MIXTURES

MIXTURES Mixtures are fluid preparations intended for internal administration. Simple Mixture: if the solute is soluble in the vehicle (large fluid component of the mixture). Compound Mixture: if the solute is insoluble or dispersed in the vehicle. Mixtures are used in acute cases such as cough, indigestion, diarrhea, constipation for which short period of treatment is adequate.

Classification of Mixtures A. Simple mixtures. B. Mixtures containing insoluble diffusible solids. C. Mixtures containing insoluble in-diffusible solids. D. Mixtures containing slightly miscible liquids. E. Mixture containing precipitate forming liquids. F. Miscellaneous mixtures.

Simple Mixtures Those preparations containing soluble ingredients e.g Iron Ammonium Citrate Mixture (used in case of iron deficiency) R/ Iron ammonium citrate……………. 0.3 gm Tr. Nux Vomica……………………...0.1 ml Spirit Chloroform…………………….0.1 ml Aqua ad. …………………………… 30 ml Fait Mixture, Mitte ii Sig. Fl.oz T.D.S. N.B. Tincture Nux Vomica is tonic

Simple Mixtures PROCEDURE: Calculate the required weight and volume. Dissolve iron ammonium citrate in ¾ of the vehicle volume, noting that iron ammonium citrate is added to vehicle and not the reverse. Measure the liquid ingredients and add to iron ammnium citrate solution. Complete the volume to 60 ml with water. Transfer to clean dry glass bottle and affix the label.

Simple Mixtures General Notes: If solution is turbid, filter through cotton wool. If large crystals are used, such as sodium sulphate crystals, it should be powdered and dissolved in mortar. Scale solids must be crushed on paper and added to vehicle in a beaker. To facilitate the work of a dispenser, stock solution of commonly used soluble chemicals are often prepared (in conc. Of 25% w/v). Hygroscopic solids (CaCl2 and MgCl2) are best kept in solution. The use of hot water hasten dissolution of slowly soluble solids (e.g. borax)

B. Mixtures Containing Insoluble Diffusible Solids Mixtures containing insoluble ingredients that diffuse readily in the vehicle by shaking the bottle and remain dispersed long enough so that a dose can be poured out. A (Shake The Bottle) label must be used. Examples; magnesium carbonate, light kaolin, magnesium trisilicate, bismuth sulphate and bismuth carbonate

B. Mixtures Containing Insoluble Diffusible Solids WHITE MIXTURE: R/ Magnesium sulphate ……………4 gm Magnesium carbonate (light)……2 gm Peppermint water ad………….....30 ml Fait Mixture, Mitte ii (60 ml) Sig., two table spoonful to be taken half an hour before breakfast - Used as laxative.

B. Mixtures Containing Insoluble Diffusible Solids Procedure: 1. Dissolve magnesium sulphate in about 30 ml of peppermint water. 2. In dry clean mortar triturate magnesium carbonate (light) to a smooth past with a little of vehicle, transfer to a measuring cylinder with successive portions of the vehicle. 3. Add to the magnesium carbonate suspension the prepared magnesium sulphate solution with stirring, and complete to volume with vehicle. 4. Transfer to white glass bottles and affix the label together with shake the bottle label.

C. Mixtures Containing Insoluble In-diffusible Solids Those mixtures containing insoluble solids that settle down very rapidly and not remain evenly distributed in the vehicle long enough to ensure uniformity of the measured dose. They required a suspending agent. As a general rule, the suspending agent ordered by the prescriber should be used, when no suspending agent is ordered, the dispenser must select the most suitable one for a particular solid.

C. Mixtures Containing Insoluble In-diffusible Solids Suspending Agents: These are substances included to keep insoluble medicament(s) in a state of suspension at least sufficiently long for a dose to be poured out of the container. 1. Gum Acacia Powder: - mixed with substance to be suspended before adding the vehicle - used in concentration of 6-10% w/v of the mixture

2. Gum Tragacanth powder: C. Mixtures Containing Insoluble In-diffusible Solids Suspending Agents (cont.) 2. Gum Tragacanth powder: - it usually make lumps when vehicle is added to it, so it is better to use it a mucilage. - used in concentration of 0.25-2.3% w/v. - used only when ordered by the prescriber.

3. Compound Tragacanth Powder: C. Mixtures Containing Insoluble In-diffusible Solids Suspending Agents (cont.) 3. Compound Tragacanth Powder: It consists of tragacanth powder, acacia powder, starch and sucrose. Starch grains prevent formation of lump. Mixed with substance to be suspended in the mortar and vehicle is added gradually with trituration. Used in concentration of 2% w/v of the mixture. Usually used when no particular suspending agent is ordered Disadvantage; starch impart opacity to the final mixture.

used in concentration of 25% of final volume C. Mixtures Containing Insoluble In-diffusible Solids Suspending Agents (cont.) 4. Mucilage of Acacia or Tragacanth used in concentration of 25% of final volume Disadv: form solid mass with some insoluble solid e.g. bismuth salts

R/ Prepared chalk…………….0.6 gm Tincture of catechu………..0.3 ml Glycerin…………………….1.0 ml Chloroform water to……….15 ml Prepare mixture, send 10 dose N.B. prepared chalk (calcium carbonate) is insoluble in-diffusible solid. This formula is used as antacid.

Calculation of the amount of suspending agent: If no suspending agent is ordered we usually use the compound tragacanth powder in 2% concentration. 15 X 2 = 0.3 gm for each dose 100 So, for 10 doses = 0.3 gm X 10 = 3 gm

D. Mixtures Containing Slightly miscible liquids Example R/ Creasote………………. 0.3 ml Sodium benzoate…….. 0.3 gm Syrup tolu……………… 2.0 ml liquid extract of liquorices….2.0 ml Camphor water ad……….. 30.0 ml Fait Mistura, Mitte ii

D. Mixtures Containing Slightly miscible liquids Procedure: Calculate the weight and volumes enough to make 60 ml. Dissolve sodium benzoate in about 10 ml of camphor water, add other liquid ingredients (syrup tolu and liquorices). In a clean dry mortar triturate 1.2 gm of compound tragacanth powder (2% w/v) with about 10 ml of camphor water. Creasote is added dropwise to the gum mucilage with continuous trituration. Transfer to cylinder containing the solution of step 2, and complete volume to 60 ml with camphor water.

E. Mixtures Containing Precipitate Forming Liquids Spirit (for example) is an alcoholic solution of volatile liquid. On dilution of spirits with water, they yield a fine precipitate (ppt). In the finally divided state the ppt is more easily dissolved by the vehicle than in case if it was added directly to it. As a rule, it is necessary to shake until the precipitated substance is dissolved.