UNIT 2 SOLID AND LIQUID DOSAGE FORMS

Transcription

1 UNIT 2 SOLID AND LIQUID DOSAGE FORMS Solid and Liquid Structure 2.1 Introduction Objectives 2.2 Solid Tablets Capsules 2.3 Liquid Advantages of Liquid Disadvantages of Liquid Classification of Liquid Monophasic Liquid Biphasic Liquid 2.4 Summary 2.5 Terminal Questions 2.6 Answers 2.1 INTRODUCTION The previous chapter has given an idea about the different kinds of dosage forms available and also about its packing. The present chapter gives an account of the solid dosage forms and various liquid dosage forms. Crude extracts and powdered drugs can be administered as such for treating diseases. But this has got many disadvantages like susceptible to microbial attack, poor solubility and poor acceptability by the patient due to unpleasant taste and odour. So it is necessary to design dosage forms that are convenient and acceptable for administering drug to patient. Let us first study about solid dosage form. Objectives After studying this unit, you should be able to: discuss solid dosage form; explain advantages and disadvantages of solid dosage form; discuss liquid dosage form; explain advantages and disadvantage of liquid dosage form; and classify liquid dosage form. 25

2 Pharmaceutics 2.2 SOLID DOSAGE FORMS The solid dosage forms commonly used in olden days, are cachets, pills, moulded tablets, etc. Cachets are wafers made up of rice flour; powders are enclosed in these wafers and sealed so that their taste can be masked. These are less widely used due to some disadvantages like difficulty in swallowing. Moulded tablets are powders moulded into tablets. These are cylindrical or circular disc shaped. Usually drugs that require only fewer doses are made into this form. These are also seen very rarely nowadays. Pills are widely used before the introduction of the tablets. The medicament mass is rolled into pipe of uniform thickness and it is cut into suitable sizes. Then it is rounded by using a pill rounder, usually it is spherical or ovoid in shape. Later by the introduction of tablets and capsules all the above forms are largely replaced by them Tablets Fig.2.1: Solid dosage form 26 Tablets are solid dosage form in which one usual dose of the drug has been accurately placed (Fig. 2.2). They are the most popular form of medication. They come in different sizes and shapes. Size varies from a few mm to a cm. It depends upon the quantity of medicament. Medicines in tablet have some advantages and some disadvantages. Let us discuss them separately.

3 Solid and Liquid Advantages Fig.2.2: Tablets Tablets have following advantages: i) It is easy to administer a correct dose. Here there is no need of any measurement of the dose. The dose is accurately placed in a rigid compact form. ii) Their cost is lowest of all oral dosage forms. The price for the tablet is low when compared to other dosage forms. iii) It is a stable dosage form. The tablets are very stable to various physical conditions. iv) It is convenient to carry. The tablets can be packed in convenient and user friendly light weight and easy to carry packages.. v) It is easy to swallow. It is easy to swallow with a draught of water. Disadvantages Tablets have some disadvantages also i.e. i) Some powders cannot be compressed into tablets. ii) Geriatric and paediatric patients find difficulty in swallowing tablets. Types of tablets There are different types of tablets. Some of them are given below: a) Tablets that disintegrate readily when swallowed, these tablets have rapid absorption. These tablets do not have any coating. They are uncoated tablets. b) Lozenge tablets: Lozenges are solid dosage form that do not disintegrate readily and are intended to dissolve slowly in the mouth. They produce a local action on the throat. 27

