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Biomedical subjects

T C Fagan

Publications and source records attributed to T C Fagan.

46 records · Page 3Linked to original sources
PubMed1981

Food-induced increase in propranolol bioavailability--relationship to protein and effects on metabolites.

The influence of a meal on the disposition and metabolism of oral propranolol was examined in six normal subjects. The meal induced a mean 53% increase in propranolol bioavailability (range 2% to 92%; P less than 0.01) without affecting time to maximum concentration, half-life, or the amount of unchanges drug in urine. There was no effect on the plasma concentrations of 4-hydroxypropranolol or four other metabolites. The increased bioavailability was linearly related to the protein content of the meal (r = 0.884, P less than 0.02) above a threshold content of about 7 gm.

Adult↗
PubMed1980

4-Hydroxypropranolol and its glucuronide after single and long-term doses of propranolol.

The disposition of the pharmacologically active 4-hydroxypropranolol (HO-P), its glucuronic acid conjugate (HO-P-G), and propranolol were compared after single intravenous and oral doses of propranolol in 6 normal subjects and after long-term therapy in 32 patients with hypertension or coronary artery disease. The areas under the plasma concentration/time curves (AUCoo, ng . hr/ml) after 4-mg intravenous doses of propranolol were 6.6 +/- 2.2 (mean +/- SEM) for HO-P and 55 +/- 11 for propranolol. After 20- and 80-mg oral doses the AUCoo for HO-P were 59 +/- 9 and 162 +/- 21 and for propranolol were 72 +/- 9 and 306 +/- 46. Peak HO-P concentrations were reached at 1 to 1.5 hr after the oral doses. Although there was a rapid decline in plasma HO-P between 1.5 and 3 hr when HO-P-G was still rising to levels above HO-P levels 3.5- to 5-fold, the apparent half-lifes (t1/2s) after 3 hr were in the same range for HO-P, HO-P-G, and propranolol (3.0 to 4.2 hr). While during long-term therapy plasma HO-P rose over the whole dose range (40 to 960 mg daily) in an apparently linear fashion, the HO-P/propranol plasma level ratio fell from 1.07 +/- 0.13 at 40 mg daily to only 0.09 +/- 0.01 at 640 mg daily. Plasma HO-P-G rose exponentially with dose and demonstrated significant cumulation. HO-P and HO-P-G in urine accounted for about 9% of long-term propranolol doses. This study suggests a significant contribution of HO-P to pharmacologic effects, in particular at low single and long-term oral doses of propranolol and saturation of naphthalene ring oxidation as a main determinant of propranolol bioavailability.

Administration, Oral↗
PubMed1979

Presystemic and systemic glucuronidation of propranolol.

The relative importance of presystemic and systemic glucuronidation of propranolol was examined in normal subjects given single oral and intravenous doses of propranolol. The areas under the plasma concentration--time curves (AUCs) of propranolol glucuronide (PG), 41 +/- 15 ng . hr/ml, and propranolol, 48 +/- 15 ng . hr/ml, were of the same order after the intravenous dose (0.05 mg/kg). After oral doses of 20 and 80 mg, the AUCs of PG were 302 +/- 105 and 1,398 +/- 409 ng . hr/ml; these were 7 times the AUCs of propranolol, 44 +/- 15 and 220 +/- 38 ng . hr/ml. The time lapse to peak concentration, 1.5 to 3.0 hr, and the plasma half-life, 3.2 to 3.7 hr, were the same for PG and propranolol. These results demonstrate glucuronidation as an important determinant of propranolol bioavailability.

Administration, Oral↗
PubMed1979

Propranolol glucuronide cumulation during long-term propranolol therapy: a proposed storage mechanism for propranolol.

The comparative disposition of propranolol glucuronide (PG) and propranolol was determined in 35 patients with hypertension or coronary artery disease during initiation of propranolol therapy, during steady-state conditions, and after discontinuation of propranolol (dose range, 40 to 960 mg daily, every 6 hr). The 2.3-fold PG cumulation in plasma was identical to propranolol cumulation. PG plasma levels were about 4 times as high as propranolol levels over the whole dose range. Unexpectedly slow terminal elimination rate of propranolol (t1/2 approximately 16 to 24 hr) on discontinuation of propranolol appeared to be related to equally slow PG elimination. PG and propranolol could be detected in plasma and urine up to 3 to 5 days after propranolol discontinuation. The PG formed in man was deconjugated to propranolol in the dog after intravenous administration, suggesting that PG may serve as a storage pool for propranolol. Observations consistent with systemic and enteric deconjugation of PG, including enterohepatic recirculation, may, at least in part, explain the observed propranolol cumulation as well as the slow elimination of propranolol after its discontinuation. PG renal clearance (29 to 70 ml/min) and PG plasma levels were highly dependent on glomerular filtration rate, suggesting that PG may cumulate abnormally in patients with severe renal disease.

Adolescent↗
PubMedDate not supplied

Once- and twice-daily nitrendipine in patients with hypertension and noninsulin-dependent diabetes.

One hundred and six patients with uncomplicated mild to moderate essential hypertension received nitrendipine 10 mg twice a day or 20 mg once a day in a double-blind, randomized design. At the end of the dosing interval, supine and standing blood pressures were lowered 6/4 and 6/3 mm Hg respectively with the former regimen, and 2/3 mm Hg with the latter. In 10 patients, blood pressure variability through the dosing interval was not increased by nitrendipine 10 mg twice daily, but in another 10, 20 mg daily increased the variability by 28% compared to placebo. Significantly more patients had adverse effects with 20 mg daily than 10 mg twice daily; and both regimens caused more side effects than placebo. In 20 patients, serum glucose levels did not change significantly during treatment with nitrendipine, but in 10 of those with noninsulin-dependent diabetes, the range of maximum plasma insulin in response to a high-carbohydrate meal was 7 times as great during treatment with nitrendipine as it was during treatment with placebo. Nitrendipine lowers blood pressure when given once or twice daily, but twice-daily administration appears to be better tolerated.

