UNIT 1  INTRODUCTION TO                                                                                                                            Introduction to 
                                         PHARMACEUTICS                                                                                                             Pharmaceutics 
               Structure 
               1.1 Introduction 
                Objectives 
               1.2         The Prescription  
               1.3 Posology 
                           Dosage Calculation for Children 
                           Calculation of Doses for Adults 
               1.4 Dosage Forms 
                           Need for Dosage Forms 
                           Classification of Dosage Forms 
                           Additives in Dosage Forms 
                           Some Commonly used Dosage Forms   
               1.5         Packaging of Dosage Form 
                           Types of Container  
                           Material for Construction of Containers 
               1.6       Summary 
               1.7       Terminal Questions 
               1.8       Answers 
               1.1 INTRODUCTION                                                          
               Pharmaceutics is the area of study concerned with the formulation, 
               manufacturing stability and effectiveness of pharmaceutical dosage form. In 
               the previous unit various communicable, non-communicable disorders were 
               described. In this unit we will study how the drugs are administered in the body 
               to be effective. Drugs are rarely used alone. They are used as a part of a 
               formulation with other non-drug substances. These non-drug substances or 
               additives serve specific function. The drugs presented in the dosage form are 
               given in a specific quantity i.e. dose for a specific period. These dosage forms 
               are available in various forms as required for a specific disease condition. 
               Packaging of dosage form is another important aspect as the dosage form 
               should not degrade during storage. A good packaging is necessary to protect 
               the drug component from any type of deterioration till it reaches the consumer. 
               In this unit, we will describe the prescription, methods to calculate the dose of 
               drug, various types of dosage forms and packaging materials used for 
               pharmaceuticals. 
               Objectives 
               After studying this unit, you should be able to: 
               •     explain prescription and its various parts;                                                                                                                      5
                                                  
            Pharmaceutics                        •    describe various types of dosage form; and 
                                                 •    describe the need of packaging and various packaging materials used. 
                                                  
                                                 1.2 THE PRESCRIPTION           
                                                 A prescription is a medication order written by a doctor, dentist or a veterinary 
                                                 surgeon for the supply of a medicine, dressing or a surgical instrument to a 
                                                 patient. A prescription contains the following parts. 
                                                 i)     Prescribers office information 
                                                 ii)    Information about patient or patient information 
                                                 iii)  Date 
                                                 iv)  Superscription or Symbol Rχ 
                                                 v)     Inscription 
                                                 vi)  Subscription 
                                                 vii)  Signature or Signa 
                                                 viii) Prescriber’s signature, and license No. 
                                                 ix)  Special labelling, refill and other instructions 
                                                 Let us discuss each of these separately. 
                                                 i)      Prescribers Office Information 
                                                         This part of the prescription is generally printed and it contains the name 
                                                         of the hospital, department and also the name of the prescriber. 
                                                 ii) Patient Information 
                                                         Patient information is necessary for identification purpose. Full name and 
                                                         address, age and sex of the patient must be written on the prescription. 
                                                         For a child, the age is very important as it helps in checking the dose of 
                                                         drug. If the patient’s full name and address is not written on the 
                                                         prescription then pharmacist should ask the patient about these particular, 
                                                         to avoid any possibility of giving products to any other patient. 
                                                 iii) Date 
                                                         Date on the prescription is written by the prescriber when it is written and 
                                                         also when they are received and filled in the pharmacy. The date on the 
                                                         prescription helps a pharmacist to find out the time lapse between the 
                                                         time of writing the prescription and when it is brought for filling. In case 
                                                         of unusual time lapse the pharmacist can question if the intention of the 
                                                         prescriber on the need of the patient can still be met. 
                                                 iv)     Superscription or Rχ Symbol 
                                                         The superscription is represented by symbol Rχ. R is an abbreviation for 
                                                         the Latin word recipe meaning take though and letter j is an invocation to 
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                        Jupiter, the God of healing so Rχ is combination of both meaning you                                                                      Introduction to 
                        take.                                                                                                                                      Pharmaceutics 
               v) Inscription 
                        This is the main part of the prescription. It contains the names and 
                        quantities of medicaments to be supplied. The medicaments may be 
                        prescribed as an official preparation or as a proprietary product together 
                        with the quantity required. The medicament may also be sometimes 
                        prescribed as a special formula in which the quantities of each ingredient 
                        is given together with the type of preparation e.g. a solution, emulsion or 
                        ointment etc. The prescriptions orders requiring the pharmacist to mix 
                        ingredients are known as compounded prescriptions. 
               vi) Subscription 
                        This part of prescription consists of directions to the pharmacist for 
                        preparing the prescription. These may include the dosage form to be 
                        prepared and the number of doses to be dispensed. But now-a-days in 
                        majority of the prescriptions, the subscription serves merely to give 
                        directions about the dosage form and the number of doses to be supplied.  
               vii)  Signature or Signa 
                        This part of the prescription consists of directions for the patients. These 
                        directions are also to be placed on the label. It usually indicates the 
                        quantity of medicament or number of dosage units to be administered or 
                        applied. How much time in a day or what time to be administered or 
                        applied. The diluent if required or the means of application (e.g. brush). 
               viii)  The Prescriber’s Signature, License Number 
                        The name and signature of prescriber authenticate the prescriptions and 
                        avoids danger of dispensing of a spurious prescription. 
               ix)      Special labelling and other instructions 
                        The number of refills should be indicated on each prescription by the 
                        prescriber. 
                
               1.3 POSOLOGY  
               Posology deals with the dose or quantity of drug which is administered to 
               produce the therapeutic action.  
               Dose of a drug is the amount of a medicinal preparation or of radiation to be 
               administered at one time. 
               Dosage 
               Determination of the amount, frequency and number of doses of medicine to be 
               given to a particular patient.                                                                                                                                         7
                                        
         Pharmaceutics                 1.3.1   Dosage Calculation for Children 
                                       Various rules for calculating infant’s and children’s dosages are used. All of 
                                       these methods give approximate dosage. Children are sometimes more 
                                       susceptible than adults to certain drugs. 
                                       The following rules are used for calculation of doses for infants and children. 
                                       1.  Young’s Rule (for Children 2 to 12 years) 
                                                          Child dose =     Age in years    ×Adult dose 
                                                                        Age in years +12
                                       2.  Clark’s Rule (for Children below 2 years) 
                                                         Child's dose = Weight in pounds ×Adult dose 
                                                                                150
                                       3.  Fried’s Rule for infants up to 2 years 
                                                          Infant's dose = Age in months ×Adult dose   
                                                                                150
                                       4. Dilling’s Formula  
                                           Child's dose= Age in years +3×Adult dose 
                                                                              30
                                       5. The square meter surface area method is more reliable method of 
                                           relating dosage. This method relates the surface area of individual to dose 
                                           of drug. 
                                         Child's dose = Body surface area of child×Adult dose 
                                                                       Body surface area of adult
                                                                                                                          2
                                       The average body surface area for an adult is taken as 1.73 sq. meter (m ). 
                                       Hence, 
                                                                Body surface area of child (m2)
                                                  Child dose   
                                                              =                1.73                ×Adult dose 
                                       1.3.2  Calculation of Doses for Adults 
                                       Many physiological functions such as metabolic rate and kidney functions are 
                                       proportional to body surface area. The dose for some drugs may be given as the 
                                                          2
                                       amount of drug/m  body surface area. In such cases the dose for an individual 
                                       may be calculated as follows: 
                                                                                       2                            2
                                              Individual’s dose = Amount of drug/m  × Body surface area in m  
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