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Biomedical subjects

J Feely

Publications and source records attributed to J Feely.

At least 127 records · Page 7Linked to original sources
PubMed1984

Use of beta-adrenoceptor blocking drugs in hyperthyroidism.

There is an increasing use and variety of beta-adrenoceptor blocking agents (beta-blockers) available for the treatment of hyperthyroidism. Recent comparative studies suggest that atenolol (200mg daily), metoprolol (200mg daily); acebutolol (400mg daily), oxprenolol ( 160mg daily), nadolol ( 80mg daily) and timolol (20mg daily) produce a beneficial clinical response equal to that seen with propranolol ( 160mg daily). Most beta-blockers reduce resting heart rate by approximately 25 to 30 beats/min, although a lesser reduction is seen with those possessing intrinsic sympathomimetic activity such as oxprenolol and pindolol. While earlier studies employing large doses of intravenous propranolol concluded that beta-blockade reduced myocardial contractility, more recent non-invasive studies suggest that the predominant cardiac effect is on heart rate. In patients with cardiac failure, beta-blockers may, however, produce a profound fall in cardiac output. Nevertheless, in combination with digoxin they may be useful in controlling the atrial fibrillation of thyrocardiac disease. beta-Blockers improve nervousness and tremor (although to a lesser extent with cardioselective agents) and severe myopathy, and they also reduce the frequency of paralysis in patients with thyrotoxic periodic paralysis. There is often subjective improvement in sweating but usually no major effect on eye signs. Recent studies show a 10% reduction in oxygen consumption/basal metabolic rate with long term oral use of selective or nonselective beta-blockers. In addition, many agents (propranolol, metoprolol, nadolol and sotalol but not acebutolol, atenolol or oxprenolol) reduce circulating tri-iodothyronine (T3) concentration by between 10 and 40%, although the clinical significance of this effect (if any) is not established. beta-Blockers may also have endocrinological effects on gastrin, cyclic AMP, catecholamines and other hormone levels. Given in adequate dosage, propranolol has been shown to control thyrotoxic hypercalcaemia. Minor side effects (nausea, headaches, tiredness, etc.) are quite common but overall beta-blockers are well tolerated by the thyrotoxic patient. The major use of these drugs is in symptomatic control while awaiting definitive diagnosis or treatment. As an adjunct to antithyroid drugs or radioactive iodine, beta-blockers will produce a satisfactory clinical response in the weeks to months before these forms of therapy produce a euthyroid state. beta-Blockers are more convenient than antithyroid drugs in the control of patients receiving therapeutic radioiodine, in that continuous therapy and assessment of biochemical response is possible.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic beta-Antagonists↗
PubMed1983

Antidepressants.

Explore the source record for details and available documents.

Antidepressive Agents↗
PubMed1983

Effect on apparent liver blood flow of histamine-receptor blockers and inhibition of prostaglandin synthesis.

We have recently shown that histamine H2-receptor blockade with cimetidine reduces apparent liver blood flow. To determine the effects of inhibition of prostaglandin synthesis and of H1-receptor blockade and of their additive effects when combined with cimetidine (600 mg), we estimated liver blood flow from the clearance of a single dose (0.5 mg/kg) of indocyanine green (ICG) in six healthy subjects after indomethacin (50 mg. three times during 24 hr) and chlorpheniramine (8 mg. three times during 24 hr). Indomethacin and chlorpheniramine reduced ICG estimated liver blood flow by 18 +/- 3% and 13 +/- 4% (mean +/- SEM). When cimetidine was added to indomethacin or chlorpheniramine, the reductions in flow of 22 +/- 6% and 19 +/- 5% were not significantly greater than that after indomethacin, chlorpheniramine, or cimetidine alone (16 +/- 6%). These data suggest that both histamine acting through H1- and H2-receptors and prostaglandins may influence liver blood flow in man and are consistent with evidence from animal experiments that suggest a role for prostaglandins in H2-mediated vascular responses.

Adult↗
PubMed1983

Effect of thyrotoxicosis on liver blood flow and propranolol disposition after long-term dosing.

