Imre Klebovich

Automated determination of levodopa and carbidopa in plasma by high-performance liquid chromatography-electrochemical detection using an on-line flow injection analysis sample pretreatment unit

An automated analytical procedure is described for the parallel determination of L-3,4-dihydroxyphenylalanine (levodopa, L-dopa, LD) and the analogous hydrazine compound carbidopa (CD) in dog plasma by ion-pair high-performance liquid chromatography with electrochemical detection (HPLC-ED). After deproteinization of the plasma samples with perchloric acid the catecholamines were extracted from the supernatant by adsorption on a small column filled with alumina. The extraction and redissolution were automatically performed in a flow injection analysis unit (FIA) coupled to the HPLC system. The performance of the whole system was tested on dog plasma samples including specimens taken after oral administration of the anti-Parkinsonism drug Duellin, which is a combination tablet of levodopa and carbidopa.

Developing and advancing dry powder inhalation towards enhanced therapeutics.

Enhanced therapeutics are drug products derived from existing generic drugs that provide additional benefits to the patients and the healthcare system. Enhanced therapeutics are considered to be an important and relatively low risk source of innovation. Pulmonary drug delivery is the major delivery route to treat chronic respiratory diseases and has been proven as a potential delivery route for complex drugs that cannot be delivered orally. Development of dry powder inhalation systems targets the delivery of fine drug particles to the deep lung surface by a combination of drug formulation, primary packaging and a device, whereby each contributes to the overall performance. Various methodologies for the non-clinical and clinical performance testing of orally inhaled products have been proposed and applied with variable success. Regulatory pathways have been developed and applied since. Considerable efforts have been made during the past decade to understand and optimize pulmonary drug delivery including their efficient commercial manufacturing. Pulmonary drug delivery remains an area of future innovation in the effective treatment of pulmonary diseases as well as the systemic delivery of systemically active complex drugs.

Aqueous solvent system for solubilization of azole compounds

Azoles have a wide spectrum antimycotic activity, but due to some derivatives exhibiting poor water solubility their parenteral administration is limited. The influence of solubilizers on the aqueous solubility of the itraconazole, ketoconazole and miconazole was investigated in order to enhance their solubility for a possible parenteral dosage form. The solubilizer effect of acetate, phosphate and gluconate solutions were studied, along with ethanol, glycerol, macrogol 400, propylene glycol and surfactants, such as polysorbate 20, 60, 80 and sodium taurocholeate. The solubilizing effect of these excipients in binary or ternary combinations was also studied. An HPLC method was used for the solubility assay of the azoles. All of the assessed excipients showed considerable solubility enhancement characteristics, moreover the binary and ternary combinations showed synergistic effects solubilizing more miconazole than what they solubilized separately. Ternary combinations were capable of solubilizing more than 30 mg/ml miconazole, and more than 135 mg/ml of ketoconazole, which in both cases is a very substantial increase in solubility compared to their water solubility. The amount of solubilized drugs may well be used therapeutically, and the formulated solvent system can serve as a base for parenteral solutions.

Sensitive high-performance liquid chromatographic determination of nifedipine in dog plasma using an automated sample preparation system with laboratory robot

Nifedipine, a calcium-channel blocking drug was analysed in dog plasma after oral dosing with two different formulations. Sample preparation was automated with a laboratory robot. Quantitative determination of the drug was performed on a reversed-phase HPLC system with electrochemical detection (ED) using an internal standard. Validation of the analytical method showed that the system is well suited for pharmacokinetic studies on dogs. The assay was linear in the range 1-50 ng/ml. Inter-day and intra-day variability were between 6.43-18.15% C.V. and 1.57-5.53% C.V., respectively.

Oral, Intraperitoneal and Intravenous Pharmacokinetics of Deramciclane and its N‐desmethyl Metabolite in the Rat

The pharmacokinetic properties of deramciclane fumarate (EGIS‐3886), a new potential anxiolitic agent, and its N‐desmethyl metabolite have been investigated in Wistar rats after 10 mg kg−1 deramciclane fumarate was administered orally, intraperitoneally or intravenously.

Multiple ABC Transporters Efflux Baicalin

Baicalein, the aglycone formed by hydrolysis of baicalin in the intestine, is well absorbed by passive diffusion but subjected to extensive intestinal glucuronidation. Efflux of baicalin, the low passive permeability glucuronide of baicalein from enterocytes, likely depends on a carrier‐mediated transport. The present study was designed to explore potential drug–herb interaction by investigating the inhibitory effect of baicalin on the transport of reporter substrates by transporters and to identify the transporters responsible for the efflux of baicalin from enterocytes and hepatocytes. The interaction of baicalin with specific ABC transporters was studied using membranes from cells overexpressing human BCRP, MDR1, MRP2, MRP3 and MRP4. Baicalin was tested for its potential to inhibit vesicular transport by these transporters. The transport of baicalin by the selected transporters was also investigated. Transport by BCRP, MRP3 and MRP4 was inhibited by baicalin with an IC50 of 3.41 ± 1.83 μM, 14.01 ± 2.51 μM and 14.39 ± 5.69 μM respectively. Inhibition of MDR1 (IC50 = 94.84 ± 31.10 μM) and MRP2 (IC50 = 210.13 ± 110.49 μM) was less potent. MRP2 and BCRP are the apical transporters of baicalin that may mediate luminal efflux in enterocytes and biliary efflux in hepatocytes. The basolateral efflux of baicalin is likely mediated by MRP3 and MRP4 both in enterocytes and hepatocytes. Via inhibition of transport by ABC transporters, baicalin could interfere with the absorption and disposition of drugs. Copyright

