Determination of salbutamol in human serum by reversed-phase high-performance liquid chromatography with amperometric detection

Development and validation of simultaneous spectrophotometric and TLC-spectrodensitometric methods for determination of beclomethasone dipropionate and salbutamol in combined dosage form

Spectrophotometric and TLC-spectrodensitometric methods were developed and validated for the simultaneous determination of beclomethasone dipropionate (BEC) and salbutamol (SAL). The spectrophotometric methods include dual wavelength, ratio difference, constant center coupled with a novel method namely, spectrum subtraction and mean centering with mean percentage recoveries and RSD 99.72±1.07 and 99.70±1.12, 100.25±1.12 and 99.89±1.12, 99.66±1.85 and 99.19±1.32, 100.74±1.26 and 101.06±0.90 for BEC and SAL respectively. The TLC-spectrodensitometric method was based on separation of both drugs on TLC aluminum plates of silica gel 60 F254, using benzene: methanol: triethylamine (10:1.5:0.5 v/v/v) as a mobile phase, followed by densitometric measurements of their bands at 230 nm. The mean percentage recoveries and RSD were 99.07±1.25 and 101.35±1.50 for BEC and SAL respectively. The proposed methods were validated according to ICH guidelines and were applied for the simultaneous analysis of the cited drugs in synthetic mixtures and pharmaceutical preparation. The methods were found to be rapid, specific, precise and accurate and can be successfully applied for the routine analysis of BEC and SAL in their pharmaceutical formulation with no need for prior separation. The results obtained were statistically compared to each other and to that of the reported HPLC method. The statistical comparison showed that there is no significant difference regarding both accuracy and precision.

Sensitive detection of salbutamol using europium-enhanced fluorescence with trioctylphosphine oxide (TOPO) as coligand

In this work a simple and sensitive fluorimetric method for determination of salbutamol (4-[2-(tert-butylamino)-1-hydroxyethyl]-2-(hydroxymethyl) phenol) using an Eu enhanced signal was developed. The employed methodology is based on the formation of a ternary complex formed with Eu, salbutamol and trioctylphosphine oxide (TOPO). Intermolecular transfer of energy from the excited organic molecule to the lanthanide followed by lanthanide emission is responsible for excitation of the lanthanide ion in complex solutions and fluorescent enhancement. The luminescence properties of the ternary complex formed with TOPO and optimum formation conditions were investigated. The calibration curve is linear in the range between 6.92-180 microg l(-1) of salbutamol. The detection limit was 2.31 microg l(-1). Common excipients for these formulations were not found to interfere. A proposed method for the assay in commercial aerosols and nebulizer solutions containing salbutamol was applied with very good precision.

Effects of inhaled salbutamol in exercising non-asthmatic athletes

BACKGROUND

Beta-2 agonists such as salbutamol are used, not only by asthmatic athletes to prevent exercise induced asthma, but also by non-asthmatic athletes as a potentially ergogenic agent. We have investigated whether inhaled salbutamol enhances endurance performance in non-asthmatic athletes.

METHODS

A prospective double blind, randomised, three way crossover design was used to study the effects of 200 microg and 800 microg inhaled salbutamol versus a placebo in 12 trained triathletes. The treatments were compared in three identical cycle ergometer sessions at 85% of the predetermined maximal oxygen uptake. Lung function, endurance time, metabolic parameters (glucose, potassium, lactate, free fatty acid, and glycerol), and psychomotor performance were evaluated.

RESULTS

Neither endurance time nor post-exercise bronchodilation were significantly different between the treatments. Metabolic parameters were affected by exercise but not by treatment.

CONCLUSIONS

Inhaled salbutamol, even in a high dose, did not have a significant effect on endurance performance in non-asthmatic athletes, although the bronchodilating effect of the drug at the beginning of exercise may have improved respiratory adaptation. Our results do not preclude an ergogenic effect of beta2 agonists given by other routes or for a longer period.

