ODISHA STATE BOARD OF PHARMACY
D. Pharm - II Examination - 2015 (I)
PHARMACEUTICS - II (THEORY)
Time - 3 Hours Full Marks - 80
__________________
(Answer any five questions including question no-1)
1. (A) Write the full Latin term and English meaning of the following Latin abbreviations
(1×5=5)
(i) q.q.h;
(ii) q.i.d;
(iii) a.c.;
(iv) s.o.s.;
(v) t.i.d.s
(B) Define the terms:
(1×5)
(i) Tincture
(ii) Effervescence;
(iii) Shampoo;
(iv) Paste
(v) Poultice
(C) Give the calculation and result of the following.
(2 + 2 + 2+ 4 = 10)
(i) Calculate the volume of 100 gm of glycerin. The density of glycerin is 1.25.
(ii) The dose of a drug is 80 mg. Calculate the dose for a child of 09 kg body weight by using Clark's Formula.
(iii) Calculate the quantity of NaCl required for preparation of 200ml of 0.9% w/v solution.
(iv) How much 70% and 20% alcohol are required to prepare 300 ml of 50% alcohol.
2. Define a prescription. Describe the parts of a prescription with a typical example.
[2+ 10+ 3= 15
3. What are powders? Write the Advantages anddisadvantages of powder. Write the method of preparation of a compound powder.
(3 +5 + 7 = 15)
4. Write notes on
(7.5 X 2=15)
(i) Supposi
(ii) Dentrifices
5. What do you mean by diffusible and indiffusible suspensions? Write the dispensing method for mixtures containing dffusible solids.
(6+9=15)
6. Describe the method of preparation of parenteral liquids.
(15)
7. Write notes on.
(7.5 x 2 = 15)
(i) Ointment base
(ii) Physical incompatibility
ANSWER TO 2015
1. A.
(i) q.q.h: quaue quarta hora - every fourth hour
(ii) q.i.d = quarter in die = four times day
(iii) a.c: anti cibos - before meals
(iv) s.o.s: si opus sit - when required or when necessary
(v) t.i.d: ter in die - Three times a day
(B) Define the terms:
(i) Tincture
Ans.
It is a type of herbal preparation in which the alkaloids, glycosides, minerals & essential oils of a plant are extracted into a solvent (mostly alcohol)
(ii) Effervescence;
Ans.
Effervescence - It is the escape of gas from an aqueous solution and the foaming or fizzing that results from a release of the gas.
(iii) Shampoo;
Ans.
Shampoos may be defined as a preparation containing surface active agents which are used to remove dirt, grease and debris from the hair, scalp and other parts of the body without the affecting the natural gloss of hair. Shamppo also helps to keep the hair fragrant, lustrous, soft and manageable.
(iv) Paste
Ans.
Pastes are semi-solid preparations intended for external application to the skin. The pastes are generally very thick and stiff. They do not melt at ordinary temperature and thus form a protective coating over the area where they are applied. They are used mainly as antiseptic protective or soothing dressings which are often spread on lint before being applied.
(v) Poultice.
Ans.
This is a soft, viscous wet mass of solid substances applied to the skin for their fermentation action in order to provide relief from pain or reduce inflammation or to act as a counter irritant.
2. Define a prescription. Describe the parts of a prescription with a typical example.
Ans.
Prescription is a written order from a registered medical practitioner, or other properly licensed practitioners, such as dentist, veterinarian etc. to a pharmacist to compound and dispense a specific medication for the patient. Prescription is a media through which treatment is provided for a patient by the combined skill and services of both the physician and the pharmacist. The prescriptions are generally written in the English language but Latin words or abbreviations are frequently used in order to save time.
