Verapamil

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: Verapamil

Examples of brand names: Isoptin [DE]

ATC code: C08DA01

Main use (for orientation): Hypertension; arrhythmias

Documented research summary

No established clinical CBD/THC–verapamil drug–drug interaction. CBD inhibited verapamil-stimulated P-gp ATPase in vitro (IC50 39.6 µM); this is not a verapamil pharmacokinetic experiment. THC did not antagonise verapamil-induced vasorelaxation in isolated rat vessels. A ventricular tachycardia case improved with verapamil AND cannabis cessation, so no co-medication interaction was demonstrated. Synthetic agonists/endocannabinoid modulators in cell/animal models are considered separately from THC/CBD.

Uncertainties and limitations

Do not interpret micromolar cell concentrations as clinical exposure. No human pharmacokinetic effect established; historical full-text access unresolved.

Separately recorded findings

2 separately recorded findings. Each statement applies to its documented study context.

CBD – laboratory and animal studies

Finding ID: B0169

Type of result: Preclinical mechanism

Observation: CBD inhibited verapamil-stimulated ATPase activity in a concentration-dependent manner, IC50 39.6 µM; other cannabinoids investigated did not substantially inhibit this endpoint.

Mechanism: P-gp ATPase inhibition in the laboratory

Study type: Transporter/ATPase assay

Context studied: Zhu 2006; THC, THC-COOH, CBN and CBD tested.

Clinical interpretation: No measured verapamil pharmacokinetic effect

Limitations and uncertainties: ATPase stimulation is not clinical verapamil clearance; no patient-dose prediction.

Original sources for this finding: Characterization of P-glycoprotein inhibition by major cannabinoids from marijuana [ME05]

THC – laboratory and animal studies

Finding ID: B0170

Type of result: Preclinical null/contrary finding

Observation: THC did not antagonise verapamil-induced vasorelaxation in the rat vessels investigated.

Mechanism: Isolated vascular pharmacodynamics

Study type: Isolated rat mesenteric vessels

Context studied: O'Sullivan 2005; THC 1/10 µM in the antagonist comparison.

Clinical interpretation: Not transferable to cardiovascular safety in humans

Limitations and uncertainties: Vessel/concentration-specific endpoint, not whole-organism pharmacokinetics.

Original sources for this finding: The effects of Delta9-tetrahydrocannabinol in rat mesenteric vasculature, and its interactions with the endocannabinoid anandamide. [CA_P_15821751]

References and access status

[CA_L_D0207] VERAPAMIL HYDROCHLORIDE (VERAPAMIL HYDROCHLORIDE) INJECTION [MICRO LABS LIMITED]

Original source / bibliographic reference

Authors: Micro Labs Limited

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_L_D0207_ORAL] Vera-Til SR 120mg Tablets – Summary of Product Characteristics

Original source / bibliographic reference

Authors: Tillomed Laboratories Ltd

Year: 2024

Source type: Approved SmPC

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

Bibliographic attribution or source identity cross-checked.

[ME05] Characterization of P-glycoprotein inhibition by major cannabinoids from marijuana

Original source / bibliographic reference

Authors: Zhu HJ; Wang JS; Markowitz JS; Donovan JL; Gibson BB; Gefroh HA; DeVane CL

Year: 2006

Source type: Original study: transporter/cell assays

DOI: 10.1124/jpet.105.098541

PMID: 16439618

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)

[CA_P_15821751] The effects of Delta9-tetrahydrocannabinol in rat mesenteric vasculature, and its interactions with the endocannabinoid anandamide.

Original source / bibliographic reference

Authors: O'Sullivan SE, Kendall DA, Randall MD.

Year: 2005

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

DOI: 10.1038/sj.bjp.0706218

PMID: 15821751

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)

PubMed Central – full-text access according to the literature database – Archive attribution confirmed by Europe PMC metadata. Direct retrieval was not fully verified here; access may require a browser check.

Europe PMC – full-text access according to the literature database – Listed as freely available HTML full text in the official Europe PMC metadata. Direct retrieval was not fully verified here.

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