Search PubMed⌕ Search

Biomedical subjects

S R Smith

Publications and source records attributed to S R Smith.

At least 289 records · Page 16Linked to original sources
PubMed1987

The effects of four beta-adrenoceptor antagonists during modest exercise on plasma ammonia and heart rate.

Plasma ammonia and heart rate were measured in normal volunteers before, during and after an exercise test following administration of placebo, propranolol, pindolol, metoprolol and nadolol. Small changes in plasma ammonia occurred during exercise after placebo. However, all four beta-adrenoceptor antagonists produced considerably greater rises. This effect was most marked after propranolol with the response to pindolol, metoprolol and nadolol being similar and intermediate between placebo and propranolol. Resting heart rate was reduced by all the beta-adrenoceptor antagonists except pindolol. Exercise induced changes in heart rate were significantly reduced to a similar degree by all the beta-adrenoceptor antagonists.

Adrenergic beta-Antagonists↗
PubMed1987

Ranitidine and cimetidine; drug interactions with single dose and steady-state nifedipine administration.

The effect of ranitidine 300 mg once daily and cimetidine 800 mg once daily on the disposition of nifedipine was studied in two groups of 12 volunteers. Both investigations were placebo-controlled cross-over studies. The first group received ranitidine, cimetidine or placebo for 5 days with 20 mg nifedipine given on the 5th day. Each period was separated by 1 week. The second group received nifedipine 10 mg three times daily for 5 days together with the H2-receptor antagonist or placebo. Cimetidine produced a significant increase in the AUC of both single and steady state dosing of nifedipine. Peak nifedipine levels were significantly increased only in the chronic dose study compared to placebo. Ranitidine did not produce any significant changes in either study.

Adolescent↗
PubMed1987

The pharmacokinetics of oxprenolol following oral and rectal dosing--a comparison of delivery systems and routes of administration.

Plasma oxprenolol concentrations were measured in eight healthy volunteers who received equivalent oral doses of the drug in the form of an aqueous solution and a 10/170 oxprenolol Oros drug delivery system. Absorption from the lower gastrointestinal tract was assessed by measurement of plasma concentrations after rectal administration of the pre-equilibrated Oros systems. Because three of the first four volunteers suffered local irritation, however, the other four volunteers received Slow Trasicor 160 mg orally as a comparative preparation. The rate of in vivo absorption after oral administration of the Oros system closely mirrored its in vitro release rate. Drug availability from Oros was reduced, however, and was equivalent to 77% of that from the oral solution. Oxprenolol was well absorbed from the rectum while the system was present in this segment of the gut. The reduced systemic availability in three of the volunteers could be accounted for largely by drug loss when the system was expelled. Slow Trasicor produced higher peaks but lower 24 h plasma concentrations than the orally administered Oros system. As judged from the relative areas under the plasma concentration-time curve, however, the availability of the drug from the two dosage forms was comparable.

Administration, Oral↗
PubMed1987

The influence of beta-adrenoceptor blockade on the lipolytic response to exercise.

The influence of beta-adrenoceptor blockade on the free fatty acid (FFA) response during and after submaximal exercise was studied in a group of normal volunteers. The study showed that the exercise-induced rise in serum FFA concentrations seen with placebo was reduced after pretreatment with propranolol. Furthermore, the palmitic, stearic, oleic and linoleic acid responses showed progressive attenuation with increasing doses of propranolol. Different beta blockers were studied using comparable doses: metoprolol and nadolol had little effect and produced FFA profiles that were similar to placebo whereas the changes on pindolol were comparable with those on propranolol.

Adrenergic beta-Antagonists↗
PubMed1987

Effect of nifedipine on serum theophylline concentrations and asthma control.

The effect of adding slow release nifedipine to oral theophylline has been studied in eight patients with stable but symptomatic asthma, a double blind placebo controlled crossover protocol being used. No change in asthma control occurred during the nifedipine treatment period as assessed by serial peak flow measurements and symptom scores. Serum theophylline concentrations were significantly lower after nifedipine than after placebo (6.8 v 9.7 micrograms/ml) and in three patients were well below the therapeutic range (less than 4 micrograms/ml).

Aged↗
PubMed1987

A study of the immunosuppressive properties of Sch 24937.

Sch 24937 (6-bromo-5-chloro-2-1[(methylsulfonyl) acetyl] 3-(2-pyridyl indole) was previously shown to be an immunosuppressant with potent inhibitory effects on B lymphocyte mediated immune responses. The present investigation was primarily designed to compare the immunopharmacological profile of Sch 24937 with that of cyclosporin A (CSA) a well-known immunosuppressive drug that has selective effects on T-lymphocyte-mediated immune responses. The results show that while the immunosuppressive activity of CSA in vitro is superior to that of Sch 24937, in general the latter agent is a more potent inhibitor of immune responses in vivo. The activity of Sch 24937 in rat models of adjuvant arthritis and experimental allergic encephalomyelitis is also described. While Sch 24937 exhibits the type of immunopharmacological profile that is likely to yield a good therapeutic effect in the treatment of immune-mediated chronic inflammatory diseases, hepatotoxicity associated with the compound precludes its development for the treatment of non-life threatening human autoimmune conditions.

