Volume Of Drug Solution Research Articles

Coupling biological detection to liquid chromatography: a new tool in drug discovery.

Procedures to characterize drugs that can be obtained from plant extracts or combinatorial chemistry are tedious, and they consume considerable resources (e.g., animals) and time. Thus, we have looked for a way to streamline this process. We describe here a novel system for the pre-characterization of drugs based on liquid chromatography coupled to biological detection using perifused or perfused organs. This novel system allows the on-line detection of pharmacologically active substances in hydrosoluble mixtures from vegetal extracts or combinatorial chemistry libraries. Depending on the volume of drug solution and concentration of the samples, the procedure can work through either medium pressure liquid chromatography or HPLC, and it enables the fingerprints of drugs to be assessed based on their contractile activity on combinations of different isolated tissues. As an example, we show how the system can identify active fractions from an extract of Stevia rebaudiana Bertoni, an activity that was later associated with rebaudioside N. Coupling liquid chromatography to biological detection offers a rapid way to focus attention on active products in complex samples, mostly from hydrosoluble species, helping to considerably reduce the time and cost of the pre-characterization of drugs.

Definition of formulation design space, in vitro bioactivity and in vivo biodistribution for hydrophilic drug loaded PLGA/PEO–PPO–PEO nanoparticles using OFAT experiments

Modified nanoprecipitation method was used for improved incorporation of hydrophilic drug (irinotecan hydrochloride) into the PLGA/PEO–PPO–PEO blended and blended/adsorbed nanoparticles. One factor at a time (OFAT) variation experiments were conducted in order to determine key formulation factors (concentration and volume of drug solution, evaporation rate and PLGA/PEO–PPO–PEO ratio) influencing nanoparticle properties (particle size and size distribution, encapsulation efficiency, drug content, zeta potential, drug dissolution rate, as well as protein binding capacity). The insight into in vivo behavior of prepared nanoparticles and their potential for effective anticancer treatment was gained by performing biodistribution and cell culture studies as part of OFAT experiments. The mean particle size, mainly dependent upon PLGA/PEO–PPO–PEO ratio, was in the range of 112–125nm, with narrow unimodal distribution (PDI∼0.1). Encapsulation efficiency (32–63%) was impacted by evaporation rate and PLGA/PEO–PPO–PEO ratio. Drug content (0.2–1.51%) and controlled release properties were related to the influence of all tested formulation factors. Structural information for the studied nanoparticles was obtained using DSC and FT-IR spectroscopy. Zeta potential values indicated that presence of PEO–PPO–PEO in the formulations shielded the high surface negative charge of PLGA. PEO–PPO–PEO surface coverage of PLGA/PEO–PPO–PEO blended as well as blended/adsorbed nanoparticles depended upon amount of used PEO–PPO–PEO during preparation procedure and was related to the protein resistant characteristics of nanoparticles. Results from in vivo studies evidenced prolonged blood circulation time of the prepared nanoparticles, while cell culture studies indicated higher in vitro bioefficacy compared to free drug. Performed experiments defined possible design space and justified further optimization of formulation using experimental design studies.

Pharmacokinetic modulation of irinotecan metabolites by sulphobromophthalein in rats.

The purpose of this study was to modulate the pharmacokinetics of irinotecan metabolites, SN-38 and SN-38-glucuronide, by possibly reducing biliary excretion, which in turn could lower irinotecan toxicity. SN-38-glucuronide is associated with severe diarrhoea that occurs after irinotecan therapy as a result of enteric injury caused by SN-38. Sulphobromophthalein is used clinically as a drug for testing liver function and is considered to be a safe drug. We investigated the effect of sulphobromophthalein on the disposition of irinotecan metabolites after CPT-11 (7-ethyl-10-[10-4-(1-piperidino)-1-piperidino]-carbonyloxy-camptothecin) administration. Wistar rats were administered CPT11 (500 microg/body) in saline as a bolus injection into the femoral vein through a catheter. The volume of drug solution injected into each animal was 1 mL. Rats were either administered CPT-11 alone or simultaneously with sulphobromophthalein (20 mg/body). After administration, blood and bile samples were taken at appropriate intervals and analysed by HPLC. Co-administration of sulphobromophthalein partially inhibited the biliary excretion of SN-38-glucuronide with a concomitant increase in its area under the plasma concentration-time curve (AUC) but did not significantly alter the biliary excretion and AUC of the active metabolite SN-38. These results suggested that cotreatment of CPT-11 with sulphobromophthalein might decrease intraluminal SN-38 concentrations without altering the pharmacokinetics of SN-38.

Interaction between paraventricular nucleus and septal area in the control of physiological responses induced by angiotensin II.

