PHARMACOLOGY
MPH/BSC/MED EDUC’/PHARM
(Complete NOTES)
Learning Objectives
By the end of this Module, the learners should be able to administer
... [Show More] drugs professionally to patient’s.
INTRODUCTION TO PHARMACOLOGY
• Definition of terms:
Pharmacology is the study of effects of chemical substances on the function of living systems.
pharmacology is the science of drugs which includes their preparation, use and effects.
It is also the science that deals with the origin, chemistry, effects and uses of drugs.
Pharmacy: Branch of health science that deals with preparation and dispensing of drugs.
pharmacotherapy: The study of therapeutic uses and effects of drugs.
Terminology
Pharmacognosy: the study of drugs that come from natural sources
e.g. plants, animals and minerals as well as search for new drugs from natural sources.
Pharmacokinetics :this is the study of the body acts on the drugs; it is characterized by absorption, distribution,
metabolism(biotransformation)and excretion/elimination. It can further be described as how the body handles a drug from site of
administration to the site of action and elimination.
Pharmacodynamics/mechanism of action: the study of how drugs act on the body.
Terminologies Cont…
Pharmacogenetics: the study of the effects that genetics have on an individuals response to drugs.
Contra-indication: A health condition/ state that will prelude the administration of a drug e.g. aspirin is contraindicated in peptic ulcer disease.
Half life or half time (t1/2):Time taken for plasma concentration to fall by half following its elimination in the body.
Terminologies Cont…
• Toxicology: This branch of pharmacology which deals with the an desirable effects of chemicals on living systems from individual cells to complex body systems.
• Drug: Any substance used in diagnosis, cure, treatment and prevention of disease/condition or any substance that brings a change in biological functions through its chemical actions. The term drug, medication, and medicine are used synonymously.
Terminologies Cont…
Drug interactions :effects produced when some drugs are given concurrently.
Desired therapeutic effect: This should indicate the mechanism of action of a drug e.g.an analgesic is for pain relief, accompanied by central nervous system depression inhibition of inflammation, neutralization of acid in the stomach, vasodilation in angina or muscle relaxation.
Placebo: Any component of therapy that is without specific biological activity
e.g. inactive substance such as normal saline or distilled water usually used in clinical trials research and for psychological treatment.
Drug Reactions and Interactions
Any physiologically active drug has the potential to cause an undesirable reaction that may induce illness in the recipient. These include toxic reaction, side effects, allergic reactions, cumulative reaction, tolerance and dependence and detrimental drug reaction.
• Side effects: these are physiological effects exerted by the chemicals that are not related to the desired therapeutic effects. you must therefore be familiar with serious side effect and commonly occurring effects.
• Adverse drug reaction: this an injury occurring by taking medication .It may occur following a single dose or prolonged administration of a drug or result from a combination of two or more drugs. The study of ADR is known as pharmacovigilance.
Drug reactions and Interactions Conti….
• Drug interaction: this is when an interactant chemical modifies the therapeutic results that are anticipated with a drug the interact may be another drug, some combination of a drug, natural or artificial components in the diet, pollutants chemical from the environment, endogenous body chemicals and Chemicals used for diagnostic laboratory test. Drug interaction may be detriment or beneficial drug and may vary from one person to another. This may affect the absorption, distribution ,metabolism or excretion of the drugs.
• Allergic reactions: This the body's immunological response to a drug following previous exposure to the same drug.
Drug reactions and Interactions Conti…..
• Idiosyncratic reactions: this is genetically determined, un expected response to a drug. The response may take the form of extreme sensitivity to low doses or extreme insensitivity to high doses to the drug.
• Chain reaction: Medication are often added to a regime to control side effects of other drugs. This can initiate a chain reaction e.g. cortisone is prescribed to treat a serious inflammatory condition it can cause hypertension, ulcers, diabetes and a reactivation of arrested tuberculosis.