Adult↗
PubMedDate not supplied

Time course of development of the antihypertensive effect of propranolol.

Ten patients with essential hypertension were hospitalized and treated with placebo, followed by their usual dose of propranolol. Systolic and diastolic blood pressure decreased significantly after the first dose of propranolol, and by the third day of propranolol treatment reached 84% to 92% of the maximum decrease achieved during the 6 days of treatment. Mean maximum falls in blood pressure were 13/12 mm Hg supine and 12/13 mm Hg standing. This development of the decrease in heart rate and blood pressure over 48 hours occurred in parallel with cumulation of propranolol to steady state in plasma. The decrease in diastolic, but not systolic, arterial pressure was directly related to pretreatment blood pressure, but not significantly related to pretreatment plasma renin activity (PRA) or change in PRA. Thus, single doses of propranolol lowered blood pressure in patients with essential hypertension, and with continued therapy, near maximum antihypertensive effects were achieved within 48 hours.

Adult↗
PubMedDate not supplied

Prospective study of the safety and financial benefit of ketoconazole as adjunctive therapy to cyclosporine after heart transplantation.

In a prospective study of the relative safety and potential benefit of concomitant ketoconazole and cyclosporine after heart transplantation, 15 transplant recipients were followed up for up to 1 year (mean, 10.7 months) after ketoconazole was added to their immunosuppressive regimen of cyclosporine, prednisone, and azathioprine, and these patients were compared with a matched cohort over the same time. There was an 88% reduction in the mean (+/- SD) dose of cyclosporine, from 394 (115) mg/day to 47 (21) mg/day (p less than 0.0005) in the ketoconazole group, compared with an insignificant change in the control group. The projected annual cost of cyclosporine was reduced by 88%, with a 72% reduction in the projected cost of immunosuppressive drugs and prophylactic antifungal therapy, from a mean of $6800 to $1862 per year per transplant recipient in the ketoconazole-treated group. Other beneficial effects found over the study period included a significant reduction in the mean and diastolic systemic arterial pressure and a significant reduction in serum cholesterol. The mean total serum cholesterol fell from 265 (44) to 204 (38) mg/dl in the ketoconazole group but did not change significantly in the control group (p less than 0.005). Low-density lipoprotein cholesterol also fell from a mean of 167 (32) mg/dl to 112 (28) mg/dl (p less than 0.005). Renal function was not significantly affected by ketoconazole when compared with the control group. Ketoconazole and other drugs of potential use in organ transplant recipients should be evaluated for financial as well as for other potential clinical benefits in the long-term management of these patients.

Azathioprine↗
PubMedDate not supplied

Efficacy and tolerability of extended-release felodipine and extended-release nifedipine in patients with mild-to-moderate essential hypertension.

The efficacy and tolerability of extended-release felodipine (felodipine-ER) and nifedipine gastrointestinal therapeutic system (nifedipine GITS) were compared in a multicenter, prospective, open-label clinical trial of 277 patients with mild-to-moderate uncomplicated essential hypertension (sitting diastolic blood pressure [SiDBP] > or = 95 and < or = 115 mm Hg). After a 3-week washout period, patients were randomized to receive felodipine-ER (5 mg once daily) or nifedipine GITS (30 mg once daily); during a subsequent 6-week titration phase, the once-daily felodipine-ER dose could be increased to 10 mg and the nifedipine GITS dose to 60 or 90 mg in an attempt to achieve adequate blood pressure response (SiDBP < or = 90 mm Hg, or < 100 mm Hg with a > 10-mm Hg reduction from baseline, as measured 24 hours after dosing [trough]). At the end of titration, the mean daily doses of felodipine-ER and nifedipine GITS were 8 and 50 mg, respectively. Mean changes in sitting systolic blood pressure (SiSBP)/SiDBP were -14/-12 and -16/-13 mm Hg, respectively. All reductions were significant when compared with baseline (P < 0.01), but there were no significant differences between treatment groups. Adequate blood pressure response occurred in 77% of the felodipine-ER group and 80% of the nifedipine GITS group; this difference was not significant. Blood pressure changes were similar among sex and race subgroups. A higher percentage of older patients (> 55 years of age) than younger patients (< or = 55 years of age) reached goal SiDBP with both drugs. Patients with adequate SiDBP response continued receiving their assigned medication for an additional 6-week maintenance period. Reductions in SiDBP and SiSBP from baseline continued to be significant in both treatment groups. No clinically important changes in heart rate were noted. A total of 28 patients (15 in the felodipine-ER group and 13 in the nifedipine GITS group) withdrew from the study because of inadequate blood pressure response. At least one adverse experience occurred in 55% of the felodipine-ER group and 63% of the nifedipine GITS group, prompting withdrawal of 14 patients (10%) and 16 patients (11%), respectively. Headache and edema were the most common adverse experiences. The incidence and pattern of adverse experiences did not differ significantly between treatments. The results of this study demonstrate that once-daily felodipine-ER and nifedipine GITS are similarly highly effective and generally well tolerated in patients with essential hypertension.

Adult↗