Pregnancy- Associated Changes in Pharmacokinetics and their Clinical Implications

Area of Science:

• Pharmacology
• Maternal-Fetal Medicine
• Drug Metabolism

Background:

• Pregnancy induces significant pharmacokinetic alterations affecting drug disposition.
• These changes can lead to lower maternal serum drug concentrations, impacting therapeutic efficacy.
• Lower protein binding in pregnancy increases the free fraction of many drugs, enhancing metabolism and reducing total drug levels.

Purpose of the Study:

• To critically review pregnancy-induced pharmacokinetic changes.
• To explore the clinical application of understanding these pharmacokinetic shifts.
• To highlight the challenges in establishing pregnancy-specific drug dosing regimens.

Main Methods:

• A structured literature review was conducted.
• Databases searched included Pubmed and MBASE.
• Relevant published books were also included in the review.

Main Results:

• Advanced pregnancy is associated with decreased maternal serum concentrations for many drugs.
• Lower protein binding increases the free drug fraction, leading to higher metabolism and lower total drug concentrations.
• Increased volume of distribution can lower peak drug concentrations, potentially hindering therapeutic level achievement.

Conclusions:

• Currently, no pregnancy-targeted drug dose schedules exist, unlike those for renal failure.
• Well-designed studies are needed to compare dose-effect relationships across pregnancy stages and non-pregnant states.
• Pharmacokinetic-pharmacodynamic modeling, using parallel measurements of drug effects and concentrations, can guide evidence-based dosing adjustments during gestation.