Omeprazole

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: Omeprazole

Examples of brand names: Antra [DE]

ATC code: A02BC01

Main use (for orientation): Reflux; ulcer

Documented research summary

Direct human pharmacokinetics: CBD-rich THC extract increased omeprazole AUC; the THC-containing extract without CBD showed no signal after this single dose. Opposite direction: omeprazole did not alter nabiximols pharmacokinetics to a statistically established extent; all nine 90% confidence intervals include 1, and none lies entirely within 0.80–1.25. Equivalence is therefore not established. In vitro probe inhibition and static predictions are separate, not additional clinical confirmation.

Uncertainties and limitations

Do not extrapolate CBD/THC findings to the other 26 cannabinoids. No general reassurance about safety.

Historical label evidence supplemented by an available, more recent single-ingredient SPL; no claim to cover every national authorisation status. Consider formulation-dependent absorption.

Separately recorded findings

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

CBD + Δ9-THC (oral extract) – clinically studied

Finding ID: B0021

Type of result: Positive finding / indication

Observation: AUC +207%.

Mechanism: CYP2C19 probe

Study type: Randomised crossover pharmacokinetic study

Context studied: n=18; omeprazole 20 mg as part of a combined CYP-probe cocktail 30 minutes after CBD-rich plant extract (640 mg CBD + 20 mg THC) in a brownie versus placebo. Double-blind, randomised crossover; at least one week of washout; standardised low-fat breakfast one hour before the brownie; samples 0–24 h.

Clinical interpretation: Pharmacokinetic signal; clinical consequences undetermined

Limitations and uncertainties: Not a CBD-only study.

Original sources for this finding: Evaluation of Cytochrome P450-Mediated Cannabinoid-Drug Interactions in Healthy Adult Participants [CL09]

Δ9-THC (oral extract without CBD) – clinically studied

Finding ID: B0026

Type of result: No / minor effect under the conditions studied

Observation: No inhibition signal.

Mechanism: CYP probe

Study type: Randomised crossover pharmacokinetic study

Context studied: n=18; omeprazole 20 mg as part of a combined CYP-probe cocktail 30 minutes after THC plant extract (20 mg THC, without CBD) in a brownie versus placebo. Double-blind, randomised crossover; at least one week of washout; standardised low-fat breakfast one hour before the brownie; samples 0–24 h.

Clinical interpretation: Null finding

Limitations and uncertainties: Single administration; no general assurance of safety.

Original sources for this finding: Evaluation of Cytochrome P450-Mediated Cannabinoid-Drug Interactions in Healthy Adult Participants [CL09]

CBD + Δ9-THC (nabiximols) – clinically investigated

Finding ID: B0045

Type of result: No / minor effect under the conditions studied

Observation: No statistically established pharmacokinetic difference in the regimen investigated. Geometric ratios, combination/alone, for THC, CBD and 11-OH-THC: Cmax 1.125/1.320/0.866; AUC0–t 0.964/1.326/0.869; AUC∞ 0.962/1.096/0.869. All nine 90% CIs include 1, but none lies entirely within the prespecified no-interaction range of 0.80–1.25.

Mechanism: CYP2C19 inhibition investigated

Study type: Randomised open-label phase I crossover pharmacokinetics

Context studied: 12 healthy men; oral omeprazole 40 mg once daily for a total of six days (five pretreatment days plus co-administration on the sixth day). Nabiximols as a single dose of four oromucosal sprays = 10.8 mg THC + 10 mg CBD. Cmax/AUC0–t: n=12 each; AUC∞ for CBD: n=11, for THC/11-OH-THC: n=12.

Clinical interpretation: Null finding with uncertainty

Limitations and uncertainties: Equivalence not established: all nine 90% CIs cross at least one boundary of 0.80–1.25. High variability, small group of healthy men and a single nabiximols dose; do not infer general safety or exclusion of CYP2C19 involvement.

Original sources for this finding: A Phase I, open-label, randomized, crossover study in three parallel groups to evaluate the effect of Rifampicin, Ketoconazole, and Omeprazole on the pharmacokinetics of THC/CBD oromucosal spray in healthy volunteers [CL18]

References and access status

[BWEB01] Omeprazole delayed-release capsules US label

Original source / bibliographic reference

Authors: Citron Pharma / DailyMed

Year: 2015

Source type: Regulatory product information / SmPC

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

Bibliographic attribution or source identity cross-checked.

[V2_LABEL_D0267_Prilosec] PRILOSEC (omeprazole magnesium), granules for delayed-release oral suspension

Original source / bibliographic reference

Authors: Covis Pharma US, Inc

Year: 2024

Source type: Official US SPL / DailyMed

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

Bibliographic attribution or source identity cross-checked.

[CL09] Evaluation of Cytochrome P450-Mediated Cannabinoid-Drug Interactions in Healthy Adult Participants

Original source / bibliographic reference

Authors: Bansal S; Zamarripa CA; Spindle TR; Weerts EM; Thummel KE; Vandrey RG; Paine MF; Unadkat JD

Year: 2023

Source type: Randomised placebo-controlled crossover probe study

DOI: 10.1002/cpt.2973

PMID: 37313955

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.

[CL18] A Phase I, open-label, randomized, crossover study in three parallel groups to evaluate the effect of Rifampicin, Ketoconazole, and Omeprazole on the pharmacokinetics of THC/CBD oromucosal spray in healthy volunteers

Original source / bibliographic reference

Authors: Stott C; White L; Wright S; Wilbraham D; Guy G

Year: 2013

Source type: Randomised open-label phase I crossover study

DOI: 10.1186/2193-1801-2-236

PMID: 23750331

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

Bibliographic attribution or source identity cross-checked.

PubMed – bibliographic reference / abstract

DOI – publisher access (access restrictions may apply)

[BMED35115300] Comprehensive Predictions of Cytochrome P450 (P450)-Mediated In Vivo Cannabinoid-Drug Interactions Based on Reversible and Time-Dependent P450 Inhibition in Human Liver Microsomes.

Original source / bibliographic reference

Authors: Bansal S, Paine MF, Unadkat JD.

Year: 2022

Source type: Primary publication; abstract reviewed

DOI: 10.1124/dmd.121.000734

PMID: 35115300

Source access – 23 October 2026: Automated direct retrieval was restricted; this does not establish that the link is broken.

Bibliographic attribution or source identity cross-checked.

PubMed – bibliographic reference / abstract

PubMed Central – archived text

DOI – publisher access (access restrictions may apply)

[BMED23318708] Cannabidiol is a potent inhibitor of the catalytic activity of cytochrome P450 2C19.

Original source / bibliographic reference

Authors: Jiang R, Yamaori S, Okamoto Y, Yamamoto I, Watanabe K.

Year: 2013

Source type: Primary publication; abstract reviewed

DOI: 10.2133/dmpk.dmpk-12-rg-129

PMID: 23318708

Source access – 23 October 2026: Automated direct retrieval was restricted; this does not establish that the link is broken.

Bibliographic attribution or source identity cross-checked.

PubMed – bibliographic reference / abstract

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.

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