim modifikacijama (PCR-RFLP, AS-PCR). Koncentracija karbamazepina u serumu merena je nakon postignutog ravnotežnog stanja metodom tečne hromatografije visokih preformansi (engl. high performance liquid chromatography, HPLC). Efikasnost lečenja procenjivana na osnovu kontrole napada i EEG promena tokom trajanja studije, a bezbednost na osnovu laboratorijskih parametara i pojave neželjenih događaja. Takođe, sprovedena je populaciona farmakokinetička analiza, sa ciljem da dodatno proceni efekat ispitivanih polimorfizama, ali i izabranih demografskih i kliničkih faktora, na srednju vrednost klirensa karbamazepina. Učestalost ispitivanih varijacija CYP3A5, CYP2C8 i CYP1A2 gena iznosila je 97,5% za CYP3A5*3, 17,5% za CYP2C8*3 i 65,0 % za CYP1A2*1F, dok CYP3A5*2, CYP2C8*5 i CYP1A2*1C nisu detektovani. Analiza uticaja CYP3A5*3 na farmakokinetiku karbamazepina pokazala je da kod homozigotnih nosilaca varijantnog alela postoji tendencija ka nižim dozama ( ±σ: 15,06 ± 4,45 mg/kg naspram 18,74 ± 5,55 mg/kg, p= p=0.26), višim postignutim koncentracijama ( ±σ: 0,45 ± 0,13 mg/kg naspram 0,38 ± 0,03 mg/kg, p=0,47). Ispitivanje uticaja CYP2C8*3 pokazalo je da je korelacija između dnevne doze i postignute serumske koncentracije karbamazepina nakon prilagođavanja doze bila je značajna samo u grupi ispitanika bez CYP2C8*3 polimorfizma (r=0,52, p=0,002). Pritom, kod nosilaca ove varijacije uočena je tendencija ka nižim dnevnim dozama ( ±σ: 14,19 ± 5,39 mg/kg naspram 15,46 ± 4,35 mg/kg, p=0,5) i višim dozno normalizovanim koncentracijama leka ( ±σ: 0,54 ± 0,18 mg/ml naspram 0,43 ± 0,11 mg/ml, p=0,04). Populaciona farmakokinetička analiza koja je uključila CYP2C8*3 pokazala je da na klirens karbamazepina utiču pol i dnevna doza leka (CL (L/h)=0.215+0.0696*SEX+0.000183*DD, gde SEX ima vrednost 1 za muški i 0 za ženski pol, a DD odgovara ukupnoj dnevnoj dozi karbamazepina izraženoj u mg), ali ne i ispitivani CYP2C8 polimorfizam. Analiza uticaja CYP1A2*1F na farmakokinetiku karbamazepina pokazala je značajnu korelaciju između dnevne doze i postignute serumske koncentracije leka, ali samo u prisustvu CYP1A2*1F varijacije (r=0,68, p=0,0004). Kod homozigotnih nosilaca CYP1A2*1F varijacije uočena je i tendencija ka višim dozama ( ±σ: 16,23 ± 3,83 mg/kg naspram 14,43 ± 4,92 mg/kg, p=0,21) i nižim dozno- normalizovanim serumskim koncentracijama leka ( ±σ: 0,42 ± 0,12 mg/kg naspram 0,47 ± 0,14 mg/kg, p=0,26). Uticaj CYP1A2 −163A/A genotipa, ali i pola i ukupne dnevne doze leka, na klirens karbamazepina potvrđen je i populacionom farmakokinetičkom analizom, koja je rezultirala jednačinom CL(l/h)=0.176+0.0484*SEX+0.019*CYP1A2+0.000156*DD. Analiza uticaja ispitivanih polimorfizama na efikasnost i bezbednost terapije karbamazepinom nije pokazala statistički značajne razlike u praćenim parametrima među genotipski različitim grupama. U zaključku, učestalost ispitivanih varijacija CYP3A5, CYP2C8 i CYP1A2 gena kod Srba odgovara prethodno publikovanim podacima za belu populaciju. Za sada nema dovoljno kliničkih dokaza u korist uvođenja rutinske genotipizacije ispitivanih CYP3A5 i CYP2C8 polimorfizama kod dece srpske populacije na terapiji karbamazepinom. Međutim, dokazano je da CYP1A2 −163C>A (CYP1A2*1F) polimorfizam značajno utiče na farmakokinetiku leka. S obzirom na pokazanu učestalost ovog polimorfizma u srpskoj populaciji, primena rutinske genotipizacije bi mogla doprineti adekvatnijem izboru doze karbamazepina kada je indikovana njegova primena.Carbamazepine in epilepsy treatment includes significant inter-individual variability in efficacy and safety, which led to the fact that the therapy outcome is unpredictable in some patients. Carbamazepine