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What is the difference between Pharmacokinetics and Pharmacodynamics?
- Pharmacokinetics: way drugs are used in the body
- (distinct processes factors, and processes whereby drugs are absorbed and distributed in the body biotransformed and excreted from the body)
- Pharmacodynamics: properties of drug effects
- including time to onset of action, time to reach peak effects duration of action expected times for drug clearance... these can be impacted by pharmacokinetic changes
What is altered absorption and two examples of altered absorption?
Combo of two or more drugs impedes/inhibits the absorption of one or more drugs being taken. Drugs may inhibit absorption of the other drugs across a physiologic membrane
- Chelation-when Al, Mg, Ca, Fe containing meds irreversibly bind to antibiotics like doxycycline or an oral fluroquinolone (ciprofloxacin, levofloxacin) therby reducing the amount of drug absorbed
- Prevention of absorption- Dicloxacillin: empty vs full stomach (85-100% absorbed on empty, absorption dropped when full)
What's the difference between additive effects, synergism, potentiation?
1 + 1 = 2
: 1+1 = 3 Response greater than the combined response of the individual drugs(refers to intended clinical effect not ADE) i.e. Vancomycin and gentamicin for endocarditis)
- Potentiation: 0 + 1 = 2 A drug w/no principal effect enhanves the effect of a second drug
- amoxicillin with clavulanate (= augmentin): the combo may have an effect on bacteria that are amoxicillin resistant, clavulanate prevent amoxicillin from being broken down.
Altered Excretion is when _____________________. An example of this would be.....?
Drugs act on kidneys to reduce/enhance excretion of specific drugs
i.e. Mannitol with cisplatinum
Competition for Serum protein binding =
Drugs that bind to serum proteins may compete with other drugs for protein binding spots
I.e. displacement of drug A from serum proteins by drug B may increase concentration of the unbound drug A in the serum
Oral (PO) administration need to be acid stable and able to be absorbed and passed through intestinal lining in order to enter the bloodstream.
How quickly meds pass through the stomach and intestinal peristalsis can also effect the absorption of orally administered meds. Name one condition where patients may have trouble absorbing PO meds and why.
Diabetes, gastrophoresis = slowing down of the GI transit time
Name the 12 things that must be on a Rx and 4 other things that could be on a Rx.
- 1) Doctor Name
- 2) Doctor Address
- 3) Doctor phone number
- 4) Patient name
- 5) Patient Address
- 6) Date of issue
- 7) Quantity of drug
- 8) Name of the drug
- 9) Direction for drug use
- 10) Doctor signature
- 11) doctor license classification
- 12) TPA #
- 1) no refills
- 2) refills
- 3) do not substitute (with generic)
- 4) Reason for why drug/device is Rx
If a patient took a 100mg dose of a medication that has a half life of 4 hours, how many half lives would it take for 95% of the medication to be eliminated?
with continuous infusion the serum concentration of the drug will reach steady state after how many half lives?
Drug based factors like formulation, molecular weight, ionization, and solubility can affect its absorption through tissues/membranes. What kind of molecules have a great ability to pass thorugh plasma membranes?
Lipid-soluble drugs with smaller molecular structure which are not ionized have a better ability to pass through plasma membranes
Give an example of a drug that using a serum binding protein
Azithromycin (Z-Pak): up to 51% of the drug can be protein-bound, this plus a long elimination half life can deliver the equivalent of 7-10 days of therapy with 5 days of dosing.
Drug deposition = when drugs deposit & accumulate in tissues, can result in slower drug release/change of the tissues.
Name two drugs that are examples of this:
- Heart med deposit in cornea and effect vision
- ADE = optic neuritis, neuropathy, visual disturbances, halos
- tetracycline antibiotics localize in organs/tissues like teeth, bone, liver, spleen