What molecule am I?
Polyhexanide [formally, poly(hexamethylene biguanide)] is an unusual water-soluble polymer with five nitrogen atoms in each repeating unit, three of them in the polymer’s backbone. It was first described in late 1960s in British, French, and South African patents to Imperial Chemical Industries (London).
Since its inception, polyhexanide and its hydrochloride salt1 have been used for a wide range of sanitizing purposes. Examples are protecting crops from molds and bacteria in the field and in storage, preserving meat and fish products, and sanitizing swimming pools. In medicine, it has been used primarily for treating keratitis (corneal infection), but also for dressing wounds.
The use of polyhexanide products may be coming to an end. In 2011, the European Chemical Agency designated it as a suspected carcinogen. Since then, its uses have been increasingly restricted in Europe. In 2017, the US Food and Drug Administration declined an application for polyhexanide as an orphan drug for keratitis.
1. CAS Reg. No. 32289-58-0.
Polyhexanide hazard information*
| Hazard class** | GHS code and hazard statement | |
|---|---|---|
| Skin sensitization, category 1 | H317—May cause an allergic skin reaction |  |
| Serious eye damage/eye irritation, category 1 | H318—Causes serious eye damage |  |
Acute toxicity, inhalation, category 3 | H331—Toxic if inhaled | |
| Carcinogenicity, category 2 | H351—Suspected of causing cancer |  |
| Specific target organ toxicity, repeated exposure, inhalation, category 1 | H372—Causes damage to organs through prolonged or repeated exposure if inhaled | |
*Information for 20 wt% aqueous solution.
**Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.
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Polyhexanide fast facts
| CAS Reg. No. | 28757-47-3 |
| SciFinder nomenclature | Poly(iminocarbonimi- doylimino- carbonimi- doylimino-1,6-hexanediyl) |
| Empirical formula | (C8H17N5)n |
| Molar mass | Variable |
| Appearance | White to pale yellow solid |
| Melting point | Variable |
| Water solubility | ≈400 g/L |
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