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  • 1
    ISSN: 1432-1041
    Keywords: salbutamol ; asthma ; controlled-release formulation ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Fifteen patients with asthma were given salbutamol controlled-release (SCR) 4 mg or 8 mg twice daily for seven days, in a randomised double-blind cross-over design. Plasma salbutamol levels were measured after the first and fifteenth doses for a 12 h period following drug ingestion. At steady-state the geometric mean values for Cmax were 8.2 ng/ml for 4 mg, and 16.1 ng/ml for 8 mg. Median tmax values were 300 and 240 min respectively. The geometric mean AUC (0–12) were 4507 ng·min·ml−1 and 8980 ng·min/ml. Peak to trough fluctuation ratios were 0.577 and 0.572. There were no significant differences between 4 mg or 8 mg formulations, for any of the parameters measured, after appropriate corrections for dose. The concentration-time profiles at steady-state showed little fluctuation in plasma salbutamol levels over the twelve hour dosing interval. These results show that 4 mg and 8 mg formulations of SCR provide smooth plasma profiles at steady-state with a twice daily dosing regime.
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  • 2
    ISSN: 1432-1041
    Keywords: Asthma ; Salbutamol ; Tachyphylaxis ; Beta-adrenoceptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Tremor (Tr), chronotropic (HR) and metabolic (K, Glu) responses to cumulative doses of inhaled salbutamol (100 μg to 4000 μg) were compared in an age and sex matched group of 7 normal (N) and asthmatic (A) subjects. Comparison of regression lines between groups showed differences in HR and K. This was also reflected in attenuation of maximum responses in group A, for HR and K. These results show subsensitivity of chronotropic and hypokalaemic responses in patients with asthma, which may reflect tachyphylaxis from the effects of long term inhaled salbutamol therapy.
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  • 3
    ISSN: 1432-1041
    Keywords: Atenolol ; bisoprolol ; β-adrenoceptor ; cardioselectivity ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A dose-ranging study was performed to compare the β1-adrenoceptor selectivity of bisoprolol with that of atenolol and nadolol. Seven normal subjects (mean age 26 y) were given single oral doses of bisoprolol 5 mg (B5), 10 mg (B10), 20 mg (B20); atenolol 50 mg (A50), 100 mg (A100); nadolol 40 mg (N40); and placebo (PL), in a single blind randomised cross-over design. β2-adrenoceptor responses were assessed by attenuation of finger tremor and cardiovascular responses to graded isoprenaline infusions. Dose-response curves were constructed, and doses of isoprenaline required to increase finger tremor by 100% (IT100), heart rate by 25 beats/min (IH25), SBP by 25 mm Hg (IS25), cardiac output by 35% (IC35), and decrease DBP by 10 mm Hg (ID10), after each treatment were calculated. These indices were compared with placebo response and expressed as dose-ratios. Exercise heart rate (EHR) was used to assess β1-adrenoceptor blockade. There were dose-related increases in plasma concentrations of bisoprolol and atenolol. Reduction of EHR was significantly less with B5 (16.8%) in comparison with all other treatments: B10 21.9%, B20 23.1%; A50 22.5%, A100 22.6%; N40 22.9%. There were small but significant reductions in isoprenaline-induced tachycardia with bisoprolol and atenolol, although mean dose-ratios were considerably less in comparison with N40 (IH25 dose-ratios): B5 2.55, B10 3.18, B20 3.93, A50 2.91, A100 4.89, N40 17.23. There were similar patterns for the other isoprenaline responses. These results show that conventional doses of bisoprolol (10 mg) and atenolol (50 mg) produced equal antagonism of β1 and β2-adrenoceptors, and therefore possess equal degrees of β1-adrenoceptor selectivity. Increasing doses of bisoprolol and atenolol were associated with partial loss of selective β1-adrenoceptor blockade, although antagonism of β2-adrenoceptors was significantly less compared with the effects of nadolol.
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  • 4
    ISSN: 1432-1041
    Keywords: beta-adrenoceptor ; salbutamol ; airways response ; tremor ; haemodynamic response ; metabolic response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The aim of the present study was to quantify and compare the airways and systemic beta-adrenoceptor responses to inhaled salbutamol in normal subjects. Seven non-atopic, normal subjects were given cumulative doubling doses of inhaled salbutamol (100 µg to 4000 µg) or placebo in a single-blind cross-over design. Airways (sGaw, FEF 50%, FEF 25%), tremor, haemodynamic and metabolic responses were measured at each dose increment. There were dose-related changes in sGaw, FEF 50% and FEF 25% up to a plateau at 1.0 mg. Analysis of individual responses showed that most subjects required either 1.0 or 2.0 mg for maximum bronchodilatation, independent of the parameter of airflow. There was no correlation between maximum response and baseline airway calibre. In contrast to airways effects, systemic beta-adrenoceptor responses did not occur until 500 µg, and a ceiling in the dose-response curve was not reached. Therer were significant correlations between air-ways, tremor and haemodynamic responses, and between different metabolic variables. The intraindividual variability was greatest for tremor and sGaw, although this was small in comparison to the size of maximum change with salbutamol. The converse applied to the hypomagnesaemic response.
