Determination of albuterol in plasma after aerosol inhalation by gas chromatography-mass spectrometry with selected-ion monitoring

Synthesis and comparative molecular field analysis (CoMFA) of argentatin B derivatives as growth inhibitors of human cancer cell lines

Synthesis, characterization, anticancer activity, and comparative molecular field analysis (CoMFA) of 14 argentatin B (1) analogs are described. The effect of argentatin B derivatives on the growth of K562 (leukemia), PC-3 (prostate), U251 (CNS), and HCT-15 (colon) human cancer cell lines was determined using the sulforhodamine B test. The most active compound in this series, 2-formyl-(16beta,24R)-16,24-epoxy-25-hydroxycycloart-1-en-3-one (12), was about 35-50 times more potent than argentatin B (1). Structures were built using the X-ray crystallography of six derivatives for 3D modeling with Sybyl6.9. CoMFA of Log (1/IC50) in K562 cell line gave q2 = 0.507, r2 = 0.907, and three components. The standard deviation CoMFA contours indicate that increased activity is associated with a bulky group at C-2, a C1-C2 double bond, and low electronic density at C-25. Experimental Log P values for argentatin B and one derivative were 1-2 Log units more hydrophilic than the calculated CLog P values.

Pharmacological Approach to Evaluate Aerosol Pulmonary Deposition

Drug delivery to the lung in vivo may be assessed using pharmacokinetic or pharmacodynamic techniques. The choice of method depends on drug class specificities. Pharmacokinetic determination of deposition to the lung for drugs without hepatic first-pass effect, such as short acting beta2-agonists, has to be done shortly after inhalation to minimize the effect of gastrointestinal absorption. For medication undergoing important hepatic first-pass metabolisation, such as inhaled corticosteroid, plasma concentration indirectly reflects bronchial deposition. The pharmacodynamic profile should be assessed through clinical effects and adverse events induced by inhaled drugs. Dose ranking of lung deposition for bronchodilators requires patient selection with sufficient bronchial obstruction to maintain room for improvement after the first dose. To assess dose effect relationship between inhaled corticosteroid, the Finney parallel line bioassay is the reference method with a study period of at least 6 weeks. Analysis of side effects with high doses of beta2-agonists or inhaled corticosteroids may also be used to compare lung deposition. Finally, pharmacological evaluation of lung deposition provides complementary information to scintigraphic studies, based on their clinical relevance.

Effect of propellant on the pharmacokinetics and pharmacodynamics of inhaled albuterol in asthmatic subjects

Hydrofluoroalkane (HFA) propellants have largely replaced chlorofluorocarbon (CFC) propellants in metered dose inhalers (MDI). It is important to document the pharmacokinetics (PK) and pharmacodynamics (PD) of medications delivered using HFA propellants compared to CFC propellants. Six adult asthmatics with mild to moderate asthma were selected for the study. Each subject inhaled 180 microg of albuterol from an MDI with holding chamber. Venous blood was collected for measuring albuterol levels at intervals over 12 h, and spirometric measurements of airflow were measured over the same time period. Plasma samples were analyzed using a GC/MS assay developed in our laboratory. PK and PD parameters were calculated by nonlinear regression using WinNonlin. There were no statistically significant differences between PD parameters for HFA versus CFC propellants. The area under the plasma albuterol concentration versus time curve (AUC) was 72% greater for the HFA formulation, indicating a greater lung bioavailability (p = 0.015). This difference in bioavailability did not result in a statistically significant difference in FEV(1) values between the two propellants.

