Influence of posture on pharmacokinetics

Area of Science:

• Pharmacokinetics
• Physiology

Background:

• Body position influences physiological factors like perfusion, gastrointestinal function, and plasma volume.
• These physiological changes can interact with drug absorption, distribution, metabolism, and excretion (ADME).

Purpose of the Study:

• To summarize current data on the effects of posture on physiological characteristics and pharmacokinetics.
• To assess the clinical relevance of these postural effects in patient care and pharmacokinetic studies.

Main Methods:

• Systematic literature search.
• Analysis of existing data on posture's impact on physiological parameters and drug pharmacokinetics.

Main Results:

• Upright postures (sitting, standing, recumbent right) accelerate gastric emptying and drug absorption, increasing peak plasma concentration (Cmax) and potentially total exposure (AUC).
• Postural changes affect splanchnic-hepatic blood flow, influencing the metabolism of drugs with high or saturable first-pass metabolism.
• Plasma volume changes due to posture can alter total plasma concentrations of highly protein-bound drugs.

Conclusions:

• Patient positioning can be used clinically to modulate drug absorption, beneficial in situations like toxic ingestions or for bedridden patients.
• Precise posture control in pharmacokinetic trials, such as bioequivalence studies, is crucial for reducing variability and improving study reliability.