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  • 5
    ISSN: 1432-1041
    Keywords: atenolol ; salbutamol ; beta-adrenoceptor antagonists ; cardioselectivity ; metabolic response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The aim of the present study was to evaluate whether metabolic responses to inhaled salbutamol may be used to measure the cardioselectivity of beta-adrenoceptor antagonists. We therefore studied the effects of oral doses of atenolol 50 mg, 100 mg, 200 mg (A50, A100, A200), propranolol 40 mg (P40), and placebo (Pl) on the hypokalaemic (K) and hyperglycaemic (Glu) responses to inhaled salbutamol in five healthy subjects. Increasing doses of atenolol were associated with a progressive attenuation of ΔK compared with placebo: −0.72 mmol·l−1 (Pl) vs −0.20 mmol·l−1 (A200). However, ΔK with A200 was significantly different from the response with P40: +0.12 mmol·l−1. There were partial reductions in the hyperglycaemic response with the beta-adrenoceptor antagonists, although this was only significant (compared with Pl) for P40: ΔGlu 1.92 mmol·l−1 (Pl) vs 0.76 mmol·l−1 (P40). These results show that beta2-adrenoceptor blockade by atenolol is a dose-dependent phenomenon, which may be measured by the attenuation of salbutamol-induced hypokalaemia. However, beta2-adrenoceptor blockade by atenolol 200 mg was less than that by propranolol 40 mg. The glucose response to salbutamol was only partially blocked by propranolol and may therefore not be suitable to assess beta2-adrenoceptor antagonism.
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  • 6
    ISSN: 1432-1041
    Keywords: salbutamol ; asthma ; metabolism ; potassium ; glucose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the biochemical effects of high doses of inhaled salbutamol in 14 asthmatic patients age 38 years, FEV1 62%. Cumulative doubling doses of inhaled salbutamol were given every 20 min as follows: 100 µg, 200 µg, 500 µg, 1000 µg, 2000 µg, 4000 µg. Plasma glucose, potassium, and magnesium were measured at each step of the doseresponse curve. Salbutamol produced significant hypokalaemic and hyperglycaemic effects, but no significant change in magnesium. There were linear log-dose responses for both glucose (r/it=0.58) and potassium (r=−0.46). There were wide individual variations in maximum responses to salbutamol 4000 µg (as means and 95% confidence intervals): Δ glucose 1.46 (0.83 to 2.09) mmol/l, Δ potassium −0.38 (−0.64 to −0.12) mmol/l. Thus, hypokalaemic and hyperglycaemic effects may occur with doses of salbutamol similar to those curently used for nebulizer therapy (2.5–5 mg). We postulate that during acute exacerbations of airflow obstruction these changes may be accentuated and become clinically relevant.
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  • 7
    ISSN: 1432-1041
    Keywords: salbutamol ; sublingual ; oral ; inhaled ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Administration of drugs by the sublingual route provides rapid systemic absorption and avoids first-pass metabolism. The purpose of the present study was to assess the pharmacokinetics, efficacy and adverse effects of standard salbutamol tablets given by this route to patients with asthma. Seven asthmatic patients were given either sublingual salbutamol tablet 2 mg (SL), swallowed tablet 2 mg (O), metered dose inhaler 200 µg (MDI) or placebo (PL), in a randomized single-blind cross-over design. Airways responses (FEV1, FVC, PEFR), finger tremor (Tr), heart rate (HR), plasma potassium (K) and plasma salbutamol were measured over a 6 h period following drug administration. There were highly significant changes in FEV1 with MDI, O and SL routes compared with PL, although the response to MDI was greater and more rapid than with O or SL. There were similar findings for FVC and PEFR responses. There were no adverse effects with MDI, whereas both 0 and SL produced significant tremor responses. There were no differences between O and SL for any of the pharmacodynamic parameters. In addition, pharmacokinetic profiles for O and SL were also similar apart from an initial delay in absorption with SL. There were however, no significant differences in any of the pharmacokinetic parameters, between O and SL. This suggests that buccal absorption of salbutamol was negligible, and that systemic absorption occurred after swallowing of the dissolved sublingual tablet. These results show that sublingual administration of salbutamol tablet has no clinical benefit over the oral route.