4 Pharmaceutics c) Solution tablet: These tablets have to be dissolved in water for administration. It can be used either externally or by injection. d) Chewable tablet: These tablets are chewable in the mouth and are not intended to be swallowed. e) Buccal tablets: These are placed in the buccal pouch. Here they dissolve or disintegrate slowly and is absorbed directly without passing into alimentary canal. f) Sublingual tablet: These are placed under the tongue. Here they dissolve or disintegrate slowly and is absorbed directly without passing into the alimentary canal. g) Implants: These tablets are placed under the skin by means of a minor surgical operation and are slowly absorbed. Coated Tablets Some medicaments that are compressed into tablets are coated with sugar or a film made from a suitable polymer. Accordingly they are called sugar coated and film coated tablets. The coating is done because of: To provide physical and chemical protection to the drug To improve the appearance To mask the unpleasant taste / colour / colouration of the drug Method of Preparation The medicament is compressed along with some additives. Additives or excipients are added for easy compression. The additives used are a) Diluents: These are added to increase the bulk of the medicament for easy compression e.g. lactose. b) Lubricants: They are added to increase the flow property of the powder e.g. talc. c) Glidants: They are added to increase the flow property of the powder e.g. talc. d) Disintegrants: These are added to disintegrate the tablet into small parts e.g. starch. e) Colouring agents: They give colour which improves the appearance of the product e.g. amaranth. f) Flavorings agents: They are added to impart flavour e.g. mint. g) Sweetening agents: They give sweetness to the product e.g. sucrose. 28 The compression of the powder into tablet is carried out by tablet making machine. Hand operated tablet machines and rotary tablet machines for large scale manufacturing are available.

5 Packaging of Tablets In the olden days tablets are packed in amber coloured glass bottle, jar or vial. It is inconvenient to carry as it is bulky. This is very susceptible to crushing while transportation and hence adequate protection was required. Later packing in a single row in a narrow tube sealed with a plug type plastic closure was employed. Modern method of tablet packing includes strip or blister packs. Solid and Liquid Fig.2.3: Strip packing i) Strip pack: The tablets are hermetically sealed within strips of aluminium or plastic foil (Fig. 2.3). The tablet can be removed from this pack by tearing or cutting. This method is attractive, hygienic and is suitable for large scale production. Fig.2.4: Blister packing ii) Blister pack: The film enclosing the tablet is formed into a blister. The tablet can be removed by pressing on the blister and force the tablet through the backing strip. This is also attractive, hygienic and suitable for large scale production. On completion of this section you would come to know about the following aspects. SAQ 1 Fill in the blanks: a) Tablet triturates are prepared by moulding powder into. b) The compression of powder into tablet is carried out by. c) tablets are placed in the buccal pouch. d) are placed under the skin by means of a minor surgical procedure. 29

6 Pharmaceutics SAQ 2 What are the solid dosage forms commonly used in the olden days before the introduction of tablets? SAQ 3 What are the different types of tablets? Capsules Capsules are solid dosage form in which the drug substance is enclosed in water soluble shell or an envelope (Fig.2.5). They are in water soluble shell because it can dissolve. Capsule shell is made up of gelatin. Gelatin is a protein obtained from animal collagen. The capsules are available in eight sizes. The size is designated as numbers from 000 (largest) to 5 (smallest) and capsule capacities vary accordingly i.e. Fig.2.5: Capsules Capsule No: Content mg:

7 Solid and Liquid Fig.2.6: Capsule sizes On the basis of their shell capsules are classified as i) hard gelatine capsule and ii) soft gelatin capsules. Advantages i) They mask the taste and odour of unpleasant drug. ii) They are attractive in appearance. iii) They are slippery when moist, hence easy to swallow. iv) Less additives are necessary for the preparation when compared to tablet. v) It provides rapid and uniform release of medicament in the gastro intestinal tract. vi) The shell can be coloured to give protection from light. vii) They protect the medicament from air and moisture due to very fine limits of the shell. viii) The capsule shell is physiologically inert, easily and quickly digested in the gastro intestinal tract Disadvantages i) The drugs that absorb moisture cannot be filled in the capsule. ii) It is expensive. There are two types of capsules: hard and soft gelatin capsules. Hard Gelatin Capsules The capsule shell of hard gelatin capsule consists of two parts, a body and a cap. They are cylindrical in shape (Fig. 2.7). The medicament of these capsules is in the form of powder or granules. These capsules are sealed after filling. Fig.2.7: Hard gelatin capsules 31

