At the end of presentation learners will be able to:
- Discuss the terminologies related to pharmacology
- Discuss the history of pharmacology briefly
- Identify the purposes of medication
- Identify the source of medication
- Discuss the classification of drugs
- Describe the three type of drug supply system.
- Discuss the drugs standards and legislation.
- Identify resource to collect and utilize drug information.
- Learn to prepare drugs cards
- Definition: Pharmacology is the science that deals with the study of drugs and their interaction with the living systems.
- The word Pharmacology is derived from Greek – pharmakon means drug and logos means study.
- In actual use, however, its meaning is limited to the study of the actions of drugs.
- Pharmacology has been defined as “an experimental science which has for its purpose the study of changes brought about in living organisms by chemically acting substances (with the exception of foods), whether used for therapeutic purposes or not.”
- Pharmacology studies the effects of drugs and how they exert their effects.
- There is a distinction between what a drug does and how it acts.
- Thus, amoxicillin cures a strep throat, and cimetidine promotes the healing of duodenal ulcers.
- Pharmacology asks “How”? Amoxicillin inhibits the synthesis of cell wall mucopeptide by the bacteria that cause the infection, and cimetidine inhibits gastric acid secretion by its antagonist action on histamine H2 receptors
Scope Of Pharmacology
- The scope of Pharmacology is rapidly expanding and Provides the rational bases for therapeutic use of drug.
- On the basis of study of drug it is divided into two branches .
Branches of Pharmacology
Basic Pharmacology : the study of drugs in isolated tissues animals and other related living beings such as bacteria and viruses for experimental work is called basic Pharmacology.
- The study of drugs in human beings is called clinical pharmacology.
- The study of drugs in animals for treatment of diseases is also called clinical pharmacology.
General Definition of Drug
- Any chemical agent that is used for diagnosis, prevention, treatment and curement of disease is called drug.
- This disease oriented definition of drug is not applicable to some drugs such as oral contraceptives and general anesthetics etc.
WHO definition of drug
- In 1966 WHO define drug as: “Any agent that is used or intended to be used for the treatment of disease or modifying pathological/physiological condition or to explore pathological/physiological condition is called drug”.
- Drug means any substance which change the physiology of cell tissue, organ, or organism.
- Medicine: Whenever, a drug is formulated into a suitable dosage form for prevention, cure, and diagnose of a disease in a proper dose.
- Dose means the amount of medicine taken
- Dosage form means the physical form of the medicines (solids, liquids, gas etc.)
- Therapeutics: Therapeutics deals with the use of drugs in the prevention and treatment of disease.
- Toxicology: Toxicology deals with the adverse effect of the drug and also the study of poisons, i.e detection ,prevention and treatment of poisoning. (Toxicon =poison in greek.
- Pharmacodynamics means the mechanism by which the drug exerts its effect. For example, how aspirin work as analgesic. What the drug does to the body.
- Pharmacokinetics means the movement of drugs within the body (absorption, distribution, biotransformation, and excretion). What the body does to the drug.
- Over the counter (OTC) medicine: those medicines for which the physician prescription is not required. For examples, analgesics, antacids.
- Analgesic means those medicines which are used for pain
- Antipyretics means those drugs which are used for fever
- Idiosyncratic means unexpected drug reaction
- Teratogenic means harmful effects of drugs on the fetus
- Synergism means when the combination of drugs increase the effect
- Antagonism means when the combination of drugs decreases the effects
- Patient compliance: The extent to which the patient follows
- the clinical prescription
- Pharmacopoeia is an official publication, containing a list of medicinal drugs with their effects and directions for their use.
- BP: British Pharmacopoeia.
- USP: United States Pharmacopeia
- Active ingredient means biologically active substance which produce effect
- An excipient is a pharmacologically inactive substance formulated alongside the active pharmaceutical ingredient of a medication e.g.. Cellulose derivatives
- Purposes served by excipients:
- Provide bulk to the formulation.
- Facilitate drug absorption or solubility and other pharmacokinetic considerations.
- Provide stability and prevent from denaturation.
- Efficacy means maximum effect that a drug can produce regardless of dose.
- Potency means amount of a drug that is needed to produce a given effect
- Bioavailability is the degree to which or the proportion of the drug that is available to the site of action or target tissue to produce the desired effect.
- Half-life (t1/2) is the time taken by the plasma concentration of the drug to decrease by 50%, or reach half of the original concentration. Initially, If a drug has plasma concentration of100 mg/ml and after passing 2 hours it reduces to 50 mg/ml, then the half life would be????..