The effects of thyrotoxicosis on Liver blood flow and propranolol disposition were followed in five patients while thyrotoxic and when euthyroid. Propranolol was taken orally to achieve steady state and then radiolabeled drug was given simultaneously by intravenous injection. Thyrotoxicosis was associated with doubling of both oral and systemic clearances of unbound propranolol, which resulted in an approximately 50% reduction in blood concentrations after oral doses. These changes were attributable to increases in hepatic blood flow and drug-metabolizing activity of the liver. The propranolol elimination t 1/2 was not affected by thyrotoxicosis since the enhanced clearance was offset by a change in volume of distribution. These findings may explain the reduction of plasma propranolol concentration and many of the therapeutic failures reported in the treatment of thyrotoxicosis. The dose required to achieve therapeutic blood concentrations of propranolol in thyrotoxic patients is variable and will usually be substantially larger than that required for euthyroid patients.

Administration, Oral↗
PubMed1983

Interaction of cimetidine with other drugs.

After five years' extensive use of cimetidine, drug interactions have emerged as one of its major adverse effects. Clinically important interactions with warfarin, phenytoin, diazepam, chlormethiazole, propranolol, lidocaine, and a number of other drugs have been reported. An appreciation of the variety of underlying mechanisms, inhibition of drug metabolism, decreased liver blood flow, and altered drug distribution should reduce the risk of further drug interactions with cimetidine.

Aged↗
PubMed1983

Effect of inhibitors of prostaglandin synthesis on hepatic drug clearance.

The effect of inhibition of prostaglandin synthesis on the systemic clearance of indocyanine green and antipyrine was studied in seven subjects. Antipyrine clearance was not altered by indomethacin suggesting that oxidative metabolism was not affected. Both aspirin and indomethacin decreased the clearance of indocyanine green presumably by reducing liver blood flow. These results suggest that an effect of inhibitors of prostaglandin synthesis on hepatic drug clearance is likely to be confined to high clearance drugs when given systemically.

Adult↗
PubMed1983

Lack of effect of ranitidine on the disposition of lignocaine.

Cimetidine has been shown to alter the disposition of lignocaine and other drugs that are highly extracted by the liver. In a placebo controlled study ranitidine (150 mg twice daily) did not alter the elimination half-life, systemic clearance or distribution of lignocaine (mg/kg) in six healthy subjects. The interaction with cimetidine appears to be unrelated to histamine H2-receptor antagonism.

Adult↗
PubMed1983

Effects of feeding on the systemic clearance of indocyanine green and propranolol blood concentrations and plasma binding.

In six healthy subjects a 250 g steak significantly increased the systemic clearance of indocyanine green. During a steady-state infusion of propranolol there was a rapid decrease (mean 35%) in blood propranolol concentrations within 5 min of feeding and levels were reduced for 30 min before gradually returning towards the pre-feeding. These results suggest that the systemic clearance of high extraction drugs may be increased immediately following food.

Adult↗
PubMed1983

Enzyme induction with rifampicin; lipoproteins and drug binding to alpha 1-acid glycoprotein.

Hepatic enzyme induction has been reported to increase lignocaine binding, alpha 1-acid glycoprotein concentration and high density lipoprotein (HDL) cholesterol. In eight volunteers treated with rifampicin for 3 weeks there was no significant alteration in these three variables although their antipyrine clearance was significantly increased. In 10 patients with pulmonary tuberculosis treated with rifampicin (mean 5 months) the degree of serum protein binding of lignocaine, alpha 1-acid glycoprotein and HDL-cholesterol concentration was not different from that of matched control patients. These results suggest that differential induction of these variables may occur.

Adult↗
PubMed1983

Antithyroid effect of chlorpropamide?

1 The relationship between plasma chlorpropamide concentration and thyroid function was examined in 87 maturity onset diabetic patients receiving chronic therapy. 2 Although plasma chlorpropamide concentration was weakly negatively correlated with serum thyroxine (r = 0.33, P less than 0.01) the mean serum thyroxine and thyrotrophin (TSH) were not different from that of a matched control group of diabetics treated with diet alone. 3 Serum thyroxine was negatively correlated with the duration of diabetes in both groups. 4 These results suggest that chlorpropamide does not have a clinically significant antithyroid effect.

Adult↗