Extrapulmonary effects of terbutaline during prolonged administration

Area of Science:

• Pharmacology
• Endocrinology
• Metabolism

Background:

• Terbutaline is a beta-agonist medication.
• Its metabolic effects are not fully understood.
• Investigating tolerance to terbutaline is important for its clinical use.

Purpose of the Study:

• To investigate the metabolic and physiological effects of terbutaline.
• To assess the development of tolerance to terbutaline's effects.

Main Methods:

• Healthy men received terbutaline via infusion and oral administration.
• Measurements included hand tremor, heart rate, plasma insulin, blood glucose, and plasma potassium.
• Levels were monitored during acute and repeated dosing over 13 days.

Main Results:

• Terbutaline infusion and initial oral doses increased plasma insulin and blood glucose, and decreased plasma potassium.
• Heart rate and hand tremor increased with terbutaline administration.
• By day 13, the metabolic effects and hand tremor were reduced, despite similar plasma terbutaline concentrations, indicating tolerance.

Conclusions:

• The body develops tolerance to the metabolic effects of terbutaline with repeated oral dosing.
• Tolerance appears to be mediated by reduced sensitivity of effector organs rather than altered drug levels.
• Understanding this tolerance is crucial for optimizing terbutaline therapy.