Supplements and Amlodipine.
Amlodipine, sold under the brand names Istin, Norvasc, is a calcium channel blocker: it relaxes vascular smooth muscle and reduces afterload.
Amlodipine is a long-acting calcium channel blocker in the dihydropyridine class. Prescribing is mostly hypertension and stable angina. It blocks L-type calcium channels in arterial smooth muscle, dropping peripheral resistance and afterload. The side effect most often reported is ankle oedema, from preferential dilation of arterioles over venules. It scales with dose. It is not a sign of heart or kidney trouble. Amlodipine is metabolised by CYP3A4, but the therapeutic window is wide enough that 3A4 interactions rarely matter at standard doses. Where supplements meet amlodipine, the main signal is additive blood pressure lowering. Beetroot extract, hibiscus, garlic, and the nitrate pathway compounds can stack on top. Sometimes useful. Sometimes pushing systolic too low. The combination flagged in the BNF is grapefruit juice, since 3A4 inhibition can push amlodipine plasma levels up by 20 to 30 percent. Anyone titrating an antihypertensive supplement stack alongside amlodipine should keep a home BP log rather than assume the baseline holds.
Below are the 11 documented pairs we have explicitly assessed against Amlodipine in the Distil database: 10 amber and 1 green. The pairs cluster around 3 mechanisms: Additive blood-pressure lowering, Reduced blood-pressure-medicine effect, and CYP3A4 inhibition. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.
Documented interactions
Additive blood-pressure lowering
Beetroot lowers blood pressure through the nitric oxide pathway. Amlodipine lowers blood pressure through calcium-channel blockade in vascular smooth muscle. Both mechanisms cause vasodilation, so the combined effect tends to be larger than either alone. Watch for dizziness on standing or ankle swelling, especially in the first two weeks. If symptoms appear, tell your GP.
Berberine can lower blood pressure modestly. Added to amlodipine the effect may stack, which is sometimes helpful but can occasionally cause dizziness or a blood pressure that runs lower than your GP intended. Check your blood pressure when you start berberine and tell your GP.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Garlic supplements mildly lower blood pressure, and amlodipine lowers it too. The combined effect tends to be a little larger than either alone. It is usually manageable, but watch for dizziness on standing or ankle swelling in the first couple of weeks, and tell your GP if symptoms appear.
Hibiscus tends to lower blood pressure on its own, and amlodipine lowers it by relaxing blood vessels. Taken together the blood-pressure effects may stack, so watch for dizziness on standing, especially in the first couple of weeks. If symptoms appear, tell your GP.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
L-citrulline lowers blood pressure modestly through the nitric oxide pathway, and amlodipine lowers blood pressure by relaxing blood vessels through calcium-channel blockade. Used together, the combined blood-pressure effect is mild but real. Watch for dizziness on standing, especially in the first two weeks. If symptoms appear, tell your GP.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Pine bark extract (pycnogenol) mildly lowers blood pressure, and amlodipine lowers it too. The combined effect tends to be a little larger than either alone. It is usually manageable, but watch for dizziness on standing in the first couple of weeks and tell your GP if symptoms appear.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Spirulina has a mild blood-pressure-lowering effect of its own, shown in human trials. Amlodipine lowers blood pressure through calcium-channel blockade. Used together, the combined effect tends to be a little larger than the medicine alone. Watch for dizziness on standing in the first couple of weeks, and tell your GP if it happens so your dose can be reviewed.
Taurine tends to lower blood pressure on its own, and amlodipine lowers it by relaxing blood vessels. Taken together the blood-pressure effects may stack, so watch for dizziness on standing, especially in the first couple of weeks. The added effect tends to be modest. If symptoms appear, tell your GP.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
L-theanine can take the edge off a stress-driven rise in blood pressure, but it does not lower resting blood pressure the way a blood-pressure medicine does. At normal supplement doses it is not expected to push your blood pressure too low when taken with amlodipine. If you monitor at home and see readings lower than usual, mention it to your GP.
Reduced blood-pressure-medicine effect
Melatonin has been shown to raise blood pressure and heart rate in people taking the related blood-pressure drug nifedipine, working against it. Amlodipine is in the same drug family, so the same effect may apply. If you take amlodipine, it is worth discussing melatonin with your prescriber and monitoring your blood pressure rather than starting it on your own.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
CYP3A4 inhibition
Bergamot is grapefruit-family citrus and can raise amlodipine blood levels by slowing its clearance. The clinical impact depends on dose, but flag this to your GP before combining, particularly if your blood pressure is well controlled and you do not want a sudden drop.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.
How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
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This page checks the pairs you enter. The personalised Distil report goes further:
- the same graded, cited interaction check across your whole stack, not just the pairs you thought to type in
- where your current routine may be leaving you short of your goals
- the evidence-backed compounds worth adding, and the ones worth dropping
It's a paid report: £79, or £49 for the first 25 customers. The interactions check is one section of it, and you can read a real one in full before you buy.
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