Cbd Interactions

CBD inhibits CYP3A4, CYP3A5, and P-glycoprotein, the main pathways that clear tacrolimus. Case reports and a controlled pharmacokinetic trial show that adding CBD raises tacrolimus blood levels substantially, risking nephrotoxicity, neurotoxicity, and over-immunosuppression in transplant recipients, while stopping CBD abruptly can let levels crash and risk rejection.

CBD inhibits CYP2C19, the enzyme that clears N-desmethylclobazam, the active metabolite of clobazam. Taking the two together raises N-desmethylclobazam levels substantially, increasing sedation, drowsiness, drooling, and unsteadiness. This interaction is documented in the FDA-approved Epidiolex prescribing information and in clinical studies in children with epilepsy.

Taking CBD (including prescription Epidiolex and over-the-counter products) together with valproate raises the chance of liver enzyme elevations well above either drug alone, and the combination has been linked to high blood ammonia that can cause confusion or worsening seizures even when liver tests look only mildly abnormal. This pairing should be managed by the prescribing neurologist with baseline and follow-up liver testing.

CBD inhibits the liver enzymes (notably CYP2C9, and also CYP3A4) that clear warfarin, especially its more potent S-enantiomer. Adding CBD to a stable warfarin regimen can slow warfarin breakdown, raise its blood level, push the INR upward, and increase bleeding risk. A published case report described a patient who needed a meaningful warfarin dose reduction after starting CBD.

CBD inhibits CYP2C19, one of several enzymes that help break down sertraline, so adding CBD can raise sertraline exposure. A single published case report describes low sodium (hyponatremia) and cognitive decline in an older intermediate-metabolizer patient who added over-the-counter CBD to long-standing sertraline. The evidence is limited to this one report, so treat it as a reason for caution and prescriber discussion rather than a strong contraindication.

Simvastatin is cleared mainly by the liver enzyme CYP3A4, and CBD inhibits that same enzyme. Combining them is expected to raise simvastatin exposure, which could increase the risk of muscle pain and, rarely, more serious muscle injury. This is a predicted, mechanism-based interaction rather than one confirmed by a direct human study.

CBD weakly inhibits CYP2D6, the liver enzyme that clears beta-blockers such as metoprolol, propranolol, and carvedilol, so in theory it could nudge their plasma levels up. CBD also has a mild blood-pressure-lowering effect of its own. Both actions point in the same direction as the beta-blocker, but the CYP2D6 effect is weak and its real-world clinical significance has not been demonstrated in humans.