Effects of inhaled salbutamol in exercising non-asthmatic athletes

BACKGROUND

Beta-2 agonists such as salbutamol are used, not only by asthmatic athletes to prevent exercise induced asthma, but also by non-asthmatic athletes as a potentially ergogenic agent. We have investigated whether inhaled salbutamol enhances endurance performance in non-asthmatic athletes.

METHODS

A prospective double blind, randomised, three way crossover design was used to study the effects of 200 μg and 800 μg inhaled salbutamol versus a placebo in 12 trained triathletes. The treatments were compared in three identical cycle ergometer sessions at 85% of the predetermined maximal oxygen uptake. Lung function, endurance time, metabolic parameters (glucose, potassium, lactate, free fatty acid, and glycerol), and psychomotor performance were evaluated.

RESULTS

Neither endurance time nor post-exercise bronchodilation were significantly different between the treatments. Metabolic parameters were affected by exercise but not by treatment.

CONCLUSIONS

Inhaled salbutamol, even in a high dose, did not have a significant effect on endurance performance in non-asthmatic athletes, although the bronchodilating effect of the drug at the beginning of exercise may have improved respiratory adaptation. Our results do not preclude an ergogenic effect of β2 agonists given by other routes or for a longer period.

Beta2-agonist extraction procedures for chromatographic analysis

Normally, different procedures were necessary to prepare sample matrices for chromatographic determination of beta2-agonists. The present review includes sampling, pre-treatment and extraction/purification for urine, plasma, liver, meat, feeds, hair and milk powder, as previous steps for chromatographic analysis of beta2-agonists. Six methodologies were especially revised for extraction/purification namely, liquid-liquid extraction, solid-phase extraction (SPE), matrix solid-phase dispersion, immunoaffinity chromatography, dialysis and supercritical fluid extraction. SPE was discussed in detail and five mechanisms were described: adsorption, apolar, polar, ion-exchange and mixed phase. A brief conclusion in this field was also outlined.

Multiresidue analysis of beta2-agonist in human and calf urine using multimodal solid-phase extraction and high-performance liquid chromatography with electrochemical detection

Various beta2-agonists are used as illegal growth promoters in man and in animals. We developed a multiresidue procedure for the analysis of four beta-agonists in human and calf urine. The sample was pre-extracted with an Extrelut column at alkaline pH. The beta-agonists were eluted with a mixture of tert.-butylmethyl ether and hexane. Then the extract was further cleaned with a mixed mode SPE column, or with a combination of immunoaffinity chromatography (IAC) and the mixed mode SPE column. The IAC column contained antibodies against salbutamol, which were suitable for multiresidue extractions. The extract was then brought onto a mixed mode SPE column at an acidic pH. The column was washed with 70% methanol in water. Thereafter, the beta-agonists were eluted with ammoniated ethanol-hexane. The extract was analysed with an HPLC method with electrochemical detection. The beta-agonists were separated on a reversed-phase column using a mobile phase buffered at pH 5.5 and containing an ion-pair reagent. Recoveries were higher when the IAC procedure was not performed (90-105% vs. 65-75%), but the extracts were cleaner when the latter step was included. Detection limits in human and calf urine were in the low ng/ml range. The study indicated that beta2-agonists can be analysed in human and calf urine without the selectivity of a mass spectrometer, but that comprehensive clean-up is required to avoid the interference of urine matrix components.

