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  • 1
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 37 (1979), S. 459-474 
    ISSN: 1432-1106
    Keywords: Late receptor potential ; Photoreceptor density ; Outer segments ; Inner segments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The postnatal development of the photoreceptor of the cat was studied using physiological and anatomical methods. The late receptor potential (LRP) was recorded in vitro and the threshold and maximum amplitude determined. The same specimens used in the electrophysiological studies were then prepared for microscopy, and rod cell outer and inner segment length and diameter, photoreceptor density, and inter-receptor distance were determined. A small LRP was first recorded at 9–10 days, but only at very high stimulus intensities. Thereafter, there was a rapid decrease in the threshold and an increase in the amplitude of the LRP. The threshold reached adult values at 17–18 days, while the amplitude of the LRP was adultlike at 23–26 days. Of the anatomical parameters examined, inter-receptor spacing and rod cell diameters seem to be most clearly associated, respectively, with the attainment of adult LRP threshold and amplitude. Outer segment length was adult-like at 35–43 days of age and thus postdated physiological maturity of the photoreceptor. These observations suggest that the surface area of the rod cell outer segment tips is more critical in the development of the adult LRP than is the number of discs in the outer segment. In addition, changes over time in the mean diameter and length of rod cell inner segments follows the pattern of ontogenetic changes in LRP amplitude. These findings imply a close relationship during ontogeny between the metabolic functions of the inner segment and phototransduction at the outer segment disc.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Late receptor potential ; Photoreceptor density ; Outer segments ; Inner segments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The postnatal development of the rod photoreceptor of normally-reared and dark-reared pigmented rabbits was studied using physiological and anatomical methods. The late receptor potential (LRP) was recorded in vitro and the threshold and maximum amplitude determined. The same specimens used in the electrophysiological studies were then prepared for microscopy, and rod cell outer and inner segment dimensions and photoreceptor spacing were determined. In the light-reared animals a small LRP was first recorded at 5 days, but only at very high stimulus intensities. Thereafter, there was a rapid decrease in the threshold and an increase in the amplitude of the LRP. The threshold and amplitude of the LRP reached adult values at 14 days. Of the anatomical parameters, maturation of inter-receptor spacing (14 days) is clearly associated with the attainment of the adult LRP amplitude levels. Outer segment length was also adultlike by 14 days of age and thus paralleled physiological maturity of the photoreceptor. Changes over time in the mean diameter and length of rod cell inner segments (adultlike at 21 days) follows the pattern of ontogenetic maturation of the LRP. These findings imply a close relationship during ontogeny between the LRP and development of the outer segment. In dark-reared pups there is a delay in the maturation of the photoreceptor mosaic, but by 4 weeks of age, physiological characteristics of the photoreceptor are adultlike.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1041
    Keywords: Pharmacokinetics ; drug input equations ; constant plasma drug concentrations ; lignocaine therapy of myocardial infarction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A constant plasma drug concentration can be achieved and maintained by the intravenous administration of an initial bolus loading dose in conjunction with a constant rate and an exponential intravenous drug infusion. The drug input required to achieve a constant plasma drug concentration is derived without making any assumptions about the nature of drug distribution within the body or elimination from the body.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 383-390 
    ISSN: 1432-1041
    Keywords: Acebutolol ; N-acetyl metabolite ; drug plasma concentrations ; plasma renin activity ; hypertension ; β-blockade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Relationships between plasma concentrations of acebutolol (Ac) and its N-acetyl metabolite (Am) and pharmacological effects were studied in patients with essential hypertension. In an acute study (N=7) 400 mg oral acebutolol produced similar peak plasma levels of Ac and Am but Am had a longer half life. Group mean pulse and blood pressure fell significantly, although the size of individual blood pressure fall varied five-fold. There was no significant change in plasma renin activity. Correlations were found between drug concentration and β-blockade, assessed as % reduction in exercise tachycardia, and between both of these and the fall in post exercise systolic blood pressure. Similar comparisons were made in a chronic optimum dose study (N=11) both pre-dose and three hours post-dose. Am concentration was consistently higher than Ac at both times. Blood pressure was lowered equally pre-and post-dose when compared to placebo and plasma renin activity (PRA) was reduced on active treatment. Correlations were again shown between drug concentrations and β-blockade but none were found with changes in blood pressure or PRA. Between subject differences in blood pressure response could not be fully explained in terms of the other measurements but it is unlikely that pharmacokinetic differences are the major source of this variability.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 26 (1984), S. 533-534 
