NutriStack
Diltiazem and L-Theanine, a caution.
L-Theanine modestly lowers stress-induced blood pressure increases and has mild relaxing effects on vascular tone. Layered on top of diltiazem's bradycardia, vasodilation, and negative inotropy, the combination can produce additive drops in heart rate or blood pressure, particularly in patients who are already well-controlled or volume-depleted.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
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At a glance
- Substances
- Diltiazem and L-Theanine
- Pair type
- Caution
- Evidence (highest tier)
- Emerging
- Source citations
- 2 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Emerging evidence
Caution
What is happening. L-Theanine modestly lowers stress-induced blood pressure increases and has mild relaxing effects on vascular tone. Layered on top of diltiazem's bradycardia, vasodilation, and negative inotropy, the combination can produce additive drops in heart rate or blood pressure, particularly in patients who are already well-controlled or volume-depleted.
Mechanism. L-Theanine attenuates sympathetic outflow and lowers stress-induced pressor responses through GABAergic and glutamate-receptor effects. This adds to diltiazem's negative chronotropic and vasodilatory action.
Recommendation. If you take diltiazem, L-theanine doses up to 200-350 mg/day supplemental elemental magnesium are usually well-tolerated, but check your blood pressure and pulse when you start. Reduce or stop the supplement if you develop dizziness, fatigue, or a resting heart rate below 50 bpm.
Sources (2)
- Yoto A, Motoki M, Murao S, Yokogoshi H. Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. J Physiol Anthropol. 2012;31(1):28. PMID 23107346
- Mills TA, Kawji MM, Cataldo VD, et al. Profound sinus bradycardia due to diltiazem, verapamil, and/or beta-adrenergic blocking drugs. J La State Med Soc. 2004;156(6):327-31. PMID 15688675
Stack Score
How this pair moves the number.
Effect on the composite score
If both Diltiazem and L-Theanine are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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