Pharmacology

[[Pharmacology[[
  • the study or science of drugs and their actions on living organisms
  • derived from the word <strong>pharmakon</strong><strong>pharmakon</strong> which means drug or medicine and also from the word logos which means science
[[Drug[[
  • any chemical that affects the physiologic processes of a living organism
  • includes medications such as therapeutic drugs

<<Drug Names<<

[[Chemical Name[[
  • a chemical constitution and molecular structure
  • ex: N-(4-hydroxyphenyl)
[[Generic Name[[
  • a common name
  • it is universally accepted
  • ex: acetamide, acetaminophen
[[Brand Name/Trade Name[[
  • propriety name
  • trademark
  • ex: Tylenol

<<Classifications<<

  1. Body system that is affected    * ex: respi, CV
  2. Therapeutic use or clinical indications    * ex. anti HPN, OHA
  3. Physiologic or Chemical action    * ex. anticholinergic
  4. Prescription/non-prescription drugs
  5. Illegal drugs    * ex. recreational drugs

<<Classification based on Chemical Nature<<

[[Inorganic Drugs Metals and their salts:[[
  • Ferrous Sulphate
  • ZInce Sulphate
  • Magnesium Sulfate
  • Non-metals: Sulphur
[[Organic Drugs[[
  • Alkaloids: Atropine, Morphine
  • Glycosides: Digitoxin, Digoxin
  • Protein: Insulin, Oxytocin
  • Esters: Amide, Alcohol, Glycerides

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<<Classification based on Source<<

[[Natural Source[[
  • Plants: Morphine, Atropine, DIgitoxin
  • Animals: Insulin
  • Microorganism: Penicillin
  • Mineral: Sodium Chloride
[[Synthetic Source[[
  • Suphonamides

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<<Classification based on Target Organ<<

[[Drug acting on CNS[[
  1. Barbiturates    * Phenobarbitone
[[Drugs acting on Respiratory System[[
  1. Mucolytics    * to cut the production of mucus      * Bromhexine
[[Drugs acting on Cardiovascular System[[
  1. Glycosides    * alleviate the symptoms of myocardial infarction or heart attack      * Digitoxin, Digoxin
[[Drugs acting on Gastrointestinal Tract[[
  1. Antibacterial    * destroys bacteria or suppresses their growth or their ability to reproduce      * Sulphadimidine
[[Drugs acting on Urinary System[[
  1. Tocolytic    * prevent the contraction of the uterus in the pre-mature labor patients      * Magnesium Sulphate - lesson the seizure of pregnant woman
[[Drugs acting on Reproductive System[[
  1. Oxytocic Hormones    * induce labor or strengthen uterine contractions, or to control bleeding after childbirth      * Oxytocin      * Estrogen

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<<Classification based on Mode of Action<<

[[Inhibitor of Bacterial Cell Wall Synthesis[[
  • Treats infections caused by bacteria on the cell wall and destroys the wall   * Penicillin
[[Inhibitor of Bacterial Synthesis[[
  • Tetracycline
[[Calcium Channel Blocker[[
  • If calcium is produced too much, it excites the heart too much which results in dysrhythmic and then dysrhythmia   * Verapamil   * Nifedipine

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<<Classification based on Physical Effects<<

[[Emollients[[
  • Substances that soften and moisturize the skin and decrease itching and flaking   * Lanolin, Vaseline
[[Caustics[[
  • Substances that burn or destroy organic tissue by chemical action, generally a strong corrosive alkali   * Silver Nitrates
[[Demulcents[[
  • Substances that relieve irritation of the mucous membranes by forming a protective film
  • For diaper rash   * Zinc oxide, Tannic acid

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<<Classification of Information Sources<<

[[Primary Sources[[
  • Clinical research studies both published and unpublished
  • 40 population
[[Secondary Sources[[
  • References that are either index or abstract are the primary literature, with the goal of directing the user to relevant primary literature
[[Tertiary Sources[[
  • information that has been summarized or filtered by the author or editor to provide a quick and easy summary of a topic   * ex. textbooks, compendia, review articles in journals

[[Black Box Warnings[[

  • Notifications within a prescription drug’s package inserts provided by the FDA to call attention to an extremely adverse drug effect
  • Primary alerts for identifying extreme adverse drug reactions

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Drug Action: Pharmacokinetics and Pharmacodynamic Process (2 Phases of Medicine)