Determination of the enantiomers of albuterol in human and canine plasma by enantioselective high-performance liquid chromatography on a teicoplanin-based chiral stationary phase

A sensitive enantioselective high-performance chromatographic (HPLC) method was developed validated to determine low levels of (-)-R and (+)-S-albuterol in plasma. Baseline resolution was achieved by using a teicoplanin-based chiral stationary phase with a polar organic mobile phase consisting of methanol/ acetonitrile/glacial acetic acid/diethylamine, 40:60:0.3:0.2, (v/v/v/v) and a flow-rate of 1.0 ml/min. Enantioselectivity (alpha) equaled 1.18 and resolution (RS) equaled 1.8. By using fluorescence detection maximized at 230 and 310 nm for excitation and emission, respectively, concentrations of each enantiomer could be measured down to 125 pg/ml from a 1-ml plasma sample. Initially, the method was applied to plasma samples from a small single-dose inhalation study of racemic albuterol in a human volunteer and, later, to in vivo samples from a canine inhalation study of the single enantiomer, (-)-R-albuterol. Results from the canine study showed that no chiral inversion of (-)-R-albuterol occurs in the dog.

Enantioselective disposition of albuterol in humans

The study of enantioselective disposition of chiral drugs is important to provide a rationale of plasma concentration-effect relationships, which are often misleading when based on total drug concentration. It is also important when considering new dosage routes or formulations in order to optimize therapeutic plasma concentrations of the active enantiomer. Improvements in the sensitivity and selectivity of biological assays coupled with the developments in chiral analysis have made it possible to study the enantioselective disposition of drugs. Although valuable pharmacokinetic data were obtained for the beta 2-agonists by nonenantioselective methodology, more recent chiral studies have revealed the existence of extensive enantioselectivity in the disposition of these agents. The most significant features of the enantioselective disposition of albuterol are the relatively rapid plasma clearance and low bioavailability of the eutomer. Although this in itself does not necessarily justify the development of a single enantiomer formulation, the implications of the high levels of distomer after i.v. and oral dosing await clarification. Similarly, more work is required to elucidate the consequences of the major difference in disposition between albuterol and terbutaline in humans through both in vivo and in vitro studies of the mechanisms giving rise to this phenomenon. The enantioselective disposition of the other clinically used beta 2-agonists, such as fenoterol, formoterol, and salmeterol also needs to be characterized. The metabolism of the majority of beta 2-agonists is generally by conjugation to give one major metabolite. The situation is therefore uncomplicated by multiple metabolic pathways, which may differ in the extent and direction of their enantioselectivity. Many beta 2-agonists are excreted largely unchanged in the urine making studies of urinary excretion accessible without the requirement for very sensitive assays. The realization that the enantiomers of beta 2-agonists previously thought of as "inactive" may be associated with toxic effects is a further compelling reason to study the enantioselective pharmacokinetics of this class of drugs. In addition, the role of enantiomers in producing side effects, such as tremor and reduction in renal function, needs to be reassessed. The beta 2-agonists can be looked on as textbook examples of the inherent danger of ignoring chirality in the study of pharmacokinetics and pharmacodynamics. The growing body of information on the enantioselective disposition of beta 2-agonists in humans will enhance the rational use of these drugs in the future management of patients.

Determination of salbutamol enantiomers in human plasma and urine by chiral high-performance liquid chromatography

Enantiomers of salbutamol were directly separated (Rs = 1.16) and quantitated at therapeutic concentrations after solid-phase extraction from human plasma and urine by normal-phase high-performance liquid chromatography on a chiral column with fluorescence detection. The assay was linear for each enantiomer between 1.25 and 500 ng ml-1 and had a minimum limit of detection of 250 pg ml-1. A 3-ml plasma or 1-ml urine sample was required for quantitation at therapeutic doses. Inter-day variation was 5.0% for S-(+)- and 6.5% for R-(-)-salbutamol. The assay was used to compare enantioselective disposition after single doses of racemate by the intravenous, oral and rectal routes.

