Homework answers / question archive / Week 5 Pharmacology and Classification of Drugs • Pharmacology: the branch of science that deals with the interaction of chemical agents with living organisms • Traditionally, the major concern of pharmacology has been the study of intended for medicinal use, such as drugs used to diagnose, prevent, treat, or cure disease • However, with the introduction of oral contraceptives in the 1950’s, pharmacologist had to revise their definition of a drug • The “pill” was not used in the diagnosis, prevention, treatment, or cure of disease, unless pregnancy was to be considered a disease • The contraceptives caused pharmacologist to revise their definition of a drug

Week 5 Pharmacology and Classification of Drugs • Pharmacology: the branch of science that deals with the interaction of chemical agents with living organisms • Traditionally, the major concern of pharmacology has been the study of intended for medicinal use, such as drugs used to diagnose, prevent, treat, or cure disease • However, with the introduction of oral contraceptives in the 1950’s, pharmacologist had to revise their definition of a drug • The “pill” was not used in the diagnosis, prevention, treatment, or cure of disease, unless pregnancy was to be considered a disease • The contraceptives caused pharmacologist to revise their definition of a drug

Law

Share With

Week 5 Pharmacology and Classification of Drugs • Pharmacology: the branch of science that deals with the interaction of chemical agents with living organisms • Traditionally, the major concern of pharmacology has been the study of intended for medicinal use, such as drugs used to diagnose, prevent, treat, or cure disease • However, with the introduction of oral contraceptives in the 1950’s, pharmacologist had to revise their definition of a drug • The “pill” was not used in the diagnosis, prevention, treatment, or cure of disease, unless pregnancy was to be considered a disease • The contraceptives caused pharmacologist to revise their definition of a drug. • The “pill was not used in the diagnosis, prevention, treatment, or cure of disease, unless pregnancy was to be considered a disease PHARMACOLOGY Because of the pill, pharmacology have revised their definition of drugs to include “all chemicals that affect living process.” This newer definition of seems more appropriate now, especially with the increased use of “street drugs,” many of which never had any intended medical use The science of pharmacology has given rise to three major subdivisions now recognized as special area of study and practice: 1. Psychopharmacology- the study of where and how drugs act in the body, how drugs are changed by the body, and how drug action affects behavior 2. Therapeutics-the use of drugs in treating disease. When drugs are used specifically to destroy or weaken invading organisms, the treatment is referred to as chemotherapy 3. Toxicology-the study of poisons and the treatment of drug poisoning, including intoxication, resulting from the presence of harmful chemicals in the body The Nervous system • To understand the impact of various drugs on the human body, you first must understand the nervous system • People take drugs recreationally to feel good and to alter their consciousness • Consciousness takes place through the nervous system • All drugs are capable of producing more than a single response • Psychoactive drugs or substances have their primary effect on the human nervous • The nervous system is separated into three major divisions • This three divisions are not independent of each other • They interact; they are subsystems of the total system of our body • The three major divisions include the central nervous system, the autonomic nervous system and the peripheral nervous system The Central Nervous System • The central nervous system (CNS) is composed of the brain and spinal cord • The central nervous system is encased in bone • The brain is covered by the skull, and the spinal cord resides with in the vertebral column. • The spinal cord serves as the conduit of information bringing signals to the brain form organs and muscles • In turn, the brain sends messages to motor fiber, which effect change in the activity of gland and muscles Neurotransmitters: The Mediators of the Nervous system • A neurotransmitters is a naturally occurring chemical in the nervous systems which carries electoral impulses between neurons (brain cells) • The brain and peripheral nervous system is comprised of neurons separated by small gaps called “synapses.” • Neurotransmitters act at the synapse to determine the quantity and quality of electrical impulses between neurons (brain cells) • Although there are one hundred chemicals in the brain, no more than about two dozen are probably true neurotransmitters • Research to date indicates that some of these are very important in the development and continuation of drug dependence Neurohormones: the Regulators of the body • A neurohormone is a chemical that is made in a gland, leaves it, and acts on nervous tissue and/or other glands to