<<Pharmacokinetic Phase<<

[[Liberation[[
  • The first phase of drug action is the release of the drug from its dosage form   * Disintegration - breakdown of a tablet into smaller particles   * Dissolution - dissolving of the smaller particles in the GI fluid before absorption

%%Excipients%% - fillers and inert substances that allow the drug to take on a particular size and shape to enhance drug dissolution

Drugs are disintegrated and absorbed in faster acidic fluids (pH of 1 or 2)

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<<Pharmacokinetic Phase (ADME)<<

[[Absorption[[
  • movement of drug particles from the GI tract to body fluids by passive absorption, active absorption, pinocytosis   * passive absorption – occurs by diffusion (higher to

    lower); no energy needed   * active absorption - requires a carrier (enzyme or

    protein); needs energy   * pinocytosis – engulfing the drug particles

Nsg Mngt:

• Administer with adequate amount of fluid • Give parenteral drugs properly • Reconstitute and dilute with recommended diluent

  • Drugs that are lipid soluble and nonionized are   absorbed faster than water-soluble and ionized   drugs
  • First-pass effect (hepatic first pass) – a process in which the drug passes to the liver first
  • Bioavailability – the percentage of the administered drug dose that reaches the systemic circulation 100% for IV

 

[[Factors that affect bioavailability:[[

a. drug form b. route of administration c. GI mucosa and motility d. food and other drugs e. changes in liver metabolism

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[[Distribution[[
  • transportation of drugs throughout the body by body fluids to the sites of action or to the receptors

\ Factors:

a. rate of blood flow b. drug’s affinity to the tissue c. protein-binding effect

\ %%Protein-binding effect%% - inactive drugs are bound to varying degrees

with protein (albumin)

%%Free drugs%% – active that can cause pharmacologic response

@@Nsg Resp:@@ To avoid possible drug toxicity, check the protein-binding percentage of drugs administered. Check also plasma protein and albumin levels.

\ General or selective

  • Blood-brain barrier - only few drugs can bind
  • Placental barrier - selective

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[[Metabolism or Biotransformation[[
  • process by which the body chemically changes drugs into a form that can be
  • liver and liver enzymes (cytochrome P450 system)

\ %%Half-life – t1/2%%

  • time it takes for one-half of the drug concentration to be eliminated

  • affected by metabolism and excretion

  • short half-life (4 to 8 hours); long half-life (24 hours or longer)

%%Steady state%%

  • the amount of drug administered is the same as the amount of drug being eliminated

  • after four to five half-lives

%%Loading Dose%%

  • large initial dose given to achieve a rapid minimum effective concentration in the plasma
  • ex. Digoxin (Digitek, Lanoxin)

  Phenytoin

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[[Excretion[[
  • elimination of drugs from the body
  • lungs eliminate volatile drug substances and products metabolized to CO2 and H2O
  • kidney filter-free unbound drugs, water-soluble drugs, unchanged drugs
  • intestines (biliary excretion); taken by the liver, released into the bile, eliminated in the feces

\ NOTES:

  • The more acidic the stomach the faster the absorption of drugs
  • Lipid soluble is faster because of the fats lining inside the stomach
  • Cancer affects the metabolism in the stomach
  • If the liver is not functioning well, the drug that is supposed to be metabolized will not be metabolized causing toxicity

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<<Pharmacodynamics<<

  • study of the way drugs affect the body
  • Primary effect - desirable
  • Secondary effect - undesirable

  ex. Benadryl

\ Dose Response Relationship

  • Magnitude of the drug effect depending on the drug   concentration at the receptor site

Graded-Dose Response Relationship

  • As the concentration of a drug increases, its   pharmacologic effect also gradually increases until all the   receptors are occupied
  • Graded effect (response is continuous and gradual)
  1. Potency – amount of drug necessary to produce an effect of a given magnitude
  2. Efficacy - magnitude of response a drug causes when it interacts with a receptor
  • Maximal efficacy – point at which increasing a drug’s   dosage no longer increases the desired therapeutic   response

\ Therapeutic Index and Therapeutic Range (Therapeutic Window) Therapeutic index (TI)

  • estimates the margin of safety of a drug
  • relationship between a drug’s desired   therapeutic effects (ED50) and its toxic dose   (TD50)

\ PHARMACODYNAMIC PHASE