Learning Lab 1
Pharmacodynamics
- interaction between a drug and its selective receptor - determines the nature and intensity of the drug
Therapeutic Index
- measure of drug's safety - LD50/ED50
Measuring plasma drug concentrations
- minimal effective concentration (MEC) - toxic concentration - therapeutic range
Simply occupancy theory
- more receptors occupies = increased intensity of response - does not account for differences in potency and maximal efficacy
Routes of administration
- oral - sublingual - buccal - enteral - parenteral
Pharmacology consists of 2 processes
- pharmacokinetics -pharmacodynamics
Absorption
- routes of administration
Drug-receptor relationship
- simply occupancy theory - modified occupancy theory
when giving medications to an elderly patient, what specific organ function should be considering in terms of drug excretion?
Kidneys
Competitive
reversible - can be kicked off by agonist
Half-Life Factors
(Time it takes for body to eliminate 50% of the drug) - renal disease -hepatic disease - enzyme inhibitors - enzyme inducers
3 factors that affect distribution
- blood flow to areas - ability of drug to exit vasculature (if it has difficulty leaving the vessels it cannot reach cells to produce an effect) - ability to enter cells
Modified Occupancy Theory
- increased affinity = increased potency - increased intrinsic activity = increased max. efficacy Why does this matter? - agonists - antagonists (competitive vs. non (competitive) intensity of response related to number of receptors occupied. modified occupancy theory. solve problems of single occupancy by introducing concepts of affinity and intrinsic activity. affinity. strength of attraction between drug and receptor, analogous/related to potency, drugs with high affinity are potent.
Pharmacokinetics Processes
1. Absorption 2. Distribution 3. Metabolism 4. Excretion
Pharmacodynamics Factors
1. dose-response relationships 2. drug receptor relationships 3. inter-patient variability 4. therapeutic index
2 properties of drugs that affect *dose-response* relationships
1. maximal efficacy 2. relative potency
The client is taking a drug that affects the body by increasing cellular activity. Where does this drug work on the cell? A. Receptor sites B. Endoplasmic reticulum C. Cell membrane D. Golgi body
A
The nurse is explaining to the client what bioavailability is. What statement is true of bioavailability? A. It is the portion of a dose that reaches the systemic circulation and is available to act on body cells. B. It is the portion of a dose that is absorbed by the system to achieve a therapeutic drug level. C. It is the portion of a dose that causes toxicity. D. It is the portion of a dose that reaches the systemic circulation.
A
What unique characteristic is present in lipid soluble drugs? A. can cross the blood-brain barrier B. can inhibit abnormal cellular function C. can achieve therapeutic drug levels D. can achieve 100% bioavailability
A
When researching information about a drug, the nurse finds that the drug tightly binds to protein. The nurse would interpret this to mean that the drug will: A. have a long duration of action. B. be released fairly quickly. C. lead to toxicity when given. D. be excreted quickly.
A
The nurse is caring for a group of clients and is aware that which client may require a reduction in medication dosage? (Select all that apply.) A. client with cancer of the liver B. client with chronic hepatitis C C. client with a hip replacement D. client with cirrhosis of the liver E. client with meningitis
A, B, D
The nurse is assessing factors that may affect the absorption of a drug that the nurse will soon administer. What factor should the nurse prioritize? A. the client's blood urea nitrogen and creatinine levels B. the route of administration that has been prescribed C. the client's liver enzyme levels D. the date on which the client began taking the medication
B
The nurse is caring for a client who is receiving gentamicin, 250 mg, and fluconazole, 500 mg, at the same time. What effect should the nurse anticipate if these two drugs competed with each other for protein-binding sites? A. Gentamicin will be metabolized faster than usual. B. The effectiveness of both drugs will be altered. C. Potential positive benefits of each drug will cancel each other out. D. Risks of adverse drug effects will increase.
B
A nurse is caring for a client who has been receiving a drug by the intramuscular (IM) route at a dose of 0.25 mg. After discharge, the client will be prescribed the same medication orally at a dose of 2.5 mg. What phenomenon should the nurse describe when explaining the reason for the increased dosage for the oral dose? A. Active transport B. first-pass effect C. Glomerular filtration D. Passive diffusion
B
A post-surgical client rates the pain at 10/10. The nurse confirms that there are standing orders for the administration of opioid analgesics as needed. What route of administration should the nurse choose to achieve the fastest effect? A. Oral B. Intravenous C. Subcutaneous D. intramuscular
B
The nurse's discussion of the role of cytochrome P-450 (CYP) enzymes is focusing on what aspect of pharmacokinetics? A. Elimination of drug proteins through the process of denaturing B. Drug metabolism that takes place in the liver C. The role of the kidneys in pharmacokinetics D. Drug transported through the cells of the GI tract
B
Which client would a nurse expect to experience alterations in drug metabolism? A. 41-year-old man with kidney stones B. 50-year-old man with cirrhosis of the liver C. 35-year-old woman with cervical cancer D. 62-year-old woman in acute renal failure
B
A patient requires a high dose of a new antihypertensive medication because the new medication has a significant first-pass effect. What does this mean? a. The medication must pass through the patient's bloodstream several times to generate a therapeutic effect. b. The medication passes through the renal tubules and is excreted in large amounts. c. The medication is extensively metabolized in the patient's liver. d. The medication is ineffective following the first dose and increasingly effective with each subsequent dose
C
The nurse administers amoxicillin 500 mg. The half-life of this drug is approximately 1 hour. At what point would the drug level in the body be 62.5 mg if the drug was not administered again? A. 4 hours after the original dose B. 1 hour after the original dose C. 3 hours after the original dose D. 2 hours after the original dose
C
The nurse is preparing to administer a prescribed drug to a client with a history of renal disease. Why should the nurse anticipate administering a lower dose than for a client with healthy kidneys? A. Distribution will be delayed, increasing the risk of adverse effects. B. Absorption will be increased because of fluid accumulation. C. Excretion is likely to take place slowly. D. The client likely has impaired drug metabolism.