biotransformation depends on activity of several CYP enzymes including CYP3А5, CYP2C8 and CYP1А2. The aim of the present study was to investigate the frequency of some of functionally important variants of genes: CYP3А5, CYP2C8 and CYP1А2 in Serbian pediatric population, and to assess their influence on pharmacokinetic, efficacy and safety of carbamazepine. The study involved 40 pediatric epileptic patients on steady-state carbamazepine treatment. Genotyping was included CYP3A5*2 (g.27289C>A, rs28365083), CYP3A5*3 (g.6986A>G, rs776746), CYP2C8*3 (g.416G>A, rs11572080), CYP2C8*5 (g.475delA, rs72558196), CYP1A2*1F (g.-163C>A, rs762551) и CYP1A2*1C (g.-3860G>A, rs2069514) variations, and conducted using polymerase chain reaction (PCR) and their modifications (PCRRFLP, AS-PCR). Carbamazepine steady state serum concentrations were determined by high performance liquid chromatography (HPLC). The efficacy was assessed based on the control of attacks and EEG changes during the study, and safety was assessed based on assessments of laboratory parameters and adverse events reported during the study. The population pharmacokinetic analysis was additionally assessed the effect of investigated genes polymorphisms, as well as the effect of chosen demographic and clinical factors on the carbamazepine clearance. Frequencies of investigated CYP3А5, CYP2C8 и CYP1А2 gene variations were 97,5% for CYP3A5*3, 17,5% for CYP2C8*3 and 65,0 % for CYP1A2*1F, while CYP3A5*2, CYP2C8*5 and CYP1A2*1C were not detected. Analysis of CYP3A5* influence on pharmacokinetic of carbamazepine showed that in homozygous carriers of variant allele compared to other subjects there was a tendency observed towards lower dose requirements ( ±σ: 15,06 ± 4,45 mg/kg vs. 18,74 ± 5,55 mg/kg) and higher drug concentrations ( ±σ: 0,45 ± 0,13 mg/kg vs. 0,38 ± 0,03 mg/kg). Analysis of CYP2C8*3 influence showed that correlation of daily doses and serum concentrations after dose adjustments was significant only in the group without CYP2C8*3 polymorphism (r=0,52, p=0,002). In carriers of this variation there was tendency observed towards lower daily doses ( ±σ: 14,19 ± 5,39 mg/kg vs 15,46 ± 4,35 mg/kg, p=0,5) and higher dose normalized concentrations of the drug ( ±σ: 0,54 ± 0,18 mg/ml vs 0,43 ± 0,11 mg/ml, p=0,04). The population pharmacokinetic analysis which included CYP2C8*3 revealed that the sex and daily dose, but not this CYP2C8 polimorphism, affect carbamazepine clearance (CL(L/h)=0.215+0.0696*SEX+0.000183*DD, where SEX has value 1 for male and 0 for female, аnd DD has value of carbamazepine total daily dose in mg). Analysis of CYP1A2*1F on carabamezepine pharmacokinetic revealed the significant correlation of daily doses and concentration only in the group of CYP1A2*1F carriers (r=0,68, p=0,0004). In homozygotes carriers of CYP1A2*1F variation the tendency towards higher doses ( ±σ: 16,23 ± 3,83 mg/kg vs 14,43 ± 4,92 mg/kg, p=0,21) and lower dose normalized serum concentration of the drug ±σ: 0,42 ± 0,12 mg/kg vs 0,47 ± 0,14 mg/kg, p=0,26) was detected. The influence of CYP1A2 −163A/A genotype and sex and total daily dose on the carbamazepine clearance was additionally confirmed by population pharmacokinetic analysis, with the equitation CL(l/h)=0.176+0.0484*SEX+0.019*CYP1A2+0.000156*DD. The analysis of the effect of investigated genes polymorphisms on efficacy and safety of the carbamazepine therapy did not revealed any statistically significant difference among different genotypes’ groups. In conclusion, the frequency of CYP3А5, CYP2C8 и CYP1А2 gene polymorphisms correlated well to previously published data for Caucasians. As for now, there is no significant clinical evidence that could support routine genotyping of investigated CYP3A5 and CYP2C8 polimorphisms in Serbian epileptic children on carbamazepine treatment. However, it has been proven that CYP1A2 −163C>A (CYP1A2*1F) polymorphism significantly affects the drug pharmacokinetic. Considering the observed frequency of this polymorphism in Serbian population, the use of the routine genotyping could contribute to the more adequate carbamazepine dosing when it is indicated as therapy