    ISSN: 1432-1041
    Keywords: amiodarone ; bioavailability ; clearance estimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 26 (1984), S. 659-659 
    ISSN: 1432-1041
    Keywords: metoprolol ; drug adjustment ; elimination ; poor metaboliser ; drug oxidation ; drug reaction monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1041
    Keywords: acetylator phenotype ; hydralazine response ; hypertension ; blood pressure control ; lupus syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The role of acetylator phenotype in determining the response to hydralazine when it was added to diuretic and β-blocker at doses not exceeding 200 mg daily was examined in 57 hypertensive patients. 81% of rapid acetylators needed 200 mg hydralazine daily compared to 38% of slow acetylators (p〈0.01). Despite higher doses of hydralazine the blood pressure was controlled in only 27% of rapid acetylators compared to 65% of slow acetylators (p〈0.02). The relation of acetylator phenotype to blood pressure response was statistically independent of initial blood pressure, age, sex, body weight and serum creatinine (p〈0.005). Current recommendations on hydralazine dosage are unsatisfactory for the 40% of hypertensive patients who are rapid acetylators. We suggest measurement of the acetylator phenotype in patients who respond incompletely to 200 mg hydralazine daily. About 70% of these patients will be rapid acetylators in whom the dose of hydralazine can be increased safely.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 33 (1987), S. 423-426 
    ISSN: 1432-1041
    Keywords: Ketanserin ; pharmacokinetics ; hypertension ; ketanserinol ; predicted plasma concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the pharmacokinetics of ketanserin in 6 hypertensive patients after a single oral 40 mg dose and at steady-state after 4 weeks treatment with 20 mg and then 40 mg 12-hourly. Pharmacokinetic variables after a single dose were similar to those reported in healthy volunteers, with median values for Cmax 112 ng·ml−1, tmax 1 h, and t1/2 19 h. The corresponding values for the metabolite ketanserinol were Cmax 155 ng·ml−1, tmax 2 h, and t1/2 25 h. The median AUC was 3.3 times greater for ketanserinol than for the parent drug. These results were used to predict the mean steady-state plasma concentrations of ketanserin and ketanserinol. Predicted values were on average similar to those observed after four weeks treatment with 40 mg 12-hourly, although there were marked differences between the observed and predicted values in some patients. There was no evidence of time- or dose-dependent kinetics for ketanserin, but the study had insufficient power to exclude the occurrence of these phenomena entirely.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 28 (1985), S. 85-88 
    ISSN: 1432-1041
    Keywords: debrisoquine oxidation ; metoprolol metabolism ; oxidation phenotype ; β-blockade ; hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary After a single 200 mg oral dose of metoprolol tartrate the mean metoprolol AUC was found to be six-fold higher in poor metabolizers (PMs) of debrisoquine than in extensive metabolizers (EMs). This was associated with impaired metabolic clearance via α-hydroxylation and O-dealkylation. A population study (n=143) has shown a bimodal distribution in the ratio of metoprolol: α-hydroxymetoprolol recovered in urine which was correlated highly with the debrisoquine metabolic ratio. Nine per cent of the population were PMs. Plasma metoprolol concentrations three hours after a 100 mg oral dose of metoprolol were greater than 200 ng/ml in PMs but were lower than this in most EMs. This dose of metoprolol given once daily provided a clinically significant reduction (16%) in exercise heart rate in PMs after 24 hours. EMs require conventional doses (100 mg b.d.) to achieve the same degree of β-blockade. Preliminary data from family studies support the view that the defect in metoprolol oxidation is inherited. In 12 hypertensive patients who were EMs we compared the β-blocking activity and antihypertensive effect of chronic treatment with metoprolol 200 mg once daily (conventional and long-acting formulations), with those of atenolol 100 mg once daily and placebo. The effects of all active preparations were similar at 3.5 hours but atenolol was superior to all metoprolol formulations at 24 hours after dosing. It is concluded that for the majority of patients metoprolol should be prescribed twice daily when using currently available dosage forms. Relationships between oxidation phenotype and side-effects should be examined.
    Type of Medium: Electronic Resource
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