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22 Cards in this Set

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What two ways do drugs move around in the body?
-Bulk flow transfer (i.e. in the bloodstream)
-Diffusional transfer (i.e. molecule by molecule, over short distances)
What are two main characteristics about drugs that affect their actions in the body?
- diffusional characteristics
- lipid solubility affect ability to cross hydrophobic diffusion barriers
Name ways in which drugs will go through lipid bilayer.
- diffusion through lipid (most common)
- diffusion through aqueous channels
- transmembrane carrier proteins (also very important and common)
- pinocytosis
What can be predicted from knowledge of a drugs lipid solubility?
- rate of absorption from the gut
- penetration into the brain and other tissues
- the extent of renal elimination
Many drugs are weak acids or bases. How does this affect drug solubility?
- They exist in unionized and ionized form.
- The ionized BH+ and A- cannot pass through the membrane unless there are special carriers.
- the uncharged form pass through lipids very well.
- This group could be very large depending on how large the difference between the two compartments are.
How does urinary acidification affect drug excretion?
accelerates excretion of weak bases and retards that of weak acids
How does urinary alkalinization affect drug excretion?
reduces excretion of weak bases and increases excretion of weak acids
How does increasing plasma pH affect the diffusion of drugs?
-causes weakly acidic drugs to be extracted from the CNS into the plasma
How does decreasing plasma pH affect the diffusion of drugs?
causes weakly acidic drugs to become concentrated in the CNS, increasing their neurotoxicity
- ie can decrease plasma pH by administering carbonic anhydrase inhibitor, acetazolamide
What is p-glycoprotein?
- It is a the drug transporter responsible for multidrug resistance in neoplastic cells. Transport drugs OUT of the cell.
- present in renal tubular brush border membranes, in bile canaliculi, in astrocyte foot processes in brain microvessels and in the gastrointestinal tract
- plays an important part in absorption, distribution and elimination of many drugs
Drugs bind to plasma proteins, the most important one being albumin. What are examples of drugs they bind to, and what factors affect the bind of the drugs?
- warfarin (non-steroidal anti-inflammatory drugs). binds to many acidic drugs.
- chlorpromazine (tricyclic antidepressents). bind to some basic drugs.

- the concentration of free drug
- its affinity for the binding sites
- the concentration of protein
What is the drug-binding capacity of plasma albumin?
- 1.2 mmol/L. there are 2 binding sites on albumin.
- most drugs, the total plasma concentration required for clinical effect is much less than 1.2 mmol/L. binding site are far from saturated...unless multiple drugs and competitively bind.
Where does thiopental accumulate?
In fat. Fat:water ratio is 10:1
Most drugs have issues being stored in fat. Why?
1. most drugs have a low fat:water partition coefficient
2. body fat has low blood supply
When lipid-soluble drugs are given chronically, accumulation of body fat is often significant. What can occur, especially with xenobiotics (environmental contaminates), THC from marijuana, and LSD?
Drug redistribution of drug released from fat over time. If LSD or marijuana, will get a "flashback high" every now and then.
Btw...alcohol and cocaine clear out quickly. Tobacco, marijuana, and LSD don't clear out quickly.
Four stages of drug disposition.
- absorption from the site of administration
- distribution within the body
- metabolism
- excretion
What is high first pass effect?
if give drug orally, not going to achieve a systemic effect because after first pass through liver, it is cleared. So can give it through IV.
What are the factors affecting gastrointestinal absorption of drugs?
- gastric emptying rate (access of drug to increased intestinal surface area increases rate of absorption, remember Fick’s Law)
- gastrointestinal motility
- splanchnic blood flow
- particle size and formulation
- physicochemical factors
Interesting fact: can eat animals killed with curare because very strong base and is not absorbed well in intestines.
Why should you not drink milk with tetracycline?
Tetracylcine binds strongly with Ca2+ and prevents absorption.
What are some examples of drugs that are mixtures of stereoisomers?
sotalol, warfarin and cyclophosphamide
Why would pharmaceutical companies want to create pure stereoisomers of a drug like warfarin?
Stereoselectivity- want to avoid toxicity that may be linked to one of the stereoisomers.
During a phase I reaction, drug oxidation by the monoxygenase P450 system requires what?
drug (substrate, “DH”), P450 enzyme, molecular oxygen (one will for into a hydroxyl group and another H20), NADPH and a flavoprotein (NADPH-P450 reductase)