Micrograms Of Drug Research Articles

Development and validation of a semi-automated assay for the highly sensitive quantification of Biolimus A9 in human whole blood using high-performance liquid chromatography–tandem mass spectrometry

Drug-eluting stents are sustained-release intra-coronary devices that are usually coated with a few hundred micrograms of drug. Measuring the drugs that are released over weeks in order to assess human pharmacokinetics is a challenge that requires assays with high sensitivity. We developed and validated a semi-automated LC–MS/MS assay for the quantification of Biolimus A9, a proliferation signal inhibitor that was specifically developed for coating on drug-eluting stents in human EDTA blood. The only manual step was the addition of a zinc sulfate/methanol protein precipitation solution which included the internal standard. Samples were injected into the HPLC and extracted online. The assay had the following performance characteristics: range of reliable response 0.01–100 ng/mL ( r 2 > 0.99), inter-day accuracy (0.033 ng/mL): 111.7%, and inter-day precision: 8.6%. There was no ion suppression, matrix interferences or carry-over. Extracted samples were stable in the autosampler at +4 °C for at least 24 h and could undergo three freeze–thaw cycles. The assay, with a lower limit of detection of 333 fg/mL and a lower limit of quantitation of 10 pg/mL, was sufficiently sensitive and robust for quantifying Biolimus A9 in clinical trials after IV injection and after stent implantation.

Corneal penetration of simultaneously applied topical levofloxacin, norfloxacin and lomefloxacin in human eyes

This study was performed to assess the corneal penetration of three topically applied fluoroquinolones (levofloxacin, norfloxacin and lomefloxacin) in corneal buttons obtained from patients undergoing penetrating keratoplasty. Fourteen patients received three drops each of 0.5% levofloxacin, 0.3% norfloxacin and 0.3% lomefloxacin (the standard clinically available preparations) over a 30-min interval beginning 90 mins before their scheduled keratoplasty. Corneal samples obtained from excised buttons at the time of surgery were stored at - 80 degrees until analysis. The concentration of the administered fluoroquinolones was measured using high-performance liquid chromatography. The mean corneal concentration of levofloxacin (4.6 +/- 3.5 microg/g, mean +/- standard deviation) was significantly higher than that of lomefloxacin (2.7 +/- 1.8 microg/g, p = 0.0018) and norfloxacin (1.3 +/- 1.2 microg/g, p = 0.00012). Levofloxacin achieves a higher mean corneal concentration than norfloxacin and lomefloxacin in the human cornea.

Stomach-specific anti- H. pylori therapy : Part III: Effect of chitosan microspheres crosslinking on the gastric residence and local tetracycline concentrations in fasted gerbils

The main objective of the present study was to examine the effect of chemical crosslinking of chitosan microspheres on the gastric residence and local tetracycline concentrations following oral administration in fasted gerbils. Radioiodinated [ 125 I ] glyoxal-crosslinked chitosan microsphere suspension in deionized distilled water was administered for the gastric residence studies. At different time points, the animals were sacrificed and the radioactivity in tissues and fluids was measured. Stomach tetracycline concentrations were determined using tritiated-[ 3 H ]-tetracycline-loaded crosslinked chitosan microspheres. The radioactivity, measured with a liquid scintillation analyzer, was used to determine the microgram of drug per gram of tissues or fluids. After 2 h in the fasted stomach, approximately 10% of the non-crosslinked chitosan microspheres remained. On the other hand, 17% of the crosslinked chitosan microspheres remained in the fasted stomach after the same time period. The microspheres were predominantly found in the colon after 6 h of administration. There was no detectable radioactivity in the plasma, urine, small intestine, liver, and kidneys. Tetracycline concentration profile in the stomach from the crosslinked microsphere formulation was higher than that of the aqueous solution and the non-crosslinked microsphere formulation. While the area-under-the-curve ( AUC 0.5→10 h ) for tetracycline solution and non-crosslinked chitosan microspheres was 447.3 and 358.2 μg h/g of tissue, respectively, the AUC 0.5→10 h for the crosslinked chitosan microspheres was 868.9 μg h/g of tissue. The drug was predominantly found in the colon and urine after 6 h of administration. Results of this study show that chitosan microspheres prepared by chemical crosslinking provide a longer residence time in the fasted gerbil stomach than either tetracycline solution or microspheres prepared by ionic precipitation.

