NUR213 - LESSON 1.1.pdf

NURSING PHARMACOLOGY Pharmacology BSN 2C | Prof. Andelyn Espiritu | SEM 1 2024 INTRODUCTION TO DRUGS PHARMACEUTIC Nurses need to have knowledge about the actions and It is the first phase of drug action....

NURSING PHARMACOLOGY Pharmacology BSN 2C | Prof. Andelyn Espiritu | SEM 1 2024 INTRODUCTION TO DRUGS PHARMACEUTIC Nurses need to have knowledge about the actions and It is the first phase of drug action. effects of medications. To safely and accurately administer medications, nurses need to have an understanding of pharmacologic principles. PHARMACOLOGY The study of drugs and their action on living organisms. Disintegration The study of biological effects of chemicals. The breakdown of a tablet into smaller particles. o Rate limiting is the time it takes the drug to DRUG disintegrate and dissolve to become available A natural or artificial substance given to treat or prevent for the body to absorb it. disease. Chemicals that are introduced into the body to cause Dissolution some sort of change. The dissolving of the smaller particles in the GI fluid before absorption. PHARMACOTHERAPEUTICS Clinical pharmacology; a branch of pharmacology that PHARMACOKINETICS uses drugs to treat, prevent, and diagnose diseases. It is how the body acts on the Its concerns are the body’s response to the drug drug. (pharmacokinetics) and the drug’s effects on the body Involves drug movement (pharmacodynamics). through the body to reach sites of action, metabolism, and PHARMACOGNOSY excretion. The study of natural (plant and animal) drug sources. Specific processes (life cycle of a drug) are absorption, distribution, metabolism, and EXCIPIENTS excretion. These are filters and inert substances. o Critical concentration is the amount of drug that These are materials used in drug preparation to allow the is needed to cause a therapeutic (desired) drug to take on a particular size and shape and to effect. enhance drug dissolution. o Loading dose is a higher dose than that usually used for treatment. HALF-LIFE Absorption The time it takes for the amount of drug in the body to decrease to one-half of the peak level it previously Process that occurs from the time a drug enters the body achieved. to the time it enters the bloodstream to be circulated. Example is if the patient takes 20 mg. of a drug with a Factors affecting absorption include dosage form, route half-life of 2 hours: of administration, blood flow to the site of administration, o After 2 hours, 10 mg. of the drug would remain. gastrointestinal function, and presence of food or other o After 4 hours, 5 mg. of the drug would remain. drugs. o After 6 hours, 2.5 mg. of the drug would remain. For many medications, food in the stomach slows absorption. The rate at which a drug leaves its site of administration ADDITIONAL NOTES and the extent to which absorption occurs. ✓ The half-life of a drug is the time it takes for the amount of o Water-soluble (simple diffusion) and lipid- a drug’s active substance in the body to reduce by half. soluble drugs enable to rapidly penetrate the This depends on how the body processes and gets rid of cellular membrane across the blood-brain the drug. It can vary from a few hours to a few days, or barrier. sometimes weeks. ADDITIONAL NOTES ✓ Routes with slow absorption include oral, buccal, DRUG ACTION sublingual, enteral, rectal, vaginal, topical, transdermal, 80% of drugs are taken by mouth and goes through three intraocular, intraotic, and nasal. phases: pharmaceutic, pharmacokinetic, and ✓ Routes with faster absorption include inhalation, pharmacodynamic. intradermal, subcutaneous, intramuscular, and intravenous.  ADDITIONAL NOTES ✓ Specialized infusions with much faster absorption include epidural (into the space around the spinal cord), intrathecal (into the sub-arachnoid space directly into the CSF), intrapleural (into the pleural cavity), intraperitoneal (into the peritoneum), intraosseous (into the bone marrow), and intra-articular (into the joints). The three major processes for drug absorption through the gastrointestinal membrane are passive absorption, o Protein Binding active absorption, and pinocytosis. ▪ If proteins are tightly bound, they are released very slowly, resulting into very long duration of action and excretion. ▪ If proteins are loosely bound, they act and excreted quickly. o Blood-Brain Barrier ▪ Protective system of cellular activity that keeps many things (foreign invaders and poisons) away from the CNS. ▪ Highly lipid soluble pass and non-lipid soluble cannot pass. o The first-pass effect is a o Placenta and Breast Milk phenomenon in which drugs ▪ If it passes to the placenta towards the given PO are carried directly fetus, it can result to teratogenic to the