Pacing after myocardial infarction

Epidemiologic features of urinary infections due to enterobacteriaceae resistant to nalidixic acid and trimethoprim

For a period of one year we identified all urinary isolates of Enterobacteriaceae resistant to either nalidixic acid (NA) or trimethoprim (TMP). Host and organism characteristics associated with the occurrence of 68 NA and 61 TMP-resistant isolates were compared with 61 matched antimicrobial-susceptible controls. Minimum inhibitory concentrations to NA and TMP were carried out on all isolates, Escherichia coli isolates were biotyped and TMP-sulfamethoxazole (SMX) synergy studies were performed on TMP-resistant isolates. Study patients were reviewed with regard to age, renal function, presence of structural urinary tract abnormality, history of antimicrobial treatment and persistence of study strains within the urinary tract. Resistance to both drugs was associated with prior treatment with the relevant antimicrobial and with underlying urinary tract abnormality. No association was noted between resistance and patient age or renal function. Once resistant organisms infected an abnormal urinary tract, they were able to persist almost indefinitely. Patients with persistent urinary infections associated with structural urinary tract abnormality account for most NA or TMP-resistant infections in our hospital and constitute an identifiable group in whom the therapeutic usefulness of these drugs is limited.

An open study of acebutolol, given as a single daily dose in the management of hypertension in the Chulalungkorn Hospital, Thailand

In an open study of fifteen patients with essential hypertension, acebutolol, a cardioselective B 1-adrenoceptor antagonist given orally once daily at dosages of between 400 mg and 1200 mg, produced a substantial and progressive reduction in systolic and diastolic arterial pressure and in the tension time index both in the lying and standing position over the 3 months of the trial. The changes from pre-trial values of blood pressure assessments were statistically significant (p less than 0.001). No side-effects were reported and laboratory monitoring of biological parameters revealed no untoward effects of treatment.

A study of the relationship between cardiac beta-adrenoceptor blockade and intrinsic sympathomimetic activity in rats depleted of catecholamines

1. The intrinsic sympathomimetic activity of a range of beta-adrenoceptor antagonists and its relationship to beta-adrenoceptor blockade was studied in pentobarbitone-anaesthetized, vagotomized rats which had been depleted of catecholamines by pretreatment with syrosingopine. Dichlorisoprenaline, practolol, oxprenolol, pindolol and acebutolol, produced dose-dependent positive chronotropic responses in this preparation. 2. The relationship between the dose requirements for this intrinsic sympathomimetic activity and beta-adrenoceptor-blocking activity was not the same for all drugs: (i) dichlorisoprenaline and practolol had intrinsic activity at all beta-adrenoceptor-blocking doses; and (ii) oxprenolol, pindolol and acebutolol had predominantly beta-adrenoceptor blockade at the lower dose levels and agonist activity only became significant at high doses relative to those producing beta-adrenoceptor blockade. 3. The positive chronotropic response to both practolol and pindolol was observed in rats which had been pithed and was antagonized by propranolol (0.1-3.0 mg/kg, i.v.), indicating that beta-adrenoceptors were involved. 4. It was concluded that the intrinsic sympathomimetic activity of beta-adrenoceptor antagonists was not a simple property as it was described by the relationship between the dose requirements for intrinsic sympathomimetic activity and for beta-adrenoceptor blockade as well as the degree of partial agonist activity.

The influence of temperature upon reserpine-induced supersensitivity of guinea-pig isolated atria to isoprenaline and salbutamol

1. The aim of this investigation was to determine whether supersensitivity of isolated atria to sympathomimetic amines following pretreatment with reserpine was evident at low temperatures, which alone induced supersensitivity. 2. Cumulative dose-response curves for the positive inotropic and chronotropic responses of isolated guinea-pig atria to isoprenaline and the partial agonist salbutamol were plotted as a percentage of the maximum response to isoprenaline. 3. In atria from reserpine-pretreated guinea-pigs set up at 38 degrees C, supersensitivity of both rate and tension responses was observed as a shift of the curves to the left and an increase of the maximum responses to salbutamol. Tension responses were potentiated more than rate responses. At 30 degrees C the supersensitivity became less apparent and at 25 degrees C was virtually absent. 4. The dose-response curves in untreated atria at low temperatures revealed that hypothermia itself produced supersensitivity of rate and tension responses. The dose-response curves were displaced to the left and the salbutamol maxima were raised so that at 25 degrees C it became almost a full agonist. The hypothermia-induced supersensitivity was therefore sufficient to mask any supersensitivity resulting from pretreatment with reserpine. 5. The hypothermia-induced supersensitivity of the rate response was dependent upon the method of plotting. When plotted in absolute units of beats per min no supersensitivity of the rate response was evident. Supersensitivity of the tension response at the lower temperatures and of both rate and tension responses following pretreatment with reserpine were independent of the plotting method.

Haemodynamic observations with KO. 1366 (bunitrolol), a new beta-adrenergic blocking agent

The haemodynamic effects of a new beta-adrenergic blocking agent KO.1366 (bunitrolol) were assessed in 10 males admitted to hospital for investigation of chest pain. Measurements were made at rest, during atrial pacing at 100 beats/min, and during hand grip exercise, before and afterintravenous administration of KO.1366 at a dosage of 0.05 mg/kg body weight. There was a 12% (p less than 0.01) slowing in resting heart rate and alpha 4% (p less than 0.05) slowing in exercise heart rate after drug administration. Resting left ventricular end diastolic pressure rose by 2.2 mm Hg (p less than 0.01) following the drug, but there was no significant change during pacing or exercise. Left ventricular systolic pressure and its first derivative did not change significantly. Cardiac output rose slightly, and stroke volume at rest and during exercise showed a considerable increase. In the dosage used, KO.1366 has an important chronotropic effect on the heart without causing significant myocardial depression.