Analysis of beta-agonists in urine and tissues by capillary gas chromatography-mass spectrometry: in vivo study of salbutamol disposition in calves

The fate of salbutamol sulphate given orally has been investigated in calves. The urinary excretion rate and the tissue distribution of this beta-agonistic drug were studied by capillary gas chromatography coupled to low resolution mass spectrometry (GC-LRMS) under electron impact (EI) ionization mode, using an hexadeuterated salbutamol analogue as the internal standard. The parent drug and metabolites were extracted via solid phase extraction (SPE) mixed-phase-containing disposable columns and analysed as their trimethylsilyl derivatives. A more efficient clean-up had to be carried out for tissue samples. An acidic precipitation followed by a liquid-liquid extraction were therefore performed before the SPE. Moreover, the problem of tissue digestion was elucidated by means of an ultrasonic probe. Samples were also analysed before and after enzymic hydrolysis using purified beta-glucuronidase and a mixture of beta-glucuronidase and arylsulphatase, to obtain evidence of phase II conjugation mechanisms. Both free salbutamol and conjugated metabolites were detected in urine and tissue samples. Except for liver or kidney, salbutamol was rapidly cleared from most tissues after a withdrawal period. The possible excretion of some phase I metabolites was also investigated, using further analyses under positive chemical ionization LRMS and high resolution mass spectrometry (HRMS).

Matrix solid-phase dispersion as a multiresidue extraction technique for beta-agonists in bovine liver tissue

A procedure for the extraction of salbutamol including conjugated forms of the drug, from liver samples, is described. It combines matrix solid-phase dispersion with radioimmunoassay for the measurement of salbutamol residues at the sub-ppb level. Inter- and intra-assay validation, carried out on fortified liver samples, show good recoveries over the range 1-5 ppb of salbutamol. An enzyme hydrolysis procedure was optimized for the deconjugation of incurred residue. The developed procedure is shown to be suitable for the extraction and determination of other beta-agonists such as clenbuterol, mabuterol, terbutaline, and cimaterol at residue levels of less than 1 ng g-1.

Optimization of a column liquid chromatographic procedure for the determination of plasma salbutamol concentration

A reversed-phase column liquid chromatographic procedure with fluorescence detection for the determination of salbutamol in plasma is described. A l-ml aliquot of the sample, after the addition of bamethan as the internal standard, is passed through a Bond Elut silica extraction column. The column is selectively washed to remove neutral, acidic, and weakly basic compounds. The desired compounds are eluted with a l-ml aliquot of methanol. The eluate is evaporated under vacuum at ambient temperature and the residue is reconstituted in 40 microliters of the mobile phase which contains octanesulfonic acid as the ion-pairing reagent. The entire extract is injected onto a 150 x 4.6 mm I.D. column packed with 5-micron octylsilica particles. Peaks are detected with a fluorescence detector (excitation wavelength = 275 nm, emission wavelength = 310 nm). In the resulting chromatogram, salbutamol and the internal standard give sharp peaks that are well resolved from the extraneous peaks. The procedure allows the quantitation of salbutamol down to 0.2 ng/ml.

Serum concentration and cardiovascular effects of salbutamol after oral and rectal administration in healthy volunteers

In order to evaluate rectal administration of salbutamol (SB), five healthy volunteers were dosed orally and rectally with racemic SB (0.1 mg/kg) solution. Compared with the oral SB, the rectal SB gave significantly higher serum SB concentration immediately after dosing but slightly lower levels in the elimination phase. The Cmax following rectal administration was 17.9 ng/ml (17.0 ng/ml for oral administration), the tmax 0.67 h (1.5 h for oral administration) and the AUC 98.2 ng/ml/h (100 ng/ml/h for oral administration). Heart rate also rose more rapidly to a maximum of 70% above baseline values after rectal dosing. The rate continued to be twice larger than after oral dosing for up to 5 h. The concentration versus response curves indicated that rectal SB was more effective than oral SB at increasing heart rate at the same SB concentration in serum. A plausible explanation for this phenomenon might be a difference in the stereo-selective first-pass metabolism of the two enantiomers. Therefore, the rectal dose of SB administered as a suppository for prophylactic treatment of asthma should be lower than that used orally.

