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Appendices 1-18 to: Report on the Health Effects of Selected Pesticide Coformulants

25   Toxicokinetics

25.1   Absorption

Hexamethylenetetramine is rapidly absorbed in humans following oral administration. However, from 10 to 30 % of an orally administered dose of hexamethylenetetramine is hydrolysed in the gastric fluid to yield formaldehyde and ammonia. (CIR 1992, Loeper & Berzins 1995).

25.2   Distribution

Hexamethylenetetramine is distributed to blood and organs (not further specified) (Loeper & Berzins 1995).

It can pass the placenta and is detectable in the amniotic fluid and in milk (CIR 1992).

25.3   Elimination

The half-life for hexamethylenetetramine in 10 healthy volunteers administered 2 g per day for 8 days of two different formulations of tablets was about 4 hours. Following a single dose, approximately 82 % of the hexamethylenetetramine was recovered in the urine in 24 hours as the parent compound. During administration twice daily for 8 days, approximately 88 % of the dose was excreted as the parent compound within a 12-hour dosing period. (Klinge et al. 1982 – quoted from CIR 1992).

Part of hexamethylenetetramine is decomposed to formaldehyde and ammonia in the urine. The half-life of conversion of hexamethylenetetramine to formaldehyde is pH-dependent (about 20 hours at pH 5.0 and about 400 hours at pH 6.5). (Grady Strom & Won Jun 1993 – quoted from Loeper & Berzins 1995).

In slightly acidic environments, such as in sweat, hexamethylenetetramine partially degrades to formaldehyde and ammonia. (Loeper & Berzins 1995).
In addition, hexamethylenetetramine has been reported to produce formic acid upon contact with the skin (Dreyfors et al. 1989).

25.4   Mode of action

No relevant data have been found.

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