GPAT 360

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 emulsi...

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.  Cre...

  LINCTUSES What is a Linctus? Linctuses are sweet, viscous liquid oral preparations containing medicinal substances which have demulscent, expectorant or sedative properties. These contain high proportions of syrup and glycerin which exert demulscent effect on the mucous membrane of throat. In order to obtain prolonged local action, linctuses should be administered slowly in undiluted form. Formulation of Linctus  1. Vehicle : Syrups are mostly used as vehicles in the linctuses. Tolu syrup is preferred in cough preparations due to its aromatic odor and flavour. Glycerol syrup and invert syrup are also used as vehicles. Linctus preparation for diabetic patients contain sorbitol syrup (vehicle). Medicament is first dissolved in little amount of water and then added into vehicle. Syrups are viscous and contain less amount of water, this limits (affects) the dissolution of medicament in syrup. 2. Additives: Colouring agents : Amaranth, Erythrosin, Tartrazine. Flavouring agents : ...

SYRUPS :  Monophasic Liquid Dosage Form Syrups are sweet and viscous or nearly saturated aqueous solutions of sugar or sugar substitute. Syrups containing therapeutic agent(s) are known as medicated syrups . Syrups containing flavouring agents but not medicinal substance / therapeutic agent are known as flavoured vehicles . Role/advantages of syrups : 1. Palatable : nauseous, bitter tasting, saline drugs can be administered with ease. 2. Pediatric patients : Medicated syrups are the most frequently administered dosage forms in pediatrics.  3. Little or no alcohol : Syrups are preferred for children due to less or no alcohol in syrups unlike elixirs. Commonly Used sweeteners in syrup formulations: 1. Sugars : Sucrose, Dextrose 2. Non-sugars : Sorbitol, Glycerin, propylene glycol. Why concentration of sucrose in sugar based syrup is important? Reasons are: the dilute solution of sucrose may cause microbial growth in formulation while the saturated sucrose solution may lea...

  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 a...

AROMATIC WATERS Aromatic waters are the saturated solutions of volatile oils or other aromatic substances.   Methods of preparation of aromatic waters: Distillation: Crude drug/material is placed in sufficient amount of purified water in flask. After heating water forms a steam which is condensed to obtain a condensate which contain aromatic principles. This method is expensive, tedious and time consuming. Examples: Orange flower water NF, Strong Rose water NF. Solution method: In this method, the volatile oil is shaken for 15 min with sufficient quantity (500 times) of water to make a solution. The resultant solution is kept aside for 12 hrs then filtered through wet filter paper.  Examples: Dill water, Peppermint water, Chloroform water, Camphor water, etc. Alternate solution method: The volatile oil is mixed with an inert adsorptive material ( Talc, Kieselghur, purified siliceous earth) then 1 ltr of purified water is added and agitated for 10 min. Resulting solution is...

MONOPHASIC LIQUID DOSAGE FORMS Mono-Single Monophasic – single phase dosage forms Examples: solutions, aromatic waters and tinctures A.   SOLUTIONS Monophasic system of two or more substances, e.g. sodium chloride solution, Pharmaceutical solutions are defined as the liquid preparations containing one or more chemical substances usually dissolved in water. Methods of preparation 1. Simple dissolution: Solute + suitable solvent → with/without heat → solution e.g. Morphine hydrochloride solution, Adrenaline hydrochloride solution. 2. Solution by chemical reaction: Reaction of two or more solutes → in suitable solvent. e.g. Aluminium acetate solution Al 2 (SO 4 ) 3 +3CaCO 3 +4CH 3 COOH → 2Al.(CH 3 COO) 2 .OH +3CaSO 4 +3CO 2 +H 2 O  3.  Solutions by extraction: Removal of active constituents from crude drugs with the help of solvent. e.g. liquid extracts and tinctures. Solutions for internal use: Taken orally: mixtures, elixirs, tinc...