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  • 1
    ISSN: 1432-1041
    Keywords: doxazosin ; hypertension ; alpha1-adrenoceptor inhibitor ; elderly patients ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The α1-adrenoceptor antagonist doxazosin has been compared with placebo in 40 elderly hypertensive patients (mean age 71.4 years). At the end of 10 weeks once daily treatment with doxazosin the mean 24-h post-dose changes in standing and supine blood pressure compared with placebo were −6.9/−5.6 mmHg (systolic/diastolic) and −6.2/−5.5 mmHg respectively. The reductions in standing and supine diastolic blood pressures were statistically significant compared with placebo. At the end of treatment steady-state pharmacokinetics were evaluated in 18 patients. The plasma elimination half-life during the dose interval in these patients was 16.1 h (range 10.1–27.1 h) and the median time to peak plasma concentration was 3 h (range 1–4 h). One patient was withdrawn because of adverse effects (headache, weakness, and sweating) during doxazosin treatment. Once daily doxazosin reduced diastolic blood pressure and was well tolerated in these elderly hypertensive patients.
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  • 2
    ISSN: 1432-1041
    Keywords: Captopril ; sublingual ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of pH on the buccal and sublingual absorption of captopril was evaluated using in vitro techniques and human studies. Partitioning of captopril into n-octanol was lowest over the pH range 5 to 8 and highest at pH values 3, 4 and 9. Using the buccal absorption technique, the partitioning of captopril (2 mg) was examined in six healthy male volunteers from buffered solutions (pH 3, 4, 5, 6, 7, 8, and 9). Lowest buccal partitioning occurred at pH 3 while maximal buccal partitioning occurred at pH 7. These data clearly indicated that the buccal absorption of captopril did not obey the classical pH/partition hypothesis suggesting that mechanisms other than passive diffusion were involved in its absorption. Captopril pharmacokinetic and pharmacodynamic parameters were determined after administration of buffered sublingual captopril (pH 7, optimal pH for absorption as determined from the buccal partitioning data) and unbuffered sublingual captopril. The study was performed in eight healthy volunteers in a randomised single-blind cross-over fashion. The tmax for captopril was found to be approximately 11 minutes earlier after buffered versus unbuffered sublingual administration and AUC0–30 min increased by approximately 30% in the case of buffered captopril. Cpmax, AUC0–180 min and relative bioavailability did not differ between the buffered and unbuffered administration. Pharmacodynamic parameters (BP, heart rate and plasma renin activity) did not differ significantly between buffered and unbuffered sublingual administration. The increased rate of captopril absorption after buffered sublingual administration was small and is likely to offer little therapeutic advantage over conventional sublingual formulation.
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  • 3
    ISSN: 1432-1041
    Keywords: Key words Congestive heart failure ; Captopril; sublingual ; pharmacokinetic ; pharmacodynamic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The pharmacokinetics and pharmacodynamics of buffered sublingual captopril were assessed in patients with congestive heart failure (CHF). Methods: The study was carried out in a randomised single-blind cross-over fashion (n = 6, 4 males and 2 females) and involved two study days , at least 7 days apart. Baseline measurements were carried out for plasma renin activity (PRA), blood pressure (B.P.) and heart rate (H.R.). Captopril (12.5 mg) was administered sublingually with dibasic potassium phosphate which maintained salivary pH at 7, or perorally with 100 ml of water. Further B.P., H.R. measurements and venous blood samples were taken over a 3 hour period post-drug administration. Blood samples were analysed for captopril and PRA levels. Results: tmax after buffered sublingual administration of captopril, which ranged from 40–60 min (median = 40  min), was significantly shorter than after peroral administration (range 60–120 min, median = 90 min). Cmax was slightly greater after buffered sublingual than after peroral administration with mean values of 108.2 vs. 94.0 ng ⋅ml−1. AUC values were similar after both routes of administration. Systolic and diastolic B.P. vs. time profiles for each administration method were significantly different i.e. sublingual administration produced an earlier reduction in B.P., however, HR did not differ significantly between the two routes. Conclusion: The data indicate that this novel administration method of captopril leads to an increased rate, but an unchanged extent of captopril absorption, suggesting a modest therapeutic advantage with the use of buffered sublingual captopril if a rapid reduction in blood pressure is required.