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  • 8
    ISSN: 1432-1041
    Keywords: Betaxolol ; atenolol ; nadolol ; cardioselectivity ; β-adrenocepter antagonism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six normal subjects were given once daily treatment for 15 days with placebo (PL), betaxolol 10 mg (B10), 40 mg (B40); atenolol 100 mg (A100); and nadolol 40 mg (N40). Measurements of β1-adrenoceptorblockade (reduction of exercise heart rate) and of β2-adrenoceptor-blockade (attenuation of isoprenaline induced finger tremor) were made after the first, eighth and fifteenth doses of each drug. Plasma concentrations showed dose related increases between 10 mg and 40 mg doses of betaxolol, and there was significant drug accumulation at steady state compared with after single dosing. The reduction in exercise heart rate (EHR) with B10 was less in comparison with all other treatments. There were no significant differences in effects between single and chronic-dosing for any of the treatments (% reduction EHR compared with placebo, on days 1 and 15): B10 (18.2, 19.0), B40 (28.6, 26.5); A100 (22.7, 23.1); N40 (26.6, 23.8). Dose-ratios for attenuation of isoprenaline-induced finger tremor (IT100) were significantly greater with B40 compared with B10 or A100 (no dose-ratio for finger tremor could be calculated for N40). There were no differences between single and chronic-dosing (IT100 dose-ratios on days 1 and 15): B10 (3.0, 2.5), B40 (4.4, 5.3); A100 (3.0, 3.0). The attenuation of isoprenaline-induced chronotropic response (IH25) by N40 was significantly greater in comparison with all other treatments. IH25 dose-ratios (on days 1 and 15) were as follows: B10 (2.8, 3.6), B40 (5.1, 5.8); A100 (3.6, 3.6); N40 (19.0, 17.4). Thus, despite drug accumulation after chronic-dosing, there was no evidence of any increase in either β1 or β2-adrenoceptor antagonism at steady-state in comparison with after single-dosing. The apparent dissociation between plasma concentration and β-adrenoceptor antagonism after chronic-dosing my be a consequence of β-adrenoceptor up-regulation, resulting in partial attenuation of β-blockade.
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  • 9
    ISSN: 1432-1041
    Keywords: Salbutamol ; male ; female ; β2-adrenoceptor ; menstrual cycle ; systemic responses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Extrapulmonary β2-adrenoceptor mediated responses to salbutamol were evaluated in 9 healthy female subjects during the follicular (day 2–4, Visit 1) and luteal (day 21–23, Visit 2) phases of the menstrual cycle, and were compared with those of 9 age-matched male controls. At each visit, salbutamol was given by intravenous infusion for 30 minutes at a dose of 0.2 mg · kg−1 · min−1. Plasma salbutamol concentration and responses in heart rate (HR), finger tremor (Tr), Q-T interval (Q-Tc), serum potassium (K), serum insulin (Ins) and serum glucose (Glu) were measured at baseline and at 10, 20 and 30 minutes after commencing the infusion. Comparisons were made between sexes and between visits for peak responses calculated as percentage change from baseline. Mean plasma salbutamol concentration (ng · ml−1) were not significantly different between males and females on Visit 1: 6.9 (95% CI 6.01, 7.82) vs 7.3 (95% CI 6.4, 8.3), or on Visit 2: 6.9 (95% CI 6.0, 7.8) vs 7.2 (95% CI 6.3, 8.1). On Visit 1, significantly greater responses were demonstrated in females, compared with males for K (as mean difference): 6 (95% CI 1, 11)%, Tr: 17 (95% CI 1, 33)%, Q-Tc: 8 (95% CI 2, 14)% and Ins: 276 (95% CI 71, 481)%. In addition, a significantly greater response was demonstrated in females on Visit 1 compared with males on Visit 2 for HR (as mean difference): 32 (95% CI 1, 63)%, and for Ins: 262 (95% CI 57, 467)%. Thus, despite no difference in plasma salbutamol concentrations, female subjects exhibited greater responsiveness to salbutamol compared with males during the follicular phase of the menstrual cycle. This suggests that in vivo, females have enhanced sensitivity of extrapulmonary β2-adrenoceptors.
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  • 10
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    Springer
    ISSN: 1432-1041
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
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