Semisolid preparation

Topicals— These are semisolid preparations such as creams, ointments, or gels intended to be applied to the skin or certain mucous membranes... 

Ointments are semisolid preparations that are intended for external use. Ointments may contain either finely powdered drugs or their mixtures, liquids, and other drug forms incorporated into appropriate bases. They are applied to the skin for their physical effects as emollients (which make the skin more pliable), protectants, lubricants, and drying agents. Ointment bases are also used as vehicles in which to incorporate topical medications which exert specific effect. There are four types of ointment bases, namely, oleaginous, absorption, water removable, and water soluble bases. 

Creams are semisolid preparations meant for external application as emollients or as topical medications. They are semisolid emulsions of either the oil-in-water or the water-in-oil type. 

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. 

Amongst the various types of semisolid preparations, ointments represent the type of extemporaneous preparations most likely to be prepared by a pharmacist. A variety of ingredients may be included in the formula of semisolid dosage forms. 

When semisolid preparations of certain strength are diluted with ointment bases (also referred to as diluents), the strength of the mixture will be lowered. The percentage strength decreases as the quantity increases. To calculate the percent by weight strength of a semisolid mixture, an equation may be used as follows ... 

In addition to the stabilization of pharmaceutical preparations against chemical and physical degradation due to changed environmental conditions within a formulation, certain liquid and semisolid preparations also must be preserved against microbial contamination. 

Ointments are semisolid preparations to be applied externally to the skin or mucous membranes they soften or melt at room temperature. Pastes are thick, stiff ointments... 

Creams are semisolid preparation (usually emulsion) for external use. They are oily and non-greasy in nature. 

Sample Applications About 300 mg of the semisolid preparation is placed uniformly on the membrane and kept occluded to prevent solvent evaporation and compositional changes. This corresponds to an infinite dose condition. 

G. Creams or ointments Semisolid preparations intended for topical application. Excipients include petrolatum, isopropyl... 

Intravaginal creams are semisolid preparations formulated to produce a product that is miscible with vaginal secretions. They are generally delivered to the vagina using an applicator device... 

Ointments are semisolid preparations intended for topical application. They are used to provide protective and emollient effects on the skin or carry medicaments for treating certain topical ailments. They are also used to deliver drugs into eye, nose, vagina, and rectum. Ointments intended for ophthalmic purposes are required to be sterile. When applied to the eyes, they reside in the conjunctival sac for prolonged periods compared to solutions and suspensions and improve the fraction of drug absorbed across ocular tissues. Ophthalmic ointments are preferred for nighttime applications as they spread over the entire corneal and conjunctival surface and cause blurred vision. 

Microbial Screening Semisolid preparations are required to be free from any microbial contamination. Hence, most of the topical ointments are screened for the... 

Ointments Ointments generally consist of a dissolved or dispersed drug in an appropriate vehicle base. They are the most commonly used semisolid preparations as they are well tolerated and fairly safe and increase the ocular bioavailability of the drug. The instilled ointment breaks up into small oily droplets that remain in the cul-de-sac as a drug depot. The drug eventually gets to the ointment-tear interface due to the shearing action of the eyelids [178]. 

The problem of temperature control needs to be addressed because even below the melting point of semisolid preparations, their structure may be affected by the temperature and thus the photostability of the formulation will change. 

Ointments Semisolid preparations intended for application to the skin with or without inunction. 

Fig. 8 Illustration of the use of release rates from semisolid preparations to determine drug solubility within a formulation. Data show the release rates of benzocaine from propylene glycol/water gels as a function of drug concentration in the formulation. (Redrawn from Ref...

Liquid or semisolid preparations may require the presence of ancillary excipients to effect solvation or dispersion of the active ingredient. In particular, formulations containing drugs in the suspended state may require viscosity-enhancing agents or other additives to ensure that the drug remains homogenously dispersed. Otherwise, the accuracy of the dose may be compromised. 

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