Historical Background, Dosage Forms, Prescription and Posology

 Chapter 1

Historical Background, Dosage Forms, Prescription and Posology

History of Pharmacy 

• Origin and Development of Pharmacy

• Pharmacy (from the Greek pharmakon' = drug) is the health profession that links the health sciences with the chemical sciences, and it is charged with ensuring the safe and effective use of medication.

• It was in 9th century in the civilized world around Baghdad that the profession of pharmacy started acquiring shape. It slowly spread to Europe as alchemy and finally developed into chemistry. The artisans of Mesopotamia, Egypt and China carried out the first known chemical process. However, in the 19th century it completely sprouted out from medicine and started developing as a separate profession. This happened only when the role of pharmacist as a compounder of medicines were identified and differentiated from physician whose role was accepted as the therapist. The practice in those times was restricted to compounding, dispensing medication, and manufacturing medicaments in bulk lots not for general sale. The medicament commonly produced was simple elixirs, spirits, and powders in contrast to the complex pharmaceutical remedies of the present era.

Pharmacy as a Career 

• Pharmacy (from the Greek 'pharmakon' = drug) is the health profession that links the health sciences with the chemical sciences, and it is charged with ensuring the safe and effective use of medication.

• Scope of Pharmacy.

• The scope of pharmacy practice includes more traditional roles such as compounding and dispensing medications, and it also includes more modern services related to patient care, including clinical services, reviewing medications for safety and efficacy, and providing drug information.

• Types of Pharmacy Practice Areas

• Pharmacists practice in a variety of areas including retail, hospitals, clinics, nursing homes, drug industry and regulatory agencies. Pharmacists can specialize in various areas of practice including hematology/oncology, infectious diseases, nutrition support, drug information, critical care, pediatrics, etc.

• Wholesale Pharmacy

• It offers opportunities to a limited number of pharmacists to run wholesale business of drugs and medicines. The wholesalers serve as an intermediary between manufacturer and retailer.

• Industrial Pharmacy

• Pharmaceutical industry offers opportunity to pharmacist of all educational levels. It provides job to a pharmacist in the following fields:

• I Production 

• II. Analytical and Quality Control

• III Research and Development and New drug discovery IV. Medico-marketing and sales clinical trials V. Clinical Trials. 

Introduction to Pharmacopoeia 

 Pharmacopoeia 

• Derived from Greek words 'Pharmakon' means drug and 'Poeia' means to make. The books containing the standards for drugs and other related substances are known as pharmacopoeias and formularies. Collectively these books are known as Drug Compendia.

Compendia

• The pharmacopoeias contain a list of drugs and other related substance regarding their source, descriptions, tests, formulae for preparing the same, action and uses, doses, storage conditions etc. It is a legal and official book issued by recognized authorities usually appointed by Government of each country. These books are revised from time to time as to introduce the latest information available as early as possible after they become established.

• Classification

• The drug compendia are classified as: 

(1) Official compendia. 

(2) Non-official compendia.  

 

Indian Pharmacopoeia 

• The development of IP was started with an aim to promote public health by bringing out authoritative and officially accepted standards for quality of drugs including active pharmaceutical ingredients, excipients, dosage forms and medical devices for use by health professionals, patients and consumers.

• In pre-independence days, British Pharmacopoeia was used in India. In 1946 Government of India issued one list known as 'The Indian Pharmacopoeia list' which was used as supplement to British Pharmacopoeia. Committee under chairmanship of Sir R. N. Chopra along with other nine members prepared 'The Indian Pharmacopoeia list'. It was prepared by Department of Health, Government of India, Delhi in 1946. In 1948 Government of India appointed an Indian Pharmacopoeia committee for preparing 'Pharmacopoeia of India'. Tenure of this committee was five years. In 1955 first edition of Indian Pharmacopoeia committee under chairmanship of Dr. B. N. Ghosh was published. 

