Pregnancy hormones likely alter how the body processes THC | Research

The takeaway

Pregnancy hormones induce the liver enzymes that metabolize THC (CYP2C9 and CYP3A4), potentially changing how THC and its psychoactive metabolite 11-OH-THC are processed, with unknown effects on maternal and fetal safety.

Pregnant individuals using cannabis, pharmacologists, obstetricians

>70% of THC cleared by pregnancy-induced CYP2C9

What the researchers found

THC is primarily (>70%) cleared by CYP2C9 to its psychoactive metabolite 11-OH-THC, with CYP3A4 contributing <30%. Both enzymes are induced during pregnancy by pregnancy hormones, which is predicted to alter THC and 11-OH-THC disposition and pharmacodynamic effects.

Why it matters

Cannabis is the most widely used drug of abuse during pregnancy, yet almost nothing is known about how pregnancy changes THC processing. If CYP2C9 induction increases 11-OH-THC production, pregnant users might experience stronger psychoactive effects than expected.

The numbers in context

THC clearance: >70% via CYP2C9 (to 11-OH-THC), <30% via CYP3A4. Both enzymes are induced during pregnancy.

How the study worked

Narrative review of literature on THC metabolism, pharmacokinetics, and how pregnancy-related physiological and hormonal changes may alter cannabinoid disposition.

What this study cannot tell us

Predictions based on known enzyme induction patterns, not direct measurement of THC pharmacokinetics in pregnant women. In vitro enzyme studies may not fully predict in vivo changes. Individual genetic variation in CYP2C9 adds further complexity.

How to read the evidence

Thorough review of pharmacokinetic principles with predicted but not directly measured effects of pregnancy on THC disposition.

When this study was published

2024 review of THC pharmacokinetics and pregnancy physiology

The bigger picture

Most cannabis safety discussions focus on whether THC reaches the fetus, but this review raises a different concern: pregnancy may change how THC is metabolized in the mother, potentially increasing levels of the active metabolite. This adds another layer of uncertainty to prenatal cannabis use.

Questions still open

Do pregnant cannabis users experience different psychoactive effects due to altered metabolism? Does increased 11-OH-THC production affect fetal exposure?

Common questions

Does pregnancy change how the body processes THC?

Likely yes. The liver enzymes that break down THC (CYP2C9 and CYP3A4) are induced during pregnancy, which is predicted to change how quickly THC is processed and how much of its active metabolite is produced.

Could this make THC effects stronger during pregnancy?

It is possible. If CYP2C9 induction increases production of 11-OH-THC (which is also psychoactive), the effects could differ from what non-pregnant users experience, though this has not been directly measured.

Read the original research

The impact of pregnancy and associated hormones on the pharmacokinetics of Δ9-tetrahydrocannabinol.

Expert opinion on drug metabolism & toxicology, 20(1-2), 73-93

View on PubMed ↗Publisher’s paper ↗

Citation

Authement, Aurora K; Isoherranen, Nina. (2024). The impact of pregnancy and associated hormones on the pharmacokinetics of Δ9-tetrahydrocannabinol.. Expert opinion on drug metabolism & toxicology, 20(1-2), 73-93. https://doi.org/10.1080/17425255.2024.2309213