NMN/NR and Simvastatin Interaction: What Clinicians and Patients Need to Know

What the simvastatin label says about niacin

Zocor's prescribing information lists niacin among the drugs that raise the risk of myopathy and rhabdomyolysis when taken with simvastatin. For niacin at 1 g/day or more, the label says to weigh the benefit against the risk and monitor for muscle symptoms [2]. For Chinese patients it goes further: lipid-modifying doses of niacin, 1 g/day or more, are not recommended alongside simvastatin [2].

Niacin sits in a different part of the label from the drugs that carry fixed dose caps. The label's caps are: no more than 20 mg of simvastatin daily with amlodipine, amiodarone or ranolazine; no more than 10 mg daily with verapamil, diltiazem or dronedarone; and a 50% simvastatin reduction, to no more than 20 mg daily, with lomitapide [2]. The label's contraindications are narrower still: strong CYP3A4 inhibitors such as itraconazole, clarithromycin or ritonavir, plus cyclosporine, danazol and gemfibrozil [2]. Niacin appears on neither list.

The label sets the maximum recommended simvastatin dose at 40 mg once daily, taken in the evening. It reserves 80 mg for people who have already taken it long term, for example 12 months or more, without muscle toxicity, and the 5 mg and 80 mg tablets are no longer marketed [2].

Does the niacin warning apply to NMN or NR?

The label's niacin statement concerns lipid-modifying niacin doses of 1 g/day or more [2]. NMN and NR are NAD+ precursors that the body converts to NAD+, a coenzyme in cellular energy metabolism and a substrate for sirtuins and PARP enzymes [3]. No study identified here tested whether the niacin statement extends to NMN or NR [1].

Human trials have given NMN at 250 mg/day for 12 weeks, at 300 to 900 mg/day for 60 days, and at 1,250 mg once daily for up to 4 weeks; NR has been given at 1,000 mg/day in older men [5][6][7][8]. Those studies reported adverse events, safety laboratory tests and blood NAD+ metabolites, including NAAD and nicotinamide-methylation products [5][8].

Does NMN or NR change simvastatin levels?

Simvastatin is a lactone prodrug. After absorption it is hydrolyzed to simvastatin acid, the active HMG-CoA reductase inhibitor [2]. It is metabolized by CYP3A4, and simvastatin acid is a substrate of the OATP1B1 transporter; under 5% of an oral dose reaches the general circulation because of extensive first-pass extraction in the liver [2]. Simvastatin is not itself a CYP3A4 inhibitor [2].

CYP3A4 inhibitors can change simvastatin exposure a great deal. In the label's study, itraconazole 200 mg daily raised the AUC of simvastatin acid and of simvastatin about 13-fold each [2]. In 10 healthy volunteers, 200 mL of double-strength grapefruit juice three times daily for two days raised simvastatin AUC 16-fold and simvastatin acid AUC about 7-fold [9]. The label says to avoid grapefruit juice with Zocor [2].

No human interaction study of NMN or NR with simvastatin, CYP enzymes or transporters was found in a PubMed search [1].

How often myopathy happens on simvastatin

The label defines myopathy as unexplained muscle weakness, pain or tenderness with creatine kinase above 10 times the upper limit of normal [2]. It reports myopathy in about 0.03% of patients taking 20 mg, 0.08% taking 40 mg and 0.61% taking 80 mg in a group of 24,747 treated patients followed for a median of at least four years [2]. In the SEARCH trial, 12,064 survivors of a myocardial infarction took 80 mg or 20 mg daily for a mean of 6.7 years, and myopathy occurred in 0.9% versus 0.03% [10]. The label cites rhabdomyolysis of about 0.4% on 80 mg versus about 0% on 20 mg in that trial [2]. The label says risk is highest in the first year [2].

The label's risk factors are age 65 or older, uncontrolled hypothyroidism, renal impairment, interacting drugs and higher dose, and it notes that Chinese patients may be at higher risk [2]. In a high-risk cardiovascular trial of simvastatin 40 mg daily with median follow-up of 3.9 years, myopathy was about 0.24% in Chinese participants (n=5,468) and 0.05% in non-Chinese participants (n=7,367) [2].

Do NMN or NR help muscle in people?

The idea comes from animal work. Twelve months of oral NMN in mice enhanced mitochondrial oxidative metabolism in skeletal muscle, along with other effects [12].

In people, the muscle results have been modest or null. A 2025 systematic review and meta-analysis of randomized trials in older adults found NMN had no significant effect on skeletal muscle index, handgrip strength, gait speed or the 5-times chair-stand test [13]. In 12 men aged 70 to 80, NR 1 g/day for 21 days did not raise muscle NAD+ itself (210 versus 197 pmol/mg, p=0.22), although a marker of NAD+ synthesis (NAAD) doubled; mitochondrial respiration, grip strength, insulin sensitivity and muscle blood flow were unchanged [8]. A separate 2025 meta-analysis of 12 trials with 513 participants found NMN raised blood NAD, but most clinical outcomes, including fasting glucose, triglycerides and cholesterol, were not significantly different from control [14].

One small trial did find a metabolic effect. In a 10-week randomized, placebo-controlled trial of NMN 250 mg/day in postmenopausal women with prediabetes who were overweight or obese, 25 women completed (13 on NMN, 12 on placebo). Insulin-stimulated glucose disposal rose about 25% on NMN with no change on placebo, and no adverse events were reported [3]. It was a single-center study, and a published Comment disputed the analysis.

Regulatory status of NMN and NR

NMN and NR are sold in the United States as oral dietary supplements. Neither is an FDA-approved drug, and no NAD+ precursor product is approved by FDA to treat aging or any disease [4].

For NMN specifically, trade press reported that FDA took the position in late 2022 that it was excluded from the dietary supplement definition. FDA then reversed that position: its response to a citizen petition in the docket is dated 2025-09-29, and NMN is now treated as lawful in dietary supplements, subject to the normal new-dietary-ingredient notification rules [4].