Parts of a Prescription :
Prescrptions are generally written on a typically format which are usually kept as pads. A typical prescription consists of following parts;
(i) Date
(ii) Name, age, sex and address of the patient
(iii) Superscription
(iv) Inscription
(v) Subscription
(vi) Signatura
(vii) Renewal instructions
(viii) Signature, address, and registration number of the prescriber
(i) Date: It helps a pharmacist to find out the date of prescribing and date of presentation for filling the prescription. The prescription which prescribe narcotic or other habit forming drugs, must bear the date, so as to avoid the misuse of prescription if it is presented by the patient, a number of times for dispensing.
(ii) Name, age, sex and address of the patient: Name, age, sex and address of the patient must be written in the prescription because it serves to identify the prescription. In case, if any of these information is missing in the prescription, the same may be included by the pharmacist after proper enquiry from the patient. Age and sex of the patient, especially in case of children, help the pharmacist to check the prescribed dose of medication. In some cases the weight of the patient may also be required in order to calculate the appropriate dose.
(iii) Superscription: It is represented by a symbol R which is written before writing the prescription. R is an abbreviation of th Latin word recipe. meaning "You take' (Take thou). In olden days, the symbol was considered to be originated from the sign of Jupiter, God of healing. The symbol was employed by the ancient in requesting God for the quick recovery of the patient.
(iv) Inscription: This is the main part of the prescription order, contains the names and quantities of the prescribed ingredients. The name of ingredients are generally written in English language but common abbreviation used can be written both in English and Latin languages. The name of each ingredient is written on a separate line along with its quantity, In complex prescriptions containing several ingredients the inscription is divided into following parts;
(a) Base: The active medicaments which are intended to produce the therapeutic effect.
(b) Adjuvant: It is included either to enhance the action of medicament or to improve the palatability of the preparation.
(c) Vehicle: it is included in the prescription either to dissolve the solid ingredients or to increase the volume of the preparation.
Nowadays, the majority of the drugs are prescribed which are already in a suitable formulation. The pharmacist is required to dispense the ready-made form of drugs. So, compounding of prescription is almost eliminated.
(v) Subscription: This comprises direction to the pharmacist for preparing the prescription and number of doses to be dispensed. These days, the prescribers are omitting the specific instructions to the pharmacist because the majority of the prescriptions are not compounded and dispensed.
(vi) Signatura: This consists of the direction to be given to the patient regarding the administration of the drug. It is usually written as 'Sig' on the prescription. The instructions given in the prescription are required to be transferred to the label of the container in which the medicament is to be dispensed, so that the patient can follow it. The instruction may include the following:
(a) The quantity to be taken
(b) The frequency of administration or application
(c) The mode of administration
(d) The special instructions such as dilution direction.
(vii) Renewal instructions: The prescriber indicate on every prescription order, whether it may be renewed and if so, how many times. It is very important particularly in the prescription containing the narcotic and other habit forming drugs to prevent its misuse.
(viii) Signature, address & registration number of the prescriber: The prescription must bear the signature of the prescriber along with its registration number and address. It is very important particularly in the prescription containing the narcotic and other habit forming drugs, to prevent its misuse.
3. What are powders? Write the Advantages and disadvantages of powder. Write the method of preparation of a compound powder.
Ans.
Powder, advantages & disadvantages A pharmaceutical powder is a mixture of finely divided drug and/or chemicals in dry form. These are solid dosage form of medicament which are meant for internal and external use. They are available in crystalline or amorphous form. The particle size of powder plays an important role in physical, chemical and biological properties of the dosage forms. There is a relationship between particle size of powder and dissolution. absorption and therapeutic efficacy of drugs.
Advantages of Powders
(1) Powders are one of the oldest dosage form and are used both internally and externally.
(2) Powders are more stable than liquid dosage form.
(3) It is convenient for the physician to prescribe a specific amount of powdered-medicament depending upon the need of the patient.
(4) The chances of incompatibility are less as compared to liquid dosage form.
(5) The onset of action of powdered drug is rapid as compared to other solid dosage form, e.g, tablets, capsules or pills. Due to smaller particle size of powder, it get dissolved easily in body fluids. This rapid dissolution increases the blood concentration in the shorter time and hence the drug action is produc a shortest period.