British Pharmacopeia 

• First edition of BP was published in 1864. It consists of two sections: Part I: Materia Medical and Part II: Preparation and compounding. Second edition of BP was published in 1867. Third edition of BP was published in 1884. Fourth edition of BP was published in 1898. Next edition of BP was published in 1914. Next edition of BP was published in 1953. In this edition titles of drugs and preparations were in English instead of Latin and metric system. It has been published annually. In BP 2007 monographs has been introduced for material specifically used in preparation of Traditional Chinese medicines. BP 2008 contains approximately 3100 monographs for substances, preparations and articles used in practice. It has been made effective from 1st January 2008. BP 2007, 2008, 2009 were given in six volumes i.e. volume I to volume VI. Volume I and II contains medicinal substances. 

United State Pharmacopoeia 

• The United States Pharmacopoeia and National Formulary (USP-NF) is an official public standards-setting authority for all prescription and over-the-counter medicines and other health care products manufactured or sold in the United States. USP also sets recognized standards for food ingredients and dietary supplements. These standards help to ensure the quality, purity, strength, and consistency of products made for public consumption. USP's standards are recognized and used in more than 130 countries around the globe. USP's work is aided by the participation and oversight of volunteers representing pharmacy, medicine, and other health care professions as well as academia, government, the pharmaceutical and food industries, health plans, and consumer organizations. The United States Pharmacopoeia was originally published in 1820 under the authority of the United States Pharmacopoeia Convention and the National Formulary was published in 1888 under the guidance of American Pharmaceutical Association. In 1974 the National Formulary was purchased by the United States Pharmacopoeia Convention and from 1980 onwards only one official book of drug standards was published under the heading, The United States Pharmacopoeia and The National Formulary (USP-NF). The United States Pharmacopoeia-National Formulary (USP-NF) 2009 is a book of public pharmacopoeia standards. 

Extra Pharmacopoeia

• The Extra Pharmacopoeia was first produced in 1883 by William Martindale and is still known as "Martindale". This is an authorized reference book on drugs and is used throughout the world. It provides all sorts of latest information on drugs and medicines. The Extra Pharmacopoeia is prepared by consulting the pharmacopoeias of other countries. The twenty-eighth edition was published in December 1982. The twenty-ninth edition was published in January 1989, by direction of the council of The Royal Pharmaceutical Society of Great Britain and prepared in the Society's Department of Pharmaceutical Sciences. Martindale contains information on drugs in clinical use worldwide, as well as selected investigational and veterinary drugs, herbal and complementary medicines, pharmaceutical excipients, vitamins and nutritional agents, vaccines, radiopharmaceuticals, contrast media and diagnostic agents, medicinal gases, drugs of abuse and recreational drugs, toxic substances, disinfectants and pesticides. 

Introduction to Pharmaceutical Dosage Form

• Dosage forms are the safe, effective and stable terms in which medication will be delivered into the body. Dosage forms are essentially pharmaceutical product which are marketed for use typically involving a mixture of active drug components and excipients (non-drug components). These dosage forms are classified in a number of ways as mentioned below by which drug molecules are delivered to the site of action. 1. Form wise: (0) Solid dosage form (ii) Liquid dosage form (iii) Semi-solid dosage form 2. Route wise: (0) Oral dosage form (ii) Topical dosage form (iii) Parenteral dosage form 3. Release rate: (1) Sustained release (ii) Prolonged release (iii) Controlled release (iv) Targeted drug delivery. 

Prescription

• A prescription is a legal document or order written by a qualified health care professional for diagnosis, prevention or treatment of a specific patient's disease. Is written by a licensed practitioner Is written as part of a proper physician-patient relationship Is a legal document, "prima facie" evidence in a court of law. (Note: A prima facie case is a lawsuit that alleges facts adequate to prove the underlying conduct supporting the cause of action and thereby prevail.)

Definition

• Literally, "Recipe" means simply "Take..." and when a medical practitioner writes a prescription beginning with "Rx", he or she is completing the command. It is probably originally directed at the pharmacist who needed to take a certain amount of each ingredient to compound the medicine (rather than at the patient who must take/consume" it).

Parts of the Prescription 

• 1. Date 2. Patient Information 3. Superscription 4. Inscription 5. Subscription 6. Signa 7. Signature lines, signature, degree, brand name indication 8. Prescriber information 9. DEA (Drug enforcement administration) if required 10. Refills 11. Warnings/Labe.

 Date

• All prescriptions expire after one year. In case of narcotics and other habit-forming drugs, the date prevents the misuse of the drugs by the patient. It helps a pharmacist to know when the medicine was last dispensed if the prescription is brought for redisposing...

