Diltiazem

For an informed discussion with your doctor or pharmacist. This information collection is not a clinically validated interaction checker. Missing data do not establish safety. Do not change or stop prescribed medicines on the basis of this information. The findings apply to the specific conditions studied; laboratory and animal studies cannot be directly extrapolated to humans.

Active substance: Diltiazem

Examples of brand names: Dilzem [DE]

ATC code: C08DB01

Main use (for orientation): Hypertension; angina

Documented research summary

Direct in-vitro finding: CBD competitively inhibits diltiazem N-demethylation by CYP3A4, CYP3A5 and human liver microsomes (Ki 1.00/0.195/6.14 µM); THC/CBN were weaker for CYP3A4/5 (IC50 >35 µM). No human pharmacokinetic evidence. Cell/animal findings with CP55,940 and ACEA/URB597 are not clinical CBD/THC data.

Uncertainties and limitations

Laboratory inhibition alone does not predict patient AUC. Parent substance and active metabolite may respond differently; do not infer changes in effects solely from CYP pathways.

Separately recorded findings

1 separately recorded finding. Each statement applies to its documented study context.

CBD/THC/CBN – laboratory and animal studies

Finding ID: B0168

Type of result: Preclinical mechanism

Observation: Competitive CBD inhibition: Ki CYP3A4 1.00 µM, CYP3A5 0.195 µM, human liver microsomes 6.14 µM; THC/CBN weaker, with IC50 >35 µM for 3A4/3A5.

Mechanism: Inhibition of diltiazem N-demethylation

Study type: Recombinant CYP/microsome study

Context studied: Yamaori 2011; diltiazem as an enzyme probe.

Clinical interpretation: Clinical effect unquantified

Limitations and uncertainties: No human interaction study; concentrations/protein binding prevent direct extrapolation to AUC or dose changes.

Original sources for this finding: Potent inhibition of human cytochrome P450 3A isoforms by cannabidiol: role of phenolic hydroxyl groups in the resorcinol moiety. [CA_P_21356216]

References and access status

[CA_L_D0208] CARTIA XT (DILTIAZEM HYDROCHLORIDE) CAPSULE, EXTENDED RELEASE [ACTAVIS PHARMA, INC.]

Original source / bibliographic reference

Authors: Actavis Pharma, Inc.

Year: 2026

Source type: Official human-use SPL / DailyMed

Source access – 23 October 2026: Source destination was accessible when checked.

Bibliographic attribution or source identity cross-checked.

[CA_P_21356216] Potent inhibition of human cytochrome P450 3A isoforms by cannabidiol: role of phenolic hydroxyl groups in the resorcinol moiety.

Original source / bibliographic reference

Authors: Yamaori S, Ebisawa J, Okushima Y, Yamamoto I, Watanabe K.

Year: 2011

Source type: Primary / secondary publication; design and use described in the individual review

DOI: 10.1016/j.lfs.2011.02.017

PMID: 21356216

Source access – 23 October 2026: Direct retrieval could not be fully verified; availability remains unresolved.

Bibliographic attribution or source identity cross-checked.

DOI – publisher access (access restrictions may apply)

Research as of 23 October 2026. Not all original full texts could be reviewed in full. Source accessibility and the strength of scientific evidence must be assessed separately. An accessible link does not establish medical approval; a bibliographic record with an abstract does not replace the original full text.

Drug search and explanation of the evidence · Guide: cannabinoids and medicines · Author and responsibility