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Öğe Application of HPLC to investigate the physicochemical properties and intestinal permeability of Ketoprofen(Bentham Science Publishers B.V., 2017) Kaynak M.S.; Çelebier M.; Akgeyik E.; Sahin S.; Altınöz S.Introduction: The main objective of this study was to investigate the effect of pH on the solubility and intestinal permeability of ketoprofen by using HPLC. Ketoprofen is a slightly soluble acidic drug, and its solubility in aqueous phase is affected by pH changes dramatically. However, there is no data in the literature to support whether this pH dependent water solubility of ketoprofen will influence its absorption/bioavailability. Method: In this study, the distribution-coefficient (log D) of ketoprofen at various pH values between 4.5 and 7.5 were investigated using HPLC, and then it was made an attempt to correlate the log D values with the intestinal permeability values. For this reason, in vivo intestinal permeability studies were performed at pH 4.5 and pH 7.5. The concentrations of model and reference compounds and also the blank buffers passed though the rat intestine were analyzed by means of a validated HPLC method. Result: A nonlinear relationship was found between the results of in vitro and in vivo studies indicating that the diffusion of ketoprofen was not only related with passive diffusion, but also could be related with active transport. © 2017 Bentham Science Publishers.Öğe Bioavailability file: Amlodipine(Ankara University, 2011) Kaynak M.S.; Bogacz A.; Stelmasi?ski M.; Şahin S.Amlodipine (AML), a third-generation dihydropiridin, is a long-acting L-calcium channel blocker used in the treatment of hypertension and angina pectoris. It exerts its effects by blocking the voltage-dependent L-calcium channels and binding to both dihydropiridin and nondihydropiridin binding sites. AML is well absorbed (96%) after oral administration and its bioavailability is between 64-90%. Its volume of distribution is about 16 to 21 L/kg and protein binding is 98% after oral administration. AML is extensively metabolized in the liver and its elimination from the plasma is biphasic with a terminal half-life of 30 to 50 h. It is excreted by renal route about 60%. According to Biopharmaceutics Classification System, AML is classified as class I drug by WHO. In this review physicochemical properties, pharmacology, analytical methods, pharmacokinetics and bioavailability of amlodipine are discussed.Öğe Determination of amlodipine and furosemide with newly developed and validated rp-hplc method in commercially available tablet dosage forms(Hacettepe University, Faculty of Pharmacy, 2012) Şimşek F.O.; Kaynak M.S.; Şanlı N.; Şahin S.The aim of this study was to develop a new, fast, reliable and validated RP-HPLC method for the simultaneous determination of amlodipine and furosemide in tablet dosage forms. A C18 column (Fortis™ 250x4.60 mm 5 ?m) which was heated at 45oC during the analysis, was used for the separation and quantification of these drugs. The mobile phase consisted of water (15 mM o-phosphoric acid, pH 5.0) and acetonitrile (50:50 v/v). Analyses were run at a flow rate 1.0 mL.min-1 and UV detector was set at 238 nm. The injection volume was 20 ?L and total run time for an assay was approximately 5 min. The developed method was validated according to the ICH guideline. For the application of the proposed RP-HPLC method, commercially available four different AML containing tablets (one reference (Norvasc) and three generic (Dilapin, Monovasc, Penvasc) tablets) and commercially available two different FSM containing tablets (one reference (Lasix) and one generic (Desal) tablet) were obtained from the market and analyzed for their drug content. Under the given chromatographic conditions, AML and FSM were eluted at 4.28 and 3.68 min., respectively. The method was linear in the concentration range of 1.0 to 16.0 ?g.mL-1 and 0.1 to 12.0 ?g.mL-1 for AML and FSM, respectively with a correlation coefficient >0.999. LOD and LOQ were 0.642 ?g.mL-1 and 2.139 ?g.mL-1 for AML 0.010 ?g.mL-1 and 0.031 ?g.mL-1 for FSM, respectively. Under the conditions used, the analysis completely fulfilled the system suitability test limits suggested by FDA for the quantitative chromatographic methods. The method was successfully applied for the analysis of these drugs in commercially available tablets. © 2012, Hacettepe University, Faculty of Pharmacy. All rights reserved.Öğe Determination of in vitro dissolution profiles of amlodipine besylate and olmesartan medoxomil using a new "HPLC method"(Syscom 18 SRL, 2013) Kaynak M.S.; Çelebier M.; Sahin S.; Altinöz S.The aim of this study was to develop an HPLC method for simultaneous determination of these active compounds and to apply this method to determine the dissolution of AML and OLM from a commercially available tablet. Valsartan (VAL) was used as an internal standard (IS). Separation of AML, OLM and VAL was performed using Phenomenex C18 column (Luna 5 ?, 100A, 250x4.6 mm; California, USA) protected with a Phenomenex C18 guard column (4.0x3.0 mm; California, USA). The chromatographic separation operated isocratically at room temperature using a mobile phase consisted of phosphate buffer (pH 4.0,0.04 mol/L):methanol: acetonitrile (40:45:15, v/v/v) delivered at a flow rate of 0.8 mL/min and injection volume was 10 ?L. The diode array detector was set at 234 nm and 205 nm wavelengths for the quantirication of AML and OLM respectively. In vitro dissolution studies revealed that 85% of the labeled amounts of AML and OLM were released within 25 min from their fixed combination tablet dosage form. The developed HPLC method was validated according to the ICH guidelines and it is proposed for dissolution studies of the combination dosage forms of these compounds.