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21 Cards in this Set
- Front
- Back
What are the two courses a drug can take upon entering the body? |
The drug can either be absorbed or liberated before entering into the bloodstream (liberation is more likely for drugs that are ionized in the intestine and can't feely diffuse into the blood) |
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What is the concentration of drug in the plasma that we measure and what does this ignore? |
Free drug, therefore ignoring drug in the plasma that is protein bound and also drug that has settled into extravascular spaces (i.e. the fat if lipophilic) |
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Which drugs are most likely to go through biotransformation/metabolism? |
Drugs that are lipophilic and therefore won't stay in the urine |
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What influences oral drug efficacy? |
Compliance, drug must properly release, drug must dissolve and mix with GI fluids, and it must be absorbed |
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What is the lag period in drug therapy? |
The time it takes for the plasma concentration to rise to a level that begins to provide the therapeutic effect |
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What is the therapeutic window? |
The plasma concentrations where the drug both gives the desired response and avoids the negative side effects |
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What causes the drug effectiveness to peak at a certain time point post administration? |
This occurs when the rate of absorption is matched by the rate of metabolism (excretion if inactivated) and therefore the graph peaks and the rate is zero |
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Four methods by which a drug can cross a membrane? |
Passive diffusion, facilitated diffusion, active transport and endocytosis |
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What is the driving force for passive diffusion and what drugs are favoured? |
The driving force is the concentration gradient and more lipophilic drugs are favoured because they freely pass through the membrane |
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What is requirement for drugs that use facilitated diffusion? |
They have to structurally mimic the endogenous substrate that uses the transporter |
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What is the advantage and disadvantage of facilitated diffusion? |
The process enables the transport of larger more hydrophilic molecules although it is limited by the number of channels available |
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Why does active transport require energy? |
It moves substances against a concentration gradient effectively concentrating them further |
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What are two common active transport systems, which functions for absorption and which for excretion? |
SLC (absorption) and ABC (excretion) proteins Not all SLC proteins are active transporters |
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What is the slowest form of absorption and what drugs rely on it? |
The slowest method of absorption is endocytosis and it is utilized by protein based drugs |
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What is bioavailability? |
The extent and rate of active drug reaching systemic circulation |
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What is important to know in addition to drug maximal concentration? |
The amount of time it exists at that concentration for |
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In decreasing order which methods of administration produce the greatest bioavailability? |
1. Intravenous 2. Intramuscular 3. Subcutaneous 4. Oral |
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What influences absorption for IM/SC injections? |
The amount of perfusion to the respective tissue |
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How do GI tract features impact drug absorption? |
The microflora can impact the absorbability of a drug along with the GI motility in certain disease states it is sped up so that absorption time is decreased |
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What five factors affect drug distribution? |
Molecular size Perfusion pKa of drug and environment pH Protein binding Lipophilicity blood-tissue barriers |
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Tissue Binding |
Drug can bind to other macromolecules near the site of action (some drugs have greater propensity to bind bone and others fat) |