liver after absorption effects. may be largely inactivated ▪ It is best not to administer any drugs by liver enzymes before they to pregnant women because of the can enter the general possible risk to the fetus. circulation. ▪ If it passes the breast milk o Bioavailability refers to the (breastfeeding), it will reach the percentage of administered neonate. drugs that reaches systemic circulation and available for Metabolism activity, and is affected by Biotransformation, where drugs are changed into new, absorption and first-pass less active chemicals. metabolism. The site is in the liver (hepatic enzyme system). Method by which drugs are inactivated or biotransformed Distribution by the body, It is the movement of a drug to the body’s tissues. Some drugs yield metabolites that are also active and The factors involved are lipid solubility and ionization and exert effects on the body until they are excreted perfusion of the reactive tissue. (normeperidine). Involves the transport of drug molecules within the body. Most drugs are lipid soluble which aids their passage After the drug is absorbed into the bloodstream, it is across the cell membrane. carried by the blood or tissue fluids to its sites of o Hepatic Microsomal System pharmacologic action, metabolism, and excretion. ▪ Phase 1 is the oxidation, reduction, or Protein binding is an important factor in drug distribution. hydrolysis of the drug, resulting to Drug distribution into the CNS is limited because of the cytochrome P450 system of enzymes. blood-brain barrier. ▪ Phase 2 is the conjugation reaction, o Blood-brain barrier is composed of capillaries where there is less polar drug and with tight walls which limits movement of drug readily excreted by the kidneys. molecules into brain tissue. o Only drugs that are lipid soluble or have a Excretion transport system can cross the blood-brain It is the removal of a drug from the barrier and reach therapeutic concentrations in body. brain tissue. The site is in the kidneys. Drug distribution during pregnancy and lactation is o Nephrons is the basic unique as most drugs cross the placenta or in the case functional unit of the of lactation, pass into breastmilk. kidneys. o Glomerular filtration is the passage of water and water-soluble  components from the plasma into the renal tubule. ADDITIONAL NOTES ✓ Common tests used to determine renal function include glomerular filtration rate (GFR), creatinine clearance, creatinine, and BUN (blood urea nitrogen). PHARMACODYNAMICS It is how the drug affects the body. o Noncompetitive antagonist prevents the It is the study of what the drug does to the body and the reaction of another chemical with a different mechanism of drug actions in living tissues. receptor site on that cell. Its primary effects are desirable while its secondary effects may be desirable or undesirable (e.g., diphenhydramine (Benadryl) is an antihistamine and its primary effects treat symptoms of allergy while its secondary effects cause CNS depression which leads to drowsiness). The drug works: o To replace or act as substitutes for missing chemicals. o To increase or stimulate certain cellular Drug-Enzyme Interaction activities. The enzymes in the liver, called the cytochrome P450 o To depress or slow cellular activities. enzymes, are responsible for the mechanism of many o To interfere with the functioning of foreign cells. drugs and transforms systems that allow for movement ▪ Peak drug level is the highest blood of many drugs across the cell membrane. plasma concentration of a drug at specific level (i.e., oral drugs have 2-3 Selective Toxicity hours of peak drug level, IV drugs have 30-60 minutes of peak drug It is the ability of the drug to attack only those systems level, IM drugs have 2-4 hours of peak found in foreign cells. drug level). Receptor Sites FACTORS INFLUENCING DRUG EFFECTS These are specific areas on cell membranes. Weight They react with certain chemicals, which cause an effect Age within the cell. Gender It is like a “key working in a lock,” where the key is the Physiologic Factors chemical and the lock is the receptor site (cell Pathologic Factors membrane). Genetic Factors Its effects include increase/decreased cellular activity, Immunological Factors changes in cell membrane permeability, and alteration in Psychological Factors cellular metabolism. Environmental Factors Poor fit has no effect, some fit has slight effect, and Tolerance excellent fit has therapeutic response (agonist). Drug-Drug Interaction o Agonist interaction is when drugs interact Drug-Food Interaction directly with receptor sites to cause the same Drug-Laboratory Interaction activity (natural chemicals). o Competitive antagonist blocks normal stimulation and has no effect.