maintain equilibrium in the body • Many neurohormones are made in the pituitary gland which is located at the base of the brain • The pituitary gland makes hormones which regulate most of the glands in the body. Some of these glands are: thymus, thyroid, pancreas, ovary, testicle, adrenal, and breast. • The pituitary gland also make the neurohormones that are greatly responsible for: pain relief, stress relief, and mental stability Receptor Sites • in 1974, the opioid receptor site was discovered. Opioids include heroin, morphine, codeine, Talwin, Darvon, Dilaudid, Demerol, Methadone, Percodan, fentanyl, and many other chemicals. • When one of these drugs is taken, it goes to the brain and attaches to the opioid receptor sites. • The opioid receptor site is known to help the brain: • Relieve Pain • Promote Mental Stability • Regulate food intake • Produce Euphoria • Control stress • Prevent Depression • Control Breathing Rate How Drugs Enter the Body • In order for a drug to have any more than a superficial effect, such as antacids in the stomach or antidandruff shampoos on the scalp, the chemical agent must enter the blood vascular system • It must be absorbed or transported from the site of administration into the bloodstream, and then distributed by the blood throughout the body • The manner in which the drug is introduced (the route of administration) is an important factor in determining how fast the drug acts, how long its effects will be sustained, the intensity of the drug’s action, and the degree of localization of the drugs action • Drugs can be administered in several ways: • They are usually given orally , rectally, parentally, and by inhalation. • Most commonly drugs are taken into body by way of the mouth • From the mouth, the liquid or solid drug passes into the stomach, and eventually into the intestine where most of the chemicals are absorbed into the blood stream How Drugs Enter the body • Oral administration is convenient, permits self medication and avoids the physical and psychological discomforts of injection. • However, this route of administration is not ideal for all drugs • Absorption is slow by the presence of food in the stomach and the excessive movement of gastrointestinal tract. • Less commonly, drugs can be given rectally • This method is advantageous if the person is unconscious, has difficulty in swallowing, or is vomiting • The only problem with drugs administered rectally is the drug my not be completely absorbed How Drugs Enter the Body • The term “parenteral” describes the administration of drugs, such as antibiotics, insulin, and anticlotting medicine, into the bloodstream directly or indirectly by injection with out have to be absorbed through the digestive tract. • This can be accomplished by intravenous injection (known as an IV or mainlining in which a drug is inserted directly into a vein) • Intramuscular injection or “skin-popping”( just beneath the skin’s surface) • While each of these routes of administration has it distinct advantages and disadvantages, How Drugs Enter the Body • Administration of drugs by injection 1. Produces a more rapid response than other methods 2. Achieves more accurate dosage because drug destruction in the digestive tract is avoided 3. Bypasses the unpredictable absorption process occurring in the stomach and intestine 4. Provides insufficient time, in comparison with orally taken drugs, to counteract unexpected drug reactions or accidental overdose 5. Requires sterile conditions in order to avoid infectious disease 6. Presents a potentially painful situation for the drug taker How Drugs Enter The Body • Certain drugs can be administered by inhalation in which chemicals are absorbed into the blood stream by passing through the lungs. • Volatile gases, paint thinner and gasoline vapors, and non-volatile aerosols, as well as tobacco and marijuana smoke and crack cocaine can pass through the thin membranes of the lung’s air sacs and readily enter the bloodstream • In certain instances inhalation of drugs produces an effect nearly as fast as , or faster than, intravenous injection • A variation of inhalation is known as snorting, it is the inhalation through the nasal passage. • A water-soluble drug such as cocaine is snorted, being absorbed through the moist mucous membranes that line the nasal passages • The drug enters the blood vessels near the surface lining Drug Distribution and Elimination • After a drug has been absorbed into the bloodstream, it is widely distributed throughout the body • Four basic patterns of drug distribution have been identified: 1. Some drugs, including blood-plasma substitutes, remain largely with the bloodstream 2. Other compounds, such as ethyl alcohol and sulfa drugs, become almost uniformly distributed throughout each and every body cell 3. Most drugs are unevenly distributed in the body in accordance with their ability to penetrate different membranes of the body 4. Very few drugs actually concentrate in one or more body tissues or organs that may not even be the sites of drug action Drug Distribution and Elimination • It