The influence of genes’ polymorphism of CYP3A5, CYP2C8 and CYP1A2 metabolising enzymes on efficacy and safety of carbamazepine therapy in children

Primena karbamazepina u terapiji epilepsija praćena je značajnom inter- individualnom varijabilnošću u efikasnosti i bezbednosti, zbog koje je ishod terapije kod jednog dela pacijenata neizvestan. Biotransformacija karbamazepina zavisi od aktivnosti niza CYP enzima, uključujući CYP3A5, CYP2C8 i CYP1A2. Cilj ovog ispitivanja bio je da utvrdi učestalost nekih od funkcionalno značajnih varijacija gena CYP3A5, CYP2C8 i CYP1A2 u srpskoj pedijatrijskoj populaciji, kao i da proceni njihov uticaj na farmakokinetiku, efikasnost i bezbednost karbamazepina. Studija je uključila 40 pacijenata sa epilepsijom lečenih karbamazepinom. Genotipizacija je obuhvatila CYP3A5*2 (g.27289C>A, rs28365083), CYP3A5*3 (g.6986A>G, rs776746), CYP2C8*3 (g.416G>A, rs11572080), CYP2C8*5 (g.475delA, rs72558196), CYP1A2*1F (g.-163C>A, rs762551) i CYP1A2*1C (g.-3860G>A, rs2069514) varijacije, a sprovedena je metodom lančanog umnožavanja DNK (engl. polymerase chain reaction, PCR) i njenim modifikacijama (PCR-RFLP, AS-PCR). Koncentracija karbamazepina u serumu merena je nakon postignutog ravnotežnog stanja metodom tečne hromatografije visokih preformansi (engl. high performance liquid chromatography, HPLC). Efikasnost lečenja procenjivana na osnovu kontrole napada i EEG promena tokom trajanja studije, a bezbednost na osnovu laboratorijskih parametara i pojave neželjenih događaja. Takođe, sprovedena je populaciona farmakokinetička analiza, sa ciljem da dodatno proceni efekat ispitivanih polimorfizama, ali i izabranih demografskih i kliničkih faktora, na srednju vrednost klirensa karbamazepina. Učestalost ispitivanih varijacija CYP3A5, CYP2C8 i CYP1A2 gena iznosila je 97,5% za CYP3A5*3, 17,5% za CYP2C8*3 i 65,0 % za CYP1A2*1F, dok CYP3A5*2, CYP2C8*5 i CYP1A2*1C nisu detektovani. Analiza uticaja CYP3A5*3 na farmakokinetiku karbamazepina pokazala je da kod homozigotnih nosilaca varijantnog alela postoji tendencija ka nižim dozama ( ±σ: 15,06 ± 4,45 mg/kg naspram 18,74 ± 5,55 mg/kg, p= p=0.26), višim postignutim koncentracijama ( ±σ: 0,45 ± 0,13 mg/kg naspram 0,38 ± 0,03 mg/kg, p=0,47). Ispitivanje uticaja CYP2C8*3 pokazalo je da je korelacija između dnevne doze i postignute serumske koncentracije karbamazepina nakon prilagođavanja doze bila je značajna samo u grupi ispitanika bez CYP2C8*3 polimorfizma (r=0,52, p=0,002). Pritom, kod nosilaca ove varijacije uočena je tendencija ka nižim dnevnim dozama ( ±σ: 14,19 ± 5,39 mg/kg naspram 15,46 ± 4,35 mg/kg, p=0,5) i višim dozno normalizovanim koncentracijama leka ( ±σ: 0,54 ± 0,18 mg/ml naspram 0,43 ± 0,11 mg/ml, p=0,04). Populaciona farmakokinetička analiza koja je uključila CYP2C8*3 pokazala je da na klirens karbamazepina utiču pol i dnevna doza leka (CL (L/h)=0.215+0.0696*SEX+0.000183*DD, gde SEX ima vrednost 1 za muški i 0 za ženski pol, a DD odgovara ukupnoj dnevnoj dozi karbamazepina izraženoj u mg), ali ne i ispitivani CYP2C8 polimorfizam. Analiza uticaja CYP1A2*1F na farmakokinetiku karbamazepina pokazala je značajnu korelaciju između dnevne doze i postignute serumske koncentracije