Effect of Oral Ranitidine on Urinary Excretion of N-Nitrosodimethylamine (NDMA): A Randomized Clinical Trial

JAMA. 2021 Jul 20;326(3):240-249. doi: 10.1001/jama.2021.9199.


Importance: In 2019, the US Food and Drug Administration (FDA) received a citizen petition indicating that ranitidine contained the probable human carcinogen N-nitrosodimethylamine (NDMA). In addition, the petitioner proposed that ranitidine could convert to NDMA in humans; however, this was primarily based on a small clinical study that detected an increase in urinary excretion of NDMA after oral ranitidine consumption.

Objective: To evaluate the 24-hour urinary excretion of NDMA after oral administration of ranitidine compared with placebo.

Design, setting, and participants: Randomized, double-blind, placebo-controlled, crossover clinical trial at a clinical pharmacology unit (West Bend, Wisconsin) conducted in 18 healthy participants. The study began in June 2020, and the end of participant follow-up was July 1, 2020.

Interventions: Participants were randomized to 1 of 4 treatment sequences and over 4 periods received ranitidine (300 mg) and placebo (randomized order) with a noncured-meats diet and then a cured-meats diet. The cured-meats diet was designed to have higher nitrites, nitrates (nitrate-reducing bacteria can convert nitrates to nitrites), and NDMA.

Main outcome and measure: Twenty-four-hour urinary excretion of NDMA.

Results: Among 18 randomized participants (median age, 33.0 [interquartile range {IQR}, 28.3 to 42.8] years; 9 women [50%]; 7 White [39%], 11 African American [61%]; and 3 Hispanic or Latino ethnicity [17%]), 17 (94%) completed the trial. The median 24-hour NDMA urinary excretion values for ranitidine and placebo were 0.6 ng (IQR, 0 to 29.7) and 10.5 ng (IQR, 0 to 17.8), respectively, with a noncured-meats diet and 11.9 ng (IQR, 5.6 to 48.6) and 23.4 ng (IQR, 8.6 to 36.7), respectively, with a cured-meats diet. There was no statistically significant difference between ranitidine and placebo in 24-hour urinary excretion of NDMA with a noncured-meats diet (median of the paired differences, 0 [IQR, -6.9 to 0] ng; P = .54) or a cured-meats diet (median of the paired differences, -1.1 [IQR, -9.1 to 11.5] ng; P = .71). No drug-related serious adverse events were reported.

Conclusions and relevance: In this trial that included 18 healthy participants, oral ranitidine (300 mg), compared with placebo, did not significantly increase 24-hour urinary excretion of NDMA when participants consumed noncured-meats or cured-meats diets. The findings do not support that ranitidine is converted to NDMA in a general, healthy population.

Trial registration: ClinicalTrials.gov Identifier: NCT04397445.

Publication types

  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Administration, Oral
  • Adult
  • Cross-Over Studies
  • Dimethylnitrosamine / urine*
  • Double-Blind Method
  • Female
  • Histamine H2 Antagonists / administration & dosage
  • Histamine H2 Antagonists / pharmacokinetics*
  • Humans
  • Male
  • Placebos / pharmacokinetics
  • Ranitidine / administration & dosage
  • Ranitidine / pharmacokinetics*


  • Histamine H2 Antagonists
  • Placebos
  • Ranitidine
  • Dimethylnitrosamine

Associated data

  • ClinicalTrials.gov/NCT04397445