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Biomedical subjects

P W Trembath

Publications and source records attributed to P W Trembath.

17 recordsLinked to original sources
PubMed1998

Patients prefer sedation for fibreoptic bronchoscopy.

This study was carried out in order to determine if intravenous (i.v.) sedation with diazepam, at the time of procedure, made fibreoptic bronchoscopy more tolerable and if these perceptions persisted on later questioning. Methodology consisted of a sequential, parallel group design comparing sedation with no sedation for bronchoscopy in a tertiary referral hospital. Patient comfort and sedation desired for hypothetical repeat bronchoscopy were assessed both immediately and after at least 1 month. Patients who received sedation rated bronchoscopy as more comfortable (P = 0.01). Those who received sedation were also more likely to want no change in sedation if the bronchoscopy were repeated (P < 0.01). These differences were more evident at later questioning. Sedation was not associated with an increased complication rate but was associated with a prolonged recovery room stay (no sedation, 19.2 min (SEM 3.8) compared with sedation, 76.1 min (5.4), P < 0.001). In contrast to previous studies, our patients found bronchoscopy more comfortable with i.v. diazepam sedation. This was supported by patients who received sedation being less likely to want any change in future sedation if a repeat bronchoscopy were required. The benefit seen with sedation was more marked at later questioning supporting a previously postulated amnesic effect. However, sedation was associated with a prolonged room stay and potentially greater attendant cost.

Bronchoscopy↗
PubMed1986

Theophylline pharmacokinetics in patients from a geriatric hospital: influence of cigarette smoking.

The influence of cigarette smoking on plasma theophylline elimination half-life was examined in a group of elderly in-patients, to determine whether the modifying effect of cigarette smoking is also present in this age-group. The plasma theophylline half-life was determined in five non-smokers and seven smokers aged 66-88 years after administration of 320 mg of theophylline syrup. A wide range of plasma theophylline half-lives was observed in each group. However, there was a significant difference (P less than 0.05) between the mean plasma theophylline half-life in smokers (5.41 h, SEM 0.69 h) and non-smokers (10.40 h, SEM 1.90 h). It was concluded that, although plasma theophylline half-life tends to be longer in this age-group, the modifying influence of cigarette smoking on plasma theophylline half-life can be demonstrated in the elderly, as well as in young adults.

Aged↗
PubMed1981

Influence of environmental temperature and humidity on bronchial responses during assessment of selectivity of beta-adrenoceptor antagonists in man.

1 The effects of beta-adrenoceptor antagonists given intravenously in single doses were examined in a double-blind, placebo controlled study performed in six healthy volunteers. Heart rate and peak expiratory flow rate (PEFR) were measured at rest and during standardised exercise. 2 Atenolol 0.2 mg/kg, betaxolol 0.15 mg/kg, practolol 1 mg/kg and propranolol 0.2 mg/kg all reduced heart rate to a similar extent during exercise at 2 and 4 h after administration; betaxolol 0.6 mg/kg had a significantly greater effect than the other treatments at all times. Only betaxolol 0.15 and 0.6 mg/kg significantly inhibited exercise tachycardia at 24 h. 3 None of the treatments studied had any effect on PEFR at rest or during exercise. 4 A second study was performed to determine whether this lack of effect of propranolol on exercise PEFR could have been due to the warm and humid conditions prevailing during the experiment. Eight healthy men underwent a standardised exercise test under alternately 'warm and humid' and 'cool and dry' conditions before and after propranolol 0.2 mg/kg or saline placebo intravenously. 5 Propranolol treatment did not influence resting or exercise PEFR in either environment, but did reduce FEV1 immediately after exercise under the cool and dry conditions but not under the warm and humid conditions. 6 Comparison of the effects of beta-adrenoceptor antagonists on exercise heart rate and PEFR is not a reliable or sensitive method of measuring the cardioselectivity of these drugs. 7 Environmental temperature and humidity should ideally be controlled when the action of any drug on airflow resistance is being studied.

Adrenergic beta-Antagonists↗
PubMed1980

Pharmacokinetics of a sustained-release theophylline formulation.

1 Plasma theophylline concentrations following administration of sustained-release (SR) theophylline tablets were determined in ten healthy volunteers using a dose of 190 mg or 380 mg 12 hourly. 2 The plasma theophylline levels during the first 12 h period confirmed the sustained-release formulation characteristics, with the plasma drug concentrations reaching a plateau for the last 6 hours. 3 During the fifth 12 h dosing period the mean maximum and minimum plasma theophylline concentrations were 7.25 and 4.30 microgram/ml after 190 mg SR theophylline 12 hourly (n = 6) and 12.96 and 7.36 microgram/ml after 380 mg 12 hourly (n = 5), although there was marked between-subject variation in plasma theophylline concentrations. 4 One subject withdrew from the study due to side effects, which were more common when the higher dose of SR theophylline was given.

Adult↗
PubMed1979

Plasma theophylline levels after sustained-release aminophylline.

