Hard fat

• BPHard Fat
• Ph. Eur.Hard Fat
• USP–NFHard Fat

Adeps neutralis; adeps solidus; Novata; semi-synthetic glycerides; Suppocire; Witepsol

Mixture of triglycerides, with smaller amounts of mono- and diglycerides, of saturated C8–C18 fatty acids (mainly lauric acid) · [—]

Polymer, mixture or material of variable composition — no single molecular formula applies.

Semi-solid base, emollient

Typical concentrations: — · Dosage forms: Semi-solid

Used chiefly as a base for suppositories and pessaries, where it has largely replaced theobroma oil. Many grades are available, differing in melting range, hydroxyl value and emulsifier content, so that the base can be matched to the drug and the climate. Hard fat is also used in some oral and topical products and in lipid-based capsule fills.

A white or almost white, waxy, brittle mass, practically odourless and with a greasy feel. When heated to about 50 °C it melts to a colourless or slightly yellowish liquid.

Melting range

30–45 °C depending on grade; grades melting at about 33–37 °C are typical for suppositories

Hydroxyl value

≤ 50 (grade-dependent)

Saponification value

210–260

Iodine value

≤ 3

Acid value

≤ 0.5

Solubility

freely soluble in ether; slightly soluble in ethanol; practically insoluble in water

More stable than theobroma oil and much less prone to troublesome polymorphism, so it can be melted and poured without special tempering. Some grades show post-hardening on storage, with a small rise in melting point and slower release. Store protected from light and heat, below about 25 °C.

Some drugs, for example those soluble in the base, lower the melting point of hard fat and can give soft suppositories. Its compatibility depends on the grade; grades with a high hydroxyl value are more reactive towards drugs that interact with free hydroxyl groups.

Made by esterifying glycerol with saturated fatty acids obtained from hydrogenated vegetable oils such as coconut or palm-kernel oil, or by interesterification and hydrogenation of natural fats. Emulsifier-containing grades include added mono- or diglycerides or other surfactants.

Generally regarded as non-toxic and non-irritant. Occasional mild rectal irritation has been reported with some grades, particularly those containing emulsifiers.

Observe normal precautions for the quantity handled; protect hands and eyes when working with the molten material.

Included in the FDA Inactive Ingredient Database (rectal and vaginal suppositories; oral preparations) and in non-parenteral medicines licensed in Europe.

Theobroma oil; polyethylene glycol suppository bases; glyceryl palmitostearate; hydrogenated vegetable oil.

When choosing a grade, consider the drug's solubility in the base (dissolved drug lowers the melting point), the drug load (high loads need grades with low viscosity when molten) and the hydroxyl value, which affects water absorption and the speed of solidification. The displacement value of the drug should be used to calculate the amount of base per mould.