Theophylline pharmacokinetics in advanced age

Area of Science:

• Pharmacology
• Geriatric Medicine
• Drug Metabolism

Background:

• Theophylline is a common medication with known variability in its metabolism.
• Age-related changes can significantly impact drug pharmacokinetics, particularly in the elderly.
• Accurate assessment of drug disposition requires consideration of factors like plasma protein binding.

Purpose of the Study:

• To compare theophylline pharmacokinetics in elderly and young adults.
• To investigate the influence of plasma protein binding on theophylline disposition in different age groups.
• To identify age-related differences in theophylline metabolic and excretory pathways.

Main Methods:

• Single oral dose theophylline administration in elderly and young healthy subjects.
• Measurement of total and unbound plasma theophylline concentrations over time.
• Analysis of urinary excretion patterns of theophylline metabolites.
• Calculation of pharmacokinetic parameters, including volume of distribution (Vd) and clearance, considering plasma protein binding.

Main Results:

• Elderly subjects exhibited higher unbound theophylline levels and a greater area under the curve (AUC) for unbound drug.
• When plasma protein binding was considered, elderly individuals showed a significant reduction in Vd and overall plasma clearance.
• The elderly excreted a higher fraction of the dose as 1-methyluric acid and a lower fraction as unchanged theophylline, indicating altered metabolism and renal excretion.

Conclusions:

• Theophylline elimination is less efficient in the elderly due to impaired metabolism and renal excretion.
• Plasma protein binding significantly influences theophylline pharmacokinetics in the elderly.
• Assessment of plasma protein binding is essential for accurate drug disposition studies in geriatric populations.