8 Pharmaceutics Soft Gelatin Capsules These capsules shell is a single unit. They are round, oval, pear or tube shaped (Fig. 2.8). The medicament of these capsules is in the form of liquid or paste. The soft gelatin capsules are round, oval, pear or tube shaped. Unlike hard gelatin capsules, their shell is a single unit. The soft gelatin capsules are most suitable for liquids semi-liquids and also for vitamins and multivitamins. Liquid medicines with unpleasant taste and odour can be conveniently administered in soft capsules. Ointments that are used in the eye are frequently packed in unit dose tube shaped soft capsules. The filling and sealing of capsules are combined operation. Manufacturing of capsules Fig.2.8: Soft gelatin capsules The capsules can be filled either by hand or by a semi-automatic device or by automatic filling machine. A rotary capsule filling machine is used for large scale preparation of soft gelatin capsules. SAQ 4 Fill in the blanks: a) A capsule shell is made from. b) The shell can be to give protection from light. c) The contents of hard gelatin capsules are in the form of. SAQ 5 What are the advantages of capsule? 32

9 2.3 LIQUID DOSAGE FORMS Liquid dosage forms are either monophasic or biphasic. A monophasic liquid dosage form is one which contains only one phase. That is, it is a true solution (Fig. 2.9). A true solution is a homogenous mixture of solid, liquid or gas in a liquid. A biphasic liquid dosage form contains two phases. Solid and Liquid Fig.2.9: Liquid dosage forms Advantages of Liquid i) They are the most suitable dosage form for infants, children and geriatric patients. ii) The unpleasant taste of the drugs can be masked by adding sweetening and flavouring agents. iii) It is attractive in appearance and gives beneficial psychological effects. iv) The drug is rapidly available for absorption Disadvantages of Liquid i) The liquid dosage forms have less stability when compared to solid dosage forms. ii) It is bulky to carry. iii) A spoon is needed to administer a dose. iv) Accidental breakage of the container results in loss of whole dosage form Classification of Liquid Liquid dosage forms are broadly classified into two groups: a) Monophasic liquid dosage forms b) Biphasic liquid dosage forms 33

10 Pharmaceutics Monophasic Liquid It is the simplest form of presenting medication for rapid absorption of the drug. It is a one phase system consisting of two components, solute and the solvent. The component that get dissolved is called a solute and the medium in which solute dissolves is called a solvent. The monophasic liquid dosage form are broadly classified into four groups. Each one can be further classified into different groups as shown below: Monophasic Liquid Oral use External use Special use Parenteral Use Mixtures Lotions Gargles Elixirs Liniments Mouth washes Syrups Collodions Throat paints Linctuses Nasal drops & sprays Draughts Douches Drops Enemas A. Oral Used Preparations Eye drops Eye lotions Ear drops Inhalations Aerosols There are six different types of orally used preparations i.e. mixtures, elixirs, syrups, linctuses, draughts and drops. Let us studies them separately. i) Mixtures A mixture is a liquid preparation meant for oral administration in which a medicament or medicaments are dissolved or suspended in a suitable liquid. They should be freshly or recently prepared and used fairly quickly, usually within a month. They are mainly prescribed for short term therapy like cough, diarrhoea, constipation etc. Mixtures are further classified into five different groups i.e. a) Simple mixtures containing soluble substances: It contains only soluble ingredients. 34 b) Mixtures containing diffusible solids: Diffusible solids are those which do not dissolve in water, but may be mixed by shaking. As a result it is evenly distributed throughout the liquid for sufficient time.

11 c) Mixtures containing indiffusible solids: Indiffusible solids are those which are not soluble in water and do not remain uniformly distributed in the solvent for sufficiently long time. So we have to add a substance to suspend (suspending agent) these particles in the solvent. Solid and Liquid d) Mixtures containing precipitate forming liquids: Some mixture contains liquids that get precipitate when mixed with water. This precipitate will stick to the sides of the bottle and is difficult to distribute uniformly. So we have to add a suspending agent. e) Mixtures containing slightly soluble liquids: Some liquids contains insoluble portion which is not distributed uniformly. Here also we have to add a suspending agent. ii) Elixirs Elixirs are clear, flavoured, sweetened, hydroalcoholic preparations for oral administration. They are more stable than mixtures. Elixirs are classified into two classes. a) Non medicated elixirs: These elixirs do not contain any medicament but contain some aromatic or pleasantly flavoured substances. These are used as solvents for other liquid preparations. b) Medicated elixirs: These elixirs contain some medicinal substance along with other ingredients. iii) Syrups Syrups are liquid oral preparations in which the vehicle is a concentrated solution of sucrose or other sugars in water. The concentration of sugar in syrup is 66.7 % W/W. Syrups are further classified into 2 classes. a) Simple syrups: The simple syrups do not contain any medicament, but contains some pleasantly flavoured substances. These syrups are used as a medium for other liquid preparations. b) Medicated syrups: These syrups contain some medicinal substance along with other ingredients. Advantages of syrups Syrups prevent oxidation and decomposition of drugs. Syrups are sweet in taste and therefore bitter taste of drugs can be reduced. Disadvantages of syrups Syrups are not preferred for diabetic patients. On continuous take syrup promote dental decay. 35