leka, ali samo u prisustvu CYP1A2*1F varijacije (r=0,68, p=0,0004). Kod homozigotnih nosilaca CYP1A2*1F varijacije uočena je i tendencija ka višim dozama ( ±σ: 16,23 ± 3,83 mg/kg naspram 14,43 ± 4,92 mg/kg, p=0,21) i nižim dozno- normalizovanim serumskim koncentracijama leka ( ±σ: 0,42 ± 0,12 mg/kg naspram 0,47 ± 0,14 mg/kg, p=0,26). Uticaj CYP1A2 −163A/A genotipa, ali i pola i ukupne dnevne doze leka, na klirens karbamazepina potvrđen je i populacionom farmakokinetičkom analizom, koja je rezultirala jednačinom CL(l/h)=0.176+0.0484*SEX+0.019*CYP1A2+0.000156*DD. Analiza uticaja ispitivanih polimorfizama na efikasnost i bezbednost terapije karbamazepinom nije pokazala statistički značajne razlike u praćenim parametrima među genotipski različitim grupama. U zaključku, učestalost ispitivanih varijacija CYP3A5, CYP2C8 i CYP1A2 gena kod Srba odgovara prethodno publikovanim podacima za belu populaciju. Za sada nema dovoljno kliničkih dokaza u korist uvođenja rutinske genotipizacije ispitivanih CYP3A5 i CYP2C8 polimorfizama kod dece srpske populacije na terapiji karbamazepinom. Međutim, dokazano je da CYP1A2 −163C>A (CYP1A2*1F) polimorfizam značajno utiče na farmakokinetiku leka. S obzirom na pokazanu učestalost ovog polimorfizma u srpskoj populaciji, primena rutinske genotipizacije bi mogla doprineti adekvatnijem izboru doze karbamazepina kada je indikovana njegova primena.Carbamazepine in epilepsy treatment includes significant inter-individual variability in efficacy and safety, which led to the fact that the therapy outcome is unpredictable in some patients. Carbamazepine biotransformation depends on activity of several CYP enzymes including CYP3А5, CYP2C8 and CYP1А2. The aim of the present study was to investigate the frequency of some of functionally important variants of genes: CYP3А5, CYP2C8 and CYP1А2 in Serbian pediatric population, and to assess their influence on pharmacokinetic, efficacy and safety of carbamazepine. The study involved 40 pediatric epileptic patients on steady-state carbamazepine treatment. Genotyping was included CYP3A5*2 (g.27289C>A, rs28365083), CYP3A5*3 (g.6986A>G, rs776746), CYP2C8*3 (g.416G>A, rs11572080), CYP2C8*5 (g.475delA, rs72558196), CYP1A2*1F (g.-163C>A, rs762551) и CYP1A2*1C (g.-3860G>A, rs2069514) variations, and conducted using polymerase chain reaction (PCR) and their modifications (PCRRFLP, AS-PCR). Carbamazepine steady state serum concentrations were determined by high performance liquid chromatography (HPLC). The efficacy was assessed based on the control of attacks and EEG changes during the study, and safety was assessed based on assessments of laboratory parameters and adverse events reported during the study. The population pharmacokinetic analysis was additionally assessed the effect of investigated genes polymorphisms, as well as the effect of chosen demographic and clinical factors on the carbamazepine clearance. Frequencies of investigated CYP3А5, CYP2C8 и CYP1А2 gene variations were 97,5% for CYP3A5*3, 17,5% for CYP2C8*3 and 65,0 % for CYP1A2*1F, while CYP3A5*2, CYP2C8*5 and CYP1A2*1C were not detected. Analysis of CYP3A5* influence on pharmacokinetic of carbamazepine showed that in homozygous carriers of variant allele compared to other subjects there was a tendency observed towards lower dose requirements ( ±σ: 15,06 ± 4,45 mg/kg vs. 18,74 ± 5,55 mg/kg) and higher drug concentrations ( ±σ: 0,45 ± 0,13 mg/kg vs. 0,38 ± 0,03 mg/kg). Analysis of CYP2C8*3 influence showed that correlation of daily doses and serum concentrations after dose adjustments was significant only in the group without CYP2C8*3 polymorphism (r=0,52, p=0,002). In carriers of this variation