Determination of thyreostatics in animal feed by micellar electrokinetic chromatography.

The determination of the thyreostatics 2-thiouracil, its derivatives (4-methyl-2-thiouracil, 4-propyl-2-thiouracil and 4-phenyl-2-thiouracil) and methimazole in manufactured dried animal feed by micellar electrokinetic chromatography (MEKC) is described. A 99 +/- 5% extraction yield at the 20 micrograms g-1 level (n = 8) was achieved by shaking the milled fodder with methanol-1 M NaOH (80 + 20). Aliquots of the supernatant were injected in a 75 microns x 33.5 cm uncoated silica capillary using pressure; separation was performed at 23 degrees C with 15 kV (positive polarity) in a background electrolyte (BGE) containing 40 mM sodium dihydrogenphosphate, 50 mM sodium dodecyl sulfate and 15 mM Tween 20 at pH 9. When the surfactants were added to the BGE, all the thyreostatics were well resolved and the fodder extracts showed lower backgrounds. The peaks appeared within the 2.25-5.2 min range with efficiencies in the 2.5 x 10(4)-8 x 10(4) range; methimazole appeared in the vicinity of the electroosmotic migration time. Calibration curves were linear within the studied range (20-200 micrograms ml-1, r2 > 0.998). Limits of detection in the extracts of spiked fodder samples ranged from 0.25 to 0.4 microgram ml-1, which corresponded to 0.6-1.0 microgram of drug per gram of fodder. Peak area repeatabilities were about 4% at the 20 micrograms ml-1 level.

Albuterol delivery in a model of mechanical ventilation. Comparison of metered-dose inhaler and nebulizer efficiency.

Using an in vitro model, we compared efficiencies of jet nebulizers and metered-dose inhalers (MDI) with actuator devices to deliver albuterol in various conditions of mechanical ventilation. Factors tested included influence of humidification, MDI actuator device (Aerovent spacer or Marquest 172275 MDI adaptor), and synchronization of MDI to the respiratory cycle. With the nebulizer (AeroTech II) filled with 2.5 mg albuterol sulfate in 3 ml water and run until dry, inhaled mass was 42 +/- 2.6% and mass median aerodynamic diameter (MMAD) was 1.3 microns on a nonhumidified circuit. With the MDI+ Aerovent, the inhaled mass percentage per 90 microgm puff was 15.4 +/- 0.2% with humidification and 25.1 +/- 3.7% without humidification, actuations being synchronized with the beginning of inspiration and separated by a 1-min pause. Failure to synchronize actuations with inspiration or to pause 1 min resulted in significant reductions in inhaled mass (by 35 and 72%, respectively). The Marquest adaptor was less efficient, with an inhaled mass of 7.2 +/- 0.7% under optimal conditions. Metered-dose inhaler actuation during expiration resulted in relatively large particles (MMAD = 2.0 microns). All other MDI actuations led to essentially biphasic distributions, with particles greater than 1 micron following a distribution similar to the nebulizer and the overall MMAD estimated to be 0.22 microns. The AeroTech II delivered a cumulative 1,000 micrograms of drug (2,500 x 0.40) over 40 min. To achieve that amount, the MDI connected to the Aerovent and used in its most efficient sequence would require 45 timed puffs (90 micrograms per puff, 25.1% mean inhaled mass) and take 45 min of an experienced therapist's time.(ABSTRACT TRUNCATED AT 250 WORDS)

Liquid Chromatographic Determination of Six Sympathomimetic Drugs in Dosage Forms

A simple and rapid stability-indicating liquid chromatographic method is described for quantitative determination of 6 sympathomimetic drugs in various liquid and solid formulations. Analyses were carried out on a C18 reverse phase column using 0.01M 1-octanesulfonic acid, sodium salt in 0.2% acetic acid-methanol (70 + 30) as the mobile phase with photometric detection at 220 nm. Coefficients of variation for 5 consecutive injections of a mixed standards solution ranged from 0.62% for metaraminol to 1.40% for epinephrine. Standard recoveries ranged from 98.8% for metaraminol to 100.8% for epinephrine. The method was linear between 0.2 and 10 micrograms of drug injected and was used successfully to analyze 17 commercial products in a variety of dosage forms.

