Creams and ointments

The amounts of ointments and creams people apply are highly individualized. So are the techniques of application. Some patients vigorously rub semisolid formulations into the skin, while others just spread films until they are more or less uniform over the desired area. While pharmacokinetic assessments of a system s delivery attributes is ordinarily done using normal skin (in vitro) or on healthy volunteers (in vivo), the site of its clinical deployment is usually anything but normal. Rather, it is determined by the skin condition to be treated. Clearly, the manufacturer is without control over how a disease is expressed in a particular patient. For many diseases, disease manifestation can be anywhere on the body. Moreover, from individual to individual it varies in intensity and vastness. Thus, more area may be involved in one case than in another, and the barrier function of the skin may be more or less intact in any instance. This creates a set of imponderables with respect to delivery, efficacy, and safety. 

Mixing both phases after warming each. This method is frequently used in the preparation of ointments and creams. 

Kublin and Kaniewska [52] used a gas chromatographic method for the determination of miconazole and other imidazole antimycotic substances. The conditions have been established for the quantitative determination of miconazole and the other drugs, which are present in pharmaceuticals such as ointments and creams. The column, packed with UCW-98 on Chromosorb WAW, and flame-ionization detector were used. The statistical data indicate satisfactory precision of the method, both in the determination of imidazole derivatives in substances and in preparation. 

In the acute inflammatory stage, wet dressings are preferred because ointments and creams further irritate the tissue. 

Pastes are also semisolid preparations intended for external application to the skin, and differ from ointments and creams in that they contain a high solid content. Pastes are made stiff by the addition of powders such as starch, zinc oxide, calcium carbonate or their mixtures. 

Figure 6 Different cell types for dissolution testing using the flow-through system. Type (a) tablet cell (12 mm), (b) tablet cell (22.6 mm), (c) cell for powders and granulates, (d) cell for implants, (e) cell for suppositories and soft gelatin capsules, (f) cell for ointments and creams.

Ointments and Creams Ointments are applied to the skin for topical treatment or to be absorbed into the blood system for delivery to target areas. They are semisofid preparations obtained by mixing the API with selected ointment bases depending on intended use. These bases include petrolatum, paraffin, mineral oil, lanolin, and glycols. Preservatives are often added to ensure the ointments will maintain the recommended shelf life. 

Purified drug substances are mixed with excipients into finished dosage forms sohds, liquids, parenterals, inhalants, and ointments and creams, then packaged and labeled and shipped for distribution. 

The potentiometric method has been used for the determination of pure procaine base or its hydrochloride salt, and for procaine in pharmaceutical formulations. Lemahieu and Resibois reported the potentiometric determination of procaine hydrochloride with silver nitrate in dimethyl sulfoxide [64], Procaine was potentiometrically analyzed using a procaine-selective membrane electrode [65]. Abou-Ouf et al. have used potentiometry to determine procaine and other drugs in ointments and creams with dibromohydantoins [66]. 

The development of a simple fast-scan polarographic method for the determination of the A4-3-ketosteroid flurandrenolone in pharmaceutical preparations has been reported [134]. The polarographic peak due to the reduction of the carbon-fluorine bond is measured in ointments and creams to determine concentrations as low as 0.01 % w/w. Pulse polarographic procedures have been described for progesterones [135], A4-3-ketosteroids [136], hydrocortisone [137], and flucytosine [138] in pharmaceutical preparations. Recent studies have illus-... 

Traditionally, aloe vera is used in ointments and creams to assist the healing of wounds, bums, eczema, and psoriasis. 

Topical 0.2% solution, ointment, and cream Oxychlorosene sodium (Clorpactin)... 

TABLE 1 Some Compendial Bases Used in Ointments and Creams... 

Stearyl Alcohol Reduction of ethyl stearate in the presence of lithium aluminum hydride yields stearyl alcohol, which contains not less than 90% of 1-octadecanol. It is available as flakes or granules which are white in color and possesses a characteristic odor. It is insoluble in water and melts at 55-60 °C. Stearyl alcohol has stiffening, viscosity-enhancing, and emollient properties and hence is used in the preparation of hydrophobic ointments and creams. Its weak emulsifying properties help in improving the water-holding capacity of ointments. Hypersensitivity reactions are sometimes observed due to the presence of some minor impurities. Stearyl alcohol preparations are compatible with acids and alkalis and are preserved in well-closed containers in a cool and dry place [6]. 

Combinations of bases are sometimes used to acquire better stability. Gelling agents such as carbomers and PEG are also included in some ointment and cream preparations. Table 3 shows examples of cream bases used in some commercial cream preparations. 

Water-removable ointments and creams are basically hydrophilic-type emulsions. They are prepared by fusion followed by mechanical addition approach. Hydrocarbon components are melted together and added to the aqueous phase that contains water-soluble components with constant stirring until the mixture congeals. A hydrophilic emulsifying agent is included in the aqueous phase in order to obtain stable oil-in-water dispersion. Sodium lauryl sulfate is used in the preparation of hydrophilic ointment USP. 

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