(6) Large quantity of powdered drugs can be easily administered to the patient orally by dissolving or mixing the powder in a suitable liquid.
(7) Small children and elderly patients cannot swallow solid dosage forms, such as, tablets and capsules. They can easily take the powdered drug as such or dispersed in water or any other liquid.
(8) Powders are more economical as compared to other solid dosage form, because these are prepared extemporaneously without involving any special machinery and techniques. (9) Powders are more easy to carry than the liquid dosage forms.
Disadvantages of Powders
(1) Drugs having bitter, nauseous and unpleasant taste cannot be dispensed in powdered form.
(2) Deliquescent and hygroscopic drugs cannot be dispensed in powder form.
(3) Drugs get affected by atmospheric conditions are not suitable for dispensing in powder forms.
(4) Quantity less than 100 mg or so, cannot be weighed conveniently on dispensing balance.
Preparation of compound powder
Compound powders: Compound powders contain two or more than two substances which are mixed together and then divided into desired number of individual doses which are dispensed into each powder paper.
Example - Dispense eight powders
Rx Aspirin-300 mg
Paracetamol 150 mg
Caffeine - 50mg
Make a powder
Direction: One powder to be taken when need arises.
Method: Powdered all the ingredients and weigh the calculated quantity of each ingredient. Mix them in ascending order of their weight. Weigh 500 mg of the mixed powder for each powder. Wrap each dose in individual powder paper & then packed.
4. Write notes on
(i) Suppositories
Ans.
Suppositories are solid dosage form of medicament for insertion into body cavities other than mouth. They may be inserted into rectum, vagina or nasal cavity. Preparation of Suppositories: The suppositories are prepared by any of the following methods:
(i) Rolling method
(ii) Hot process or fusion method
(iii) Cold compression method
(i) Rolling method: It is an ancient method of preparing the suppositories. The suppository base is rolled and then desired shape is given with the hand. The method is not used nowadays.
(ii) Hot process or fusion method : This method is commonly used in the preparation of suppositories for dispensing purpose. The suppository base is melted, the medicament is incorporated in it and filled in lubricated mould. On cooling, suppositories are formed which are removed from the suppository mould.
Suppository mould: The suppository mould of various types and sizes are available in the market for commercial use. In dispensing, the suppository mould having 6-12 cavities, with desired shape and size may be used. These moulds are generally made up of stainless steel, nickel copper alloy, brass, aluminium or plastic.
The suppository mould can be opened longitudinally by removing the screw in the centre of the plates. The mould is opened at the time of cleansing, lubrication and removal of suppositories. The mould is cleaned by removing the plates and immersed in hot water containing detergent. After washing with water, the mould is dried thoroughly. Then the lubricant is applied. Every care should be taken, so that the inner surface of the cavities of the mould do not have any scratch, otherwise suppositories with uneven surface will be produced.
Lubrication of mould: The lubrication of the suppository mould id essential in case cocoa butter, or glycero-gelatin base is used for the preparation of suppositories.
Calibration of the mould:
Generally a standard mould of one gram capacity is used. The caibration of the mould is necessary, because the size of the suppository from a particular mould remains the same, but the weight varies. This is due to the reason that density of different bases and medicaments are differed. So the mould should be calibrated for individual base and medicaments. This is done by preparing a set of suppositories using the base, weighing the and then find the average mean which will indicate the true capacity of the mould.
Displacement values:
The volume of a suppository from a particular mould is uniform but its weight will vary because the densities of the medicaments usually differ from the density of the base with which the mould was calibrated. To prepare the suppositories of uniform and accurate weight, allowance must be made for the change in density of the mass due to added medicaments. For this purpose, the displacement value of the medicament is taken into consideration. Displacement value is defined as "The quantity of the drug which displaces one part of the base"
(iii) Cold compression method:
The method is useful for thermolabile and insoluble drugs because heating and stirring of the base with medicamant is not required. The various steps involved in this method are as under;
(a) Cocoa butter is grated, the ingredients are mixed with an equal quantity of grated cocoa butter. Add the remaining amount of grated cocoa butter. While calculating the amount of cocoa butter to be incorporated with the medicaments, allowances are made for unavoidable wastage during the preparation.