there was tendency observed towards lower daily doses ( ±σ: 14,19 ± 5,39 mg/kg vs 15,46 ± 4,35 mg/kg, p=0,5) and higher dose normalized concentrations of the drug ( ±σ: 0,54 ± 0,18 mg/ml vs 0,43 ± 0,11 mg/ml, p=0,04). The population pharmacokinetic analysis which included CYP2C8*3 revealed that the sex and daily dose, but not this CYP2C8 polimorphism, affect carbamazepine clearance (CL(L/h)=0.215+0.0696*SEX+0.000183*DD, where SEX has value 1 for male and 0 for female, аnd DD has value of carbamazepine total daily dose in mg). Analysis of CYP1A2*1F on carabamezepine pharmacokinetic revealed the significant correlation of daily doses and concentration only in the group of CYP1A2*1F carriers (r=0,68, p=0,0004). In homozygotes carriers of CYP1A2*1F variation the tendency towards higher doses ( ±σ: 16,23 ± 3,83 mg/kg vs 14,43 ± 4,92 mg/kg, p=0,21) and lower dose normalized serum concentration of the drug ±σ: 0,42 ± 0,12 mg/kg vs 0,47 ± 0,14 mg/kg, p=0,26) was detected. The influence of CYP1A2 −163A/A genotype and sex and total daily dose on the carbamazepine clearance was additionally confirmed by population pharmacokinetic analysis, with the equitation CL(l/h)=0.176+0.0484*SEX+0.019*CYP1A2+0.000156*DD. The analysis of the effect of investigated genes polymorphisms on efficacy and safety of the carbamazepine therapy did not revealed any statistically significant difference among different genotypes’ groups. In conclusion, the frequency of CYP3А5, CYP2C8 и CYP1А2 gene polymorphisms correlated well to previously published data for Caucasians. As for now, there is no significant clinical evidence that could support routine genotyping of investigated CYP3A5 and CYP2C8 polimorphisms in Serbian epileptic children on carbamazepine treatment. However, it has been proven that CYP1A2 −163C>A (CYP1A2*1F) polymorphism significantly affects the drug pharmacokinetic. Considering the observed frequency of this polymorphism in Serbian population, the use of the routine genotyping could contribute to the more adequate carbamazepine dosing when it is indicated as therapy

The influence of genes’ polymorphism of CYP3A5, CYP2C8 and CYP1A2 metabolising enzymes on efficacy and safety of carbamazepine therapy in children

Primena karbamazepina u terapiji epilepsija praćena je značajnom inter- individualnom varijabilnošću u efikasnosti i bezbednosti, zbog koje je ishod terapije kod jednog dela pacijenata neizvestan. Biotransformacija karbamazepina zavisi od aktivnosti niza CYP enzima, uključujući CYP3A5, CYP2C8 i CYP1A2. Cilj ovog ispitivanja bio je da utvrdi učestalost nekih od funkcionalno značajnih varijacija gena CYP3A5, CYP2C8 i CYP1A2 u srpskoj pedijatrijskoj populaciji, kao i da proceni njihov uticaj na farmakokinetiku, efikasnost i bezbednost karbamazepina. Studija je uključila 40 pacijenata sa epilepsijom lečenih karbamazepinom. Genotipizacija je obuhvatila CYP3A5*2 (g.27289C>A, rs28365083), CYP3A5*3 (g.6986A>G, rs776746), CYP2C8*3 (g.416G>A, rs11572080), CYP2C8*5 (g.475delA, rs72558196), CYP1A2*1F (g.-163C>A, rs762551) i CYP1A2*1C (g.-3860G>A, rs2069514) varijacije, a sprovedena je metodom lančanog umnožavanja DNK (engl. polymerase chain reaction, PCR) i njenim modifikacijama (PCR-RFLP, AS-PCR). Koncentracija karbamazepina u serumu merena je nakon postignutog ravnotežnog stanja metodom tečne hromatografije visokih preformansi (engl. high performance liquid chromatography, HPLC). Efikasnost lečenja procenjivana na osnovu kontrole napada i EEG promena tokom trajanja studije, a bezbednost na osnovu laboratorijskih parametara i pojave neželjenih događaja. Takođe, sprovedena je populaciona farmakokinetička analiza, sa ciljem da dodatno