2,6-Dichloroquinone chlorimide and 7,7,8,8-tetracyanoquinodimethane reagents for the spectrophotometric determination of salbutamol in pure and dosage forms

A simple, rapid and sensitive spectrophotometric method for the determination of sulbutamol in pure form and in different pharmaceutical preparations has been developed. The charge transfer (CT) reaction between salbutamol as electron donor and 2,6-dichloroquinone chlorimide (DCQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as a pi-electron acceptor have been spectrophotometrically studied. The optimum experimental conditions for these CT reactions have been studied carefully. Beer's law is obeyed over the concentration range of 1.0-30.0 microg ml(-1) and 2.0-20.0 microg ml(-1) for salbutamol using DCQ and TCNQ, respectively. For more accurate results, Ringbom optimum concentration range is calculated and found to be 10.0 to 30.0 and 8.0 to 20 microg ml(-1) for salbutamol using DCQ and TCNQ, respectively. The Sandell sensitivity is found to be 0.011 and 0.010 g cm(-2) for salbutamol using DCQ and TCNQ, respectively, which indicate the high sensitivity of the proposed methods. Relative standard deviations (R.S.D.) of 0.27 to 0.68% and 0.20 to 1.40% (n=5) were obtained for five replicates of salbutamol using DCQ and TCNQ, respectively. The results obtained by the two reagents are comparable with those obtained by British pharmacopoeia assay for the determination of salbutamol in raw materials and in pharmaceutical preparations.

Pharmacokinetics and pharmacodynamics of cumulative single doses of inhaled salbutamol enantiomers in asthmatic subjects

Objectives of this study were to compare the pharmacokinetics, pharmacodynamics and safety of single cumulative doses of active (R)-salbutamol given either as the single enantiomer or racemic mixture by inhalation to subjects with mild to moderate asthma. This was a double-blind, crossover, cumulative-dose, randomized study where all subjects received either four doses of 1.25 mg of (R)-salbutamol or 2.5 mg of racemic (RS-) salbutamol by nebulization. The pharmacokinetic parameters were determined by noncompartmental analysis and model-fitting. Changes in FEV(1), plasma potassium, plasma glucose, heart rate, and QTc interval were measured. The potassium and glucose data were fitted to indirect response pharmacodynamic models. The heart rate and QTc data were evaluated using data descriptors. No significant differences in pharmacokinetics of (R)-salbutamol given as either (R)- or (RS)-salbutamol were found with AUC values of 11.90 +/- 4.37 and 11. 47 +/- 2.88 ng.h/ml. The t(max)of about 2 h reflected serial dosing rather than delayed absorption. The t(1/2)averaged about 3.5 h. The (S)-salbutamol showed AUC of 48.46 +/- 12.11 ng.h/ml with a t(1/2)of about 5 h. The changes in FEV(1)reached a plateau after an initial increase and did not return to pre-drug values for 10 h. All pharmacodynamic parameters were similar whether (R)- or (RS)-salbutamol was given. The exposure to (R)-salbutamol was identical after inhalation of (R) -and (RS)-salbutamol by subjects with asthma. Several pharmacological responses including FEV(1)were also similar and there were no unique safety concerns with either treatment.

Pharmacokinetics of (R,S)-Albuterol after aerosol inhalation in healthy adult volunteers

The pharmacokinetics of inhaled (R,S)-albuterol following pulmonary absorption were studied in healthy human subjects. Ten subjects (5 females and 5 males) inhaled two puffs (180 microg) of albuterol via a metered-dose inhaler and spacer device. All subjects were nonsmoking and had normal pulmonary function. Charcoal slurries were ingested to block gastrointestinal absorption of drug. Venous samples were obtained from each subject at thirteen time points from 0 through 12 h post dose. (R,S)-Albuterol concentration in plasma was measured using a gas chromatography-mass spectrometry (GC-MS) assay. The plasma concentration-time profiles conformed to a two-compartment extravascular model with first-order absorption kinetics. The drug levels reached maximum in 12.6 +/- 2.2 (SD) minutes, which is in contrast with previous reports that maximum plasma concentrations occur within 2 to 4 h. The mean peak plasma level was 1469 +/- 410 pg/mL. The mean half-life of distribution was 17.9 +/- 8.2 min. The mean half-life of elimination was 4.4 +/- 1.5 h. Female subjects achieved peak concentration more rapidly than male subjects (10.4 vs 14.8 min, p = 0.01) and had a higher mean peak concentration (1778 vs 1159 pg/mL, p = 0.04).