EQUILIBRIUM CONSTANTS EXTENSION Name Drug Design & Solubility Section Date Pharm
ID: 510570 • Letter: E
Question
EQUILIBRIUM CONSTANTS EXTENSION Name Drug Design & Solubility Section Date Pharmaceutical drug design involves creating a molecule that will target a general region or site and have a therapeutic effect on the patient. When orally ingested, a drug moves from the stomach into the small intestine and then through a layer of cells before it can enter the bloodstream and be distributed throughout the body. This requires crossing through a largely non-polar cell membrane twice, first to enter the cell from the intestine side and then to exit the cell for entry into the water- based bloodstream. The drug must thus show some solubility in both aqueous and organic solvents. The partition coefficient (P) is an equilibrium constant for a solute that is partially dissolved in two different solvents. In medicine, this value is useful in estimating the distribution of drugs within the body. Given the complexity of cells, it is very difficult to directly measure partitioning of a compound between the aqueous and non-polar components of a cell. Hence, a simpler model system can be used in which octanol serves as a mimic of the non-polar cell components, and water component, blood. The partition coefficient P, often denoted as the Kow, specifically describes the degree to which a drug prefers octanol (o) or water (w), defined below: Kow [drug in octanol] rug in water Harris, M. F.; Logan, J. L. J Chem Educ 2014, 91,915 918. http:/fpubs acs org/doi pdf 10.1021 /ed400655b l. DDT, the pesticide famously investigated in Rachel Carson's book Silent Spring, has value 1.64 Using this environmental builds up information, DDT in cells of exposed animals (known as bioaccumulation) rather than getting properly flushed out through the bloodstream.Explanation / Answer
1. DDT has very high Kow, that is it has very high solubility and thus keeps getting accumulated without getting washed off from the system. This is called bioaccumulation.
2. Absorbance measured the concentration of acetaminophen in the solvent. Acetaminophen has a particular lambda-max at a certain wavelength and hence this wavelength-max can be used to estimate quatitatively the amount of drug in the system under study.
3. Separatory funnel is a glassware in which we mix our drug dissolved in one solvent with another immiscible solvent. The two liquid are then shaken together vigorousy so that the liquids come in contact with each other and the drug partitions between the two solvents. At one point the drug would be in equilibrum state with respect to the solubility of it in the two solvents and no more drug would partition any further between the two layers of solvents.
4. Partition coefficient for the drug
= amount extracted/amount remaining
= (0.5 - 0.125)/0.125
= 3
5. Side effect of drugs are considered in patient to patient case. some patients develop these symptoms after taking the drug however other may not have any side effect.
the potential side effect of acetaminophen (tylenol) is nausea, itching, headache, stomach pain among few. The patient is advised to consult the physician in case they develop any of these symptoms after consuming the drug.
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