Chemotherapy-the treatment of diseases by use of chemicals. Drug-any substance, natural or synthetic, used for its effects on bodily processes. Any substance taken to change the way in which the body or the mind functions. A drug or medicine is any chemical which does one or more of the following: Alters incoming sensory sensations Alters moods or emotion Alters physiological states, including consciousness, activity level or co-ordination. Drugs are divided into categories depending on their effects: Infection fighter-antiseptics, antibiotics, antivirals.
Those affecting body chemistry or metabolism-hormones and vitamins. Those affecting the central nervous system-stimulants, depressants, analgesics, anaesthetics. White blood cells, which are produced in the bone marrow, are one line of defense the body uses to fight infections that may come from the air, food, or water. Pharmacology-the scientific study of the interactions of drugs with the different cells found in the body. Placebo effect-refers to a pharmacologically inert substance that produces a significant reaction because of what an individual expects, desires or is told will happen.
Placebo-an inert substance used as a control in an experiment, or given to patients for its probable beneficial effects. Placebo comes from the Latin word “to please”. It is thought that the placebo effect triggers natural healing processes in the body. Three different species of animals are tested to determine an LD50 value. LD50 (lethal dose in 50%) value is used to indicate the dose of a given toxic substance in mg per kg body mass that kills 50% of the laboratory animals. The smaller the value of LD50, the more toxic the substance.
If a drug is found to be safe when given to animals: It may be taken to initial clinical tirals on volunteer as well as on patients with 50% reciving a placebo. It is subjected to thorough clinical evaluation to eliminate variables such as response and investigator bias. If it looks promising, it enters human studies with extended clinical evaluation. Methods of administration: The entire blood volume circulates in the body about once a minute and drugs are fairly evenly distributed throughout the blood. The four main methods are: Oral Parenteral by injection. Inhalation Rectal Oral:
For most drugs taken orally, the primary site of absorption is the small intestine. The form in which a drug is available, as a tablet or in liquid form, determines the rate at which the drug is absorbed. Parenteral (by injection): Beneath the skin-drug absorption is slower than intravenous. Into muscles (intramuscular)-used if immediate response is not required or when a large volume of drug needs to be injected. Directly into the blood stream (intravenous)-the drug is introduced by injection into a vein and distributed around the body within about a minute. This is the most practical. Inhalation:
Administration is rapid because of the extensive network of blood vessels in the lungs. Drug is absorbed into the blood stream to produce an effect in the brain and the whole body. Rectal: Very effective when patients experience nausea or vomiting or are unable to take medicine orally before or after surgery. Drugs that are pH sensitive and which may be destroyed by the stomach’s acidity may be delivered rectally. Drugs which dissolve readily in fats are therefore more easily absorbed. Blood-brain barrier- the capillaries of the brain are denser and prevent diffusion of many substances into the neurons of the brain.
Termination of a drug’s action takes place when it is broken down by the liver and eliminated by the kidneys. Therapeutic Window: ED5= is the effective dose for 50% of the population. If the effective does is small and the lethal dose is large, then a wide therapeutic window exists. A toxic substance is a chemical that is dangerous or causes illness or death in small amounts. Drugs can lead to dependence and or tolerance. Tolerance: Tolerance-over time and with a regular use, a user needs increasing amounts ofa drug to get the same physiological effect.
Tolerance increases the health hazards of any drug simply because the amount taken increases over time. Dependence: Physical dependence-occurs when a drug user’s body becomes so accustomed to a drug that it can only function normally if the drug is present. Psychological dependence-exists when a drug is so central to a person’s thoughts, emotions, and activities that it is extremely difficult to stop using it, or even stop thinking about it. Antacid- a remedy for excess stomach acidity. Analgesics- drugs that relieve pain without causing loss of consciousness.
These include: Mild analgesics used for relief of mild pain Strong opiates used for the relief of very severe pain Local anaesthetics General anaesthetics Depressants- calm and relax the central nervous system by interfering with nerve impulse transmission. Tranquilizers- Ex: alcohol, valium, and Librium. Sedatives- Ex: barbiturates Hypnotics-a class of drug that produces sleep. Stimulants- chemicals that stimulate the brain and the central nervous system by increasing the state of mental alertness. Antibacterials- are drugs that inhibit the growth of, or kill, microorganisms that cause infectious diseases.