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The effect of aging on the pharmacokinetics and pharmacodynamics of prazosin (1996)

Andros, E. ; Detmar-Hanna, D. ; Suteparuk, S. ; [et al.]

Springer

European journal of clinical pharmacology 50 (1996), S. 41-46

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ISSN: 1432-1041

Keywords: Key words Prazosin ; Elderly; pharmacokinetics ; age-related ; pharmacodynamics

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Medicine

Notes: Abstract. Objective: The effect of age on the pharmacokinetics and pharmacodynamics of prazosin (α1 adrenoceptor blocker) was studied in 20 healthy volunteers. Patients: Ten elderly (61–81 y) and ten young (23–28 y) subjects were studied. All subjects received 1 mg of prazosin orally in a fasting state. Serial blood samples were collected for calculation of oral pharmacokinetics, and blood pressure and pulse rate were measured during blood collection. Subjects remained supine and fasting for the first three hours post drug administration, after which they were allowed to ambulate and eat. Results: The oral pharmacokinetics of prazosin were not different in the two age groups. The serum t1/2 in the elderly was 210 min while in the young group was 139 min. The AUC0−∞ in the two groups was not different. The Cmax was identical in the two groups, and the time to Cmax was 84 min in the elderly and 114 min in the young subjects. Protein binding was 93.4% in the elderly and 93.5% in the young subjects and the serum α1 acid glycoprotein concentration was not different in the two groups of subjects. Even though the pharmacokinetics of prazosin were unchanged by age, the haemodynamic effects of the drug were greater in the elderly. The fall in systolic blood pressure and mean blood pressure was significantly greater in the elderly group at multiple time points after drug administration while the change in diastolic blood pressure was equivalent in the two age groups. Despite a greater decrease in mean blood pressure in the elderly, the compensatory increase in heart rate was similar in the two age groups suggesting a difference in the baroreceptor reflex in the two age groups. Conclusion: The results of this study demonstrate that age does not alter the pharmacokinetics of oral prazosin, but the pharmacodynamic response at equivalent plasma prazosin concentration is greater in the elderly.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002280050067

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Investigation of bias enhanced nucleation of diamond on silicon (1996)

Gerber, J. ; Sattel, S. ; Ehrhardt, H. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 79 (1996), S. 4388-4396

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The process of bias enhanced nucleation of microwave chemical vapor deposited diamond on silicon has been extensively characterized using plasma diagnostics, scanning and transmission electron microscopy (TEM), Raman spectroscopy, and x-ray diffraction. The nucleation kinetics were measured as a function of bias voltage, methane partial pressure, and substrate temperature. The nucleation is found to be transient in character, with a delay time followed by an exponential increase in nucleation density with time, and finally a saturation. The ion flux and ion energy distribution was measured by a retarding field probe. The nucleation density was found to reach a maximum at a bias at which the ion energy distribution has a maximum of 80 eV, independent of the substrate temperature. This is taken as strong evidence that nucleation enhancement involves ion subplantation. The Raman spectra and x-ray diffraction suggests that the films during nucleation consist primarily of sp2 bonded noncrystalline carbon. The presence of the (0002) interlayer graphitic peak suggests that the carbon is primarily graphitic. The diamond nuclei form in this matrix. TEM shows mainly amorphous hillocks being formed on the substrates by bias enhanced nucleation. Diffraction patterns and high resolution TEM reveal the presence of β-SiC and also a small number of diamond particles. © 1996 American Institute of Physics.