Titanium dioxide

• BPTitanium Dioxide
• JPTitanium Oxide
• Ph. Eur.Titanium Dioxide
• USP–NFTitanium Dioxide

Anatase titanium dioxide; rutile titanium dioxide; titanic anhydride; titanium oxide; titanii dioxidum; CI 77891; E171

Dioxotitanium · [13463-67-7]

TiO2 · 79.87

Coating agent, film former

Typical concentrations: q.s. · Dosage forms: Solid, Semi-solid

Used as a white pigment and opacifier in tablet film coatings, sugar coatings and hard and soft capsule shells, where it also protects light-sensitive drugs. It is also used in suspensions, dermatological preparations and cosmetics, and as a physical UV filter in sunscreens.

A white, amorphous, odourless and tasteless, non-hygroscopic powder. Particle size of pigment grades is typically a fraction of a micrometre, which gives maximum light scattering.

Crystal forms

anatase and rutile (and brookite); pharmaceutical grades are usually anatase

Density

about 3.8–3.9 g/cm³ (anatase); about 4.2 g/cm³ (rutile)

Refractive index

very high, about 2.5 (anatase) to 2.7 (rutile), which explains its opacity

Melting point

about 1850 °C

Solubility

practically insoluble in water, dilute acids and organic solvents; dissolves slowly in hot concentrated sulfuric acid and in hydrofluoric acid

Extremely stable at high temperatures and chemically inert. Store in a well-closed container in a cool, dry place.

Generally inert, but it is photocatalytically active, especially in the anatase form, and on exposure to UV light can promote oxidation and degradation of some drugs and excipients, such as polyethylene glycols.

Produced from titanium ores either by the sulfate process, in which ilmenite is digested with sulfuric acid and the hydrolysed product is calcined, or by the chloride process, in which titanium tetrachloride is formed and then oxidised.

Very poorly absorbed orally and long regarded as non-toxic and non-irritant. In 2021 EFSA concluded that genotoxicity of the nanoparticle fraction could not be ruled out and that it could no longer be considered safe as a food additive. Inhaled titanium dioxide dust is classified by IARC as possibly carcinogenic to humans (Group 2B).

Observe normal precautions for the quantity handled. Avoid generating and inhaling dust; use eye protection and a dust respirator, with local exhaust ventilation.

No longer authorised as a food additive (E171) in the European Union since 2022; its continued use in medicines is under review, and the pharmaceutical industry is evaluating alternatives. Permitted as a colour additive in foods, drugs and cosmetics in the USA, and included in the FDA Inactive Ingredient Database (oral capsules, suspensions and tablets; topical and other preparations).

Calcium carbonate; iron oxides; talc; zinc oxide.

Replacing titanium dioxide in coatings and capsule shells usually needs reformulation: alternatives such as calcium carbonate, rice starch or talc give less opacity, so thicker coats or added colourants may be needed, and photostability must be re-checked.