(b) The compression of the prepared mass is done on hand or power-operated compression machines. The prepared mass is placed in a cylinder `C' and forced through a narrow opening O' by means of a piston `p' into a mould. The threads of mass passing into mould 'G' are compressed until a homogeneous fused mass is formed. On the removal of retaining stop plate 'S' the suppositories are ejected by further pressure.
Moulds are of different sizes and contain several cavities. The mass and the compressioncylinder of the machine may be chilled to prevent heat of compression from making the mass too fluid. The method is not suitable for suppositories in which glycero-gelatin base or any other base in which melting is essential for its preparation.
(ii) Dentrifices
Ans.
Dentifrices are the preparations meant to be applied to the teeth with a tooth brush for the purpose of cleaning the accessible surface of the teeth. Dentifrices are used in the following cases :
(i) Cleaning of tooth
(ii) Polishing of the tooth
(iii) Removal of strains from the teeth
(iv) reduce incidence of tooth decay (v) Reduction of mouth odours.
(vi) Reductionof periodontal disease (disease of the gum)
(vii) prevention of formation of removal of dental plaque.
(viii) Prevention of formation of calculus
The common dentifrices are available in the form. of tooth powders, tooth pastes and liquid preparations.
Qualities of a Good Dentifrice :
Tooth paste or tooth powder should the following qualities:
(i) It should be economical
(ii) It should be non-toxic
(iii) It should be properly sweetened and flavoured.
(iv) it should give fresh and clean sensation.
(v) it should be efficient in removing food substances, plaque and other foreign particles. (vi) It should clean the teeth. In the formulation of dentifrices the following ingredients are used :
(i) Abrasives:
these are also known as polishing agents and are used to remove debris and residual strains from the teeth surface without damaging it..
(ii) Binders: Binders are used to keep the solids and liquids in the united form and to maintain the consistency. The commonly used binders are gum tragacanth, sodium alginate, methyl cellulose, etc.
(iii) Detergents: These are surface active agents which are used to enhance the action of abrasives.
(iv) Flavouring agents: There are included in the preparation to impart flavour to the preparation.
(v) Humectants: These are used in tooth paste to retain moisture and will not allow the paste to become dry.
(vi) Preservatives: The preservatives are included in dentifrices formulation to prevent the growth of bacteria in tooth paste.
(viii) Sweetening agents: These are included in dentifrices to impart sweet taste to the preparation. Saccharin in the ratio of 0.005 to 0.25% is the most commonly used sweetening agent for this purpose.
(viii) Therapeutic agents: These are included only in medicated tooth pastes in order to check dental diseases and to remove bad smell. The commonly used therapeutic agents are antibiotics, fluorides, proteolytic enzymes inhibitors, crystal growth inhibitors, chlorophyll and essential oils etc.
Method of Preparation:
Tooth powders are prepared in big blending and mixing tanks. The solid ingredients are weighed and mixed thoroughly in ascending order of their weights. Flavoring agents are sprayed during the course of mixing.
The stainless steel containers are used while preparing tooth paste. A mixture of binder and humectant is dispersed in a liquid containing saccharin and preservative. It is then allowed to swell to form a homogenous gel. The homogenous gel is then pumped into suitable mixing tank. Add slowly the abrasive agent with agitation in order to form a smooth and uniform paste. Flavouring agent and detergent is then incorporated. Tooth pastes are finally packed in collapsible tubes.
Types of Dentifrices :
(a) Liquid dentifrices: These preparations are not much popular, but still they are used for tooth cleaning purpose.
(b) Tooth powders: These are oldest, cheapest and simple preparations meant for cleaning the teeth.
(c) Tooth pastes: These are most popular and widely used preparations for cleaning the teeth. 5.
