Which supplements or medications are best not combined with NAD+?
For people undergoing chemotherapy with cisplatin, nicotinamide as an NAD+ precursor is a concrete point of concern; always discuss this with the oncologist. Combinations with herbal supplements such as Ginkgo biloba or high doses of sulforaphane may disrupt medication levels, but how large that risk is in practice has not yet been established in humans.
Nicotinamide, a widely used NAD+ precursor, can undermine the effectiveness of the chemotherapy drug cisplatin. In cell culture research using lung cancer cells, nicotinamide was found to bind directly to active cisplatin molecules, leaving fewer active cisplatin molecules available to damage cancer cells. This has been measured exclusively in the laboratory, not in humans. People undergoing chemotherapy with cisplatin are advised to discuss this risk with their oncologist before taking NAD+ supplements or nicotinamide1.
Niacin (also known as vitamin B3, another NAD+ precursor) has a specific and relevant interaction with experimental cancer drugs that block NAD+ production, known as NAMPT inhibitors. These drugs are designed to starve cancer cells by halting their NAD+ production. Because niacin can produce NAD+ via an alternative route, it may neutralise that approach. At the same time, niacin also has a protective side here: in rat studies and cell culture, it was able to reverse the platelet toxicity caused by NAMPT inhibitors. The conclusion is twofold: NAD+ precursors can undermine the intended effect of NAD+-blocking cancer drugs, but may also be investigated as protection against their side effects. Consultation with the treating physician is essential in this context2.
A broader point of attention applies to people who combine NAD+ supplements with herbal supplements such as Ginkgo biloba, soy isoflavones, or Milk Thistle. The flavonoids in these products influence liver enzymes (CYP450) that break down many medications, including blood thinners, antidepressants, and statins. Depending on the specific flavonoid, a medication may be broken down faster or more slowly, leading to blood levels that are too high or too low. The effects found were measured in laboratory research at concentrations higher than what is normally consumed through diet, but at high supplementation doses that difference becomes smaller. This is not an interaction with NAD+ itself, but a risk associated with combining multiple popular supplements at the same time3.
Broccoli extract or sulforaphane supplements, which are popular due to their purported anti-cancer properties, can reduce the effectiveness of common medications. In cell culture studies, antagonistic effects were found with furosemide (a diuretic), verapamil (a heart medication), and ketoprofen (a painkiller). The mechanism involves phase II metabolic enzymes and transport proteins involved in drug transport. This too is preclinical research, but it gives reason for caution among people who combine sulforaphane with these medications4.
Finally, fucoidan, a seaweed extract sometimes taken as a supplement, can at higher doses interfere with the same CYP450 liver enzymes and with the enzyme COMT, which is involved among other things in the breakdown of stress hormones and certain medications such as levodopa in Parkinson's disease. This is preclinical research, but it highlights a general pattern: combining multiple supplements increases the likelihood of drug interactions, even when the supplements appear harmless individually5.
All findings come from cell culture or animal research, or have an indirect relationship to NAD+ supplements. No direct human clinical studies on these interactions are available in the sources. The findings therefore represent signals, not proven clinical risks in humans.