Animals↗
PubMed1987

Effect of saline adaptation and renal portal sodium infusion on glomerular size distributions and kidney function in domestic fowl.

Experiments were designed to evaluate acute and chronic effects of sodium on glomerular size distributions and kidney function of Single Comb White Leghorns. Chicks were raised on either tap water (control) or .6% NaCl (saline) drinking water. Kidney function studies were conducted when the birds reached 14 to 16 weeks of age. Saline-adapted birds had significantly lower glomerular filtration rates and significantly higher sodium and potassium excretion rates when compared with birds raised on tap water. Acute effects of sodium on kidney function were assessed by infusing 25 mM tetrasodium pyrophosphate unilaterally into the renal portal system. For birds raised on tap water, unilateral sodium infusion caused a significant unilateral reduction in the glomerular filtration rate. However, neither the acute nor the chronic reductions in glomerular filtration rates in response to sodium were associated with a reduction in the number of filtering nephrons. Saline-adapted birds had significantly hypertrophied glomeruli.

Animals↗
PubMed1987

Testing new drugs in untreated small cell lung cancer may prejudice the results of standard treatment: a phase II study of oral idarubicin in extensive disease.

We have evaluated the orally active anthracycline idarubicin at a dose of 40 mg/m2 in divided doses over 24 hours in 21 previously untreated patients with extensive-stage small cell carcinoma of the lung (SCCL). Subsequent iv therapy was cyclophosphamide (1000 mg/m2), vincristine (1 mg/m2), and etoposide (120 mg/m2 iv on Day 1 and 250 mg/m2 orally in divided doses on Day 2; CVE) in patients who failed to respond to idarubicin and in relapsed patients. Three (14%) of 21 patients treated with idarubicin responded, with two complete responses (CR). Patients failing to respond promptly and those who relapsed were treated with CVE. Seven patients did not receive CVE for the following reasons: early death, four patients; early CNS disease, two; and refusal, one. Fourteen patients received CVE. Of 12 patients failing to respond to idarubicin, eight progressed on CVE, three achieved partial response (PR), and one achieved CR. Two idarubicin responders who received CVE achieved PR and CR. The median survival of all 21 patients was 6 months. For those with World Health Organization performance scores of 0 or 1 the median survival was 6.2 months and for the rest it was 2.6 months. Although CVE chemotherapy was instituted promptly in patients not responding to idarubicin, these results seem inferior to those previously seen in our center with standard treatment from the start. We believe that patients with extensive SCCL often require a rapid and more guaranteed response to their first treatment.

Aged↗
PubMed1987

The principles underlying graft selection for arterial reconstruction.

In the aortofemoral segment Dacron has performed well for nearly 30 years. The choice of graft should be determined more by the handling characteristics than theoretical considerations. Whichever graft is selected the surgeon must be satisfied as to its durability and above all as to his technical ability to implant it accurately. In the femoropopliteal segment saphenous vein remains the graft of choice. It is not yet clear whether the technically more difficult in-situ operation has any advantage over reversed vein except in the use of smaller-calibre veins. In the absence of saphenous vein, all synthetics perform reasonably well to the level of the knee, particularly in the short term, but at present HUV appears preferably distally. Of the synthetics PTFE is easiest to use which makes it attractive to the less frequent user. However, we still await the arrival of an ideal arterial substitute.

Arteries↗
PubMed1986

Static and sequential dynamic scintigraphy of the tibia following fracture.

Eighty patients who had sustained a fracture of the tibial shaft were studied by scintigraphy using technetium-99m labelled methylene diphosphonate (99Tcm MDP) and a gamma camera. Static scintigrams were obtained in the early stages following injury and examined for the presence of 'cold spots' which may indicate loss of blood supply to fracture fragments; these were found in 10 per cent of cases but did not bear any definite relationship to the normal progression of union. Sequential dynamic scintigrams were obtained at intervals up to 20 weeks after fracture to determine whether a pattern of uptake of tracer could be identified which correlated with the subsequent progression of union, but no significant difference was observed between fractures healing promptly (less than 20 weeks) and those in which healing was delayed (greater than 20 weeks).

Adolescent↗
PubMed1986

Potentiation of the adverse effects of intravenous terbutaline by oral theophylline.

We have studied the influence of therapeutic plasma concentrations of theophylline on some of the unwanted responses to intravenous terbutaline in normal subjects. There was a significantly greater fall in serum potassium and rise in plasma glucose, pulse rate and systolic blood pressure in response to an intravenous infusion of terbutaline when theophylline was present compared with when terbutaline was given alone. These drugs are commonly used together in the treatment of acute asthma and potentiation of side effects may be hazardous. We suggest monitoring of the serum potassium when these drugs are used together during acute exacerbations of asthma.

Administration, Oral↗