Dosing efficiency and particle-size characteristics of pressurized metered-dose inhaler aerosols in narrow catheters

An experimental in vitro model was used to determine the effects of intraluminal catheter diameter and length on the delivered dose and particle-size characteristics of salbutamol (albuterol) aerosol delivered by metered dose inhaler (MDI) (Ventolin, 100 micrograms per puff). The dose of aerosolized drug that exited a 16-cm-long tracheal tube with an inner diameter (ID) of 6 mm was compared with that from 4 catheters of differing diameters and lengths that were inserted individually into the tracheal tube. The salbutamol MDI canister was actuated ten times into each delivery system, and the effluent aerosol was trapped onto a filter. The filtrate was dissolved in methanol, and the salbutamol concentration was determined using high-performance liquid chromatography. For the 3 22-cm-long catheters, the delivered dose (mean +/- SD) of salbutamol per actuation for the 22-standard wire gauge (SWG) catheter was 97.5 +/- 3.9 micrograms, which was similar to that for the 19-SWG catheter (102.3 +/- 2.5 micrograms) but was significantly less than that for the 14-SWG catheter (108.2 +/- 4.2 micrograms) (p < 0.05). These delivered doses exceeded those of the 6.0-mm-ID tracheal tube alone (2.33 +/- 0.76 micrograms) and the 13-cm-long 19-SWG catheter (2.17 +/- 0.29 micrograms) (p < 0.001). In a second experiment using a cascade impactor, the distribution of aerosol particle diameters that exited the 6-mm-ID tracheal tube was compared with that exiting a 13-cm-long 19-SWG catheter that extended halfway down the tracheal tube and with that exiting a 22-cm-long 19-SWG catheter inserted into the distal end of the 6-mm-ID tracheal tube. The mass median aerodynamic diameter (mean +/- SD) of the salbutamol aerosols delivered through both the 6.0-mm-ID tracheal tube (1.1 +/- 0.1 microns) and that of the 13-cm-long 19-SWG catheter (1.2 +/- 0.2 microns) were significantly less than that delivered through the 22-cm-long 19-SWG catheter (2.0 +/- 0.1 microns) (p < 0.05). The authors conclude that delivery of respirable aerosol can occur through narrow catheters that function as extended nozzles for MDIs. Optimal dosing will be obtained when the catheter extends the full length of the tracheal tube.

Evaluation of a high-performance thin-layer chromatographic technique for the determination of salbutamol serum levels in clinical trials

Salbutamol concentrations were determined by high-performance thin-layer chromatography in the sera of two sets of ten volunteers at hourly intervals for 6 h after taking one 8-mg slow-release tablet. The influence of time lapse in processing of serum samples, i.e. centrifugation, extraction and chromatography, was studied. A statistical significant instability of salbutamol in the sera of patients was found which was not present in standard drug-free serum samples spiked with salbutamol and used for construction of standard curves.

Salbutamol identification in liver and urine by high-performance thin-layer chromatography and densitometry

This paper describes a rapid method for the identification of salbutamol in liver and urine. Salbutamol is extracted from liver with an acid solution, purified on Baker columns and eluted with methanol. After derivatization, salbutamol is detected on HPTLC plates as a blue spot. Urine samples are directly purified on the C18 columns and then the same procedure is followed as for the liver samples. Using this screening method, salbutamol can be semi-quantitatively determined at the micrograms/kg level.

Determination of beta 2-receptor agonists in bovine urine and liver by gas chromatography-tandem mass spectrometry

A highly specific and sensitive method for the simultaneous detection of seven beta 2-receptor agonists in bovine liver homogenates and urine was developed. A 10-g amount of liver was homogenized and treated with Subtilisin A. The resulting enzymatic digest was extracted with tert.-butanol-ethyl acetate (3:7) and the crude extract was purified on a 6-ml Bakerbond alumina neutral disposable extraction column. Subsequently, the hydrous eluate from the alumina column was buffered at pH 6 and loaded on top of a preconditioned 3-ml Bond-Elut Certify column. Urine was buffered and loaded onto a 3-ml Certify column without pretreatment. The analytes were eluted with dichloromethane-isopropanol (8:2) containing 2% ammonia. The extract obtained was trimethylsilylated and analysed by gas chromatography-tandem mass spectrometry using multiple selected reaction monitoring. The limits of detection for the beta 2-receptor agonists evaluated were between 0.5 and 5 ppb.

