How does the pharmacokinetics of drugs change during pregnancy?

During pregnancy, the pharmacokinetics of drugs is significantly altered across all key parameters: absorption, distribution, metabolism, and excretion.

Absorption may be affected by changes in gastrointestinal motility and pH, which can influence how quickly or effectively a drug is absorbed. For instance, delayed gastric emptying and increased gastric pH can enhance the absorption of some medications while hindering others.

Distribution is also altered due to physiological changes such as an increase in plasma volume and body fat. This can lead to a larger volume of distribution for hydrophilic and lipophilic drugs, respectively, affecting how drugs are dosed during pregnancy.

Metabolism changes, with increased hepatic enzyme activity noted for some drugs, leading to faster metabolism and potentially requiring dosage adjustments. Conversely, other drugs may have decreased metabolic clearance, meaning they stay active in the system longer.

Excretion is generally increased in pregnant individuals due to enhanced renal blood flow and glomerular filtration rate, which can lead to reduced serum drug levels for substances that are primarily eliminated through the kidneys.

Given these comprehensive changes, understanding the altered pharmacokinetics during pregnancy is crucial for optimal medication management and ensuring both maternal and fetal safety.