5. What do you mean by diffusible and indiffusible suspensions? Write the dispensing method for mixtures containing diffusible solids.
Ans.
Suspensions Containing Diffusible Solids : There are certain insoluble powdered substances which are light in weight and readily mix with water and remain suspended throughout the liquid for sufficient long time after shaking. Such substances are known as diffusible solids. For example, calcium carbonatem light magnesium carbonate, magnesium trisilicate, rhubarb powderand light kaolin. General method of dispensing :
(i) Carefully tare the container.
(ii) Finely powder the solid ingredients.
(iii) Mix the insoluble powders in a mortar and add enough vehicle to make a smooth cream.
(iv) Add more of vehicle to make it pourable.
(v) Examine the suspension carefully and if it contains foreign particles, strain through a muslin cloth into a tared container.
(vi) Rinse the mortar and pestle with successive volume of vehicle until they are quite clean. Transfer the rinsings to the bottle.
(vii) Add any liquid ingredient.
(viii) Add more of vehicle to produce the required. volume and mix thoroughly by shaking the bottle.
Suspensions Containing Indiffusible Solids :
Indiffusible solids are those substances which do not dissolve in water and do not remain evenly distributed in the vehicle for sufficient long time to ensure uniformity of dose.
Example:
Used Externally
Calamine
Hydrocortisone
Sulphur precipitated
Zine oxide
Used Internally
Aspirin
Aromatic chalk powder
Chalk
Phenobarbitone,
sulphadimidine,
succinyl
sulphathiazole
General method of dispensing (using compound tragacanth powder) :
(i) Finely powder all the ingredients.
(ii) Mix them together in a mortar and add compound tragacanth powder.
(iii) Measure 3/4th of the vehicle and triturate to form a smooth cream.
(iv)Examine the suspension carefully and, if it contains any foreign particles, strain through a muslin piece into a tared bottle.
(v) Rinse the mortar with small quantity of vehicle to clean it. Transfer the rinsings to the bottle.
(Vi) Add any liquid ingredients.
(vii) Add more of the vehicle to produce the required volume.
6. Describe the method of preparation of parenteral liquids.
Ans.
Parenteral preparations are those pharmaceutical products that are given by other than oral routes. Transfusion fluids and injections are parenteral preparations. Injections are the sterile solutions or suspension of drugs in aqueous or oily vehicle meant for introduction into the body by means of an injectable needle under or through one or more layers of the skin or mucous membrane. Injections should be sterile, isotonic and free from foreign particles, such as dust, fibres etc. They should be introduced through the same route for which they are intended. For example, an oily suspension meant for intramuscular injection may be very dangerous if it is administered by intravenous injection.
Processing of Parenteral Preparation :
The following steps are involved in the processing of parenteral preparations;
(i) Cleaning of containers, closures and equipment
(ii) Collection of materials
(iii) Preparation of parenteral products
(iv) Filtration
(v) Filling the preparation in final containers
(vi) Sealing the containers
(vii) Sterilisation
(viii) Evaluation of parenteral preparations
(ix) Labelling and packaging.
(i) Cleaning of containers, closures and equipment: All the containers, closures and equipment which are required during the preparation of parenteral products are thoroughly cleaned with detergents and washing is done with tap water, followed by clean distilled water and finally rinsed with water for injection. Rubber closures are washed with hot solution of 0.5% sodium pyrophosphate in water. The closures are then removed from the solution, washed with water followed by rinsing with filtered water for injection. On a small scale washing is done manually but on a large scale automatic washing machines are used.
(ii) Collection of materials: The various ingredients of the formulation of parenteral preparations are weighed and collected in the preparation room. The raw materials required in the preparation of parenteral products should be pure. Water for injection free from pyrogens and microorganisms are used in the preparation of parenteral products.
(iii) Preparation of parenteral products: The pharmacist should decide the order of mixing and exact method of preparation to be followed before preparing the enteral products. The parenteral preparations must be prepared under strict aseptic conditions. The ingredients are accurately weighed separately and dissolved in the vehicle as per method of preparation to be followed.