- Prophylactic agent is any drug that prevents a disease or illness from occurring (vaccines)
A brief history of pharmacology
- Originating in the 19th century, the discipline makes drug development possible.
- Pharmacology is one of the cornerstones of the drug discovery process.
- The birth date of pharmacology is not as clear-cut.
- In the early 19thcentury, physiologists performed many pharmacologic studies.
- François Magendie studied the action of nux vomica (a strychnine-containing plant drug) on dogs, and showed that the spinal cord was the site of its convulsant action. His work was presented to the Paris Academy in 1809.
- In1842, Claude Bernard discovered that the arrow poison curare acts at the neuromuscular junction to interrupt the stimulation of muscle by nerve impulses.
- Pharmacology was held to have emerged as a separate science in 1847, when Rudolf Buchheim was appointed professor of pharmacology at the University of Dorpat in Estonia (then a part of Russia).
- Lacking outside funding, Buchheim built a laboratory at his own expense in the basement of his home. Although Buchheim is credited with turning the purely descriptive and empirical study of medicines into an experimental science, his reputation is overshadowed by that of his student, Oswald Schmiedeberg.
Oswald Schmiedeberg (1838–1921)
- Oswald Schmiedeberg is generally recognized as the founder of modern pharmacology.
- Schmiedeberg obtained his medical doctorate in 1866 with a thesis on the measurement of chloroform in blood.
- In 1872, he became professor of pharmacology at the University of Strassburg, receiving generous government support in the form of a magnificent institute of pharmacology.
- He studied the pharmacology of chloroform and chloralhydrate.
- In 1869, Schmiedeberg showed that muscarine evoked the same effect on the heart as electrical stimulation of the vagus nerve.
- In 1878, he published a classic text, Outline of Pharmacology
- In 1885, he introduced urethane as a hypnotic.
- In the United States, the first chair in pharmacology was established at the University of Michigan in 1890 under John Jacob Abel, an American who had trained under Schmiedeberg.
- In 1893, Abel joined Johns Hopkins University in Baltimore.
- His major accomplishments include the isolation of epinephrine from adrenal gland extracts (1897–1898), isolation of histamine from pituitary extract (1919), and preparation of pure crystalline insulin (1926). His student Reid Hunt discovered acetylcholine in adrenal extracts in 1906.
- Today, there is a pharmacology department in every college of medicine or pharmacy.
Purposes of Medication
Medications can be administered for the following purposes
- Diagnostic Purpose: to identify any disease
- Prophylaxis: to prevent the occurrence of disease e.g. heparin to prevent thrombosis and antibiotics to prevent infections
- Therapeutic Purpose: to treat or cure disease / decrease symptoms, restore normal function or maintain normal function
Essentials of medication order
- The drug order, written by the physician, has 7 essential parts for administration of drugs safely. The nurse should know how to read a drug order. It should have the following components:
- Patients full name.
- Date and time.
- Drug name.
- Route of administration.
- Time and frequency of administration.
- Signature of physician.
Types of Medication Orders
- STAT order: needed immediately
- Single order: given only once
- PRN order: given as needed
- Routine orders: given within 2 hours of being written and carried out on schedule
- Standing order: written in advance carried out under specific circumstances
- Basic principles (Safety) in medication administration3 checks and 7 Rights:
- Right patient
- Right dose
- Right drug
- Right route
- Right time
- Right Frequency
- Right Documentation
Sources of Drugs
- Primitive Medicine: observing the reaction of some animals to particular herbs. Through primitive medicine quinine was discovered from Africa; used for malaria and lime juice for Ascorbic acid/Vitamin C and this is used for scurvy and gum bleeding.
- Plants; Roots, bark, sap, leaves, flowers, seeds were sources for drugs e.g. Digitalis from foxglove, opium from the poppy plant.
- Animal sources; gave us hormones for replacement in times of deficiencies e.g. Insulin from the pancreases of pigs and cattle, Liver extracts for anemia etc
- Minerals; including acids, bases and salts like potassium chloride
- Natural; OCCURRING SUBSTANCES like proteins
- Happy Chance; Discovery is by chance not by any premeditated effort.
- Synthesis of Substances; from natural products in the laboratory.
- Tara V.Shanbhag, Smita Shenoy, Veena Nayak (Pharmacology for Nurses) 2nd Edition