should be noted that although psychoactive drugs affect mood and behavior, functions controlled by the nervous system, most of these chemicals will be found outside the brain at any given time, even during states of drug intoxication and poisoning • As drugs circulate throughout the body, they undergo processes of metabolism and excretion, both of which are responsible for the elimination of the drugs and the termination of drug action • The complex chemical changes that alter drugs and convert them to substances that can be eliminated from the body are known collectively as metabolism • A special system of enzymes in the liver cells carries out these metabolic reactions • The liver is an important body organ that functions in detoxification, the natural process of making substances non-poisonous Drug Distribution and Elimination • When the recently detoxified substances are carried by the blood to the kidneys, the metabolized drug by-products are excreted, eliminated from the body in the urine • The kidneys with their filtering action are the major route of eliminating toxic substances from the human body • This action of the kidneys helps maintain the body’s chemical homeostasis---that internal state of constancy or equilibrium necessary for normal functioning • Most drugs are excreted by the kidneys, small amounts will also be eliminated via several minor pathways of excretion. • These routes include sweat, saliva, gastric secretions, bile, feces, mothers milk and lungs • Only the highly volatile drugs, such as anesthetic gases and alcohol, are excreted through the lungs Drug Actions • Drugs actions are the result of a chemical interaction with some of the human organism • In general drugs change cell function by one or more of the following actions: 1. Stimulation: an increase in the rate of functional activity. Cocaine and amphetamines speed up central nervous system function 2. Depression: a reduction in the of functional activity. Ethyl alcohol and barbiturates slow down or depress the function of the central nervous system 3. Blocking: an obstruction that effectively prevents a particular action or response. This action is probably the consequence of depression Drug Action 4. Replacement: the provision of a substitute of equivalent substance to restore an optimal condition. Insulin to diabetics is and example of replacement therapy 5. Killing or inactivating organisms: the destruction or prevention of the growth of disease-causing organisms. Antibiotics kill bacteria by interfering with the manufacture of bacterial cell walls 6 Irritation: The abnormal excitation of some body part or function. This action may be an exaggerated form of stimulation. Laxatives irritate the large intestine to initiate defecation Factors Influence Drug Actions • Dose: the quantity of amount of drug that is taken at any particular time is called the dose or dosage. The greater the dose, the greater will be the drug effect. • Threshold dose or minimal dose refers to the smallest amount of a given drug capable of producing a detectable response. • The median effective dose describes the dose required to produce a specific response in one-half or fifty percent of test subjects • If the response to a particular dose is death, the dosage is described as the lethal dose • Age: in comparison with so-called average 18-to 65-year old adults, both infants and the elderly generally display more sensitivity to the effects of drugs. As a consequence, drug actions within their bodies to be prolonged Factors Influence Drug Actions • In another instance, one drug has a special reputation for reacting differently in children than in adults. Ritalin, a powerful stimulant for adults, acts as a depressant in children • Body Weight: placing the same amount of a drug in a 90 pound person and a 200 pound person is likely to produce a significantly different results because of the greater concentration of the drug in the blood of the lighter weighted person • The heavier person with more blood and body fluids to dilute an absorbed drug thus reduces the concentration of the dissolving drug • Sex: contrary to popular belief, the sex of a drug taker has very little influence on the effect of a drug • Time: the length of time between the taking of a drug and the observation of the anticipated effect is referred to as the “onset of action” Factors Influencing Drug Actions • Disease: the presence of a disease condition will often alter a person’s response to a drug. For example, people with impaired liver and kidney function often have difficulty metabolizing and excreting drugs, and thus experience prolonged drug effects. • Such people are unable to eliminate drugs from their bodies in a period in a normal period of time • Mind-set: often referred to as the mind-set, one’s emotional state or climate is now recognized as having a potentially significant impact on drug responses • Temperament marked by anger, fear, sadness, joy, or any other emotion can bring about changes in various body processes, namely secretion of gastric juices and hormones, and alteration