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  • 4
    ISSN: 1432-1041
    Keywords: Congestive heart failure ; Captopril ; sublingual ; pharmacokinetic ; pharmacodynamic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The pharmacokinetics and pharmacodynamics of buffered sublingual captopril were assessed in patients with congestive heart failure (CHF). Methods: The study was carried out in a randomised single-blind cross-over fashion (n=6, 4 males and 2 females) and involved two study days, at least 7 days apart. Baseline measurements were carried out for plasma renin activity (PRA), blood pressure (B.P.) and heart rate (H.R.). Captopril (12.5 mg) was administered sublingually with dibasic potassium phosphate which maintained salivary pH at 7, or perorally with 100 ml of water. Further B.P., H.R. measurements and venous blood samples were taken over a 3 hour period post-drug administration. Blood samples were analysed for captopril and PRA levels. Results: tmax after buffered sublingual administration of captopril, which ranged from 40–60 min (median=40 min), was significantly shorter than after peroral administration (range 60–120 min, median=90 min). Cmax was slightly greater after buffered sublingual than after peroral administration with mean values of 108.2 vs. 94.0 ng·ml−1. AUC values were similar after both routes of administration. Systolic and diastolic B.P. vs. time profiles for each administration method were significantly different i.e. sublingual administration produced an earlier reduction in B.P., however, HR did not differ significantly between the two routes. Conclusion: The data indicate that this novel administration method of captopril leads to an increased rate, but an unchanged extent of captopril absorption, suggesting a modest therapeutic advantage with the use of buffered sublingual captopril if a rapid reduction in blood pressure is required.
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  • 5
    ISSN: 1432-1041
    Keywords: alfuzosin ; prazosin ; alpha1-adrenoceptor antagonist ; noradrenaline ; pharmacokinetics ; pharmacodynamics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In an open dose ranging study with random inclusion of placebo, alfuzosin (α1-adrenoceptor antagonist) 1, 2.5 and 5 mg was administered to 6 healthy volunteers, 3 of the volunteers received 10 mg alfuzosin. Supine systolic blood (SBP) pressure was not reduced by alfuzosin although significant increases occurred in supine heart rate (HR) after 2.5 and 5 mg. In the standing position, SBP was reduced at 2 and 4 h with 5 mg alfuzosin; significant increases in HR occurred following 1, 2.5 and 5 mg at 2, 4, 6 and 8 h after administration. Exercise SBP was not reduced; diastolic blood pressure was significantly reduced at 4 and 6 h with 5 mg alfuzosin. More marked effects were seen in the 3 subjects who received 10 mg alfuzosin. After 1 and 5 mg, tmax ranged from 1–2 h; Cmax (4.1 to 20.8 ng · ml−1; AUC (0–24) 20 to 132 ng · ml−1 · h (1 and 5 mg respectively) increased progressively with dose indicating dose dependent kinetics; no significant changes occurred in the visual analogue scale for sedation. A comparison of alfuzosin 5 mg, prazosin 1 mg and placebo each administered for 4 days, indicated that alfuzosin did not significantly reduce standing SBP on either Day 1 or Day 4; prazosin reduced SBP at 2 and 4 h on Day 1 and 6 h on Day 4 compared to placebo. Standing HR was increased by alfuzosin at 2 h on Day 1 and Day 4; increases occurred with prazosin at 2, 4, 6 and 8 h on Day 1 and 6 h on Day 4. Supine plasma noradrenaline increased with alfuzosin and prazosin at 2 and 4 h on Days 1 and 4; the increases were not significantly different. The plasma elimination half-life (t1/2) for alfuzosin was 3.4 h and 3.1 h after acute and chronic administration; (t1/2) for prazosin was 2.6 and 2.9 h. In conclusion alfuzosin causes small reductions in systolic blood pressure, accompanied by a dose dependent increase in heart rate in the supine and standing position and following exercise.
