Popular Science of Medicine: This article will take you to know the semi-solid preparation ointment for external use of skin.

External preparation for skin

Skin external agents are a class of agents that act on the skin to exert a local or systemic therapeutic effect.

Advantages: External use can reduce toxic side effects, local effects or local blood entry, and avoid the first-pass effect of the intestine and liver. Compared with other routes of administration, patient compliance increases and it is easier to terminate cases of adverse reactions.

Disadvantages: This type of dosage form does not have an accurate dosage, the matrix used for semi-solid preparations is easily oxidized, and the use of semi-solid preparations by patients has aesthetic problems, especially facial medication. There are many kinds of external skin drugs, including ointment, cream, gel, powder, aqua and lotion, among which ointment, cream and gel prescription composition is complex, mostly semi-solid preparation, with multi-phase, thermodynamic instability and so on.

Domestic and foreign and industry guidance regulations for skin external preparations

China

2015, Technical Guidelines for the Study of Bioequivalence of Generic Chemical Drugs in Human with Pharmacokinetic Parameters as Endpoint Evaluation Indicators

2018, Technical Evaluation Requirements for Newly Registered Classified Skin Generic Drugs for External Use (Draft for Comments)

2021, "Technical Guidelines for the Study of Chemical Generic Drugs for External Use on Skin" for Trial Implementation)

Ointment refers to a homogeneous semi-solid external preparation made by mixing the raw material drug with an oleaginous or water-soluble base. Ointment is divided into hydrophobic ointment, water emulsifying ointment, hydrophilic ointment, as follows:

Hydrophobic ointment: Hydrophobic (lipophilic) ointments are usually anhydrous and can only absorb a small amount of water. Typical bases for their formulations are water-insoluble hydrocarbons such as hard, soft and liquid paraffins, vegetable oils, animal fats, waxes, synthetic glycerides and polyalkylsiloxanes.

Water emulsifying ointment: Water emulsifying ointment can absorb a large amount of water. They generally consist of a hydrophobic fat base to which W/O emulsifiers, such as wool fats, lanols, sorbitan esters, monoglycerides or fatty alcohols, may be added to render them hydrophilic. They may also be W/O emulsions, allowing additional amounts of aqueous solution to be added.

Hydrophilic ointment: The hydrophilic ointment base is miscible with water. The base is usually a mixture of liquid and solid polyethylene glycol, a typical product being mupirocin ointment.