PCC2 Special Senses - Formulations

Name examples of semi-solid dosage forms ? - Ointments - Creams - Pastes - Lotions - Jellies - Foams Briefly explain the design of semisolid dosage forms ? Designed to be applied as a film and remain in physical contact with the site of application for a reasonable amount of time before being removed or washed off. What does the choice of semisolid dosage forms dependent on ? The purpose of application and the required duration of contact (resilience). - Designed for application to the skin or other mucosal membrane - They are occlusive (greasy) Ointments Why are ointments described as being occlusive ? They form a barrier on the skin preventing moisture and heat loss, enhancing drug absorption through the skin. The base which forms the bulk of its body. What do the properties of ointment depend on ? - Water soluble - Emulsion - Absorption - Hydrocarbon What are the 4 main types of ointment bases ? Characteristics - Hydrophilic polymer mixture Ointment bases - Water soluble base Applications - Drug carriers 1/5 E.g., Polyethylene glycol (PEG) Characteristics: - o/w emulsions - leaves a hydrophobic film on the surface of the skin when water evaporates Ointment bases - Emulsion Applications - Drug carriers, Foundation for makeup E.g., Hydrophilic ointment, Vanishing cream Characteristics: - w/o emulsion or hydrocarbon bases that allow incorporation of aqueous solution to form w/o emulsions - not readily water washable Ointment bases - Absorption Applications - Emollients Examples: - Anhydrous: hydrophilic petroleum and anhydrous lanolin - w/o emulsion: lanolin and cold cream Characteristics: - Anhydrous - Water insoluble - Not water washable - Form occlusive film on skin Ointment bases - Hydrocarbon Applications - Incorporation of hydrophobic drugs Examples: - Petroleum - Wax - Synthetic esters e.g., glycerol monostearate 2/5 1. Solubility characteristics of the drug 2. Desired rate of drug release from the base What is the choice of ointment base de- 3. Whether the ointment is intended as a pendent on ? topical or systemic treatment 4. Properties of the ointment base (washability) 5. Intended use (cosmetic or clinical) Creams Semi-solid dosage forms containing one or more drug substance dissolved or dispersed in a suitable o/w or w/o emulsion base. What makes creams different to other semi-solid formulations ? Less viscous than ointments and pastes as they are generally o/w emulsions. o/w creams: - aqueous creams - generally thinner, white, smooth - provide a cooling sensation - better in achieving What is the difference between o/w creams and w/o creams ? w/o creams: - oily creams - stiffer - white/translucent - creamy = they contain a higher proportion of hydrophobic emulsifying agent (e.g., beeswax, wool fat, etc.) - Be soluble in sufficient concentration - Have a relatively wide therapeutic win3/5 What factors are required for a drug being incorporated into a cream ? dow since accurate dosing using these dosage forms is difficult - Not crystallise upon evaporation of water Gels Transparent semisolid formulations consisting of small or large molecules in an aqueous liquid vehicle, thickened with a gelling agent. Describe single phase gels ? - Use high molecular weight hydrophilic polymers as gelling agents E.g., 0.5%-2% w/w in water carbomers cross-linked acrylic acid polymers Describe biphasic gels ? - Contains gelatinous, cross-linked precipitate of one substance in the aqueous phase E.g., milk of magnesia contains a gelatinous precipitate of magnesium chloride What can be included in the gels drug formulation ? - Water - Gelling agent - Drug - Co-solvents - Antimicrobial preservatives - Stabilisers Lotions - Liquid preparations intended for application to unbroken skin. - Most are o/w emulsions - May also contain an emulsifying agent to prevent separation of the aqueous and organic components What makes lotion a more suitable Has the advantage of being able to cover semi-solid formulation choice in compar- a large area of skin more efficiently as it can be spread thinly. ison to others ? Describe the properties of lotions ? - Low to medium viscosity - Can be medicated or non-medicated topical preparations 4/5 - Incorporated drug should be finely divided (small particle size) to maintain a smooth consistency and feel Pastes Semisolid preparations that contain a higher proportion of solid components in comparison to creams, ointments and lotions. - Made either of hydrocarbon bases (e.g., petroleum) or aqueous gels (e.g., cellulose) Describe the properties of Pastes ? - Thick - Stiff Advantages of Pastes ? - Well absorbed - Can absorb solution = can be used around oozing wounds - Easily removed and washable Foams - Consist of gases finely spread throughout liquids or solids - Can be used topically when other semi-solid formulations would be inappropriate 5/5