We determined the effects of losartan (40 nmol) and PD 123319 (40 nmol) (both non-peptides and selective antagonists of the AT1 and AT2 angiotensin receptors, respectively), and [Sar1, Ala8] angiotensin II (ANG II) (40 nmol) (a non-selective peptide antagonist of angiotensin receptors) injected into the paraventricular nucleus (PVN) on the water and salt appetite, diuresis and natriuresis and mean arterial pressure (MAP) induced by administration of 10 nmol of ANG II into the medial septal area (MSA) of male Holtzman rats weighing 250-300 g. The volume of drug solution injected was 0.5 micro l over a period of 10-15 s. The responses were measured over a period of 120 min. ANG II alone injected into the MSA induced an increase in all the above parameters (8.1 +/- 1.2, 1.8 +/- 0.3, and 17.1 +/- 1.0 ml, 217 +/- 25 micro Eq/120 min, and 24 +/- 4 mmHg, respectively, N = 10-12) compared with vehicle-treated rats (1.4 +/- 0.2, 0.6 +/- 0.1, and 9.3 +/- 0.5 ml, 47 +/- 5 micro Eq/120 min, and 4.1 +/- 0.8 mmHg, respectively, N = 10-14). Pretreatment with losartan and [Sar1, Ala8] ANG II completely abolished the water and sodium intake, and the pressor increase (0.5 +/- 0.2, 1.1 +/- 0.2, 0.5 +/- 0.2, and 0.8 +/- 0.2 ml, and 1.2 +/- 3.9, 31 +/- 4.6 mmHg, respectively, N = 9-12), whereas losartan blunted the urinary and sodium excretion induced by ANG II (13.9 +/- 1.0 ml and 187 +/- 10 micro Eq/120 min, respectively, N = 9). Pretreatment with PD 123319 and [Sar1, Ala8] ANG II blocked the urinary and sodium excretion (10.7 +/- 0.8, 9.8 +/- 0.7 ml, and 67 +/- 13 and 57 +/- 17 micro Eq/120 min, respectively, N = 9), whereas pretreatment with PD 123319 partially blocked the water and sodium intake, and the MAP induced by ANG II administration (2.3 +/- 0.3, 1.1 +/- 0.1 ml, and 12 +/- 3 mmHg, respectively, N = 9-10). These results suggest the angiotensinergic effect of the MSA on the AT1 and AT2 receptors of the PVN in terms of water and sodium homeostasis and MAP modulation.

Optimizing the in vitro performance of Respimat.

Aerosolization of a drug solution in a handheld device for inhalation therapy can be achieved either by vibration or extrusion through a fine nozzle. The latter method does not necessitate the use of an electrical power source and has been developed further in Respimat. The device was adapted for mass production, selecting appropriate materials for the desired size and weight as well as for stability and technical performance. After optimization of the nozzle design, Respimat produced encouraging results in its first lung deposition study in volunteers compared with a chlorofluorocarbon-driven metered dose inhaler (CFC-MDI). Respimat is a reusable device with a mode of action that differs from those of other inhalers. The mechanical power from a coiled spring forces a metered volume of drug solution through a nozzle in a unique component, the uniblock. The convergence of two fine jets of liquid generates a slow-moving aerosol of soft mist. The fine particle fraction in the aerosol, determined from experiments with the Anderson Cascade Impactor (Anderson Instruments, Inc., Smyrna, GA), is approximately 66% for an aqueous drug solution and 81% for an ethanolic solution. This value is about 2.5 times higher than the fine particle fractions determined for CFC-MDIs, and the velocity is about five times lower (e.g., 10 m/s for an aqueous solution), with both factors contributing to the improved lung deposition. In addition, the dose release duration from Respimat is considerably longer than that from CFC-MDIs at approximately 1.2 seconds, allowing more time for the patient to coordinate actuation and inspiration. The reliability and consistency of dose delivery from Respimat also have been confirmed.

Some factors influencing the efficiency of a jet nebuliser system

The operation of a commercially available nebuliser system (Medic-Aid Ltd) is reviewed and the efficiency with which it produces an aerosol assessed. Defining the efficiency of nebulisation E as the fraction of the original mass of solution released as an aerosol it is found that the internal surface area, mass of solution used, the surface tension of the solution and the angle of tilt are important factors in determining E. Reducing the internal surface area of the nebuliser by means of Perspex inserts significantly increases E for 3 g of water from 49% for the unmodified system to 67% for the modified nebuliser (P less than 0.01). E increases with the mass of solution used but only exceeds 60% when 4.5 g water are used. Decreasing the surface tension of the solution from 7.2 x 10(-3) N m-1 (water) to 3.7 x 10(-3) N m-1 and 3.1 x 10(-3) N m-1 (using two different concentrations of a detergent in water) significantly increases E for 3 g solution from 49% to 65% and 69% respectively (P less than 0.05). Operating the nebuliser at a tilt also increases E. The measurements emphasise the importance of reducing the internal surface area of this type of nebuliser, using an adequate volume of drug solution (at least 4 ml is suggested) and operating the nebuliser at an angle to the vertical (20 degrees suggested) in order to maximise E. The surface tension of the drug solution is a further important determinant of E.

Factors affecting drug delivery from a syringe-pump infusion set

In vitro testing of drug delivery via dual-lumen, small-volume i.v. extension tubing designed for use with a syringe pump was conducted. From a dual-lumen extension set with intraluminal diameters of 0.020 inch, effluent samples were collected at 5, 10, and 20 minutes after injection of a 1-mL volume of drug solution intended for delivery over 20 minutes by a syringe infusion pump. Variables were flow rate (5 or 25 mL/hr) of the primary infusion, tubing position (vertical or horizontal), and density of the drug solution (penicillin G potassium 250,000 units/mL and aminophylline 25 mg/mL represented high and low specific gravities, respectively). Each drug solution was labeled with radioactive carbon and the drug content of the effluent was analyzed by liquid scintillation. For each set of variables, samples were also tested after the tubing was flushed with 5% dextrose injection 0.2-0.6 mL. Similar procedures were followed to determine delivery of the labeled penicillin G potassium solution via a dual-lumen extension set with intraluminal diameters of 0.020 inch (for drug) and 0.060 inch (for the primary infusion); a 13-mm-diameter, 0.2 micron filter was attached to the smaller-lumen tubing. A primary infusion flow rate of 5 mL/hr and flush volumes of 0.3 and 0.6 mL were used in this study. To determine the influence of intraluminal diameter on the flush volume required for delivery of a dose of aminophylline (1-mL volume), single-lumen extension tubings with different diameters were tested. The final percentage of the drug dose delivered via the dual-lumen extension set with 0.020-inch lumens was affected only by flush volume.(ABSTRACT TRUNCATED AT 250 WORDS)