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Related Concept Videos

2° Amines to N-Nitrosamines: Reaction with NaNO201:20

2° Amines to N-Nitrosamines: Reaction with NaNO2

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Secondary amines react with nitrous acid to form N-nitrosamines, as depicted in Figure 1. Nitrous acid, a weak and unstable acid, is formed in situ from an aqueous solution of sodium nitrite and strong acids, such as hydrochloric acid or sulfuric acid, in cold conditions. In the presence of an acid, the nitrous acid gets protonated. The subsequent loss of water results in the formation of the electrophile known as nitrosonium ion.
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1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism01:37

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism

4.2K
Nitrous acid is a relatively weak and unstable acid prepared in situ by the reaction of sodium nitrite and cold, dilute hydrochloric acid. In an acidic solution, the nitrous acid undergoes protonation when it loses water to form a nitrosonium ion—an electrophile. Nitrous acid reacts with primary amines to give diazonium salts. The reaction is called diazotization of primary amines.
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Methods for Studying Drug Absorption: In situ01:09

Methods for Studying Drug Absorption: In situ

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In situ experiments, such as the Doluisio method and Single-Pass Perfusion technique, provide critical insights into drug uptake by simulating in vivo conditions for drug absorption.
The Doluisio method involves perfusing a prepared segment of a rat's small intestine with a solution of radiolabeled drug and a non-absorbable marker. This helps to differentiate between absorbed and non-absorbed drug concentrations. The intestinal segment is connected at both ends using tubing and syringes,...
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1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview01:26

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview

3.5K
Nitrous acid and nitric acids are two types of acids containing nitrogen, among which nitrous acid is weaker than nitric acid. Nitrous acid with a pKa value of 3.37 ionizes in water to give a nitrite ion and the hydronium ion.
The nitrous acid is unstable. Hence, it is formed in situ from a solution of sodium nitrite and cold aqueous acids such as hydrochloric or sulfuric acid. In an acidic solution, the –OH group of nitrous acid undergoes protonation to give oxonium ion, followed by...
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Updated: Oct 31, 2025

A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s
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In Vitro Analysis of N-Nitrosodimethylamine (NDMA) Formation From Ranitidine Under Simulated Gastrointestinal

Zongming Gao1, Michael Karfunkle1, Wei Ye1

  • 1Division of Complex Drug Analysis and Division of Pharmaceutical Analysis, Office of Testing and Research, Office of Pharmaceutical Quality, Center for Drug Evaluation and Research, Food and Drug Administration, St Louis, Missouri.

JAMA Network Open
|June 28, 2021
PubMed
Summary

N-nitrosodimethylamine (NDMA) formation from ranitidine requires very high nitrite levels, far exceeding those found in the stomach. This study suggests ranitidine is unlikely to convert to NDMA under normal physiological conditions.

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Area of Science:

  • Pharmaceutical Chemistry
  • Toxicology
  • Analytical Chemistry

Background:

  • N-nitrosodimethylamine (NDMA) is a probable human carcinogen.
  • Previous studies indicated NDMA formation from ranitidine and nitrite in simulated gastric fluid.
  • The nitrite concentrations in prior studies exceeded physiological levels found in gastric fluid.

Purpose of the Study:

  • To investigate NDMA formation from ranitidine in simulated gastric fluid.
  • To evaluate the impact of varying fluid volume, pH, and nitrite concentrations, including physiological levels.
  • To characterize the conditions under which ranitidine might convert to NDMA.

Main Methods:

  • Ranitidine tablets were added to simulated gastric fluid with controlled pH and nitrite concentrations.
  • Nitrite concentrations ranged from physiological (100 μmol/L) to supraphysiological (up to 10,000 μmol/L).
  • NDMA levels were quantified using liquid chromatography-mass spectrometry (LC-MS) after 2 hours.

Main Results:

  • NDMA formation was only detected at supraphysiological nitrite concentrations (5000-10,000 μmol/L).
  • At physiological nitrite levels (100 μmol/L), only background levels of NDMA were observed.
  • Increased fluid volume (250 mL) reduced NDMA detection even at higher nitrite concentrations.

Conclusions:

  • Ranitidine conversion to NDMA was not observed under simulated physiological gastric conditions.
  • The study suggests that NDMA formation from ranitidine is unlikely in vivo due to the high nitrite concentrations required.
  • These findings have implications for the safety assessment of ranitidine.