For the EU, AIs and ULs have the same definition as in the US, except that units are milligrams per megajoule (MJ) of energy consumed rather than mg/day. For women (including those pregnant or lactating), men and children the PRI is 1.6 mg per megajoule. As the conversion is 1 MJ = 239 kcal, an adult consuming 2390 kilocalories should be consuming 16 mg niacin. This is comparable to US RDAs (14 mg/day for adult women, 16 mg/day for adult men).ULs are established by identifying amounts of vitamins and minerals that cause adverse effects, and then selecting as an upper limit amounts that are the "maximum daily intake unlikely to cause adverse health effects." Regulatory agencies from different countries do not always agree. For the US, 30 or 35 mg for teenagers and adults, less for children. The EFSA UL for adults is set at 10 mg/day - about one-third of the US value. For all of the government ULs, the term applies to niacin as a supplement consumed as one dose, and is intended as a limit to avoid the skin flush reaction. This explains why for EFSA, the recommended daily intake can be higher than the UL.Both the DRI and DRV describe amounts needed as niacin equivalents (NE), calculated as 1 mg NE = 1 mg niacin or 60 mg of the essential amino acid tryptophan.
Hexamethylenetetramine, also known as methenamine, hexamine, or urotropin, is a heterocyclic organic compound with the formula (CH2)6N4. This white crystalline compound is highly soluble in water and polar organic solvents. It has a cage-like structure similar to adamantane. It is useful in the synthesis of other organic compounds, including plastics, pharmaceuticals, and rubber additives. It sublimes in vacuum at 280 °C. Synthesis, structure, reactivity
Hexamethylenetetramine was discovered by Aleksandr Butlerov in 1859. It is prepared industrially by combining formaldehyde and ammonia:
The reaction can be conducted in gas phase and in solution. The molecule has a tetrahedral cage-like structure, similar to adamantane. Four vertices are occupied by nitrogen atoms, which are linked by methylene groups. Although the molecular shape defines a cage, no void space is available at the interior for binding other atoms or molecules, unlike crown ethers or larger cryptand structures. The molecule behaves like an amine base, undergoing protonation and N-alkylation (e.g. quaternium-15). Applications
The dominant use of hexamethylenetetramine is in the production of powdery or liquid preparations of phenolic resins and phenolic resin moulding compounds, where it is added as a hardening component. These products are used as binders, e.g. in brake and clutch linings, abrasive products, non-woven textiles, formed parts produced by moulding processes, and fireproof materials. Medical uses
As the mandelic acid salt (methenamine mandelate) or the hippuric acid salt (methenamine hippurate), it is used for the treatment of urinary tract infection. In an acidic environment, methenamine is believed to act as an antimicrobial by converting to formaldehyde.