Comparison of Berodual<sup>®</sup> and Salbutamol in Asthma: A Multicenter Evaluation

A 2-month study was carried out to compare the efficacy and safety of Berodual (B) (Boehringer Ingelheim) and salbutamol (S) in asthma. B is a combined agent with 20 micrograms of ipratropium bromide and 50 micrograms of fenoterol in each metered aerosol puff. Each puff of S contained 100 micrograms of drug. 196 patients were included in the study and received 4 x 2 puffs a day of either B or S. FEV1 and FVC were measured every month, and peak expiratory flow rate (PEFR) 4 times a day, i.e. morning and evening before and after administration of drug. Improvement of PEFR was the same in the two groups. No tachyphylaxis occurred. No difference was observed between the two drugs with regard to heart and respiratory rate, dyspnea and blood pressure. Tremor seemed less frequent with B but this difference was not statistically significant. B achieved the same effects as S though containing less beta-2-agonist agent.

Liquid Chromatographic Determination of Coumarin Anticoagulants in Tablets

A simple and rapid liquid chromatographic method is described for the qualitative and quantitative determination of 5 coumarin anticoagulants in tablet composites and individual tablets. Analyses are carried out on a C18 reverse phase column using tetrahydrofuran-methanol-water-acetic acid (35 + 10 + 65 + 0.1) as mobile phase and photometric detection at 311 nm. The coefficients of variation for 10 consecutive injections of a mixed standards solution ranged from 0.28% for ethyl biscoumacetate to 0.78% for acenocoumarol. Standard recoveries were as follows: acenocoumarol, 99.3%; dicumarol, 99.6%; phenprocoumon, 101.6%; and warfarin sodium, 99.0%. The method was linear between 2 and 8 micrograms of drug injected. Assay results agreed favorably with those of the USP XX methods for dicumarol, phenprocoumon, and warfarin, and the NF XIV method for acenocoumarol. In addition, close correspondence was found with the results previously reported for the same drugs by a semiautomated spectrophotometric method. The content uniformity testing of individual 50 mg dicumarol tablets and 5 mg warfarin sodium tablets by the proposed method gave average (SD) values of 100.32% (0.64) and 101.00% (0.14), respectively, whereas these values were 101.60% (1.81) and 101.80% (0.18), respectively, by the method of USP XX.

Penetration of aztreonam into human bronchial secretions.

Nine intubated patients were given a single, 2-g intravenous dose of aztreonam over 5 min. Samples of serum and bronchial secretion were obtained 2, 4, and 8 h after administration and assayed for aztreonam content. The mean concentrations in bronchial secretion ranged from 1.9 to 5.2 micrograms/ml and tended to be highest at 4 h. The concentrations in bronchial secretion varied from patient to patient, but each patient had one or more bronchial secretion samples that contained at least 2.7 micrograms of drug per ml.

Intravaginal contraception with the synthetic progestin, R2323

A Silastic R intravaginal ring (IVR) containing R2323 (17α-ethinyl-l7β -hydroxy-18-methyl-4,9,11-estrien-3-one) in its center core was tested in vitro and in four women for one cycle each. Initially 330 micrograms of drug was released per day from the IVR in vitro , and after 150 days the value had declined to about 230 micrograms. Ovulation was inhibited in the four subjects due to the constant release of R2323 as evidenced by the steroid blood levels of 1 to 3 ng/ml. When the IVR was removed, R2323 blood levels quickly fell to zero. All the women had normal withdrawal bleeding, and two subjects followed during a recovery cycle had ovulatory levels of progesterone.