of blood pressure, heart rate, pulse and respiration • These bodily processes, in turn, influence drug absorption, distribution, metabolism, and excretion--- all of which can modify the response to a drug Factors Influence Drug Actions • Environmental Setting: closely related to mind-set in changing a drug response are the various factors of the environmental setting. • The environment includes not only physical place in which the drug is taken, but also the psychosocial circumstances surrounding the drug use • The impact of the environment on drug action can be very significant with mood and behavior modifying chemicals • For example, using a psychedelic drug in a controlled laboratory situation or among caring friends will likely result in fewer “bad trips” than would “street use” of the same drug. Drug Dependence • Described as a state of psychological or physical need or both, drug dependence can occur in an individual who uses a drug periodically or on a continuous basis • For many years the word, “addiction,” was used to define compulsive use of drug substances , especially the narcotics and alcohol • Eventually, the World Health Organization proposed substituting the more neutral term “drug dependence” for addiction. More recent variations in the drug abuse terminology include “chemical dependence” and “substance abuse,” more inclusive perhaps than the older terms • The most extreme form of drug dependence is characterized by: 1. Psychological dependence 2. The development of tolerance 3. Physical dependence Psychological Dependence • This is where a person takes a drug for the effects of the drug • An individual who develops a psychological dependence on a particular drug has a strong desire to repeat the use of that drug either occasionally or continuously • Although the body may not require the drug in a physical sense, the person has an intense craving for it to maintain drug induced pleasure, a feeling of well-being , to achieve a maximum level of functioning, to reduce tensions, or dull reality • When drug seeking becomes compulsive and a regular behavior pattern, psychological dependence has reached its peak intensity • deprived of the drug, the user will usually experience a period of readjustment, accompanied by some degree of anxiety, irritability, and restlessness Tolerance • With the repeated use of certain drugs, a condition known as “tolerance” develops. • Tolerance is taking more and more of the drug to obtain the same effect. • It is the development of body or tissue resistance to the effects of a drug so that bigger doses are required to reproduce the original effect. • The onset of tolerance may be rapid or gradual, depending upon the drug used. Tolerance • It should be noted that tolerance can accompany psychological dependence upon a drug without the occurrence of physical dependence • One major theory holds that tolerance is the result of alterations in how a drug is processed in the body after repeated doses are taken. • Changes occur in the normal processes of drug absorption, distribution, metabolism, or elimination • For instance , the liver begins to destroy the drug substance more quickly • One additional concern with tolerance is the development of “crosstolerance,” a condition in which the reduced pharmacological response to one drug results in a lessened response to another drug Tolerance • Cross-tolerance, however, typically occurs among drugs belonging to the same class of chemical agents. For example: • Persons tolerant to morphine are also tolerant to heroin, methadone, and other narcotics agents, but not to alcohol or barbiturates, which belong to another class of drugs, the sedatives • Tolerance to some drugs develops very rapidly after the first dose, but occurs more slowly with other drugs Rate of Tolerance Development • Fast Tolerance Developers: opioids, heroin, Cocaine • Intermediate: PCP, Amphetamines, marijuana • Slow: Benzodiazepines, ( Valium, etc.), Nicotine, Caffeine Physical Dependence • You can define physical dependence as the dependence of the body tissue on the continued presence of a drug revealed by withdrawal system that develop when the drug is discontinued • Physical dependence is a state of functional adaptation to a drug in which the presence of a foreign chemical becomes “normal” and necessary. • The presence of a drug is required for normal function • The condition of physical dependence is revealed only when drug use is discontinued • If the drug is removed abruptly, normal cell function is disturbed, resulting in hyperexcitability or overactivity of the nervous system • These drastic alterations in physical functions and behavior ,experienced after drug is terminated, are known collectively as withdrawal or the abstinence syndrome Drug dependencies which have a recognized withdrawal treatment 1. Alcohol------- Benzodiazepines 2. Heroin ------- Methadone (Clonidine) 3. Nicotine------ Nicotine Gum & Patches • Drug dependencies which have no standard medical withdrawal treatment are caffeine, cocaine, marijuana , Phencyclindine (PCP) and amphetamines ued ur