Radioimmunoassay for albuterol using a monoclonal antibody: application for direct quantification in horse urine

A monoclonal antibody was synthesized in mouse against the O-(3-carboxypropionyl) derivative of albuterol linked to bovine serum albumin. Isotyping of this material revealed the IgG1 class characterized by an affinity constant of 1.03 nM-1 and a density of sites of 0.55 nM. This antibody was found specific as its cross-reactivity to structurally related molecules was less than 1% except for clenbuterol (75%). A radioimmunoassay was set up with culture supernatant (final dilution 1/1000) and [3H] albuterol. The calibration curve was characterized by a maximum binding of 28%, an ED50 of 1.15 pmol per tube, the detection limit was 28.8 fmol/tube and the linearity of the response was up to 39.8 pmol/tube. This RIA method has been used for direct quantitation of albuterol in horse urine without any clean-up or extraction step.

Determination of albuterol concentrations in human plasma using solid-phase extraction and high-performance liquid chromatography with fluorescence detection

A fast, simple, and accurate method for determining albuterol concentrations in human plasma has been developed and validated for use in routine clinical analyses. This method involves a solid-phase extraction procedure using silica cartridges and normal-phase high-performance liquid chromatography with fluorescence detection. Regression analysis showed the method was linear over the standard curve range 1-16 ng ml-1. The percent recovery for albuterol and the internal standard, bamethane, at 5 ng ml-1 was found to be greater than 90%. The newly developed method has been applied in the analysis of plasma samples from patients and healthy volunteers.

Analysis of albuterol in human plasma based on immunoaffinity chromatographic clean-up combined with high-performance liquid chromatography with fluorimetric detection

A method combining immunoaffinity chromatography with high-performance liquid chromatography was developed for the determination of albuterol in human plasma. The immunoaffinity chromatography, based on the specific interaction of albuterol with the immobilized antibody raised against it, was used as a clean-up step. Albuterol eluted from this immunochemical solid-phase clean-up step was analysed by reversed-phase high-performance liquid chromatography with fluorimetric detection. The performance of the assay was validated on six normal volunteers after a 4-mg oral dose of albuterol, which gave a peak plasma concentration in the range 6.67-15.31 ng/ml at 3-4 h after the dose. Plasma levels (0.79-1.56 ng/ml) of albuterol could be detected up to 24 h after the dose.

Salbutamol in the 1980s. A reappraisal of its clinical efficacy

Salbutamol (albuterol) is a beta 2-selective adrenoceptor agonist which accounts for its pronounced bronchodilatory, cardiac, uterine and metabolic effects. During the intervening years since salbutamol was first reviewed in the Journal (1971), it has become extensively used in the treatment of reversible obstructive airways disease. Numerous studies in this disease (including severe acute, childhood and exercise-induced asthma) have confirmed the bronchodilatory efficacy of salbutamol, and it has been shown to be at least as effective as most of the currently available bronchodilators, if not more effective. The onset of maximum effect of salbutamol is dependent on the formulation used and the route by which it is administered. In most patients inhaled salbutamol is a first-line therapy, since it offers rapid bronchodilation, usually relieving bronchospasm within minutes. Although oral salbutamol has often proved to be less efficacious than the inhaled formulation, it still affords clinically significant bronchodilation, and it is particularly useful in those patients unable to coordinate the use of inhalers. Parenteral formulations of salbutamol are generally reserved for the treatment of severe attacks of bronchospasm and they are one of the treatments of choice in these life-threatening situations. Studies of the concomitant use of salbutamol and other agents such as anticholinergics, methylxanthines and beclomethasone dipropionate have usually shown a complementary response in the majority of patients, as might be expected from the different mechanisms of action of these groups of drugs. Salbutamol is generally well tolerated and any side effects observed are a predictable extension of its pharmacology. Since the frequency of side effects is dose related, and therefore dependent on the route of administration, it is not surprising that they are much more common following intravenous and oral rather than inhalation therapy. Tremor, tachycardia and hypokalaemia are the most frequently reported adverse effects. After nearly 20 years of use, salbutamol is well established as a 'first-choice' treatment in reversible obstructive airways disease. Indeed, throughout this time many new bronchodilatory agents have been studied but none have proved more effective. Clinical evaluation of salbutamol in the treatment of premature labour, hyperkalaemia and cardiac failure awaits further studies, although to date some encouraging results have been reported.

