Ointments Lecture 3

Ointment bases ▹ Classification based on composition Oleaginous Absorption Waterremovable Water-soluble Ointment bases ▹ Classification based on degree of skin penetration Examples Epidermic Endodermic Diadermic Little or no skin penetration Some skin penetration High skin penetration Drugs act locally on the skin surface Drugs act within the skin layers Drugs reach systemic circulation Lanolin (absorption base) Water-removable and water-soluble bases Oleaginous bases Medicated ointments: Drug release + Skin penetration Oleaginous Base Absorption Epidermic Waterremovable Endodermic Water-soluble Diadermic ▹ Depends on physicochemical properties of both Drug Hydrophilic Hydrophobic Ointment base selection Depends on careful consideration of several attributes such as: ▹ Physicochemical properties of the drug ex: aqueous solubility Oleaginous base? ▹ Chemical stability of the drug in the selected base An easily hydrolysable drug Water-containing ▹ Desired drug release rate from the base base? ▹ Intended action: topical effect versus percutaneous absorption ▹ Effect of the drug on the base properties such as consistency ▹ Whether emollient effect is required ▹ Whether ease of wash is required Occlusive base? ▹ Properties of the skin surface to which it is applied Wet oozing wounds Water-absorbing base? ▹ Desired shelf-life for the product Incorporate more water Water number of ointment bases Incorporate less water ▹ The amount of water (g) that can be taken up by 100 g of ointment base at ambient temperature, 20 ºC. ▹ Determined by titration method. ▹ A measure of the capability of an ointment base to incorporate aqueous solutions. ▹ Wool fat and high molecular weight fatty alcohols such as cetyl alcohol and stearyl alcohol Increase water number of a base Oleaginous bases ▹ Add 10-15% less water that that indicated by the water number (max)  avoid water bleeding caused by temperature variations. Preparation of Ointments ▹ Two general methods: ▹ Based on the nature of used ingredients Mechanical incorporation Fusion Mechanical incorporation ▹ Ingredients are thoroughly mixed till a uniform smooth preparation ▹ Used to incorporate drugs/substances in a fine state of subdivision into a prepared ointment base Mortar & pestle Ointment slab Ointment mill Mechanical incorporation: Mortar & Pestle ▹ In small scale compounding: ▸ When large volumes of liquid are to be incorporated ▸ When large quantities of the ointment are to be prepared (Cf. ointment slab) Mechanical incorporation: Mortar & Pestle ▹ For larger scale manufacturing: Electric mortar and pestle (EMP) Mixing blades ▹ The Unguator® Polypropylene jar with a special lid Measuring unit Mixing chamber Dispensing jar Mechanical incorporation: Mortar & Pestle Programmed for different speeds ▹ For larger scale manufacturing: Electric mortar and pestle (EMP) Homogenous formulation ▹ The Unguator® Unguator® High reproducibility Closed environment Avoids oxidation or contamination Formulation + dispensing in one pot Saves time + less cleaning Mechanical incorporation: Ointment slab ▹ Large glass or porcelain surface or pill tile that provides a hard nonabsorbable surface of mixing. ▹ For small scale compounding. ▹ Ingredients rubbed together with spatula – “Spatulation” ▹ Ointment pads: grease-proof parchment paper placed on the slab Not suitable for liquidcontaining preparations Allow easier clean-up Not suitable for sticky or thick ointments Mechanical incorporation: Ointment slab Stainless steel Long flexible wide blade Adequate shearing and mixing Large not small Iodine Rubber Tannic acid Steel Reactive drugs Mercury Salicylic acid Wood Mechanical incorporation: Ointment mill ▹ For large scale manufacturing ▹ Small scale ointment mills are also available for laboratory use Mechanical incorporation: Ointment mill ▹ ▹ ▹ Called: Three-roller mill Three adjacent horizontal stainless steel or ceramic rollers Rotate at different speeds in opposite directions to each other  Shear force  Reduce particle size  Disperse agglomerates  Homogenize viscous materials Ointments containing gritty particles are passed through the ointment mill to ensure smoothness and uniformity