Öğe Development and validation of a RP-HPLC method for determination of solubility of furosemide(2013) Kaynak M.S.; Saffln S.The objective of the Biopharmaceutics Classification System is to allow prediction of in vivo pharmacokinetic performance of drug products from in vitro measurements; therefore, it is important to determine the solubility and permeability of drug substances. Furosemide (FSM) is a loop diuretic commonly used in the treatment of edematous states associated chronic renal failure, hypertension, congestive heart failure and cirrhosis of the liver. The aim of this study was to develop and validate an HPLC method for quantification of FSM in the samples obtained from the in vitro solubility studies performed at five different pH values (pH 1.0, 2.9, 3.9, 4.9 and 7.5). Chromatographic separation of FSM was achieved on a reverse phase column (Waters Spherisorb ODS2 C18 250x4.6 mm 5 pim) with a mobile phase consisted of 0.01M KH2P04 (pH 5.5) and methanol (70:30 v/v). Analyses were run at a flow rate 1 mL/min and UV detection was performed at 235 nm. Under these conditions, the retention time of FSM was about 7.0 min. The method was linear in the concentration range of 0.5 to 50 ?/mL, and limit of quantification was 320 ng/mL. Developed and validated HPLC method was proved to be simple, reliable and also suitable as a single method for studying the solubility of FSM as a function of pH. Finally, based on our results, solubility of FSM was dependent on pH. Its solubility was low between pH 1.0 and 4.9, and was high at pH 7.5.Öğe Permeability enhancers used to increase intestinal absorption(Hacettepe University, Faculty of Pharmacy, 2013) Ateş M.; Kaynak M.S.; Şahin S.Drugs are administered through various routes to obtain systemic effect. Of these, the most commonly used route of administration is the oral route. Following oral administration, the drug has to pass through several biological membranes until it reaches the site of effect. The most important one among these membranes is the intestinal epithelium. Absorption through the intestinal epithelium occurs mainly by two mechanisms. These mechanisms are absorption through the epithelial cell membranes (transcellular route) and absorption through the tight junctions between epithelial cells. Transport of molecules through the tight junctions is called as paracellular (intercellular) transport. The most effective way to improve drug absorption by regulating paracellular permeability is the structural organization of tight junctions. It is reported that some substances such as polymers, surfactants increase the absorption of paracellulary transported drugs across membranes by means of various mechanisms. These substances are also known as permeation enhancers. In this review, physicochemical peroperties of permeability enhancers and their mechanism of effect to increase intestinal absorption were discussed. Also various examples were given for these permeability enhancers and the studies counducted using these substances were evaluated. © 2013, Hacettepe University, Faculty of Pharmacy. All rights reserved.Öğe Simultaneous determination of acyclovir, metoprolol and phenol red by a RP-HPLC method for intestinal perfusion studies(Hacettepe University, Faculty of Pharmacy, 2015) Ateş M.; Kaynak M.S.; Şahin S.Intestinal perfusion (SPIP) technique is one of the most commonly used techniques to determine the intestinal permeability of a drug. In perfusion studies, metoprolol (as tartrate) and phenol red are widely used as a refer- ence compounds to evaluate the permeability coefficient of the compound of interest (acyclovir in this study). The aim of our study was to develop and validate a reversed-phase liquid chromatographic method for the simultan- eous determination of acyclovir, metoprolol and phenol red for use in intes- tinal perfusion studies. The analysis was performed on a C18 column (4.6 mm x 250 mm, 5 ?m) using a mobile phase consisting of methanol:0.0125 M potassium dihydrogen phosphate buffer (55:45, v/v; pH 7.0). Method was validated according to the FDA guidelines for selectivity, sensitivity, linearity, precision, accuracy, stability. All calibration curves were linear (r2> 0.999). Lower limit of quantitation was 0.04 ?g/mL for acyclovir, 0.02 ?g/mL for metoprolol, 0.01 ?g/mL for phenol red. Detection limit was 0.01 ?g/mL for acyclovir 0.002 ?g/mL for metoprolol, 0.003 ?g/mL for phenol red. Precision and accuracy results of the method fulfilled the required limits. This newly developed and validated method can be readily used on a routine basis for the standardization of in situ intestinal permeability experiments. © 2015, Hacettepe University, Faculty of Pharmacy. All rights reserved.