12 Pharmaceutics iv) Linctuses Linctuses are defined as viscous oral liquids containing one or more medicament dissolved in a vehicle that usually contains high proportion of sucrose or other sugars. They are used in the treatment or relief of cough. It must be sipped slowly in small doses. This gives maximum and prolonged effect of medicament in the throat. The usual dose is 5ml. v) Draughts Draughts are liquid oral preparations, which contain only one or two large doses. Each dose is supplied in separate bottle. vi) Drops Drops are liquid preparations meant for paediatrics. Generally vitamins and antibiotics are given in the form of draughts. It must be supplied along with a dropper. B. Externally Used Preparations They are of three types: i) Lotion Lotions are fluid preparations for external applications. They are rubbed on the skin without friction. It has a cooling, soothing and protective action. ii) Liniments Liniments are viscous liquid preparations for external application. It is applied to the unbroken skin with friction and rubbing. Liniments should never be applied to broken skin because they cause irritation. They are used for relieving pain. iii) Collodions Collodions are fluid preparations for external use. They are applied with a brush or rod. After applying on the skin the vehicle evaporates and leaves a protective film covering the site. They are of two types. a) Un-medicated: It contains no medicament and is used for protecting small cuts and wounds. b) Medicated: It contains medicament. C. Specially Used Preparation There are 11 different types of specially used preparation which are discussed below: i) Gargles 36 They are aqueous solution used to prevent or treat throat infections.

13 ii) Mouth wash These are preparations used to cleanse and deodorize the buccal cavity. They are very refreshing to bed-ridden patients. Solid and Liquid iii) Throat paints Throat paints are viscous liquid preparations used for mouth and throat infections. They are applied with the help of a brush. Nasal drops and sprays. iv) Nasal drops and sprays Nasal drops are solutions of drugs that are instilled into the nostrils with the help of a dropper. Nasal sprays are the same preparations as nasal drops but instilled into the nostrils in the form of a spray. v) Douches Douches are aqueous solutions used to cleanse deodorize, soothe or medicate wounds, body orifices or cavities. vi) Enemas Enemas are preparations intended for introducing in the rectum for cleansing therapeutic or diagnostic purposes. It is used to evacuate faeces in constipation or before an operation. vii) Eye drops Eye drops are sterile preparations for instilling into the eye. It is supplied with a dropper. viii)eye lotions Eye lotions are sterile aqueous solutions used for washing the eye. It is generally used to remove foreign substances from the eye. ix) Ear drops They are medicated solutions to be instilled into the eye with the help of a dropper. It is used for cleaning and for treating the infections. x) Inhalations They are preparations containing volatile substances. They are used to relieve congestion and inflammation of the respiratory tract. They are added to hot water and the vapours are inhaled. xi) Aerosols Aerosols are liquid preparations dissolved in a solvent. The solvent is a gas. It is delivered in the form of a spray. It is mainly used for treating asthma and also for migraine. 37

