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HCA 155 Lecture 2
Lecture 2 Quiz
Question | Answer |
---|---|
Metabolism (biotransformation) | Ability of body to change a drug to a more water-soluble form that can be excreted.; Commonly, drug is metabolized to inactive metabolites, which are then excreted.; Other drugs are converted to active metabolites, which may be further metabolized or excr |
Metabolism : Where? | Mostly, liver enzymes.; Also: plasma, kidneys, intestinal membranes.; Some drugs inhibit or compete for enzyme metabolism, causing drug accumulation when given together – potential for adverse reaction or drug toxicity.; Liver has many enzymatic pathways |
Metabolism : compromised | By cirrhosis (alcohol, drugs, all forms Hepatitis); By heart failure (Congestive heart failure, right sided heart failure, not good distribution.; Age – infants have immature livers; geriatric pts. have decreased liver size, blood flow, & enzyme productio |
Excretion | Elimination of drugs from the body.; Via kidneys & urine.; Also through lungs, exocrine glands (sweat, salivary, mammary), skin, & intestinal tract if kidneys aren’t working well.) If breast feeding should follow ABCDX (same for pregnant women.) |
Excretion – Half-life | Time for ½ the drug to be eliminated – affected by rate of absorption, metabolism, & excretion. Determines dosage frequency.; One-time drug administration – usually eliminated after 5 half-lives.; Regular dosing – steady state (steady concentration) afte |
Onset of action | Time from administration of drug to beginning of therapeutic effect.; Dependent on route & drug properties. |
Peak & Duration | Peak concentration level when absorption rate equals excretion rate.; Peak concentration not always the same as the time of peak response.; Duration is length of time of therapeutic effect. |
Pharmacodynamics | Study of drug mechanisms that produce biochemical or physiological changes.; Drug action – cellular interaction with drugs, including cell membrane proteins, enzymes, & target receptors.; Drug effect – response from drug action.; Drug can modify cell func |
Pharmacodynamics (cont’d.) | Drug cannot impart a new function to a cell or target tissue.; Drug alters cell function by: modifying cells physical or chemical environment; interacting with a receptor. |
Pharmacodynamics – Agonist drugs | Drug has an affinity for a receptor (is attracted).; Drug has affinity for & stimulates a receptor.; Intrinsic activity – drug initiates a response after binding with receptor. GOOD DRUG – most drugs are agonists. |
Antagonist drugs | Drug has affinity for receptor but has no intrinsic activity.; Drug prevents a response from occurring by occupying the receptor.; Competitive antagonist – competes with agonist drug for receptor sites. Increased doses of agonist drug can overpower antag |
Antagonist drugs (cont’d.) | Noncompetitive antagonist – irreversibly binds to receptor sites & blocks agonist drug effects. Larger agonist drug doses don’t overpower antagonist drug. “irreversibly”, not “irreversible”, but the noncompetitive antagonist sits @ site for quite a while |
Receptors | Nonselective drug – acts on a variety of receptors, with multiple, widespread effects.; Receptors may be classified by specific effect, e.g., beta receptors affect pulse & bronchial relaxation. |
Potency | Drug potency equals relative amount of drug required to produce the desired response.; Used to compare 2 drugs (Figure 5-2 –B, p. 47).; Drug X is more potent than Drug Y if it produces the same effect at a lower dose. |
Maximum effect | Increase in dose yields little or no increase in response. |
Therapeutic Index | AKA “margin of safety” or “therapeutic window”; Relationship between drug’s desired therapeutic effects & its adverse effects.; Low index= narrow safety margin; the difference between effective dose and lethal dose is small. Digoxin helps increase contrac |
Therapeutic Index (cont’d.) | High Index= large safety margin; less risk of toxic effects. |
Pharmacotherapeutics – Types of therapies | Acute therapy – pt. is critically ill & requires intensive therapy.; Empiric therapy – based on practical experience rather than pure scientific data (not based on studies – based on Dr. or Practitioners knowledge).; Maintenance therapy – pt. has a chroni |
Pharmacotherapeutics – Types of therapies (cont’d) | Supportive therapy – doesn’t treat cause of disease but maintains other threatened systems.; Palliative therapy – end-stage/terminal disease for pt.’s maximum comfort.(hospice) |
Factors affecting pt.’s response to therapy | Age; Sex; Cardiovascular condition; Diet; Disease; Drug interactions; GI function (absorption thru PO); Hepatic function; Renal function /// infection. |
Drug tolerance | Decreased response to a drug over time.; Larger dose are needed to produce same effect. (Habituation, opiods) |
Drug dependence | Pt. displays physical or psychological need for drug.; Produces withdrawal s/s when drug is d/c’d.; Psychological dependence results in drug-seeking behavior. (alcohol – death can be the result when go “cold turkey” |
Drug interactions | Additive effects (1+1-2) – when you administer drugs that have similar effects, one drug adds to the effect of the other (using Tylenol and aspirin for headache).; Synergistic interaction (1+1-4) –one drug multiplies the effect of another drug. (ie: infec |
Drug interactions – (cont’d.) | Potentiation (under synergism umbrella) – specific type of synergism – 2 drugs with different actions given – one drug’s action is made greater by presence of other drug. (Morphine & Phenergan – phen. Multiplies effect of morphine which means less morphin |
Drug interactions (cont’d.) | Drug-food interactions – food can change rate & amount of drug absorbed from GI tract, affecting bioavailability. Some interactions are dangerous (MAOI & tyramine-containing food.); Adverse drug reaction (side-effect) – range from mild that stop when dru |
Dose-related adverse reactions | Secondary effects – additional effects beyond therapeutic response.; Hypersusceptibility – excessive therapeutic response &/or increase of secondary effects.; Overdose – intentional or accidental.; Iatrogenic effects – mimic pathological disorders. |
Patient sensitivity-related adverse reaction | Less common than dose-related adverse reactions.; Pt. has an unusual & extreme sensitivity to drug.; Drug allergy – immune system sees drug or metabolite as a dangerous foreign substance. Allergic reaction injures cells/tissue plus initiates cell release |