Pharmacology Lecture 2
Terms
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- Pharmacodynamics
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study of biochemical and physiological effects of drugs on the body – what drugs do to the body.
-Effects of drugs on the body, action, therapeutic effects, side effects, interactions - Dose-response relationships
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Describes relationship between size of dose and the intensity of the response it produces.
This relationship determines the minimum amount of drug to produce desired effects
(Increase or decrease dose until therapeutic) - MAXIMAL EFFICACY
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-largest effect that a drug can produce; used in drug comparison
-Important when trying to decide what kind of drug to give to patient - RELATIVE POTENCY
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amount of drug that must be given to produce effect.
- A potent drug produces its effect at a very low dose. - ED50
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average effective dose, therapeutic response in 50% of population–standard.
-doses can be increased or decreased as needed - THERAPEUTIC INDEX
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measure of a drugs safety.
-LD50/ED50. Ratio between average lethal dose (LD50) and its effective dose (ED50) - Receptors
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•Drugs produce effects by interacting with receptors in the body
•macromolecule in a cell to which a drug binds to produce its effect.
•When a drug binds to a receptor it can mimic (enhancement) or block the action of endogenous regulatory compounds – hormones, neurotransmitters -
Receptors and Selectivity
of Drug Action -
⬢More specific a drug is = fewer side effects, each type of receptors regulates a specific physiological function.
⬢Most drugs act through receptors - AGONISTS
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•Mimic the action, produce effects similar to those produced by naturally occurring hormones, neurotransmitters and other substances.
•Drugs act as agonists -> bind to receptors, mimic the action (normal responses)
•“Turn on†or “activate†receptors.
•Example: bronchodilators (beta 2 agonist), binds to beta 2 receptors - ANTAGONISTS
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•block the action of regulatory compounds
•inhibit cell function by occupying receptor sites
•Drugs act as antagonists -> block receptors, prevent receptor activation. Prevent our normal responses from occurring
•Example- anti-histamine- block histamine receptors so body doesn’t respond to histamine released - Receptor Sensitivity
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receptors can change sensitivity or number of receptors can change
•Agonist -> the cell/receptors desensitized, less responsive-> down regulation.
•Antagonists -> cells/receptors more sensitive, hypersensitive –> up regulation.
oMeds have to be changed over time due to this - Non-Receptor Drug Actions
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⬢Produce effects through physical or chemical interactions.
⬢Example: antacids- work because they change pH - Drug – Drug Interactions
- if patient takes more than one drug
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Consequences of Drug-drug
interactions -
-intensification of effects
-reduction of effects
-creation of new responses - intensification of effects
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can be beneficial b/c can
⬢increase therapeutic effects (iron is absorbed better in acidic environment)
⬢be harmful (aspirin can cause increase in bleeding) - reduction of effects
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⬢morphine has a drug that reduces reaction if too much given
⬢most cases its not beneficial - How drugs interact
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-chemical or physical interactions (check compatibility )
-pharmacokinetic interactions
-pharmacodynamic interactions
-combined toxicity - pharmacokinetic interactions
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absorption – absorption can be increased or decreased
+antacids are good example, don’t want to take with other medications; also food
distribution – protein binding or alter extracellular pH. If drugs compete for protein
metabolism – increase or decrease metabolism of drugs by affecting hepatic microsomal enzyme system (if use same metabolic pathway)
excretion - altering renal mechanisms, overall excretion of drugs - pharmacodynamic interactions
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-might act on same receptor and compete for it
⬢drugs can interact and influence same physiological processes - combined toxicity
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-increase toxic effects
-many drugs toxic on own but when combined toxicity increases - Minimizing Drug-Drug Interactions
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a. history of patient med regimen- look at all meds they’re taking
b. decrease meds- esp. if more than one drug for one purpose
c. adjust timing or dose
d. monitor for toxicity- monitor plasma levels, to make sure they are at the therapeutic level - Drug-Food Interactions
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-Drug absorption
-Drug Metabolism
-Drug toxicity
-Drug action - Drug absorption
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⬢food can increase or decrease absorption, affect rate and extent,
⬢some have to betaken with food to be absorbed, some cannot be taken with food
⬢sometimes gastric delay can delay reaction
Drug-Food Interactions - Drug Metabolism
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Grapefruit Juice- inhibits isoenzyme of cytochrome P450; increases drug levels by inhibiting isoenzyme in hepatic microsomal
Drug-Food Interactions - Drug toxicity
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increase toxicity.
