Physiological transport forces govern drug distribution for stent-based delivery.

Area of Science:

• Pharmacokinetics and Drug Delivery
• Biomedical Engineering
• Cardiovascular Research

Background:

• Early stent-based drug delivery (e.g., heparin) failed clinically despite promising preclinical data.
• Recent hydrophobic drugs (e.g., paclitaxel) show greater efficacy, prompting investigation into property-driven differences.

Purpose of the Study:

• To investigate how transport forces and stent geometry influence the distribution of hydrophilic and hydrophobic drugs delivered via stents.
• To understand the impact of physicochemical properties and targeting on drug efficacy in stent-based delivery.

Main Methods:

• Application of continuum pharmacokinetics to model drug distribution.
• Analysis of concentration gradients and variations based on drug properties (hydrophilic vs. hydrophobic) and transport forces (Peclet number).
• Evaluation of the influence of inhomogeneous stent strut placement.

Main Results:

• Stent delivery creates significant drug concentration gradients, varying widely over micrometers.
• Hydrophobic drugs achieved higher mean concentrations and localized better to the intima compared to hydrophilic drugs.
• Inhomogeneous stent placement negatively impacted hydrophilic drug concentrations more than hydrophobic ones.

Conclusions:

• Local drug concentrations and gradients, not just proximity, are critical for biological effect.
• Physiological transport forces cause significant deviations from mean concentrations, challenging effective targeting.
• Understanding these pharmacokinetic principles is crucial for optimizing stent-based drug delivery and explaining variable clinical success.