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  • 6
    ISSN: 1432-1041
    Keywords: Captopril ; sublingual ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In this study we compared the pharmacokinetics and pharmacodynamics of captopril after sublingual and peroral administration. Single 25 mg doses of captopril were administered sublingually and perorally on two different occasions in a randomised cross-over fashion to eight healthy volunteers aged 22–35 years. The kinetics of unchanged captopril, plasma renin activity (PRA), BP and heart rate were studied over three hours after both peroral and sublingual administration of captopril. Mean pharmacokinetic parameters for unchanged captopril after sublingual administration were: Cmax, 234 ng·ml−1; tmax, 45 min; AUC (0–3 h), 15.1 μg·ml−1. min. Mean pharmacokinetic parameters for unchanged captopril after peroral administration were: Cmax, 228 ng·ml−1; tmax, 75 min; AUC (0–3 h), 17.0 μg·ml−1. min. tmax was significantly shorter when captopril was administered sublingually; all other pharmacokinetic parameters were equivalent. The plasma captopril concentrations achieved post drug administration led to increases in PRA and reductions in BP. tmax for PRA was 86 min for sublingual captopril and 113 min for perorally administered drug. Peak PRA values were, however, not significantly different. BP, as expected, was not reduced dramatically in these healthy volunteer subjects, however, in systolic BP vs time profiles, BP was significantly lower after volunteers received sublingual captopril. Heart rate increased slightly after captopril administration; there were no differences between the two routes of administration. Administration of captopril sublingually, therefore led to a more rapid attainment of plasma captopril concentrations and had a more rapid onset of pharmacological effect when compared with peroral administration.
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  • 7
    ISSN: 1432-1041
    Keywords: Key words Enalapril ; Lisinopril ; Buccal absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The buccal absorption of captopril does not exhibit the classical pH/partition hypothesis, suggesting that mechanisms other than passive diffusion are involved in its absorption; animal studies have suggested that a peptide carrier-mediated transport system may be responsible for its absorption. The present study evaluated the effects of pH on octanol partitioning, and on the buccal absorption of enalapril and lisinopril, using in vitro techniques and buccal partitioning in human volunteer subjects. Methods: The partitioning of enalapril and lisinopril into n-octanol was examined over the pH range of 3–9 at room temperature. Results: Enalapril exhibited maximal partitioning into the organic phase at pH 4–5; minimal partitioning was recorded at pH values 8 and 9. The partitioning of lisinopril into n-octanol was found to be maximal at pH 9 and minimal at pH 3. Using the buccal absorption technique, the partitioning of enalapril and lisinopril (0.5 mg), was examined in six healthy male volunteers from buffered solutions (pH 3, 4, 5, 6, 7, 8 and 9). In the case of enalapril, lowest buccal partitioning occurred at pH 3, 8 and 9, while maximal partitioning occurred at pH 5; absorption of lisinopril was not extensive at any pH, but was greatest at pH 6. These results, in addition to the n-octanol partition coefficients, indicated that enalapril obeyed the normal lipid partition hypothesis with respect to buccal absorption. The buccal absorption of lisinopril also obeyed the lipid partition hypothesis over the pH range 3–7. These findings are in direct contrast to those for captopril. The buccal partitioning experiments were repeated at the maximal pH for absorption for each angiotensin converting enzyme (ACE) inhibitor, but with the addition of cephradine (0.05 mmol · l−1). Conclusion: The data indicated that the presence of this peptide transport inhibitor had no effect on the buccal absorption of enalapril (0.06 mmol · l−1) and lisinopril (0.057 mmol · l−1), which suggests that both drugs do not share a common buccal absorption pathway with cephradine.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 36 (1985), S. 103-111 
    ISSN: 1432-0630
    Keywords: 61.80 ; 68.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Ion beam induced mixing of Al-Ni has been studied using N 2 + and Ar+ bombardment. High dose (4×1017 ions cm−2) nitrogen bombardment was found to cause blister formation with no unambiguous evidence of mixing. However, using argon ions at elevated substrate temperatures (400–450 °C) led to extensive mixing of 2000 Å Al layers on Ni. The mixing mechanism is considered to be point defect mediated radiation enhanced diffusion with a possible contribution from cascade mixing and interfacial oxide layer breakdown during the initial stages of treatment.
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 175 (1955), S. 395-396 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Observation on injected mystacial pads fixed either in 80 per cent alcohol and cleared by the method of Spalteholz, or in formal-saline and sectioned on the freezing microtome at 100-150 jx, show a main artery approaching the side of each follicle. This gives branches to the striated muscles of ...
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  • 10
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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