Semisolid Dosage Forms PDF

SEMISOLID DOSAGE FORMS MSc. Dr. Zainab N. Al-kefaee  Semisolid Dosage Forms Semisolid preparations represent dosage forms that have properties in between solid and liquid dosage forms and possess characteristic rheological properties such that they can be easily applied on biological...

SEMISOLID DOSAGE FORMS MSc. Dr. Zainab N. Al-kefaee  Semisolid Dosage Forms Semisolid preparations represent dosage forms that have properties in between solid and liquid dosage forms and possess characteristic rheological properties such that they can be easily applied on biological membranes and can be retained on the site of application for a prolonged time. Semisolid dosage forms topical preparations may contain one or more active ingredients in suspended/dissolved forms for local and/or systemic effects. They may be applied to the skin, placed on the surface of the eye, or used nasally, vaginally, or rectally. Most of these preparations are used for the effects of the therapeutic agents they contain. The unmedicated ones are used for their physical effects as protectants or lubricants.  a topical product is designed to deliver drug into the skin to treat dermal disorders with the skin as the target organ. Transdermal drug delivery systems are designed for the systemic absorption of drug substances in therapeutic quantities. A transdermal drug delivery system is designed to deliver drugs through the skin (percutaneous absorption) to the general circulation for systemic effects with the skin not being the target organ.  Advantage of semi-solid dosage form It is used externally. Probability of side effect can be reduce. Local action and site specific action of drug on affected area. First pass gut and hepatic metabolism is avoided. Patient compliance is increased.  Semisolid Dosage Forms: Ointments, creams, gels, and pastes Ointments: are greasy semisolid preparations contain oil 80 ⁒- water 20 ⁒ intended for external application to the skin or mucous membranes. Ointments can be medicated or non-medicated. The non-medicated ointments are also called ointment bases and used as such for emollient, protective, or lubricating effect or as a vehicles in the preparation of medicated ointments.  Creams are semisolid emulsions for external application. O/W emulsions (aqueous creams) are most useful as water-washable bases where as W/O emulsions (oily creams) are emollient and cleansing. Creams are soft, easy to apply, cool the skin, and less greasy than ointments. Pastes are semisolid preparations for external application. They have high content of powder (20-50%) dispersed in either an aqueous or oily vehicle. Pastes usually stiffer and less greasy than ointments and are more difficult to apply and remove.  Gels (Jellies) are non-greasy semisolid preparations intended for internal or external application. It could be transparent or not. They are used for medication, lubrication, and other uses. Gels are semisolids consisting of dispersions of small or large molecules in an aqueous liquid vehicle rendered jelly like by the addition of a gelling agent. Gels are easily applied and evaporation of their water content produces a pleasant cooling effect. The residual film usually adheres well and gives protection. However, it is easily removed by washing with water.  Classification of ointment bases: 1. Oleaginous base (hydrophobic or hydrocarbon base) 2. Absorption base (emulsion base W/O) 3. Water-removable base (emulsion base O/W) 4. Water-soluble base  Preparation of ointments 1. Incorporation method (trituration method) Insoluble solids or liquids medicaments are incorporated into bases using the technique called (mixing by trituration) which can be carried out by 3 methods: 1. Using ointment slab and spatula or Muller when small quantities of ointment are to be prepared. 2. Using mortar and pestle when large quantities of ointment are to be prepared or when large quantities of liquids are to be incorporated in to a base. 3. Using an ointment mill for large quantities of ointment (a pound or more). Other device called Unguator allows to place the ingredients in a plastic ointment jar with a special lid that allows for a mixing blade to be used to mix the ingredients in the dispensing container  ointment mill Unguator jar Unguator Applicators  Preparation of ointments Mixing by trituration is carried out on an ointment slab and spatula: 1. Any powders should be reduced to a fine state before weighing to avoid grittiness. If there are more than one ingredient, they should be finely powdered and mixed by geometrical dilution method. 2. Powders are placed on the slab, rubbed with small amount of base to give concentrated ointment. 3. Then, incorporating this concentrated ointment into the reminder of the base using doubling-up method.(mixing a small quantity of powder with a large quantity) 4. Liquids (if present) are to be incorporated into the base, aqueous solution is easily mixed with absorption, water-removable, and water-soluble bases.  Preparation of ointments 2. Fusion method (melting method) Fusion method is necessary when some ingredient are solid at room temperature wax, paraffin, fatty alcohol or when medication are soluble in the melted base. All or some of the components of an ointment are combined by being melted together and cooled with constant stirring until congealed. Medicated ointments and ointment bases containing components such as beeswax, paraffin and high molecular weight PEGs are prepared by fusion.  Fusion method (melting method) Steps are: 1. Place the base constituents in evaporating dish or beaker on a water bath and melt. 2. When all the ingredients are melted, remove the beaker from the water bath and gently stir. 3. Medicaments that are soluble in the melted base should be added to the base before it congeals. 4. Insoluble medicaments should be levigated with small quantity of the melted base. After the reminder of the base is congealed, the levigated medicament can be incorporated with it (doubling-up method) 5. Water and water-soluble ingredients such as glycerin and PEG must be heated approximately the same temperature as the melted base before mixing to avoid crystallization of high melting point substances.  Preparation of creams Preparation usually involves separating the formula components into two portions: oil and aqueous. ❖ The oil portion contains all water-insoluble components and the aqueous portion the water- soluble components. ❖ Both phases are heated to a temperature above the melting point of the highest melting component. ❖ The phases then are mixed, and the mixture is stirred until the mixture has congealed. ❖ Mixing generally is continued during the cooling process to promote uniformity.  Sulphur Ointment USP Rᵪ Sulphur Ointment USP Precipitated Sulphur 100 g 1 gm Glycerin 100 g 1 ml glycerin White Ointment 800 g 8gm USP: Levigate the sulphur with the glycerin to a smooth paste, and then incorporate with the white ointment.  vanishing cream Rᵪ Vanishing Cream Stearic acid 3g Potassium hydroxide 0.14 g Glycerin 1.6g Purified water 15.3g Make cream, send 20 g Vanishing creams are o/w emulsion  vanishing cream Stearic acid melted in a container by using a water bath. Potassium hydroxide dissolved in water and glycerin is added and heated to the temperature of 75°C. This is called the aqueous phase. Leave for 10-15 min. on water bath Add the aqueous phase to oil one with stirring quickly Stearic acid (Lubricant/Emulsifier) Potassium hydroxide (Softener) Purified water (Vehicle) Use of Glycerin in Vanishing Cream helps to soften and protect the skin and heavily moisturizes dry skin.  Whitfield ointment Rᵪ Whitfield Ointment master formula working formula Benzoic acid 60 g 0.6 g Salicylic acid 30 g 0.3 g Petrolatum 910 g 9g Benzoic acid (antifungal, antiseptic) Salicylic acid (antiseptic, anti-inflammatory, keratolytic) This prescription works as a keratolytic, and for the treatment of fungal skin diseases such as tinea, ringworm, and athlete's foot. It cannot be used on inflamed and cannot be used near the eye or mucous membranes.