Nurs212 Exam 1

• Absorption = the process by which drug molecules move from their administration site to the blood. The primary pharmacokinetic factor determines the onset of drug action.
• Pharmacokinetics = what the body does to the drug. ADME.
• Faster absorption = faster onset of drug action.
• Digestion = the transport of drugs throughout the body after they are absorbed. 
• Metabolism (aka biotransformation) = the process used by the body to chemically change a drug molecule. The liver is the primary organ for drug metabolism. The types and rates of metabolic reactions are specific to each type of tissue: Reactions occurring in the liver cells are very different from brain and skin cells.
• Excretion = the process of removing substances from the body. Kidney glomerular filtration transports drugs from the bloodstream for active tubular transport to urine excretion.
• Factors that affect drug absorption = (rate and extent) are the rate of dissolution, blood flow, surface area, lipid solubility, and pH partitioning.
•  Factors influencing distribution = blood flow to the tissues, capillary permeability, barriers (blood-brain and placenta), free drug bioavailability (lipid solubility and plasma protein binding), and receptor site affinity (agonists and antagonists).
•  Factors that influence metabolism = physiological factors (age, diet hormone balance), pathological conditions (impaired liver or kidney function), genetic factors, drug-drug interactions, and stereochemistry.
• Factors influencing excretion = the physiochemical properties of the drug, the plasma concentration of the drug, blood flow to the kidneys, and urine pH. 
• IM and SC — drug is absorbed easily between the cells of the capillary wall.  No membranes to pass through, so water soluble drugs will be absorbed more quickly than lipid-soluble drugs. Hard to retrieve if there is an error. 
• IM medications are rapidly absorbed because there is increased blood flow to the muscle. Hard to retrieve if there is an error.
• IV route — has no barriers to absorption. Hard to retrieve if there is an error. Fastest reaction time.
• Mucous membranes are also highly vascular so that drugs administered vaginally, rectally, and/or sublingually are rapidly absorbed.
• Oral - Consider: Safety: Chemically stable, Predictable, Reversible, No interactions

  Effective: Target tissue selective, Therapeutic results

  Accessible: Low cost, Easily administered, Simple generic name
• Effect of altered hepatorenal function on drug effects and serum drug levels = alterations increase levels of bioavailable drugs, causing normal medication doses to become toxic. Drug action will be longer, and needs to be monitored for adverse effects for a longer time. Serum concentrations predict the intensity of therapeutic or toxic effects more accurately than dosage.
• Plasma Protein Binding =  The process where medications attach to blood proteins within the plasma. Medications will remain trapped in the bloodstream bound to plasma proteins until they are released or displaced from the drug–protein complex. Only unbound, or free, drugs can reach their target cells or be excreted by the kidneys.
• Consequences of protein binding:  restriction of distribution and drug interactions. Drug molecules can be free (unbound) or bound to plasma protein.
• First pass: The mechanism where drugs are absorbed, enter into the hepatic portal circulation and are inactivated by the liver before they reach the general circulation. The first-pass effect is often associated with the liver, a major site of drug metabolism. However, the first-pass effect can also occur in other metabolically active tissues: lungs, vasculature, gastrointestinal tract, etc. This effect can be increased by various factors such as plasma protein concentrations, gastrointestinal motility, and enzymatic activity.
• First-pass metabolism occurs BEFORE a drug reaches systemic circulation.
• Steps of first pass:

  1)the drug is taken orally by the patient.

  2) The drug is absorbed across the intestinal mucosa.

  3) The drug enters portal circulation and travels to the liver.

  4) On the first pass to the liver, the drug is metabolized to less active forms.

  5) Drug metabolites (less active) leave the liver distribution to the tissues.
• Minimal effective concentration is the minimal drug plasma concentration necessary to elicit the therapeutic drug response.
•  The therapeutic index is the ratio of a drug to its LD50 (median lethal dose) and ED50 (median effective dose).
•  Blood-brain barrier = a network of capillaries in the CNS that inhibit many chemicals and drugs from gaining access to the brain. Its purpose is to protect the brain from pathogens and toxic substances A factor that makes it more permeable is inflammation due to infection (meningitis). In newborns and infants, drugs may be able to pass the BBB because it is underdeveloped.
• Pharmacodynamics = what the drug does to the body
• Agonists - a drug that activates a receptor and produces the same type of response as the endogenous substance. It is also known as the “cause”. They have both high affinity and high intrinsic activity. They accelerate and decelerate the process and are endogenous regulators.
• Antagonists - a drug that blocks or inhibits the response of another drug. They prevent endogenous molecules and drugs from activating receptors. They have no intrinsic activity, they have receptor affinity, and no receptor effects of their own.
• Partial Agonists - medication that produces weaker, less efficacious responses than an agonist. They can act as an agonist or antagonist. They have moderate intrinsic activity but less effect than a full agonist.
• Minimum Effective Concentration (MEC): minimal drug plasma concentration necessary to elicit the therapeutic drug response
• Therapeutic Range: Drug concentration between Minimum Effective Concentration (MEC) and Maximum Safe Concentration(MSC).
• Dose-response curve: Relationship between the size of an administered dose and the intensity of the response produced. Phase 1 occurs at the lowest doses. The flatness indicates that few target cells have been affected by the drug. Phase 2 is the rising, straight-line portion of the curve. In this portion, there is a linear relationship between the amount of drug administered and the degree of response obtained from the patient. In phase 3 increasing the drug dose produces no additional therapeutic response—a plateau has been reached.
• Half-Life: The time it takes for the original drug concentration to decrease 50%. A measure of the rate at which drugs are removed from the body. Determines the dosing interval. After about 4-5 half-lives, drugs are considered removed from the body. Conversely, a steady state occurs after about four to five half-life doses.
• Loading dose – an initial higher dose of the drug to accelerate reaching the therapeutic range. The dose decreased to a lower maintenance dose. Works best with a long half-life.
• What are some advantages of a loading dose?

  The advantage is that it will quickly induce a therapeutic response.
• what are some disadvantages of a loading dose?

  A disadvantage would be for sensitive individuals to be introduced too abruptly to a drug and experience toxic concentration.
• Single-Dose – One dose drug dosing schedule. It makes the medication easier to monitor and is easy for both patient and nurse.
• Repeated Dose – Multiple dose drug dosing schedule. Multiple doses result in a steady concentration of the drug in the bloodstream. When doses are correctly timed, a plateau drug plasma level will be reached and maintained within the therapeutic range. From a pharmacokinetic perspective, at the plateau level, the amount of drug absorbed equals the amount of drug being excreted, resulting in a steady therapeutic level of drug being distributed to body tissues.
• Selectivity: A drug binds to its receptor much like a lock and key. The body has receptors for neurotransmitters, hormones, and all other molecules in the body used to regulate physiologic processes. Think of this as a magic bullet (like in Marvel or DC movies where the bullet hits directly on a target). Ex: heart.
• Nonselective: think of this as a magic shotgun with broader receptor affinity. Hits many targets. Ex: heart and lungs.
• Non-receptor drug responses: Simple physical or chemical interactions with other small molecules. Examples include antacids, antiseptics, saline laxatives, and chelating agents.