Chapter 14 disperse system

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Information about Chapter 14 disperse system
Health & Medicine

Published on September 18, 2014

Author: kennytirorx



for thy studs

DISPERSE SYSTEMS: COMPONENTS  DISPERSED PHASE The undissolved or immiscible drug (suspensoid) distributed throughout the liquid vehicle. Also called the “internal phase”

 DISPERSION MEDIUM The liquid vehicle, to which the insoluble drug is distributed. Also called “external phase”

DISPERSE SYSTEMS PARTICLE SIZES Colloidal dispersions – 1 nm to 0.5 nm  Coarse dispersions (suspensions and emulsions) – 10 um to 50 um  Fine dispersions ( magmas and gels) – 0.5 um to 10 um

SUSPENSIONS  Disperse systems containing finely divided, insoluble drug particles (“suspensoids’) distributed somewhat uniformly throughout a liquid vehicle.  Ready to use liquid form (antacids and analgesics) Labeled as “Oral Suspension”

REASONS for SUSPENSIONS  For improving product stability  Ease of administration and flexibility in administration of a range of doses

Features desired in Pharmaceutical Suspension  1. Particles should settle slowly and should be readily re-dispersed upon shaking of the container.  2. The particle size of the suspensoid should remain fairly constant throughout long periods of undisturbed standing.  3. The suspension should pour readily and evenly from its container.

DISPERSED PHASE: PHYSICAL FEATURES  Particle diameter is 1μm to 50μm  Particle size reduction is accomplished by: Micropulverization – 10μm-50μm Fluid energy grinding (jet milling or micronization) – under 10 μm

PACKAGING AND STORAGE OF SUSPENSION  packaged in wide-mouth containers having adequate airspace above the liquid to permit thorough mixing by shaking and ease of pouring  stored in tight containers protected from freezing, excessive heat, and light.

EXAMPLES OF ORAL SUSPENSIONS  Antacid Oral Suspensions are intended to counteract the effects of gastric hyperacidity and as such are employed by persons, such as peptic ulcer patients, who must reduce the level of acidity in the stomach. They are also widely employed and sold over the counter (OTC) to patients with acid indigestion, heartburn, and sour stomach.

Antibacterial Oral Suspensions  include preparations of antibiotic substances (e.g., erythromycin derivatives, and tetracycline and its derivatives), sulfonamides (e.g., sulfamethoxazole and sulfisoxazole acetyl), other anti- infective agents (e.g., methenamine mandelate and nitrofurantoin), or combinations of these (e.g., sulfamethoxazole– trimethoprim).


EMULSIONS A dispersion in which the dispersed phase is composed of small globules of liquid distributed throughout another liquid, in which it is immiscible.

PURPOSE OF EMULSIONS AND OF EMULSIFICATION  Emulsification enables the pharmacist to prepare relatively stable and homogeneous mixtures of two immiscible liquids.  It permits administration of a liquid drug in the form of minute globules rather than in bulk.  For orally administered emulsions, the o/w type permits palatable administration of an otherwise distasteful oil by dispersing it in a sweetened, flavored aqueous vehicle.

TYPES OF EMULSIONS W/O emulsion - water is the internal phase - oil is external phase  O/W emulsion - oil is the internal phase - water is external phase


SURFACE-TENSION THEORY Initially, when oil and water are mixed it becomes immiscible due to the presence of surface tension. The use of surfactants result in the lowering of interfacial tension between two immiscible liquids.

ORIENTED WEDGE THEORY This theory assumes monomolecular layers of emulsifying agent curved around a droplet of the internal phase.

 PLASTIC FILM OR INTERFACIAL FILM THEORY This theory places the emulsifying agent at the interface between the oil and water, surrounding the droplets of the internal phase as a thin layer of film adsorbed on the surface of the drops.

PREPARATION OF EMULSIONS Emulsifying Agents  the emulsifying agent must be compatible with the other formulative ingredients and must not interfere with the stability or efficacy of the therapeutic agent.  It should be stable and not deteriorate in the preparation.  The emulsifier should be nontoxic with respect to its intended use and the amount to be consumed by the patient. Also, it should possess little odor, taste, or color

1. Carbohydrate materials, such as the naturally occurring agents acacia, tragacanth, agar, chondrus, and pectin. 2. Protein substances, such as gelatin, egg yolk, and casein. These substances produce o/w emulsions 3. High–molecular-weight alcohols, such as stearyl alcohol, cetyl alcohol, and glyceryl monostearate. These are employed primarily as thickening agents and stabilizers for o/w emulsions of certain lotions and ointments used externally. 4. Wetting agents, which may be anionic, cationic, or nonionic. 5. Finely divided solids such as colloidal clays, including bentonite, magnesium hydroxide, and aluminum hydroxide.

The HLB System  HYDROPHILE – LIPOPHILE BALANCE Used to classify non-ionic surfactant. All NON –IONIC surfactants have an HLB value. The higher the HLB number, the more hydrophilic. The lower the HLB number, the more lipophilic

Application of Surfactants HLB VALUE SURFACTANT RANGE APPLICATION  1–3 Antifoaming agents  3–6 Water-in-Oil emulsifiers  7–9 Wetting agents  8 – 18 Oil-in-Water emulsifiers  13 – 16 Detergents  15 – 20 Solubilizing agents

Methods of Emulsion Preparation  WET GUM METHOD (English method) 4:2:1 of oil : water : gum Formation of Primary Gum as the nucleus of the emulsion.  DRY GUM METHOD (Continental method) 4:2:1 ratio of oil: water: gum Formation of Primary Mucilage as the nucleus of the emulsion  BOTTLE METHOD (Forbes Bottle method) 2:2: 1 ratio of oil : water : gum Applicable to emulsions containing Volatile Oils.

MICROEMULSION Thermodynamically stable system Optically transparent isotropic mixture of a biphasic O/W system stabilized with surfactants Diameter of particle: 100 Å (10 mμ) to 1000 Å (Angstrom)

EXAMPLES OF ORAL EMULSIONS MINERAL OIL EMULSION OR LIQUID PETROLATUM EMULSION >prepared by dry gum method >employed as lubricating agents with 30ml dose

CASTOR OIL EMULSION  Castor oil emulsion is used as a laxative for isolated bouts of constipation and in preparation of the colon for radiography and endoscopic examination.  the adult dose is 45 mL, about three tablespoonfuls. For children 2 to 6 years of age, 15 mL is usually sufficient, and for children less than 2 years of age, 5 mL may be given.

Simethicone Emulsion  Simethicone emulsion is a water-dispersible form of simethicone used as a defoaming agent for the relief of painful symptoms of excessive gas in the gastrointestinal tract.  The emulsion in drop form is useful for relief of gas in infants due to colic, air swallowing, or lactose intolerance.

Topical Emulsion Use to treat dry skin are o/w emulsion A number of topical emulsions, or lotions are used therapeutically to deliver a drug systemically.

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