C
What function is associated with metabolism? A. initiating the process of digestion B. aiding in the absorption of a drug C. converting fat-soluble drugs into water-soluble forms D. inhibiting cell function by occupying receptor sites
C
A client is being seen in the emergency department for a sprained ankle and is given a drug to relieve pain. When a second dose of the pain medication is given, the client develops redness of the skin, itching, and swelling at the site of injection of the drug. The most likely cause of this response is: A. An idiosyncratic response B. A hepatotoxic response C. A paradoxical response D. An allergic response
D
How would the dosage of a partly protein-bound drug be altered if another drug having a higher attraction to albumin than the first drug is administered? A. The dosage of the second drug may have to be increased. B. The dosage of the first drug may have to be increased. C. The dosages of both the first and the second drugs should be reduced equally. D. The dosage of the first drug may have to be decreased.
D
What drug administration route should be used to assure the best bioavailability as any particular drug? A. Oral B. Subcutaneous C. Intramuscular D. intravenous
D
What are some variations between patients that can affect how a drug is metabolized?
HPI, liver function, renal function etc.
Which type of drug can more readily cross cell membranes
Hydrophobic
Parenteral routes
IV, IM, subcutaneous
If a drug has a high affinity to bind with albumin, what effect does this have on distribution?
If a drug has a high affinity for albumin, it will slow distribution because the bound drug will not be able to leave the blood vessel and get to the sites of action
What might drug distribution look like for an IV administered drug with a high affinity for protein binding?
No distribution because drug is bound to protein in vascular space and cannot leave through the fenestrations/gaps at the capillary level (unless the drug dissociates from the protein or is "bumped off" by another molecule competing for that protein binding site.
What might drug distribution look like for an orally administered drug that is ionized?
No distribution because it could not get absorbed through the epithelial cells in the GI tract unless it was able to use a transporter protein (ionized molecules cannot directly penetrate the cell membrane of epithelial tissue.
What happens with the first pass effect?
Oral drugs must pass through the liver via portal blood before reaching general circulation and some undergo extensive hepatic metabolism - if this happens there may not be enough of the drug that gets into the bloodstream to cause a therapeutic effect. A higher dose may be needed
What might drug distribution look like for an orally administered drug that is hydrophobic (lipid)?
The drug is lipid soluble so it will be well absorbed (can directly penetrate the cell membrane of epithelial tissue) and can easily leave the capillaries for sites of action as long as the blood flow is good and it does not have high affinity for protein binding (protein-bound drugs cannot leave the vascular space at the capillary level while protein bound).
What does a low therapeutic index mean?
Unsafe because LD is a similar dose to the TD
intrinsic affinity
ability of a drug to ACTIVATE the receptor to cause and effect
Relative potency
amount of drug that must be given to produce a desired effect - more potent drug produces desired effect at lower dosage - implies nothing abut maximal efficacy - indicated by position of curve long x-axis - higher affinity means higher potency
Interpatient variability
drug response varies between individuals ED50 = effective dose for 50% of the population
Agonist
has affinity and intrinsic activity
Antagonist
has affinity but NO intrinsic activity
Partial
have affinity and moderate intrinsic activity: can turn into an antagonist in the presence of a full agonist because it will compete with the agonist when binding with the receptors
What is affinity?
how well a drug binds to a receptor
non-competitive
irreversible- effects only subside when entire receptor is replaced
Maximal efficacy
largest effect that a drug can produce - you can give the same dosage they might just peak at different degrees of pain relief - indicated by HEIGHT of a cure (y-axis) - intrinsic activity: more intrinsic activity = more intense receptor activation = more maximum efficacy
What are the different types of medications?
tablets, enteric coated, sustained release
what does it mean when the two overlap?
that the therapeutic does can be the lethal dose for others
When giving medication to an elderly patient, what specific organ function should you be considering in terms of drug metabolism?
the liver
Dose-response relationships
the relationship between the SIZE of the dose and the INTENSITY of response
What does a high therapeutic index mean?
the safer the drug
Pharmacokinetics
what the body does to the drug - determines drug concentration at site of action - informs dosing, route and schedules of administration
how would pharmacological therapy change in a patient who is taking Drug A and Drug B, where Drug A is an inhibitor of metabolizing enzymes for Drug B?
you need to give less of drug B because the enzymes that metabolize drug B are inhibited and that could cause it to build to toxic levels in the body