(iv) Filtration: The parenteral solution so formed is passed through bacteria proof filter, such as. filter candle, seitz filter, membrane filter, and sintered glass filters. The primary objective of filtration is to clarify the solution by removing foreign particles. If the parenteral preparations are required to be sterilised by means of bacteria proof filters. filtration should be done under strict aseptic condition to avoid contamination of filtered solution, before it is finally transferred into final container and sealed.
(v) Filling the preparation in final containers: The filtered product is filled into final containers such as, ampoules, vials and transfusionbottles. which are previously cleaned and dried. Ampoules are used for filling single doses whereas, vials are used for filling multidoses. Bottles are meant for filling transfuson fluids. On small scale, filling is done manually by using hypodermic and needle. On large scale, filling is by automatic filling machine.
The sterile powders are filled into containers bby individual weighing or by using automatic or semi automatic devices. The filling operation is carried out under strict aseptic precautions.
During the filling of ampoules, the care should be taken that the solution should be filled below the neck of ampoules and the solution should not touch the neck of the ampoules. This will prevent cracking and staining of the neck of ampoules at the time of sealing.
(vi) Sealing the containers: Sealing should be done immediately after filling. Ampules are sealed manually on a small scale by rotating the neck of the ampule in the flames of Bunsen burner. But on a large scale ampoule sealing machine is used in which tip of ampoule is fused to seal it. The vials and transfusion bottles sra sealed by closing its opening with a rubber closures. The rubber closures are held in place by crimping the aluminium caps which is done manually or by mechanical means.
(vii)Sterilisation: The parenteral preparations should be immediately sterilised after sealing in its final containers. The sterilisation is done by any one of the methods of sterilisation which depends on the nature of medicament(s) present in parenteral preparations.
For thermostable medicament, the parenteral products are sterilised either by autoclaving at a temperature of 115°C to 116°C for 30 minutes or 121°C for 20 minutes or in hot air oven at 160°C for two hours. The thermolabile preparations are sterilised by filtration through a suitable bacteria-proof filters. Parenteral preparations which are sterilised by filtration method may contain a suitable bacteriostatic agent to prevent the growth of microorganisms. When the solutions are used for intravenous or intrathecal injection in doses exceeding 15 ml, the becteriostatic agent should not be used. The sterilised product is filled into the final containers and sealed. The process of filtration, filling and sealing are done under aseptic conditions.
7. Write notes on.
(i) Ointment base
Ans.
The ointment base is that substance or part of an ointment, which serves as carrier or vehicle for the medicament. An ideal ointment base should possess the following properties:
(i) It should be inert, odourless and smooth.
(ii) It should be physically and chemically stable.
(iii) It should be compatible with the skin and with the incorporated medicaments.
(iv) It should be of such a consistency that it spreads and softens when applied to the skin with stress.
(v) It should not retard healing of the wound.
(vi) It should not produce irritation or sensitisation of the skin.
Classification of Ointment Bases:
(i) Oleaginous bases
(ii) Absorption bases
(iii) Emulsion bases
(iv) Water soluble bases
(i) Oleaginous bases: These bases consist of water insoluble, hydrocarbons, vegetable oils, animal fats and waxes. The constituents of hydrocarbon bases are soft paraffin, hard paraffin and liquid paraffin.
(a) Petrolatum (soft paraffin): It is a purified mixture of semi-solid ydrocarbons obtained from petroleum. There are two varieties of soft paraffin, one is yellow soft paraffin and other is white soft paraffin. White soft paraffin is prepared by bleaching yellow paraffin. Both these soft paraffin have melting point 38°C to 56°C. White soft paraffin is used when the medicament is white or colourless. White soft paraffin is never used in the preparation of ophthalmic ointments because the white soft paraffin may contain small traces of bleaching agent which are generally left over after bleaching the yellow soft paraffin. Hence, the white soft paraffin may cause irritation to the eye.
