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Nursing 324- Topic One: Pharmacokinetics
Terms in this set (51)
Drug classifications; classified by effects on
Particular body system (opioids are a CNS depressant), therapeutic uses (antidepressant), chemical characteristics (Beta-adrenergic blockers or benzodiazepines which work on GABA), drugs can fall into multiple categories
Drug classification; extra notes
Every drug will fall into a drug class, some drugs will have more than one but the first one counts. Ex: Lisinopril- considered to be an Ace-inhibitor, but can also be called a heart failure med, diabetes med, anti-hypertensive med, cardiac drug
Usually the first medication in class, and is a standard in which other drugs are compared in the class. Ex: morphine, fluoxetine (Prozac), Captopril
Official name of the education, will always be on testing, independent of the manufacturer, often gives the drug class ("pril," "olol," "statin")
Brand name or trade name
Decided and patented by the manufacturer; can be several different brand names. Ex: Prinivil and Zestril (lisinopril)
The interaction between the living system (person) and the foreign chemicals, the way the drug affects the body
4 ways a drug works
1. Replace or act as a substitute for missing chemicals (insulin) 2. Increase or stimulate certain cellular activities (Beta agonists) 3. Depress or slow down certain activities (Beta blockers) 4. Interfere with the functioning of foreign cells like microorganisms or neoplasms (antibiotics or chemo)
The way a drug affects the body
Primary response is desired effect, secondary response can be desired but also can be adverse
Primary: blocks histamine and stops allergy symptoms. Secondary: drowsiness
No matter how much you give (increase the dosage) the effect does not change. Ex: Say the drug is 50mg-400mg, and the pt is given 800 mg. If the max dose given is 800mg, you will not get anymore response to the ailment after 400mg. You may just get side effects after this threshold.
The smallest dosage that will give a desired result. Say the drug is 50mg-400mg. At 50mg, that is the lowest dosage the the drug can be given in that will do what it has to do.
Times it takes to reach a minimum effective concentration
Occurs when drug reaches its highest blood or plasma concentration
The length of the the drug has a pharmacologic effect
Typically the patient is very ill and needs immediate therapy. Medications that are given to pt that are acutely ill. IV nitroglycerin to someone having chest pain, antibiotics for a person with an acute infection. The patient is not going to be on this med forever, just until the problem is taken care of.
Medications given because of practical experience and known data. Say you have a sinus infection, when we know what a typical bacterial agent is, we just go ahead and give the antibiotic for what typically causes the infection rather than waiting for 5 days for the culture to come back, we just give the person an antibiotic for the expected bacteria. Ex: Bactrim given for UTI because most UTI are either E.coli or Staph saprophyticus
Maintain steady dose for chronic conditions that do not resolve. Ex: It was 10mg, then 20mg, now 30mg seems to do the trick. Now you will stay on 30mg every day. Ex: chemo in a cancer patient in remission or a patient with Crohn's disease managing symptoms.
Does not cure but maintains other function until the patient improves. Ex: NyQuil doesn't cure the cold, but it will help you be comfortable and sleep until you're better. Anti-nausea helps cancer patients during chemotherapy.
Used for end stage or terminal diseases to make person comfortable. It can be pain medication but also can be meds like chemotherapy. Ex: Heart failure patients, or chemo for a pt. with lung cancer who isn't necessarily going to die tomorrow, but to make them comfortable so that they may go to their child's wedding
Drugs act on specific areas on cell membranes proteins that each perform a specific function. Receptor site works with specific chemicals to cause an effect on the cell. All medications work on receptor sites, and go in to bind to a receptor site with whatever issue.
Occupy and activate receptors; full agonist does not need all the sites to produce desired effect. Can even be as little as 10% (MSO4 or albuterol)
Occupy receptors but do not stimulate them. Keep the agonist from occupying the same spot and producing a response (Beta-blocker, charcoal)
Naloxone blocks all of the opioid receptors; An antagonist of Drug A that binds to the same receptor sites as Drug A and prevents Drug A from binding
A competitive antagonist of Drug A that binds to different receptor sites from Drug A, but still prevents Drug A from binding
Assesses toxic levels. Margin of safety of drug. Low: narrow margin of safety. High: Less danger.