proceni efekat ispitivanih polimorfizama, ali i izabranih demografskih i kliničkih faktora, na srednju vrednost klirensa karbamazepina. Učestalost ispitivanih varijacija CYP3A5, CYP2C8 i CYP1A2 gena iznosila je 97,5% za CYP3A5*3, 17,5% za CYP2C8*3 i 65,0 % za CYP1A2*1F, dok CYP3A5*2, CYP2C8*5 i CYP1A2*1C nisu detektovani. Analiza uticaja CYP3A5*3 na farmakokinetiku karbamazepina pokazala je da kod homozigotnih nosilaca varijantnog alela postoji tendencija ka nižim dozama ( ±σ: 15,06 ± 4,45 mg/kg naspram 18,74 ± 5,55 mg/kg, p= p=0.26), višim postignutim koncentracijama ( ±σ: 0,45 ± 0,13 mg/kg naspram 0,38 ± 0,03 mg/kg, p=0,47). Ispitivanje uticaja CYP2C8*3 pokazalo je da je korelacija između dnevne doze i postignute serumske koncentracije karbamazepina nakon prilagođavanja doze bila je značajna samo u grupi ispitanika bez CYP2C8*3 polimorfizma (r=0,52, p=0,002). Pritom, kod nosilaca ove varijacije uočena je tendencija ka nižim dnevnim dozama ( ±σ: 14,19 ± 5,39 mg/kg naspram 15,46 ± 4,35 mg/kg, p=0,5) i višim dozno normalizovanim koncentracijama leka ( ±σ: 0,54 ± 0,18 mg/ml naspram 0,43 ± 0,11 mg/ml, p=0,04). Populaciona farmakokinetička analiza koja je uključila CYP2C8*3 pokazala je da na klirens karbamazepina utiču pol i dnevna doza leka (CL (L/h)=0.215+0.0696*SEX+0.000183*DD, gde SEX ima vrednost 1 za muški i 0 za ženski pol, a DD odgovara ukupnoj dnevnoj dozi karbamazepina izraženoj u mg), ali ne i ispitivani CYP2C8 polimorfizam. Analiza uticaja CYP1A2*1F na farmakokinetiku karbamazepina pokazala je značajnu korelaciju između dnevne doze i postignute serumske koncentracije leka, ali samo u prisustvu CYP1A2*1F varijacije (r=0,68, p=0,0004). Kod homozigotnih nosilaca CYP1A2*1F varijacije uočena je i tendencija ka višim dozama ( ±σ: 16,23 ± 3,83 mg/kg naspram 14,43 ± 4,92 mg/kg, p=0,21) i nižim dozno- normalizovanim serumskim koncentracijama leka ( ±σ: 0,42 ± 0,12 mg/kg naspram 0,47 ± 0,14 mg/kg, p=0,26). Uticaj CYP1A2 −163A/A genotipa, ali i pola i ukupne dnevne doze leka, na klirens karbamazepina potvrđen je i populacionom farmakokinetičkom analizom, koja je rezultirala jednačinom CL(l/h)=0.176+0.0484*SEX+0.019*CYP1A2+0.000156*DD. Analiza uticaja ispitivanih polimorfizama na efikasnost i bezbednost terapije karbamazepinom nije pokazala statistički značajne razlike u praćenim parametrima među genotipski različitim grupama. U zaključku, učestalost ispitivanih varijacija CYP3A5, CYP2C8 i CYP1A2 gena kod Srba odgovara prethodno publikovanim podacima za belu populaciju. Za sada nema dovoljno kliničkih dokaza u korist uvođenja rutinske genotipizacije ispitivanih CYP3A5 i CYP2C8 polimorfizama kod dece srpske populacije na terapiji karbamazepinom. Međutim, dokazano je da CYP1A2 −163C>A (CYP1A2*1F) polimorfizam značajno utiče na farmakokinetiku leka. S obzirom na pokazanu učestalost ovog polimorfizma u srpskoj populaciji, primena rutinske genotipizacije bi mogla doprineti adekvatnijem izboru doze karbamazepina kada je indikovana njegova primena.Carbamazepine in epilepsy treatment includes significant inter-individual variability in efficacy and safety, which led to the fact that the therapy outcome is unpredictable in some patients. Carbamazepine biotransformation depends on activity of several CYP enzymes including CYP3А5, CYP2C8 and CYP1А2. The aim of the present study was to investigate the frequency of some of functionally important variants of genes: CYP3А5, CYP2C8 and CYP1А2 in Serbian pediatric population, and to assess their influence on pharmacokinetic, efficacy and safety of carbamazepine. The study involved 40 pediatric epileptic patients on steady-state carbamazepine treatment. Genotyping was included CYP3A5*2 (g.27289C>A, rs28365083), CYP3A5*3 (g.6986A>G, rs776746), CYP2C8*3 (g.416G>A, rs11572080), CYP2C8*5 (g.475delA, rs72558196), CYP1A2*1F (g.