• Cumulative reaction: Drugs accumulate in the body whenever the dosage exceeds the amount the body can eliminate through metabolism or excretion
• Tolerance and dependence: Tolerance occurs when a person no longer responds to the drug in the way that person initially responded as a result of continued use of the drug causing a need to increase dose of a drug to achieve the same effect.
Drug reactions and Interactions Conti….
• There three basic types of tolerance.
metabolic /pharmacokinetics tolerance this occurs due to increased metabolism
of a drug leading to reduction in drug concentration at the receptor site.
cellular/pharmacodynamic tolerance this caused by adaptive changes that take
place at the receptor site or drug action site.
cross tolerance when tolerance to one drug confers tolerance to another drug. Drugs that have the same chemical structure tend to portray cross tolerance e.g. people tolerance to one barbiturates are usually tolerant to all barbiturates e.g., phenobarbital, thiopental. However drugs of similar class can also portray cross-tolerance.
• Intolerance: low threshold to normal pharmacological response. A drug causes an exaggeration of a normal pharmacological response e.g. morphine may cause coma instead of respiratory distress which occurs with administration of a normal dose.
Drug reactions and Interactions Conti…..
• Dependence: A state arising from repeated periodic or continuous administration of a drug that results in harm to the individual or sometimes society. People feel desire or compulsion to continue using the drug and feel ill if abruptly withdrawn or an antidote is used. Substance that cause dependence are taken to induce a good feelings or avoid discomfort of their absence.
Types dependence:
a. psychological dependence: usually first to appear, where the individual
have a craving for the effect the drug produces motional distress like fear, anxiety and irritability occur when the drug is withdrawn.
b. Physical dependence: this dependence is usually defined in terms of
withdrawal/abstinence syndrome that are physical in nature e.g. tremors, ataxia, shivering.
Drug reactions and Interactions Conti…..
• Iatrogenic responses: these are responses produced an intentionally during the cause of treatment e.g. penicillin may cause hepatic toxicity, steroid may cause Cushing's syndrome.
• Anaphylaxis: A sudden serious life threating allergic reaction and should be treated as a medical emergency, it causes more than one of the following ; an itchy rash throat and tongue swelling, shortness of breath ,vomiting, lightheadedness and low blood sugar.
Drug development
• After a chemicals that has shown therapeutic value has been identified, it must undergoes a series of scientific test to evaluate its actual therapeutic and toxic effects. The process is controlled by legally established bodies e.g. pharmacy and poisons board and food & drug administration (FDA)development IN Kenya and USA respectively. Before receiving legal approval to be marketed to the public ,drugs must pass through several sequential stages of development.
Pre-clinical trials: this phase involves testing the drug on laboratory animals to test their pharmacodynamics, pharmacokinetics and toxicology. The toxicity studies include mutagenic, carcinogenic and reproductive studies.
Drug Development Conti….
Phase I: clinical pharmacology
This is first phase human volunteers, usually 20-50 (healthy volunteers or volunteer patients depending on the class of drug and its safety)are used to test the drug. Pharmacodynamics and pharmacokinetics era tested. Toxicity and therapeutic effects are further tested.
Phase II: therapeutic exploration
Tests are done on patients who have the disease usually 100-200 patients are involved in the study. Pharmacodynamics and pharmacokinetics era determined as well as dosing requirements and efficacy of the drug at the given dose
Phase III: Therapeutic confirmation
The drug is used on Avast clinical market 300-3000 patients are involved. Prescriber observes patients closely for drug adverse effects and therapeutic effects.
Drug Development Conti….
Phase IV: continuous evaluation
the prescribers are expected to report to the regulatory bodies any unexpected effects which then evaluates this information. A drug may be withdrawn from the market if it produces toxic effects e.g. thalidomide.
• Orphan drug : drugs that have been discovered but are not financially viable and therefore have not been adopted by any drug company. may be useful in treating a rare disease or may have potentially dangerous adverse effects. They are often abandoned after preclinical trials or phase I studies. [Show Less]