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  • 1
    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
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    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
    Library Location Call Number Volume/Issue/Year Availability
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