-163C>A, rs762551) и CYP1A2*1C (g.-3860G>A, rs2069514) variations, and conducted using polymerase chain reaction (PCR) and their modifications (PCRRFLP, AS-PCR). Carbamazepine steady state serum concentrations were determined by high performance liquid chromatography (HPLC). The efficacy was assessed based on the control of attacks and EEG changes during the study, and safety was assessed based on assessments of laboratory parameters and adverse events reported during the study. The population pharmacokinetic analysis was additionally assessed the effect of investigated genes polymorphisms, as well as the effect of chosen demographic and clinical factors on the carbamazepine clearance. Frequencies of investigated CYP3А5, CYP2C8 и CYP1А2 gene variations were 97,5% for CYP3A5*3, 17,5% for CYP2C8*3 and 65,0 % for CYP1A2*1F, while CYP3A5*2, CYP2C8*5 and CYP1A2*1C were not detected. Analysis of CYP3A5* influence on pharmacokinetic of carbamazepine showed that in homozygous carriers of variant allele compared to other subjects there was a tendency observed towards lower dose requirements ( ±σ: 15,06 ± 4,45 mg/kg vs. 18,74 ± 5,55 mg/kg) and higher drug concentrations ( ±σ: 0,45 ± 0,13 mg/kg vs. 0,38 ± 0,03 mg/kg). Analysis of CYP2C8*3 influence showed that correlation of daily doses and serum concentrations after dose adjustments was significant only in the group without CYP2C8*3 polymorphism (r=0,52, p=0,002). In carriers of this variation there was tendency observed towards lower daily doses ( ±σ: 14,19 ± 5,39 mg/kg vs 15,46 ± 4,35 mg/kg, p=0,5) and higher dose normalized concentrations of the drug ( ±σ: 0,54 ± 0,18 mg/ml vs 0,43 ± 0,11 mg/ml, p=0,04). The population pharmacokinetic analysis which included CYP2C8*3 revealed that the sex and daily dose, but not this CYP2C8 polimorphism, affect carbamazepine clearance (CL(L/h)=0.215+0.0696*SEX+0.000183*DD, where SEX has value 1 for male and 0 for female, аnd DD has value of carbamazepine total daily dose in mg). Analysis of CYP1A2*1F on carabamezepine pharmacokinetic revealed the significant correlation of daily doses and concentration only in the group of CYP1A2*1F carriers (r=0,68, p=0,0004). In homozygotes carriers of CYP1A2*1F variation the tendency towards higher doses ( ±σ: 16,23 ± 3,83 mg/kg vs 14,43 ± 4,92 mg/kg, p=0,21) and lower dose normalized serum concentration of the drug ±σ: 0,42 ± 0,12 mg/kg vs 0,47 ± 0,14 mg/kg, p=0,26) was detected. The influence of CYP1A2 −163A/A genotype and sex and total daily dose on the carbamazepine clearance was additionally confirmed by population pharmacokinetic analysis, with the equitation CL(l/h)=0.176+0.0484*SEX+0.019*CYP1A2+0.000156*DD. The analysis of the effect of investigated genes polymorphisms on efficacy and safety of the carbamazepine therapy did not revealed any statistically significant difference among different genotypes’ groups. In conclusion, the frequency of CYP3А5, CYP2C8 и CYP1А2 gene polymorphisms correlated well to previously published data for Caucasians. As for now, there is no significant clinical evidence that could support routine genotyping of investigated CYP3A5 and CYP2C8 polimorphisms in Serbian epileptic children on carbamazepine treatment. However, it has been proven that CYP1A2 −163C>A (CYP1A2*1F) polymorphism significantly affects the drug pharmacokinetic. Considering the observed frequency of this polymorphism in Serbian population, the use of the routine genotyping could contribute to the more adequate carbamazepine dosing when it is indicated as therapy