Zinc pyrithione

Zinc pyrithione is a coordination complex of zinc. This colourless solid is used as an antifungal and antibacterial agent. This coordination complex, which has many names, was first reported in the 1930s.

Structure of the compound

The pyrithione ligands, which are formally monoanions, are chelated to Zn²⁺ via oxygen and sulfur centers. In the crystalline state, zinc pyrithione exists a centrosymmetric dimer (see figure). Each zinc is bonded to two sulfur and three oxygen centers. In solution, however, the dimers dissociate via scission of one Zn-O bond.

Pyrithione is the conjugate base derived from 2-mercaptopyridine-N-oxide (CAS# 1121-31-9), a derivative of pyridine-N-oxide.

Uses

Medical

Zinc pyrithione is best known for its use in treating dandruff and seborrheic dermatitis. It also has antibacterial properties and is effective against many pathogens from the streptococcus and staphylococcus class. Its other medical applications include treatments of psoriasis, eczema, ringworm, fungus, athletes foot, dry skin, atypical dermatitis, tinea, and vitiligo.

Zinc pyrithione is approved for over-the-counter topical use in the United States as a treatment for dandruff. It is the active ingredient in several anti-dandruff shampoos such as Head & Shoulders. However, in its industrial forms and strengths, it may be harmful by contact or ingestion.

In paint

Due to its low solubility in water (8 ppm at neutral pH), zinc pyrithione is suitable for use in outdoor paints and other products that provide protection against mildew and algae. It is an effective algaecide. It is chemically incompatible with paints relying on metal carboxylate curing agents. When used in latex paints and the water contains high amount of iron, a sequestering agent that will preferentially bind the iron ions is needed. Its decomposition by ultraviolet light is slow, providing years of protection even against direct sunlight.

In sponges

Zinc pyrithione is also used as an antibacterial treatment for household sponges, most notably by the 3M Corporation.

Mechanism of action

Its antifungal effect is proposed to derive from its ability to disrupt membrane transport by blocking the proton pump that energizes the transport mechanism. Fungi are capable of inactivating pyrithione in low concentrations.

References

External links

• Some toxicity information on industrial uses
• Article Omni Brain: Dandruff Shampoo to Calm Seizures, Apr. 2007