First pass uptake of 14C-propranolol by the lung

Area of Science:

• Pharmacology
• Cardiovascular Physiology
• Pulmonary Medicine

Background:

• The lungs play a role in the initial systemic distribution of certain drugs.
• Understanding pulmonary drug uptake is crucial for predicting drug efficacy and toxicity.

Purpose of the Study:

• To quantify the extent of 14C-propranolol uptake by the lungs during a single pass.
• To investigate whether regular oral propranolol administration affects lung uptake.
• To assess the implications of lung uptake on intravenous drug administration.

Main Methods:

• Cardiac catheterization was performed on ten patients.
• Pulmonary uptake of radiolabeled 14C-propranolol was measured during a single circulatory pass.

Main Results:

• Mean lung uptake of propranolol was 75% in treatment-naive patients.
• Mean lung uptake was significantly reduced to 33% in patients on regular oral propranolol.
• Lung uptake of propranolol is considerable and demonstrates partial saturation by oral doses.

Conclusions:

• Pulmonary uptake of propranolol is substantial in humans.
• Pre-existing oral propranolol treatment significantly reduces lung uptake, indicating saturation.
• This lung uptake phenomenon may influence the dose-response relationship of propranolol and other drugs administered intravenously.
• The employed method is simple and potentially useful for assessing endothelial cell function in various diseases.