(b) Hard paraffin: It is a purified mixture of solid hydrocarbons obtained from petrolatum. It is colourless or white translucent, odourless, tasteless wax like substance. It is used to harden or soften the ointment base.
(c) Liquid paraffin: It consists of a mixture of liquid hydrocarbons and obtained from petroleum by distillation. It is also known as white mineral oil or liquid petroleum. It is a colourless, odourless, tasteless and transparent oily liquid. It is soluble in ether and chloroform but insoluble in water and alcohol. It is used along with hard paraffin and soft paraffin to get a desired consistency of the ointment. The oleaginous bases are losing their importance nowadays for the following reasons:
(i) They are greasy.
(ii) They are sticky and are difficult to remove both from skin and clothing
(iii) They retain body heat which may produce an uncomfortable feeling or warmth.
(iv) They do not help in the absorption of medicamants. (v) They prevent drainage on oozing areas and also prevent evaporation of cutaneous secretions along with perspiration.
(ii) Absorption bases: These bases are generally anhydrous substances which have the property of absorbing (emulsifying) considerable quantities of water but still retaining their ointment-like consistency. The absorption bases are of two types:
(a) Non-emulsified bases
(b) Water in oil emulsions
The non-emulsified bases absorb water and aqueous solutions producing w/o emulsions e.g., wool fat, wool alcohol, beeswax and cholesterol. The water in oil emulsions are capable of absorbing more water and have the properties of non-emulsified bases e.g., hydrous wool fat (lanolin)..
(i) Wool fat: It is the purified fat-like substance obtained from the wool of sheep. It is also known as anhydrous lanolin. It can absorb about 50% of its weight of water. So it is used in ointments where the proportion of water or aqueous liquids to be incorporated in hydrocarbon base is too large. It is an important constituent to simple ointment base and eye ointment base.
(ii) Hydrous wool fat: It is the purified fat like substance obtained from wool of sheep. It is also known as lanolin. It is insoluble in water but soluble in ether and chloroform. Hydrous wool fat is a mixture of 70% w/w wool fat and 30% w/w/ purified water. It is used alone as emollient and as an ingredient of several other ointments
(iii) Wool alcohol: It is obtained from wool fat by treating it with alkali and separating the fraction containing cholesterol and other alcohols. It contains not less than 30% of cholesterol. It is used as an emulsifying agent for the preparation of w/o emulsion. It is also used to improve the texture, stability and emollient properties. of o/w emulsions.
(iv) Beeswax: It is purified wax obtained from honey comb of bees. It is available as yellow beeswax and white beeswax. White beeswax is obtained by bleaching the yellow beeswax. It is used as a stiffening agent in pastes and ointments. These bases have following advantages:
(i) These bases are compatible with large number of medicaments.
(ii) These bases can absorb a large quantity of water of aqueous substances.
(iii) These bases are relatively heat stable.
(iv) These bases may be used in their anhydrous form or in emulsified form.
These bases are quite greasy, but these can be easily removed from the skin as compared to oleaginous bases.
(iii) Emulsion Bases: These bases are semisolid or have a cream like consistency. Both o/w and w/o emulsions are used as ointment base. The oil in water type of emulsion bases are more popular because these can be easily removed from the skin or clothes by washing with water. The w/o type of bases are greasy and sticky. The emulsifying ointment is prepared from emulsifying wax, white soft paraffin and liquid paraffin.
(iv) Water Soluble Bases: These are commonly known as "greaseless ointment bases". The water soluble bases consist of water soluble ingredients, such as, polyethylene glycol polymers which are popularly known as "carbowaxes". The carbowaxes are water soluble, non-volatile and inert substances. Depending upon the mlecular weight, carbowaxes are available in different consistencies i.e.. liquids, liquids, semisolids and solids. Their molecular weight varies from 200 to 8000. By mixing different carbowaxes, ointments of varying consistencies can be obtained.