Healthy adult subjects were given oral sustained-release (SR) aminophylline tablets 225 mg 12-hourly (n = 12) or 450 mg 12-hourly (n = 6) for 5 doses, and all were given aminophylline 225 mg intravenously on a separate occasion to determine individual kinetic parameters. The mean plasma theophylline half-life ( 1 1/2) from the intravenous study was 5.8 hr (SD +/- 1.9). During the 12 hr after the fifth dose of SR aminophylline, the maximum and minimum mean (SD) plasma theophylline levels were 9.7 (3.2) mug/ml and 4.9 (2.0) mug/ml for the 225-mg dose, and 21.1 (2.2) mug/ml and 11.6 (4.4) mug/ml for the 450-mg dose. Side effects were generally mild in the low-dose study, but in the high-dose study 3 subjects reported headache and 1 was withdrawn after 3 doses. Two subjects also noted nausea, and 3 reported insomnia and anxiety in the high-dose study. It was concluded that there was a considerable range of doses needed to achieve adequate plasma levels, and that the formulation studied was capable of producing reasonably stable and satisfactory plasma theophylline levels once individual dose requirements had been established.

Administration, Oral↗
PubMed1979

Comparison of four weeks' treatment with fenoterol and terbutaline aerosols in adult asthmatics. A double-blind crossover study.

Fenoterol and terbutaline, two long-acting beta 2-adrenoceptor agonists in aerosol form, were compared in an 8-wk randomized double-blind crossover study in 22 mild to moderately severe asthmatics. Patients completed diary cards, recorded peak expiratory flow rate (PEFR) twice daily, and attended a clinic for measurement of PEFR, 1-sec forced expiratory volume (FEV1), and forced vital capacity (FVC) twice during each treatment period. Fifteen patients completed the study; 5 dropped out while using fenoterol, and 2 while using terbutaline. At clinic attendances, the patients had a significantly higher mean PEFR after 4 wk on terbutaline (385 L/min) than after fenoterol (316 L/min) (p less than 0.001). Similar results were found on analysis of the morning and evening PEFR recordings. On comparing each individual's PEFR recordings during the 2 treatments, it was found that there was no significant difference among the treatments in 3 patients, while 9 patients had a better response to terbutaline, and 3 patients had a better response to fenoterol. While similar number expressed a subjective preference for each treatment, the lung function data suggested that the effectiveness of fenoterol appeared to decline during the trial period.

Adult↗
PubMed1979

Effect of propranolol on the ventilatory response to hypercapnia in man.

1. The effect of a single oral dose of propranolol on the ventilatory response to hypercapnia has been studied in five healthy subjects. 2. Propranolol produced a small but significant reduction in the slope of the ventilation/end-tidal PCO2 regression line. 3. Propranolol did not significantly change vital capacity or forced expiratory volume in 1 s.

Adult↗
PubMed1979

Theophylline: biochemical pharmacology and pharmacokinetics.

Theophylline and its derivatives, such as aminophylline, have an established role as bronchodilators, although their mode of action in man is not clear. There is circumstantial evidence that therapeutic doses of theophylline may have a phosphodiesterase inhibiting effect, thus potentiating the effects of cyclic AMP. However, it remains to be established whether this is the primary mode of action of theophylline at the biochemical level. The pathways of theophylline metabolism have been clarified, although most of the enzymes involved have not been characterized. Hepatic microsomal enzyme induction by polycyclic hydrocarbons will increase the rate of theophylline elimination. There are a number of factors which influence theophylline clearance in adults, which is known to be highly variable. These factors include obesity, smoking habit, diet and the presence of such diseases as hepatic cirrhosis, acute pulmonary oedema, cor pulmonale and viral respiratory infection. There is a good correlation between plasma theophylline level and bronchodilator effect. This can be demonstrated at plasma levels as low as 5 microgram/ml, although optimal levels are usually greater than 10 microgram/ml. Unacceptable toxicity usually occurs in association with plasma levels greater than 20 microgram/ml. The maintenance of adequate plasma theophylline levels by the use of a sustained-release aminophylline tablet is discussed.

Aminophylline↗
PubMed1978

Potentiation of isoprenaline-induced plasma cyclic AMP response by aminophylline in normal and asthmatic subjects.

1 The effect of intravenous aminophylline infusion (6 mg-1 kg in 20 min, then 0.9 mg-1 kg-1 h thereafter) and its interaction with inhaled isoprenaline (800 microgram ex inhaler) on plasma cyclic AMP levels was studied in five normal and five asthmatic subjects. 2 Aminophylline infusion alone did not significantly change plasma cyclic AMP levels in either group. 3 In both groups, the plasma cyclic AMP response to isoprenaline aerosol inhalation was enhanced by aminophylline, although to a lesser degree in the asthmatic subjects. 4 The results provide in vivo evidence consistent with the hypothesis that in man, therapeutic doses of aminophylline may exert their clinical effects by inhibition of cyclic AMP phosphodiesterase.

Adult↗
PubMedDate not supplied

Pulmonary paragonimiasis in an immigrant from Laos.

A chest X-ray film, taken in a refugee camp in Thailand six months before a 25-year-old Laotian farmer arrived in Australia, demonstrated lesions which were assumed to be tubercular. Despite antituberculous chemotherapy, the lesions continued to grow. On the man's arrival in Australia, cytological examination of bronchial washings showed the presence of numerous Paragonimus ova, and the patient received treatment with praziquantel. Paragonimiasis should be suspected in a Southeast-Asian refugee who presents with a pulmonary lesion which is similar to that of tuberculosis.

Adult↗