Semisolid Dosage Forms

           Semisolid dosage forms are normally presented in the form of creams, gels, ointments, pastes, suppository or patch. They contain one or more active ingredients dissolved or uniformly dispersed in a suitable base and any suitable excipients such as emulsifiers, viscosity-increasing agents, antimicrobial agents,
antioxidants, or stabilizing agents. The choice of a base for semi-solid dosage forms depends on many factors: the therapeutic effect desired, the nature of the active ingredient(s) to be incorporated, the availability of the active ingredient(s) at the site of action, the shelf-life of the finished product, and the environmental conditions in which the product is intended to be administered. In many cases, a compromise has to be made in order to achieve the required stability. For example, drugs that hydrolyze rapidly are more stable in hydrophobic bases than in water-containing bases, even though they may be more effective in the latter. The base should neither irritate nor sensitize the skin, nor should it delay wound healing. It should be smooth, inert, odorless, physically and chemically stable, and compatible with both the skin and the active ingredient(s) to be incorporated. 

            It should normally be of such a consistency that it spreads and softens easily when stress is applied. It may be necessary for a topical semi-solid dosage form to be sterile, for example, when it is intended for use on large open wounds or severely injured skin.

I. CREAMS 

         are homogenous, semisolid preparation that is usually white and no greasy and has a water base. Creams are intended for application to the skin or certain mucous membranes for therapeutic or protective purposes. The term "cream" is most frequently used to describe soft, cosmetically acceptable types of preparations.

Example: Hydrocortisone cream, Ketoconazole cream, etc

  

II. OINTMENTS 

         are homogeneous, semi-solid and greasy preparations intended for external application to the skin or mucous membranes for therapeutic or protective purposes.

Example: Tetracycline ointment, Bepanthene ointment, Nebanol ointment, etc

III. GELS

         are usually homogeneous, clear, semi-solid, jelly- like preparations that may be used for topical medication. Gels are applied to the skin or certain mucous membranes for therapeutic, or protective purposes.

Example: Erythrogel, Metrogel, Hiruscar, etc

  

IV. PASTES

       are homogeneous, semi-solid preparations containing high concentrations of insoluble powdered substances (usually not less than 20%) dispersed in a suitable base. The pastes are usually less greasy, more absorptive, and stiffer in consistency than ointments because of the large quantity of powdered ingredients present. Pastes adhere reasonably well to the skin and they are suited for application on and around moist lesions.

Example: Orrepaste, Anagelsic and anti-inflammatory containing dental paste, etc

V. PATCHED/PLASTERS  

         are substances intended for external application made of such materials and of such consistency as to adhere to the skin. Inner surface of the patch contacts skin and allows

transdermal absorption of lipid-soluble medicines. The total amount of medicine on the patch is very large, but typically only a small fraction is absorbed.

Example: Dermal patches

                         

VI. SUPPOSITORY

           Semisolid dosage forms to be inserted into body cavity-rectum or vagina, where medication is melt at the body temperature which provides local or systemic effects.

Example: Kinal suppository, Poro suppository, Flagyl suppository, etc 

References:  

Essential Pharmacology for Health Occupations, 5TH EDITION,  RUTH WOODRAW