THC Made Chemotherapy Side Effects Worse in Some Ways, Better in Others | Research

The takeaway

THC combined with the chemotherapy drug irinotecan worsened white blood cell drops in rats but appeared to protect against liver enzyme elevation.

Cancer patients and oncologists interested in cannabis-chemotherapy interactions.

THC metabolite levels were higher when combined with irinotecan, suggesting a pharmacokinetic interaction between the two drugs.

What the researchers found

Co-administration of THC with irinotecan in rats caused greater leukopenia than irinotecan alone, but the expected rise in the liver enzyme AST seen with irinotecan alone did not occur in the combination group.

Why it matters

Many cancer patients use cannabis to manage chemotherapy side effects. This study suggests THC may have both helpful and harmful interactions with at least one chemo drug, highlighting the need to understand these interactions before combining treatments.

The numbers in context

THC dose was 7 mg/kg orally. Irinotecan dose was 100 mg/kg. Urinary THC metabolite concentrations were higher in the irinotecan + THC group compared to THC-only, suggesting a pharmacokinetic interaction.

How the study worked

Male rats received single-dose irinotecan alone or with repeated oral THC (1, 3, or 7 days). Blood and urine were analyzed for blood counts, liver enzymes, inflammatory markers, and THC metabolites.

What this study cannot tell us

Animal study using a single chemo drug and relatively high doses. Results may not translate directly to humans. Only male rats were studied. Short follow-up period.

How to read the evidence

Preliminary - single animal study with a small sample.

When this study was published

Published in 2018. More research has since explored cannabinoid-chemotherapy interactions.

The bigger picture

As cannabis use among cancer patients increases, understanding how cannabinoids interact with chemotherapy drugs becomes critical. This study provides early evidence that THC may alter both the effectiveness and toxicity profile of irinotecan.

Questions still open

Does THC interact similarly with other chemotherapy drugs? Would lower, more clinically relevant THC doses produce the same effects? What mechanism drives the protective liver effect versus the worsened blood cell counts?

Common questions

Can you use cannabis while on chemotherapy?

This rat study suggests THC may interact with the chemo drug irinotecan in complex ways - reducing some side effects while worsening others. Human data is limited, and interactions likely vary by drug.

Does THC affect how chemo drugs are processed in the body?

This study found that THC metabolite levels were higher when THC was given alongside irinotecan, suggesting the drugs may affect each other's metabolism.

Read the original research

Effects of Δ9-tetrahydrocannabinol on irinotecan-induced clinical effects in rats.

Chemico-biological interactions, 294, 128-134

View on PubMed ↗Publisher’s paper ↗

Citation

Prester, Ljerka; Mikolić, Anja; Jurič, Andreja; Fuchs, Nino; Neuberg, Marijana; Lucić Vrdoljak, Ana; Brčić Karačonji, Irena. (2018). Effects of Δ9-tetrahydrocannabinol on irinotecan-induced clinical effects in rats.. Chemico-biological interactions, 294, 128-134. https://doi.org/10.1016/j.cbi.2018.08.009