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Biomedical subjects

N Holford

Publications and source records attributed to N Holford.

5 recordsLinked to original sources
PubMed1993

Theophylline target concentration in severe airways obstruction - 10 or 20 mg/L? A randomised concentration-controlled trial.

The optimal serum concentration of theophylline for the management of acute airways obstruction was evaluated by comparing the response to target concentrations at the extremes of the usual therapeutic range. 174 patients requiring intravenous theophylline were randomly assigned to a target concentration of 10 or 20 mg/L. Control of theophylline dosage using measured theophylline concentrations and evaluation of efficacy and toxicity was performed under double-blind conditions. 87 patients (50%) required hospital admission. Of these, 54 patients (62%) were followed throughout their hospital admission and reviewed at an outpatient clinic approximately 1 week after discharge. The duration of hospital stay, and rate and extent of improvement in peak expiratory flow rate were not different between the groups. There was significantly more toxicity in the 20 mg/L group. The initial target concentration for theophylline in the management of acute airway obstruction should be 10 mg/L under circumstances where concentration is used to control theophylline dosages.

Adult↗
PubMed1993

Time and theophylline concentration help explain the recovery of peak flow following acute airways obstruction. Population analysis of a randomised concentration controlled trial.

Peak expiratory flow rate, adverse effects and serum theophylline concentration were measured during treatment of episodes of severe airways obstruction. 174 patients were randomised to target theophylline concentrations of 10 mg/L or 20 mg/L. The recovery of peak flow rate towards normal values was explicable in terms of time and theophylline concentration using semiparametric and parametric nonlinear regression models. In the absence of theophylline, recovery takes place with a half-time of 16 hours. Theophylline is less effective in achieving recovery than the passage of time but achieves 50% of possible recovery at a concentration of 11 mg/L. The action of theophylline is most marked at the start of treatment. It may no longer have important beneficial effects after 72 hours. The incidence of adverse effects increased at theophylline concentrations > 20 mg/L.

Adult↗
PubMed1980

Effects of antiarrhythmic drugs on atrioventricular conduction in patients with acute myocardial infarction.

Three hundred fifty-eight of 429 (83%) consecutive patients with acute myocardial infarction (MI) and a normal PR interval received various antiarrhythmic drugs (AD), including lidocaine and/or procainamide, quinidine, digoxin, propranolol or disopyramide. There was no significant difference in the incidence of progression to any degree of atrioventricular (AV) block or to higher degrees of AV block (Mobitz II or third-degree AV block) between those treated and not treated with AD: 38 of 358 (11%) and six of 358 (1.7%) with AD vs 11 of 71 (15%) and two of 71 (2.8%) in the untreated group, respectively. Similarly, there was no significant difference in progression between treated and untreated patients with anterior MI, 14 of 144 (10%) vs five of 32 (16%); inferior MI, 21 of 111 (19%) vs five of 26 (19%), or subendocardial MI, three of 103 (3%) vs one of 12 (8%). Bundle branch block (BBB) (without AV block) was initially present in 89 of 249 (21%). The incidence of AV block (seven of 24, 30%) was higher in treated patients with newly acquired BBB (27 patients) than in the untreated patients (none of three, p less than 0.05). The commonly used ADs did not adversely affect AV conduction in patients with acute MI with narrow QRS and either normal, first-degree, or Mobitz I AV block. Moreover, no subset of patients grouped by infarct location, specific AD used, or BBB (except perhaps for those with newly acquired BBB) appeared to be at risk of development of AV block during AD therapy.

Aged↗