Zinc pyrithione (or pyrithione zinc) is a coordination complex of zinc. It has Fungistatics (inhibiting the division of fungal cells) and bacteriostatic (inhibiting bacterial cell division) properties and is used in the treatment of seborrhoeic dermatitis
Structure of the compound
The
pyrithione ligands, which are formally
Anion, are
Chelation to Zn
2+ via
oxygen and
sulfur centers. In the crystalline state, zinc pyrithione exists as a centrosymmetric dimer (see figure), where each zinc is bonded to two sulfur and three oxygen centers.
In solution, however, the dimers dissociate via scission of one Zn-O
Chemical bond.
This compound was first described in the 1930s.
Pyrithione is the conjugate base derived from 2-mercaptopyridine- N-oxide (CAS# 1121-31-9), a derivative of pyridine-N-oxide.
Uses
Medicine
Zinc pyrithione can be used to treat
dandruff and seborrhoeic dermatitis.
It also has antibacterial properties and is effective against many
from the
Streptococcus and
Staphylococcus genera.
Its other medical applications include treatments of
psoriasis,
eczema,
ringworm,
fungus,
athletes foot,
dry skin, atopic dermatitis,
tinea versicolor,
and
vitiligo.
Paint
Because of its low
solubility in
water (8 ppm at neutral pH), zinc pyrithione is suitable for use in outdoor
and other products that protect against
mildew and
algae. It is an
algaecide. It is chemically incompatible with paints relying on metal carboxylate curing agents. When it is used in latex paints with water containing much
iron, a sequestering agent that preferentially binds the iron ions is needed. It is decomposed by
ultraviolet light slowly, providing years of protection in direct sunlight.
Sponges
Zinc pyrithione is an
antibacterial treatment for household sponges, as used by the 3M Corporation.
Clothing
A process to apply zinc pyrithione to cotton with washable results was patented in the United States in 1984.
Zinc pyrithione is used to prevent microbe growth in
polyester.
Textiles with applied zinc pyrithione protect against odor-causing microorganisms. Export of antimicrobial textiles reached US$497.4 million in 2015.
Mechanism of action
Antibacterial effect
Zinc pyrithione is known to exhibit antibacterial activity by disrupting cell membrane integrity and essential metabolic functions in bacteria.
Antifungal effect
Its antifungal effect is thought to derive from its ability to disrupt
cell membrane transport by blocking the
proton pump that energizes the transport mechanism.
A study from 2011 showed that antifungal effects of Zinc pyrithione work by
copper toxicity mechanism that targets critical iron–sulphur proteins.
Health effects
Zinc pyrithione is approved for over-the-counter topical use in the United States as a treatment for
dandruff and is the active ingredient in several anti-dandruff shampoos and body wash gels. In its industrial forms and strengths, it may be harmful by contact or ingestion. Zinc pyrithione can in the laboratory setting trigger a variety of responses, such as DNA damage in skin cells.
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Legal status
European Union
Use of zinc pyrithione is prohibited within cosmetic products in the
European Union since December 2021.
The substance was considered safe for use in rinse-off and leave-in products of different tested concentrations, but due to potential environmental toxicity consideration of the use of zinc pyrithione was made against potential alternative substance ingredients. Due to no industry submission to the regulators supporting the continued use of zinc pyrithione and/or an absence of indications that there were no suitable alternatives to the substance: the use of zinc pyrithione became automatically prohibited within cosmetic products as an intended ingredient. This was as a consequence of zinc pyrithione addition to the Cosmetic Product Regulation (EC) No 1223/2009 Annex II list.
United States
Zinc pyrithione concentration of up to 2% is allowed for products when they are formulated to be applied and then washed off after brief exposure. Alternatively, up to 0.25 percent when formulated to be left on the skin or scalp
Environmental concerns
A large Swedish study shows that it is broken down in
Water treatment and does not release into waterways.
A Danish study shows that it biodegrades quickly, but that a risk of continuous leaching from boat paint may cause environmental toxicity.
See also
-
Ketoconazole, another antifungal agent used in shampoos
-
Piroctone olamine, another antifungal agent used in shampoos
-
Selenium disulfide, an active ingredient used in shampoos such as Selsun Blue
