Butylparaben

• BPButyl Hydroxybenzoate
• JPButyl Parahydroxybenzoate
• Ph. Eur.Butyl Parahydroxybenzoate
• USP–NFButylparaben

Butyl p-hydroxybenzoate; butyl 4-hydroxybenzoate; butylis parahydroxybenzoas; butyl parahydroxybenzoate; Nipabutyl; Tegosept B

Butyl 4-hydroxybenzoate · [94-26-8]

UNII 3QPI1U3FV8 · PubChem CID 7184

C11H14O3 · 194.23

Antimicrobial preservative

Typical concentrations: — · Dosage forms: Liquid, Semi-solid

Used as an antimicrobial preservative in oral and topical pharmaceutical products, cosmetics and toiletries, usually in combination with other parabens such as methylparaben. Its low water solubility limits its use in aqueous systems. Typical concentrations: oral suspensions 0.006–0.05%; topical preparations 0.02–0.4%.

Colourless crystals or a white, crystalline powder. It is odourless or almost odourless and has a slight burning taste.

Melting point

68–71 °C

Solubility

very slightly soluble in water; freely soluble in ethanol (95%), acetone and ether; soluble in propylene glycol

pKa

≈ 8.4 (phenolic hydroxyl)

Antimicrobial spectrum

most active against yeasts and moulds; activity against Gram-positive bacteria is greater than against Gram-negative bacteria

Aqueous solutions at pH 3–6 are stable for long periods at room temperature and can be sterilised by autoclaving, whereas at pH 8 and above the ester is hydrolysed fairly quickly. Store in a well-closed container in a cool, dry place.

Antimicrobial activity is markedly reduced by nonionic surfactants such as polysorbate 80 (micellar binding) and by cyclodextrins. Parabens are absorbed by some plastics and may be adsorbed by magnesium trisilicate, talc and similar powders. Iron salts cause discoloration, and weak alkalis and strong acids cause hydrolysis.

Prepared by esterifying p-hydroxybenzoic acid with n-butanol in the presence of an acid catalyst, followed by purification.

Parabens are widely used and are of low systemic toxicity; the main adverse effects are hypersensitivity reactions, usually delayed-type contact dermatitis. Butylparaben shows weak oestrogenic activity in some test systems, and for this reason its use in cosmetics has been restricted in the EU.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended.

Included in the FDA Inactive Ingredient Database (oral and topical preparations) and in non-parenteral medicines licensed in Europe. It is not authorised as a food additive in the EU. In EU cosmetics the combined content of butylparaben and propylparaben is limited to 0.14% (as acid), and they are not permitted in leave-on products for the nappy area of children under 3 years.

Butylparaben sodium; ethylparaben; methylparaben; propylparaben.

Antimicrobial activity of the parabens rises with the length of the alkyl chain while water solubility falls, so butylparaben is the most active but least soluble of the common parabens. Combinations of parabens show additive or synergistic activity, and the sodium salt is sometimes used to improve aqueous solubility.