In vitro simulation of food effect on dissolution of deramciclane film-coated tablets and correlation with in vivo data in healthy volunteers

The in vitro dissolution profiles of deramciclane 30 mg film-coated tablets, an acid-labile new 5-HT receptor antagonist, were studied under simulated fasting and fed conditions. Artificial gastric juice with pH adjusted to that of fasting conditions was applied either alone or after adding different dietary components. The use of the USP dissolution apparatus II (paddle method) showed that the presence of dietary components has markedly affected the amount of unchanged drug dissolved. As a similar tendency had been observed in food-effect studies in healthy volunteers, cumulative area under the curve (AUC(cum)) for both fed and fasting conditions were compared and an in vitro--in vivo correlation (IVIVC) was evaluated. A linear relationship was established between logarithmic in vivo blood sampling time and in vitro dissolution time assigned to equal AUC(cum) ratios (AUC(cum, fed)/AUC(cum, fasting)). Despite its limitations, in vitro modelling of in vivo conditions might help provide a base for predicting in vivo drug behaviour.

The single dose pharmacokinetics and safety of deramciclane in healthy male volunteers.

The pharmacokinetics and tolerability of a new putative non‐benzodiazepine type anxiolytic compound deramciclane was studied in two consecutive studies. An open dose‐escalation design was used to study doses from 0.2 to 50 mg in 18 healthy male volunteers. In the second study doses from 50 to 150 mg were investigated in 14 healthy males in a double‐blind, placebo‐controlled, dose escalation study. Deramciclane was rapidly absorbed from the GI‐tract and Tmax was 2–4 h. The elimination half‐life increased from about 20 h to about 32 h with the increasing dose. Nevertheless, the AUC0–∞ values increased linearly within the studies over the dose ranges of 3–50 and 50–150 mg. However, the increase was more than the ratio of the dose over the total dose range of 3–150 mg. Therefore, non‐linear pharmacokinetics of deramciclane at high doses cannot be excluded. N‐desmethyl deramciclane, which is the active metabolite of deramciclane, was determined in plasma. Cmax was reached at about 6 h. The AUC0–48 h for the N‐desmethyl metabolite was about one third of the AUC0–∞ of the parent compound and the ratio remained constant at each dose level. Deramciclane was safe, and was well tolerated at each dose level. Copyright

In vitro food-drug interaction study: Which milk component has a decreasing effect on the bioavailability of ciprofloxacin?

The purpose of the present work was developing an in vitro dissolution test to highlight the possible molecular background causing ciprofloxacin (CPFX)-milk interaction. The in vitro dissolution of CPFX from film-coated tablets (Ciprinol) 500mg) was examined at different pH values, simulating certain parts of the gastrointestinal tract, in the presence of water, low-fat milk, casein- or calcium enriched water. In order to determine the amount of dissolved CPFX, solid phase extraction sample preparation followed by high performance liquid chromatography coupled with mass spectrometry was applied. Comparing the dissolution efficiency values in various media, it can be concluded, that casein has a more pronounced effect on the absorbable amount of the antibiotic at each pH value studied, than calcium. In the case of concomitant intake of CPFX film-coated tablet and milk or other dairy products not only the complexation with calcium, but also the adsorption of CPFX on the surface of proteins decreases the absorbable amount of CPFX.

Determination of α-methyldopa in human plasma by validated high-performance liquid chromatography with fluorescence detection

A sensitive reversed-phase gradient elution high-performance liquid chromatographic method with fluorescence detection has been developed for the determination of α-methyldopa (AMD) in human plasma. Separation of the investigated compound and the 3,4-dihydroxyphenylalanine (DOPA) internal standard was achieved on a Nucleosil 7 C18 column with a 5 mM heptanesulphonic acid sodium salt containing 0.05 M potassium dihydrogenphosphate (pH 3.2)-acetonitrile mobile phase. The composition of the mobile phase was changed according to a linear gradient time program. Detection was performed at 270 nm fluorimetric excitation and 320 nm emission. The compounds were isolated from plasma by Bond-Elut C18 solid-phase extraction. The limit of quantitation was found to be 10 ng/ml plasma. The assay was validated with respect to accuracy, precision and system suitability. All validated parameters were found to be within the 20% required limits. On the basis of the sensitivity, linearity and validation parameters the developed analytical method was found to be suitable for application in a bioequivalency study.