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25 Cards in this Set
- Front
- Back
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where are most oral drugs absorbed
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small intestine because it has the most surface area
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what are the pHs of small intestine, stomach and urine
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basic, acidic, 4.0-8.0 pH
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what is a general rule to follow when it comes to drug absorption and basicity and acidity
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basic drugs go across membranes in basic environments and vice versa
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where do some low molecular weight water soluble compounds distribute
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e.g. ethanol. uniformly distributed throughout the body water = uniform distribution
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where do most drugs distribute
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most drugs do nonuniform distribution. the liver and kidneys are often where they distribute the most
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what are the three types of capillaries in order from least porous to most porous
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continuous (muscle, skin, lung, CNS, mucous membranes), fenestrated (intestinal mucosa, kidney, endocrine glands), discontinuous (liver, spleen, bone marrow)
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what does where a drug distributes depend on
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rate of distribution (blood perfusion) and extent of distribution (intracellular binding, plasma protein binding, capillary permeability)
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breakdown of body water
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60% of total body mass is water. 40% of total body mass is intracellular, 20% is extracellular.
4% of total body mass is intravascular plasma, 16% is interstitial |
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what does a hematocrit of 0.46 mean
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46% of blood is blood cells and 54% is plasma
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what is the plasma concentration of ethanol in a person with hematocrit of 0.4 if their blood concentration of ethanol is 50 mg/mL
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0.6 x Cp + hematocrit x 0.7 x Ci = drug concentration of drug; make Ci and Cp the same variable
0.88 x Cp = 50mg/mL Cp = 55 mg/mL |
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which drugs readily cross capillary membranes
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unbound drugs (unbound to plasma proteins) of less than 60,000 (daltons, 1 C unit) molecular weight cross fenestrated/discontinuous/continuous capillaries (except for the BBB)
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where do bound to serum protein drugs exit capillaries
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liver, spleen, bone marrow
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what is the relative rate of delivery of drugs to different organs
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liver>kidney>muscle>>>brain
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what binds where to what sites on albumin
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it has a negative charge at blood pH (so positive charge drugs can bind), it has nonspecific sites so drugs with high partition coefficients (lipid solubility) can bind
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do a lot of drugs distribute to fat
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most drugs have too low a partition coefficient and besides fat has a very low blood supply so this hurts distribution
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what are the most highly perfused parts of the body
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brain, muscle, kidney, liver (L to G) receive the most CO
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which types of administration require that drugs pass membranes to reach circulation
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other than iv injection, all other methods of administration require that drugs cross membranes to enter circulation
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what are some characteristics of carrier mediated transport
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rate is independent of membrane surface area. rate is proportional to the number of transporters and drug concentration (up to saturation point). the curve is asymptotitic after saturated carriers but linear up to that point. process is saturable.
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what is the difference between active and facilitated transport
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active you can transport from lower to higher concentration otherwise the processes are the same
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what are some properties of simple diffusion
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aka passive diffusion. increases as partition coefficient increases. increases with surface area. nonsaturable. only noncharged drugs can pass thru, only molecules less than 1000 Da can pass thru
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what is the law to describe simple diffusion
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J = -D x A (C/X). J is flux across membrane. D is diffusion coefficient (proproportional to partition coefficient. A is surface area
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what influences passive transport
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aka simple diffusion: drug permeability (pKa (most important), partition coefficient, polar nature, charge, size, pH of medium), concentration grandient, surface area, temperature
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what is pK
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pH values at which 50% of drug is ionized
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do IV drugs have to go thru an absorption step
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no but all other adminstrations do
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do subligual and rectal administrations do first-pass metabolsim
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no
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