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  • 1
    ISSN: 1432-1041
    Keywords: propafenone ; 5-OH-propafenone ; antiarrhythmic effect ; pharmacokinetics ; chronic treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of propafenone and 5-OH-propafenone and their relationship with the antiarrhythmic action and side effects have been studied in 10 patients with stable, frequent, premature ventricular beats (224–928 premature ventricular complexes/h). Observations were made after a single dose of propafenone 300 mg p.o., and after 1 and 3 months (only 5 out of 10 patients) of therapy with 300 mg t.d.s. After 1 month of treatment the plasma elimination half-life of propafenone (6.7 h) was almost twice as long as after a single dose (3.5 h), and the area under the plasma propafenone concentration-time curve (7620 ng·ml−1·h) was significantly larger than after single dose (3522 ng·ml−1·h); this was also true for the metabolite. The ratio of the AUCs of 5-OH-propafenone and propafenone decreased from the single dose (0.63) to 1 month (0.32). These variables remained stable up to 3 months. Eight patients had ≧75% reduction of premature ventricular complexes after 3 days of therapy, and in 7 they were completely suppressed; the response was maintained over 1 to 3 months. Side effects were minor and in no case had the drug to be withdrawn or the dose reduced. Thus, the kinetics of propafenone were time-dependent. Its active metabolite did not accumulate greatly during chronic treatment. The lasting antiarrhythmic effect observed in some patients suggests a b.d.s. regimen instead of t.d.s. dosing in selected patients.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: atenolol ; hypertension ; plasma renin activity ; pharmacokinetics ; pharmacodynamic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To show whether repeated administration of atenolol for several days would influence its pharmacokinetic parameters and the extent and duration of the pharmacologic responses, the plasma level of atenolol and changes in heart rate, blood pressure and plasma renin activity were measured in 12 hypertensive patients at various times of day (9 a. m., 12 noon, 3 p. m. and 7 p. m.) after oral administration of the first dose of atenolol 100 mg, again during the 7th and 14th days of continued once-daily administration of the same dose, and finally during the three days following withdrawal of the drug. The peak plasma concentration of atenolol (about 600 ng/ml) was found 3 h after administration of the first dose, and measurable amounts (50–70 ng/ml) were found after 24 h. None of the pharmacokinetic characteristics were changed by administration of a single daily dose for two weeks. After withdrawal of the drug, detectable amounts of atenolol were found in plasma for at least 48 h. The first dose of atenolol caused prompt (3 h) and prolonged (up to 24 h) lowering of supine and standing systolic and diastolic blood pressures, slowing of supine and standing heart rate, reduction of the blood pressure and heart rate responses to dynamic exercise, and a decrease in plasma renin activity. The extent and time-course of all these responses were not influenced by repeated once-daily administration of the 100 mg dose for two weeks. Most of the effects continued during the withdrawal days, the lowering of blood pressure being somewhat more prolonged than the slowing of heart rate. It is concluded that a once-daily dose of atenolol 100 mg decreases blood pressure and heart rate throughout the following 24 h, without excessive daily fluctuation in its effects, and without signs of tolerance or accumulation.
    Type of Medium: Electronic Resource
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