Determination of clenbuterol and mabuterol in equine plasma by ion-pair liquid chromatography with electrochemical detection. Chromatographic and electrochemical characteristics

A method for the routine determination of the beta-adrenergic drugs clenbuterol and mabuterol in equine plasma has been developed. The drugs were isolated from alkalinized plasma by liquid-liquid extraction. The organic phase was evaporated to dryness and the residue was dissolved in the mobile phase prior to injection. The recoveries were 98% and 95% for clenbuterol and mabuterol, respectively. The drugs were separated by reversed-phase high-performance liquid chromatography and quantitated by a use of a coulometric detector set at +0.75 V vs. the internal reference electrode. The influence of pH and amounts of organic modifier and ion-pairing agent on the retention times was investigated. The relationship between peak current and concentration was linear up to 1 microgram/ml for both compounds. The limits of detection were 0.5 ng/ml for clenbuterol and 2 ng/ml for mabuterol with a signal-to-noise ratio of 3. A brief discussion of the electrochemistry of the compounds is given.

Laboratory and clinical features of self-poisoning with salbutamol and terbutaline

A method has been developed for the simultaneous determination of the sympathomimetic drugs salbutamol and terbutaline in the plasma of poisoned patients, using ion-pair high-performance liquid chromatography with amperometric detection. Plasma concentrations of the drugs, measured in 8 poisoned patients, were well above the therapeutic range. The clinical and metabolic effects of overdose with these drugs were considerably less severe than those seen in patients with plasma theophylline concentrations elevated to the same degree.

Pharmacokinetics and absolute bioavailability of salbutamol in healthy adult volunteers

Salbutamol was administered to sixteen healthy male volunteers intravenously and by mouth in liquid, tablet, and capsule form using a Latin-Squares design. Pharmacokinetic parameters from intravenous data were similar to previously reported values obtained with oral administration, with a mean terminal half-life of 3.8 h and a mean clearance of 439 ml X min-1 X 1.73 m-2. Peak plasma concentrations of 10-20 ng X ml-1 were obtained 1-3 h following oral administration. The absolute bioavailability of each of the oral preparations was 44%. While statistically significant differences in lag time and time to peak concentration were noted among the various oral preparations, the drug is rapidly absorbed in all three dosage forms and the observed differences are unlikely to be of clinical significance.

Determination of salbutamol in human plasma and urine by high-performance thin-layer chromatography

A rapid, accurate and sensitive method for the determination of salbutamol in plasma and urine is described. Salbutamol is extracted using solid-phase techniques and converted to an indoaniline dye by reaction with dimethyl-p-phenylenediamine. The indoaniline is separated using high-performance thin-layer chromatography and quantified by absorption microdensitometry at 650 nm. The method is sensitive down to 20 ng/ml in urine and to 1 ng/ml in plasma and provides data in good agreement with that obtained by gas chromatography--mass spectrometry. The method can be used for analysis of pharmacokinetic studies.