Bronchodilator can cause nervousness
Drug-Food Interactions - Drug action
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food can affect action, especially those high in vitamin K
Drug-Food Interactions - Patient Related Variables
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-Age
-Weight
-Gender
-Genetics/Race
-Health Status
-Tolerance
-Placebo - Age
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infants sensitive – organs immature
elderly sensitive - decline in function - Weight
- effects vary with body size and weight, use body surface to adjust meds (esp. w/peds
- Gender
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react differently to the same drug (side effects and efficacy).
Women respond better to
certain pain meds, especially opiates - Genetics/Race
- can affect drug metabolism, can alter the structure of drug receptors
- Health Status
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a. kidney disease: reduce excretion of drugs
b. liver disease: decrease in metabolism of drugs
c. pregnancy: affect drug metabolism, changes in kidney (bloodflow increases,
excretion increases),
liver (metabolism increases) , GI tract (slows down, absorption less) function during pregnancy.
⬢Risks to fetus -teratogenesis
(birth defects)
+FDA has categorized A-D & X - Tolerance
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decreased responsiveness to drug that develops with repeated drug administration .
.See a lot with pain medication (AIDS, cancer, sickle cell)
⬢Pharmacodyanic tolerance = requires higher doses of a med to produce the desired effects.
⬢Metabolic tolerance = increased metabolism of drug - Placebo
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no pharmacological/therapeutic activity, used for clinical trials
⬢psychological factors - Adverse Drug Interactions
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any unintended or undesired effects occurring w/ normal drug use
-Side Effects
-Toxicity
-Allergic Reactions
-Idiosyncratic Effect
-Iatrogenic
-Physical Dependence
-Carcinogenic Effect - Side Effects
- ⬢ unavoidable secondary effects occur when drugs taken at therapeutic levels, most of the time they are predictable, usually occur right after drug use and tend to diminish over time
- Toxicity
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⬢Occurs with excessive drug dosing, produces severe adverse reactions.
⬢Organ specific toxicity- some meds directly toxic to certain organs. Drug levels and function of organ monitored
⬢example- morphine can cause coma
⬢can occur with normal drug levels (chemotherapy) - Allergic Reactions
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⬢Immune response to drug.
⬢From rash to anaphylactic reaction
⬢First sensitization, re-exposure to drug triggers reaction. - Idiosyncratic Effect
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⬢Uncommon drug responses resulting from genetic predisposition
⬢Usually related to metabolism of drugs - Iatrogenic
- ⬢Conditions or diseases caused by drug use, if taken for long time
- Physical Dependence
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⬢develops with long-term use of meds
⬢body adapted to drug exposure
⬢mostly narcotics or other controlled substances - Carcinogenic Effect
- ⬢cause cancer, chemotherapy may cure but can cause different type later
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Ways to decrease adverse
reactions -
1. Monitor the patient closely for any adverse reaction
2. Be knowledgeable of the patient and their meds
3. Monitor lab values
- look at kidney and liver function -
Nursing Responsibilities-
Five Rights - Five rights of administration: THE RIGHT drug, patient, dose, route, time
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Other Nursing Responsibilities-
Beyond 5 Rights -
a. understand patient and the medical diagnosis
b. know why the patient is getting the med
c. know what the body does to the drug (pharmacokinetics)
d. know what the drug does in the body, action of the med
e. anticipate possible reactions
f. know if it is contraindicated for the patient
g. patient advocate – last defense - Assessment (preadmission)
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a. baseline data
b. ID of high-risk patients- assess factors that may increase risk (age, allergies, diet)
c. capacity for self-care- is patient willing/able to follow regimen - Analysis/Nursing Diagnosis
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a. determine if medication is appropriate
b. identify potential health problems/adverse effects/interactions
c. determine patient’s capacity for self-care - Intervention/Implementation
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a. drug administration- five rights, timing of dosage
b. interventions to promote therapeutic effect- taking or not taking with food, foods to avoid, non-drug measures (diet, exercise)
c. interventions to minimize adverse effects- avoiding side effects
d. patient education- explain simply - Evaluation
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a. therapeutic response
b. adverse drug reactions- if they occur, what can be done to minimize
c. compliance- evaluate patient’s adherence to regimen, look at serum and plasma levels
d. patient satisfaction with treatment -
Key Points -
Medication Administration -
1. Read med order carefully
2. Read med label carefully (drug, dose, route)
3. Verify dosage calculation
4. Verify patient by comparing name on wristband to order/med. 2 patient identifiers (name, birthday, MR#)
5. Do not give med if order is unclear
6. Do not give med if you do not know what the med is and why the patient is getting it
7. Explain med use etc. to patient