GPAT 360

 Formulation of Emulsions A typical emulsion consists of API (drug), oil, water and excipients (non-drug).  Type of drug depends on the internal phase. If internal phase is oil (in o/w emulsion) the drug is lipid soluble/ hydrophobic and vice versa. Excipients include antioxidants, emulsifying agents (surfactants, those obtained from natural sources [gums] and finely divided solids) and preservatives (antimicrobial agents). ANTIOXIDANTS Role : to avoid degradation of oils and drugs due to oxidation. Oxidation may occur due to slight incorporation of air during mfg. Oils also may get rancid. Oxidising agents (metal impurities) may enter in emulsions through water source. Antioxidants prevent such spoilage by either blocking chain recation or oxidation of foreign bodies. Types of oils used in emulsions : vegetable oils, mineral oils, vitamin oils. Other : Steroidal materials. Antioxidants : Alkyl gallates, Butylated hydroxy toluene (BHT), Butylated hydroxy anisole (BHA) and tocopherols.

Stability of Emulsions and Evaluation of Stability 1) Stability of Emulsions There are two principal requirements for the stability of an emulsion : i) There should not be changes in mean droplet size and size distribution of the droplets in an emulsion. ii) The suspended droplets should remain homogeneously dispersed in the continuous phase throughout it's shelf life. Stability/ instability of the emulsions can be seen by observing following phenomenon: a) Flocculation :   It is the aggregation or clumping of dispersed droplets. This aggregation is re-dispersible by shaking. As the aggregates form due to electrical charges on the droplets/ globules where interfacial film remains intact, flocculation is reversible. Sometimes, flocculation further results into coalescence where the number of globules come together and form a large globule (interfacial film breaks). b) Creaming : In o/w emulsion, dispersed oil globules migrate at the top and accumulate, whereas in w/o emulsion, d

Identification of Emulsion type. Basically, emulsions are of two types : o/w and w/o . Click here to view the article on What is an Emulsion? Following tests are conducted in order to identify the type of emulsion. 1. Cobalt chloride test: Filter paper soaked in cobalt chloride solution and dried , changes colour from blue to pink when exposed to the o/w (oil in water) emulsion. 2. Dilution test: This test is based on the miscibility of continuous phase in the oil or water. For example, if water is added with stirring in o/w emulsion , it will easily disperse in added phase (water) but w/o emulsion will not get dispersed. This method causes phase inversion of emulsions upon dilution. 3. Conductivity test: An emulsion with water as a continuous phase (o/w emulsion) passes the electric current , whereas the w/o emulsion is not able to do so. 4. Direction of creaming: When densities of the water and oil phases are known, direction of creaming test identifies emulsion type.  Creamin

  Emulsion Instead of a long definition, let's get to know this term in small divided forms. Emulsion is a thermodynamically unstable system. It consists of two immiscible liquids (one is generally water and another is oil)  It consists of one phase dispersed into another in the form of globules/ droplets. Either oil is dispersed in water (o/w) or water is dispersed into oil (w/o) This system is stabilized by adding suitable emulsifying agent(s). The liquid which is dispersed in the form of small globules is known as dispersed phase . The liquid in which globules are dispersed is known as continuous phase . For example - if paraffin oil is dispersed in the form of globules into water, paraffin oil is a dispersed phase and water is a continuous phase. This system is o/w i.e. oil in water emulsion. The dispersed phase is also known as discontinuous phase or internal phase. The continuous phase is also known as dispersion media or external phase. 1. While formulating an emu