14 Pharmaceutics D. Parenteral Solutions (Injections) Parenteral solutions are sterile drug solutions intended for administration by injections. Injections can be intravenous, intra muscular; intra dermal etc., skilled persons are required for the administration of injections Biphasic Liquid Biphasic liquid dosage form is one which contain two phases i.e. emulsions and suspensions. Biphasic Liquid Suspensions Emulsions A. Suspensions Suspensions are biphasic liquid dosage forms in which finely divided solid particles are dispersed in a liquid. It consists of two phases, a disperse phase and continuous phase. The solid particles act as disperse phase whereas liquid acts as a continuous phase. The medicaments that are insoluble or poorly soluble are formulated as suspensions. Suspensions contain a suspending agent. A suspending agent is a substance that is added to the preparation to suspend the insoluble particles in the preparation. It can be classified into four groups. a) Oral suspensions: These suspensions are to be consumed by oral route. b) Parenteral suspensions: The suspensions which are administered by parenteral route are called parenteral suspensions. c) Ophthalmic suspensions: These are used for instilling into the eye. d) Suspensions for external use: These are used for external applications. Packing of Suspensions Suspensions can be packed in narrow mouth screw caped colour less plain bottle. Suspensions that are very thick require a container with wide mouth. Suspensions should be stored in a cool place. B. Emulsions An emulsion is a biphasic liquid preparation containing two immiscible liquids one of which is dispersed as minute globules into the other. When two immiscible liquids are in contact there exists a separating surface. Vigorous shaking is necessary to break one liquid into small globules in the other. But this condition is only temporary and separate quickly on standing. Example is the mixture of oil and water. So we can add a third substance to distribute one liquid in the other with out the formation of a separate layer. This substance is 38

15 called an emulsifying agent and the product is called an emulsion. There are two types of emulsion. Solid and Liquid Medicines having an unpleasant taste and order can be made more palatable for oral administration in the form of an emulsion. Emulsions protect drugs against oxidation or hydrolysis. Emulsions are less stable. They are susceptible to microbial growth. Packing of Emulsions Emulsions can be packed in narrow mouth screw caped colourless plain bottle. Emulsions that are very thick require a container with wide mouth. Emulsions should be stored in a cool place. a) Oil in water type: This type of emulsion is the one in which the oil is dispersed in the water b) Water in oil type: This type of emulsion is the one in which the water is dispersed in the oil. Emulsions may be liquid or semi-solid. Liquid emulsions can be classified as i) emulsions for oral administration, ii) emulsion for external uses, iii) emulsion for parenteral uses, and iv) emulsion for rectal use. i) Emulsions for oral administration Some medicaments are unpleasant in taste. For example fish liver oil, we can mask this unpleasant taste by converting it into an emulsion and can be given orally. ii) Emulsions for external use The external preparation of emulsion consists of three classes. Applications, lotions and liniments, these emulsions can be either oil in water or water in oil. iii) Emulsions for parenteral use Some patients are unable to ingest food in the normal way. We can administer oil in water emulsions of nutritive oils and fats to these patients. Vitamin K that prevents blood clotting is injected in this form. iv) Emulsions for rectal use Some emulsions are given by rectal route. Semi-solid emulsions are water in oil or oil in water type. The water in oil type semi-solid emulsions are oily creams while the oil in water semi-solid emulsions are aqueous creams. Creams are easy to apply and are less greasy. 39

16 Pharmaceutics SAQ 6 Fill in the blanks: a) Liquid dosage form is most suitable for &. b) Drug is absorbed by liquid dosage forms. c) Monophasic systems mean, systems containing only one. d) Syrups are concentrated solutions of and other sugars in water. e) Elixirs are clear, flavoured, sweetened liquid preparations. f) Drops are liquid dosage forms meant for. g) Linctuses are used in the treatment or relief of. h) Gargles are used for & infections. i) are refreshing to bed ridden patient. j) & sterile aqueous solutions for instillation into the eye. k) are sterile aqueous solutions used for irrigation or washing the eye. l) Parental preparations are given in the form of. SAQ 7 Write advantages of liquid dosage form? 2.4 SUMMARY In this unit we have discussed the following points in details. The solid dosage forms commonly used in olden days, are cachets, pills, moulded tablets, etc. 40 Moulded tablets are powders moulded into tablets

