Application of chromatographic techniques to predict the absorption of gemcitabine

Farmakokinetika zauzima vrlo značajno mjesto u dizajnu novih lijekova. Često je u prošlosti razlog neuspjeha lijeka na tržištu ili čak njegovog povlačenja bila neadekvatna farmakokinetika, a korak naprijed napravljen je kada su farmakokinetička ispitivanja prebačena u najranije faze istraživanja lijekova. Sve farmakokinetičke parametre barem djelomično definira lipofilnost spoja, a najveći utjecaj ima na apsorpciju koja je i ključni korak. Lipofilnost se određuje različitim tehnikama, no u svrhu probira između velikog broja molekula, najkorisnija se pokazala tekućinska kromatografija visoke djelotvornosti obrnutih faza. Osim C18 kolone, koja je uobičajena, koriste se i neke druge, a u posljednje vrijeme sve je popularnija kolona s vezanim umjetnim membranama (IAM). Zbog svog sastava, spomenuta kolona trebala bi vjernije opisivati interakcije spoja i bioloških membrana te samim time sposobnost permeacije kroz membrane. Cilj ovog istraživanja bio je na primjeru citostatika gemcitabina ispitati primjenjivost navedenih kromatografskih metoda za određivanje lipofilnosti spojeva. Osim toga, dobiveni rezultati su uspoređeni s računalnim izračunom log P vrijednosti ispitivanog spoja. Rezultati pokazuju različito ponašanje gemcitabina na tradicionalnoj C18 i na IAM koloni, a njegovo slabo zadržavanje na obje kolone upućuje na izrazitu hidrofilnost lijeka. Isto je moguće zaključiti i iz izračuna log P pomoću računalnih programa Molinspiration i ChemAxon.Pharmacokinetics plays a key role in drug design. In the past many of the failures of drug candidates in development programs or even withdrawal medicines from market was attributed to their undesirable pharmacokinetic properties. Therefore, in the modern drug design and development the preclinical pharmacokinetic evaluation should be performed in the earliest stages of drug research. Lipophilicity is well known as a prime physico-chemical descriptor of drugs with at least partially relevance to all of the pharmacokinetic parameters. Moreover, it plays a vital role in the absorption of orally administrated drugs, leading to enhanced oral bioavailability. Today, a great number of techniques and methods are used for lipophilicity determination, still a reversed-phase high-performance liquid chromatography (RP-HPLC) has been recognized as the most useful tool for high throughput screening. Due to many advantages of chromatographic columns with immobilized artificial membrane (IAM-HPLC), in the last years the use of conventional C18 column for determination of lipophilicity is significantly decreased. The IAM columns is an innovative approach to chromatography in which the stationary phase surface emulates the lipid environment of the cell membrane; thus comparing to the C18 columns more precisely mimic interactions between a compound and biological membranes. The aim of this study was to evaluate the applicability of both above mentioned methods for determination of lipophilicity on the cytostatic drug gemcitabine. Furthermore, the obtained results were compared with the log P values predicted by Molinspiration and ChemAxon software. The obtained results indicated different chromatographic behavior of gemcitabine on C18 and IAM columns. Both experimental and theoretical data propound the high hydrophilicity of investigated compound