Tragacanth, gelatin, pectin, cellulose derivatives, bentonite, magnesium-aluminium silicate and sodium alginate are also used as water soluble bases.
(ii) Physical incompatibility
Ans.
Physical incompatibility:
When two or more than two substances are combined together, a physical change take place and an unacceptable product is formed. Physical incompatibility is usually due to immiscibility, insolubility, precipitate formation or liquefaction of solid materials. These changes which occurs as a result of physical incompatibility are usually visible and can be easily corrected by applying the pharmaceutical skill to obtain a product of uniform dosage, an attractive appearance and having satisfactory therapeutic activity. The physical incompatibilities may be corrected by using any one or more of the following methods:
(i) Change the order of mixing of ingredients of the prescription
(ii) Emulsification
(iii) Addition of suspending agent
(iv) Change in the form of ingredients
(v) By addition, substitution or omission of therapeutically inactive substance to help in compounding of the prescription.
Examples of Physical Incompatibilities and Their Methods of Correction :
(i) Immiscibility: Oils and water are immiscible with each other. They can be made miscible with water by emulsification.
Example:
Rx
Castor oil 15ml
Water upto 60ml
Make an emulsion
In this prescription castor oil is immiscible with water. To overcome this incompatibility an emulsifying agent is used to make a good emulsion.
(ii) Insolubility: Insolubility means the inability of material to dissolve in a particular solvent system. The majority of physical incompatibilities are due to insolubility of the inorganic as well as organic compounds in a particular solvent.
The liquid preparation containing indiffusible solids such as chalk, aromatic chalk powder, acetyl salicylic acid, phenacetinzinc oxide and calamine etc. a suspending agent may be incorporated, so as to increase the thickness of the preparation.
Example:
Rx
Phenacetin 3gm
Caffeine 1gm
Orange syrup 12ml
Water upto 90ml
Make a mixture
In this prescription phenacetin is an indiffusible substance. Compound powder of tragacanth or mucilage of tragacanth is used as a suspending agent to make a stable suspension.
(iii) Precipitation: A drug in solution may be precipitated, if the solvent in which it is insoluble is added to the solution e.g., resins are insoluble in water. When tincture containing resinous matter is added in water, resin agglomerates forming indiffusible precipitates. This can be prevented by slowly adding the undiluted tincture with vigorous stirring to the diluted suspension or by adding some suitable thickening agent.
Example: Prepare and dispense 100 ml of the following lotion.
Rx
Tincture benzoin compound 5.0ml
Glycerin 15.0ml
Rose water upto 100ml
Tincture benzoin compound contain resins. The change in solvent system results in an unavoidable precipitate. Addition of tincture with rapid stirring yields a fine colloidal dispersion. So there is no need of any suspending agent.
(iv) Liquefaction: When certain low melting point solids are mixed together, a liquid or soft mass known as 'eutectic mixtures' is produced. This occurs due to the lowering of the melting point of mixture to below room temperature and liberation of water of hydration. Many chemicals form hydrates, compounds with water of crystallisation, that are stable at room temperature or normal humidity. But these compounds will tend to release their water of hydration under the influence of increasing temperature or decreasing humidity. The medicaments showing this type of behaviour are camphor, menthol, thymol, phenol, chloral hydrate and aspirin. These types of substances create problems when they are dispensed in powder form. These substances can be dispensed by any one of the following methods:
(a) triturate together to form liquid and mixed with an absorbent like light kaolin or light magnesium carbonate to produce free flowing powder.
(b) The individual medicament is powdered separately and mixed with an absorbent and then combined together lightly and filled in suitable containers.
Example
Rx
Menthol 5gm
Camphor 5gm
Ammonium chloride 30gm
Light magnesium
carbonate 60gm
Make an insufflation.
In this prescription menthol, camphor and ammonium chloride get liquefied on mixing with each other. To dispense this prescription, mentho, camphor and ammonium chloride are triturated together to form liquid. Add light magnesium carbonate and mix it thoroughly to make free flowing powder.
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