17 Tablets are solid dosage form in which one usual dose of the drug has been accurately placed Solid and Liquid There are different types of tablets like Lozenge tablets, Solution tablet, Chewable tablet, Buccal tablets, Sublingual tablet and Implants The medicament is compressed along with some additives. Additives or excipients are added for easy compression Modern method of tablet packing includes strip or blister packs. Capsules are solid dosage form in which the drug substance is enclosed in water soluble shell or an envelope On the basis of their shell capsules are classified as i) hard gelatine capsule and ii) soft gelatine capsules Liquid dosage forms are either monophasic or biphasic. A monophasic liquid dosage form is one which contains only one phase Liquid dosage forms are broadly classified into two groups (i) Monophasic liquid dosage forms, (ii) Biphasic liquid dosage forms Monophasic Liquid dosage forms can be classified in to different four groups, i.e., Oral used preparation, External used preparation, Special used preparation and Parenteral used preparation Biphasic Liquid can be classified into two different groups, i.e. Suspensions and Emulsions 2.5 TERMINAL QUESTIONS 1. What are the disadvantages of tablets? 2. Differentiate hard and soft gelatin capsule? 3. Distinguish lotion and liniment. 4. What are draughts? 5. What is Suspension? 6. What are the classifications of emulsion? 7. Match the Following: i) Lotion : a) Concentrated solution of sucrose in water ii) Parenteral : b) Apply without friction iii) Syrups : c) Less stable iv) Mixtures : d) Administer in the form of injection 41

18 Pharmaceutics 2.8 ANSWERS Self Assessment Questions 1. a) Tablets b) Tablet making machine. c) Buccal d) Implants 2. The solid dosage forms commonly used in olden days, are cachets, pills, moulded tablets, etc. (Refer section 2.2.) 3. There are different types of tablets like Lozenge tablets, Solution tablet, Chewable tablet, Buccal tablets, Sublingual tablet and Implants 4. a) Gelatine b) Coloured c) Powder 5. Main advantages of the capsule are: i) They mask the taste and odour of unpleasant drug. ii) They are attractive in appearance. iii) They are slippery when moist, hence easy to swallow. iv) Less additives are necessary for the preparation when compared to tablet. v) It provides rapid and uniform release of medicament in the gastro intestinal tract. vi) The shell can be coloured to give protection from light. vii) They protect the medicament from air and moisture due to very fine limits of the shell. viii) The capsule shell is physiologically inert, easily and quickly digested in the gastro intestinal tract, a) Paediatrics & Geriatrics b) Rapidly c) Phase d) Sucrose e) Hydroalcoholic f) Paediatrics g) Cough h) Mouth & Throat i) Mouthwashes j) Eyedrops

19 k) Eye lotions l) Injectons Solid and Liquid 7. Main advantages of the liquid dosage forms are: i) They are the most suitable dosage form for infants, children and geriatric patients. i) The unpleasant taste of the drugs can be masked by adding sweetening and flavouring agents. ii) It is attractive in appearance and gives beneficial psychological effects. iii) The drug is rapidly available for absorption. Terminal Questions 1. Tablets have some disadvantages also i.e. i) Some powders cannot be compressed into tablets. ii) Geriatric and paediatric patients find difficulty in swallowing tablets. 2. Hard gelatin capsule shell is consists of two parts, a body and a cap. They are cylindrical in shape. The medicament of these capsules is in the form of powder or granules. Soft gelatin capsules shell is a single unit. They are round, oval, pear or tube shaped. The medicament of these capsules is in the form of liquid or paste. 3. Lotions are fluid preparations for external applications. They are rubbed on the skin without friction. It has a cooling, soothing and protective action. Liniments are viscous liquid preparations for external application. It is applied to the unbroken skin with friction and rubbing. 4. Draughts are liquid oral preparations, which contain only one or two large doses. Each dose is supplied in separate bottle. 5. Suspensions are biphasic liquid dosage forms in which finely divided solid particles are dispersed in a liquid. It consists of two phases, a disperse phase and continuous phase. 6. Liquid emulsions can be classified as i) emulsions for oral administration, ii) emulsion for external uses, iii) emulsion for parenteral uses, and iv) emulsion for rectal use. 7. Match the following: i) (b) ii) (d) iii) (a) iv) (c) 43