Drug concentration from minimum effective concentration to the minimum toxic concentration
Peak drug levels
Rate of absorption of the drug; usually several hours after taking depending on the med
Rate of elimination of the drug; typically drawn right before the dose
Levels assessed in drugs with narrow therapeutic index
Meaning where they need to be for the drug to be therapeutic, versus overdose is a very small window. Ex: Lithium the drug level is 0.6-1.2: at 0.5 the medication won't be working, 0.8 it is doing its job, and 1.3 the pt is overdosing.
The amount of drug that is needed to cause a therapeutic effect
A higher dose than that usually used for treatment; quickly raises the drug level
The actual concentration that a drug reaches in the body- not all of the medication gets to the body to do what it needs to do
Absorption: oral route
Typically very sick people don't get oral medications because they don't have good blood flow to the stomach; Some medications need acid so that it can be broken down and absorbed. Some medications if there is too much acid will be immediately broken down (not good) and not absorbed
The drug becomes a solution; 80% of meds are taken by mouth, but meds are not 100% "drugs"; have excipients- which allow the drug to take shape and size
Breakdown of tablet into smaller pieces
Dissolving into smaller particles in the GI fluids
High to low concentration (diffusion) Oral drugs: high concentration in GI tract to low in blood stream
Requires an enzyme or protein to move the drug against the gradient. Low to high concentration: electrolytes and meds like levodopa
Cells carry the drug by engulfing the drug particles; fat soluble vitamins
More blood-better absorption, quicker onset of activity; IM injection: blood flows faster in the deltoid than the gluteal muscle. Pain and stress response; decreased blood flow to the GI tract, ANS response. Medication won't be able to make it down to the toes if there is a blockage; it is going to get to where the blockage in the artery is and then not be able to get there
Can reach full strength at time of injection; full absorption no barriers; margin for error is very narrow; immediate and complete; no room for mistakes, we cannot get an IV medication back
Absorption takes place in the capillaries of the muscle. This takes time and must be taken to the vein. The patient must have adequate perfusion. Quicker in men, younger people; Pt must have muscle there for it to be absorbed. An older adult may not have enough muscle for this; Deltoid is preferred- if given in the flute, outer upper quadrant to avoid sciatic nerve
Absorption is a bit better guaranteed with fat; it is injected into the skin where it is absorbed slowly.
Protein drug complex is large and cannot enter the capillary/tissues, leaving protein binding sites at tissue. Many of these bind with albumin, the part that is bound is inactive, only the free drug can be therapeutic. Some are released slowly others more rapidly
Blood brain barrier
Keep things away from the CNS, high lipid soluble more likely to get across the BBB. Lipids move much easier. Very few antibiotics are lipid soluble. BBB is altered by the infection so a med can get true. Drug adverse effects are more indirect than direct on CNS tissue. The brain is essentially very difficult to treat with medication due to BBB; **
the only medications that can make it through are lipid-soluble medications; water-soluble medications do not
High level of protein binding
Diazepam, furosemide, ibuprofen, valproic acid, warfarin; the part of the drug which is bound is unavailable for use; the rest is the free drug. *If 2 highly bound drugs are given together, the drug competes for protein binding sites which causes more free drug in the drug stream, but increases risk for toxicity
Phase I of metabolism
Cytochrome P450 system
Normal drug dose is 20mg, this person may need 40mg to get the same effect hat normal people would get at 20mg (increases metabolism)
Instead of metabolizing the drug in 8 hours, it may metabolize the drug in 4 hours. A patient like this may only need 5 mg of a medication per dose (decreases metabolism)
Cytochrome P450 system
Major drug metabolism enzymes, account for metabolism of 70%-80% of medications. Many meds are substrate inhibitors and inducers of CYP enzymes. The substrates bind to the CYP enzyme and are converted to the inactive or active form known as a metabolite. Genetic variants in genes coding the CYP enzymes can alter function (inhibitors or inducers)
Swab the inside of the mouth, check for all of the gene results looking at every CP450 enzyme and see which one the pt has a hard time with. Allows us to know how a pt will metabolize a medication
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