Ointments Lecture 4

Fusion ▹ For preparation of ointments containing hard waxy ingredients such as paraffin, beeswax, stearyl alcohol or high molecular weight PEG 1 2 Melting Cooling + Continuous Stirring Homogenous ointment 1 Melting Fusion Ingredient with the highest melting point M.P. All ingredients melted together Or added in order of their increasing melting points Temperature All melt All melt Solvent effect of the first melted ingredient Not all the ingredients are subjected to the highest temperature Least temperature required for fusion (less than the highest MP) Melting point: A B C 70 ºC 60 ºC 50 ºC 1 70 ºC A 60 ºC B 50 ºC C Temperature applied Temperature applied Melting 50 ºC C 55 ºC B 60 ºC A Solvent effect of the first melted ingredient Not all the ingredients are subjected to the highest temperature Least temperature required for fusion (less than the highest MP) Fusion 2 Cooling + Continuous Stirring ▹ Stir gently while the mixture is congealing to avoid inclusion of excess air ▹ Why? as it can cause localized cooling resulting in a lumpy product Fusion ▹ Drug incorporation: Oil-soluble and heat-stable Heat-labile or volatile ingredients Solutions or solids Melted ointment base Congealing mixture after it reaches a low temperature Levigate with portion of the congealing mixture Fusion ▹ ▹ ▹ Small scale: Porcelain dish or beaker Large scale: Large steam-jacketed kettles To ensure a smooth uniform texture of the congealed ointment: Small scale Large scale Aqueous phase Emulsification ▹ For ointment bases Oleaginous phase All waterinsoluble components All watersoluble components containing an emulsion Heat to a temperature = Oleaginous phase Aqueous phase Melting Lipid phase Stir continuously while it is cooling until it congeals Incorporating solids ▹ Regardless the method used for preparation, any ointment should be: ▸ Smooth and non-gritty ▸ Uniform (no lumps, no separated liquid components and evenly dispersed solids) ▹ Incorporating solids: Solid Size reduction techniques For oleaginous bases: An aqueous drug solution is first incorporated into a min amount of hydrophilic base then this mixture is added to the hydrophobic base. Small volumes of alcoholic solutions incorporate well in oleaginous and emulsion bases Soluble Insoluble Trituration Levigation Trituration ▹ Dry grinding ▹ Solids are mixed and comminuted to a fine powder using mortar and pestle. ▹ The triturated powder is transferred to a slab to be spatulated with the ointment base ▹ Geometric dilution is employed Spatulation does not include particle size reduction, so powders to be spatulated should be in a fine form Levigation ▹ Wet grinding a solid in a vehicle in which it is insoluble, to obtain a fine smooth dispersion. ▹ Easier for solid incorporation, and makes a smooth, elegant preparation ▹ Done using a mortar and pestle to allow both reduction of particle size and uniform dispersion of the solid in the vehicle. ▹ The dispersion is then incorporated in the ointment base using the mortar and pestle or with spatulation Levigation ▹ ▹ Wet grinding a solid in a vehicle in which it is insoluble, to obtain a fine smooth dispersion. The vehicle is called: Levigating agent Base Physically and chemically compatible Drug Oleaginous external phase Aqueous external phase Ex: Mineral oil Ex: Glycerin Equal volume to the solid Not exceed 5% To avoid undue base softening Ophthalmic ointments ▹ Intended for application in the eyes ▹ Must be sterile ▹ The base should be nonirritating to the eye ▹ Its softening point should be close to body temperature ▹ Ex: ▸ Petrolatum ▸ Petrolatum-Lanolin (for incorporation of aqueous drug solutions) ▹ Collapsible tubes with elongated narrow tip, to facilitate application of a narrow band of ointment to the eye ▹ Sealed and tamper-proof Drug added as solution or fine powder Comfort Drug release Diffusion throughout eye secretions