Hydrocarbon-based ointments

Bases are classified based on their composition and physical characteristics. The U.S. Pharmacopeia (USP) classifies ointment bases as hydrocarbon bases (oleaginous... 

Hydrocarbon bases are made of oleaginous materials. They provide emollient and protective properties and remain in the skin for prolonged periods. It is difficult to incorporate aqueous phases into hydrocarbon bases. However, powders can be incorporated into these bases with the aid of liquid petrolatum. Removal of hydrocarbon bases from the skin is difficult due to their oily nature. Petrolatum USP, white petrolatum USP, yellow ointment USP, and white ointment USP are examples of hydrocarbon bases. 

Franks, A.J. Hydrocarbon bases for ointments and creams. Soap, Perfumes and Cosmetics 1964, 57, 221-319. 

Sample preparation Sandwich cream or ointment between two layers of 200 mesh silica gel, extract with carbon dioxide MeOH 95 5 at 300 atmospheres at 55° at 2 mL/min for 75 min (restrictor 300°), sonicate the SFE tube, frits, and silica gel with MeOH 100 mM HCl 25 75 containing 0.1% Tween 80 for 15 min, filter (0.2 pm), inject an aliquot of the filtrate. (SFE removes the hydrocarbon base of the cream or ointment leaving behind the insoluble pol5Tn5rxin.)... 

An ointment base containing 20 % hypromellose is often used in mouth pastes. The hypromellose, formulated in white soft paraffin, has the purpose of making the paste adhere to the mucosa. Even better adherence can be obtained by preparations in a hydrocarbon gel ointment (Plastibase ,... 

If a material other than a hydrocarbon is used as the base material of an ointment-like system, the ointment bears the name of its principal ingredient. There are silicone ointments that contain polydimethylsiloxane oil in large proportion. These reportedly act as excellent water barriers and superior emollients. Some are actually used to protect skin from the undesirable effects of long immersion in water. 

Petrolatum is a purified material consisting of a complex combination of hydrocarbons with an ointment-like consistency and is derived from petroleum (crude oil). Based on its origin, it would seem that the properties of petrolatum would vary dramatically depending on the type of crude oil used. However, since different types of crude oils have widely differing properties (depending on the source of the oil), only certain waxy crudes are suitable for the manufacture of petrolatum. 

Eczema may be so mild that no treatment is required beyond avoiding known irritants and applying a soothing and protective ointment which keeps the skin moist and so reduces inflammation. There are many such over-the-counter remedies based on liquid paraffin and soft white paraffin, both of which are hydrocarbons obtained from refined petroleum and which contain nothing that can irritate the skin. Liquid paraffin is also called mineral oil and is available under a variety of trade names, such as Nujol, while soft white paraffin is better known as Vaseline. Emulsified mixtures of liquid paraffin and soft white paraffin make excellent skin creams. 

Water-removable bases are basically oil-in-water emulsions. Unlike hydrocarbon and absorption bases, a large proportion of aqueous phase can be incorporated into water-removable bases with the aid of suitable emulsifying agents. It is easy to remove these bases from the skin due to their hydrophilic nature. Hydrophilic ointment USP is an example of a water-removable ointment base. 

Ointments are commonly used for topical application of drugs to the eye.These vehicles are primarily mixtures of white petrolatum and liquid mineral oil with or without a water-miscible agent, such as lanolin.The mineral oil is added to the petrolatum to allow the vehicle to melt at body temperature, and the lanolin is added to the nonemulsive ointment base to absorb water. This allows for water and water-soluble drugs to be retained in the delivery system. Commercial ophthalmic ointments are derivatives of a hydrocarbon mixture of 60% petrolatum USP and 40% mineral oil USP, forming a molecular complex that is semisolid but melts at body temperature. In general, ointments are well tolerated by the ocular tissues, and when antibiotics are incorporated they are usually more stable in ointment than in solution. 

Ointments Hydrocarbon (oily), adsorptive water-washable, or water-soluble bases emulsifying agents, glycols, medicating agent External... 

Ointments are composed mostly of fluid hydrocarbons meshed in a mafrix of higher melting solid hydrocarbons. Common examples of ointment bases include mineral oil, petrolatum, and polyethylene glycol. Creams are semisolid emulsion systems with an opaque... 

Ointments utilize certain bases that act as vehicles to deliver the drug and to impart emollient and lubricant properties to the preparation. Usually, but not always, they contain medicinal substances. Properties of ointments may vary from product to product depending on their specific use, ease, and extent of application. In general, ointment bases may be classified into four general groups hydrocarbon, absorption, water-removable, and water-soluble bases. 

Mineral oil—a mixture of liquid hydrocarbons obtained from petroleum. These are useful as levigating agents to wet and incorporate solid substances (e.g., salicylic acid, zinc oxide) into the preparation of ointments that consist of oleaginous bases as their vehicle. There are two types of mineral oils listed in the US. Pharmacopeia/National Formulary (USP/NF). Mineral oil USP is also called heavy mineral oil with a specific gravity between 0.845 and 0.905 and a viscosity of not less 34.5 cSt (cSt = mm /s) at 40°C. Light mineral oil, NF has a specific gravity between 0.818 and 0.880 and a viscosity of not more than 33.5 cSt. Table 2 lists the commercially available mineral oil fractions. 

White soft paraffin and yellow soft paraffin are mixtures of semi-solid hydrocarbons. They are used as bases for ointments, as emollients in skin diseases, and as lubricants in treating dry eyes. Soft paraffin is also known as petroleum jelly, petrolatum, and Vaseline. 

Viscosity (dynamic) the rheological properties of petrolatum are determined by the ratio of the unbranched chains to the branched chains and cyclic components of the mixture. Petrolatum contains relatively high amounts of branched and cyclic hydrocarbons, in contrast to paraffin, which accounts for its softer character and makes it an ideal ointment base. ... 

Uses white petrolatum is a purified mixture of semisolid hydrocarbons used as an ointment base in cosmetics leather grease and shoe polish component... 

The vast majority of ophthalmic ointments are essentially lipophilic and consist of mixtures of hydrocarbons. To improve spreading over the comeal surface and mixing with the precorneal him. small amount.s of lanolin and/or lanolin alcohols, impaning to the ointment base W/0 emulsifying properties, can be added. Suspension-type hydrocarbon ointments share with their "solution-type" homologs a poor patient acceptance, mostly due to their greasiness and vi.sion-blurring effect therefore, they are preferentially applied as nocturnal medications. 

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