Failure of chronic theophylline therapy to alter circulating catecholamines
Abstract:
An increase in circulating adrenaline and noradrenaline has been reported following acute dosing with theophyllines. This effect on catecholamines has been proposed as a possible mechanism of action of theophyllines. In a double-blind placebo controlled trial we have studied the effects of 5 days oral theophylline therapy on circulating catecholamines and adrenaline clearance. There were no significant changes in circulating catecholamines or adrenaline clearance following theophylline. We also examined the effects of theophylline on the hypokalaemic and haemodynamic actions of adrenaline. Theophylline increased the hypokalaemia, tachycardia and rise in systolic blood pressure which occurs in response to intravenous infusion of doses of L-adrenaline (0.02-0.06 microgram kg-1 min-1). Our results suggest that chronic theophylline therapy does not significantly increase circulating catecholamines. Increased circulating catecholamine concentrations are thus not an explanation for the chronic actions of theophylline. We have demonstrated significant, potentially hazardous metabolic and haemodynamic interactions between theophylline and adrenaline.
More Related Videos
Related Concept Videos
Desensitization and Tachyphylaxis
Several...
Adrenergic Agonists: Indirect-Acting Agents
One mechanism involves depleting stored catecholamines by displacing them from synaptic vesicles. These agents, known as "displacers," are transported into vesicles at the expense of noradrenaline. Examples include amphetamine and tyramine, which lack a catechol moiety, resulting in prolonged action, improved oral bioavailability, and...
Adrenergic Agonists: Mixed-Action Agents
Ephedrine and pseudoephedrine lack a catecholamine group, making them less susceptible to degradation by metabolic enzymes. They have increased oral bioavailability and lipophilicity, resulting in a longer duration of action. Their response is reduced by...
Drugs Affecting Neurotransmitter Release or Uptake
Antiasthma Drugs: Methylxanthines
Theophylline is thought to inhibit phosphodiesterase enzymes, increasing intracellular levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). This rise in cAMP and cGMP concentrations stimulates cardiac function,...
COPD: Management Using Bronchodilators and Corticosteroids