Handling of Prescription 

• The following procedures should be adopted by the pharmacist while handling the prescription for compounding and dispensing:

• (1) Receiving.

• (ii) Reading and checking.

• (iii) Collecting and weighing the materials.

• (iv) Compounding, labelling and packaging

Sources of Errors in Prescriptions 

Abbreviation:

•  In most of the prescriptions abbreviated terms are used by the prescriber that leads to major errors during interpretation by the pharmacists. For example: 'SSKI' is the abbreviated term of 'Saturated Solution of Potassium Iodide'. It is preferable to avoid these types of misleading abbreviations.

• Abbreviation used in Prescription.

Name of the drugs:

• Names of some drugs (especially the brand names) either looks or sounds alike. So any error in the name of a drug will lead to major danger to the patient. e.g. Altronic - Entronix, Aidin - Abidin etc.

Strength of the preparation:

• Drugs are available in the market in various strengths. So a drug must not be dispensed if the strength is not written in the prescription. For example, Paracetamol tablet 500 mg should not be dispensed when no strength is mentioned in the prescription.

Dosage form of the drug prescribed:

•  Many drugs are available in more than one dosage forms e.g. liquid, tablets, injections or suppositories. The dosage form intended for the patient must be mentioned in the prescription to reduce ambiguity. 5. Dose: If unusually high or low dose is mentioned in the prescription then it must be consulted with the prescriber. Sometime a sustained release (SR) dosage form is prescribed thrice or more times daily. Actually, Sustained Release dosage forms should be given once or twice a day.

Instructions to the patient:

• Sometimes the instruction for a certain preparation is either omitted or mentioned partially. The quantity of the drug to be taken, the frequency and timing of administration and route of administration should be mentioned clearly so that it is easy for patients to take medicine.

 Incompatibilities:

•  It is essential to check that there is no pharmaceutical or therapeutic incompatibilities in the prescription. If more than two medicines are prescribed then it is the duty of the pharmacist to see whether their interactions will produce any harm to the patient or not. Certain drugs has interactions with food. The pharmacist has to advise the patient about it. For example: Tetracycline should not be taken with milk or antacid. 

Posology 

• The word posology is derived from the Greek words 'pesos' meaning how much and 'logos' meaning science. So posology is a branch of medical science which deals with dose or quantity of drugs which can be administered to a patient to get the desired pharmacological actions.

Factors Affecting Posology 

• The following are some of the factors which influence the dose.

Age:

•  The pharmacokinetics of many drugs changes with age. So while determining the dose of a drug, the age of an individual is of great significance. Children and old people need lesser amount of drug than the normal adult dose, because they are unable to excrete drugs to that extent as adults. Children can tolerate relatively larger amounts of belladonna, digitalis and ethanol, whereas elderly patients are more sensitive to some drug effects. For example, hypnotics and tranquillizers which may produce confusion states in them.

Gender:

• Women do not always respond to the action of drugs in the same manner as it is done in men. Morphine and barbiturates may produce more excitement before sedation in women. Special care should be taken when drugs are administered during menstruation, pregnancy and lactation. There are certain drugs which on administration to the mother are capable of crossing the placenta and affecting the fetus e.g. alcohol, barbiturates, narcotic and non-narcotic analgesics etc. 

Formulae used in Calculations of Pediatric Dose

•  Clark's formula:

• Child's dose = weight in (lbs)/150 x

• Adult dose Child's dose = weight in (kg)/70 x adult dose 

•  Dilling's formula:

• Used for calculating dose of child from 12-20 years of age. 

• Child's dose = Age in years /20 x Adult dose.

•  Fried's formula

•  Used for calculating dose of an infant upto 24 months of age.

• Young's formula: 

• Used for calculating dose of child from 1-12 years of age.

• 5. Cowling's formula:

•  Child's dose = Age at next birthday/24 x Adult dose

• 6. Bastedo's Formula: 

• Child's dose = Age in Years/ 30 x Adult dose

• 7. Calculation based on body surface area: 

• Child's dose = body surface area of the child/1.73 sq. m x Adult dose  Child dose = Age in years/Age + 12 x Adult dose