Medicinal Chemistry Flashcards
What are the different ways to administer a drug?
Orally, through eye/ear drops, suppository, parenteral (injection), skin patches, and inhalation
Define bioavailability
The fraction of an administered drug that reaches the blood supply.
What factors affect the bioavailability of drugs?
How they are administered, their solubility, and their functional groups
What phenomenon accounts for the low bioavailability of orally administered drugs?
The first-pass effect; this means that after drugs are swallowed, enzymes in the digestive tract alter them chemically and then they are further broken down in the liver.
What are the three types of side-effects?
Beneficial, benign, and adverse
What is the difference between tolerance and addiction?
Tolerance is when the physiological effect of a drug is diminished because of repeated doses (which means more is needed to have the desired effect). Addiction occurs when an individual becomes dependent on a drug to feel normal and withdrawal symptoms occur when the drug is withheld.
What is therapeutic window?
The concentration of a drug that must be present in the blood supply for it to have the therapeutic effect but not produce adverse effects.
How is the therapeutic index calculated?
the ratio of the minimum dosage required to produce the therapeutic effect to the maximum dosage that causes adverse effects in 50% of the population (for this second measurement, toxicity is used for humans and the lethal amount is used in animal studies)
The effectiveness of a drug depends on on its ability to bind to receptor sites in the body. What type of bonding usually occurs between the drug and the receptor sites?
Non-covalent forms of bonding such as ionic and hydrogen bonds, van der Waal’s forces, or hydrophobic interactions.
What is another name for pain killers?
Analgesics
What is the name for the chemicals that activate pain receptors around the body?
Prostaglandins
How are prostaglandins produced?
They are released by cells damaged by chemical, thermal, or mechanical energy
Other than signaling pain receptors, what effect do prostaglandins have?
They cause the inflammatory response (by widening blood cells near the site of injury) and they raise the body’s temperature (fever)
There is a type of pain killer that prevent the stimulation of local pain receptors and inhibit the function of prostaglandins. There are two names for this type of pain killer. What are they?
Mild analgesics or Non-narcotics
The bark of the (1)________ tree contains (2)_______, which allows it to alleviate pain; however, it (3)_______
(1) willow
(2) salicylic acid
(3) tastes like crap
The Bayer company made a (1)______ of salicylic acid, which makes it taste better. It is called (2)_____, and it reduces pain as well as fever, making it both an analgesic and an (3)_________.
(1) ester-derivative
(2) aspirin
(3) antipyretic
What is salicylic acid reacted with to produce aspirin, what is this reaction called, and what is a byproduct of the reaction?
ethanoic anhydride
esterification
ethanoic acid
How is the ethanoic acid byproduct removed from the aspirin?
The product is cooled, which causes crystals to form then washed with water. The ethanoic acid dissolves in the water and gets washed away, but the aspirin isn’t soluble in water to it remains separate.
How is the aspirin purified after having been washed?
In a process called recrystallization, the crystals are dissolved in hot ethanol and then slowly cooled. This separates the aspirin because it is less soluble than the impurities and unreacted salicylic acid. Then filtration is used to remove the salicylic acid crystals.
How can the identity of aspirin be confirmed?
melting point determination (it has a higher and better-defined melting point than the mixture of salicylic acid and alcohol) and infrared spectroscopy
What are the main differences in the IR spectra of salicylic acid and aspirin?
salicylic acid has a peak for its hydroxyl group and acetylsalicylic acid has a peak for its ester group
What is another side effect of aspirin?
it works as an anticoagulent, which is good for people at risk of heart attacks and strokes.
What are adverse side effects of aspirin?
they cause ulcers and people can be allergic to them
How can aspirins bioavailability be increased?
It can be reacted with NaOH to make it more polar and therefore more soluble in the blood (which is polar)
penicillin is an…
antibiotic
What aspect of penecillin’s structure makes it reactive?
the beta-lactam ring has 90 degree bond angles but wants 120 or 109.5 degree bond angles. This makes the bonds in the beta-lactam extremely reactive.
What enzyme does penecillin react with that makes it useful?
it reacts with transpeptidase, the enzyme responsible for building the cell wall for bacterias. This means that water can get inside the bacteria and it bursts.
what are two limitations of penicillin?
it is easily broken down by stomach acid so has to be injected (although a pill form was developed by modifying one of its side chains) and a lot of people are allergic to it
What do some bacteria produce that allow them to be immune to penicillin?
penicillinase or beta-lactamase
How does penicillinase work?
it opens the beta-lactam ring, rendering it useless
What to penicillin derivatives were created to withstand penicillinase and how do they work?
methicillin and oxacillin; they have modified side chains, which prevent the penicillinase from breaking open the beta-lactam ring before it can react with the transpeptidase
What type of analgesic are opiates and what does that mean?
they are strong analgesics or narcotics, meaning they cut off the transmission of pain in the brain, that is, they prevent the perception of pain
To which receptors do opiates bind?
the opioid receptors in the brain
Why is it hard for opiates to enter the brain?
the blood-brain barrier is made mostly of lipids to prevent polar molecules from entering via the blood
What are the three opiates you need to know?
codeine, morphine, and diamorphine
What limits morphine’s bioavailability?
It has two O-H functional groups, which make it extremely polar, thus making it harder for it to cross the blood-brain barrier
What makes codeine a semi-synthetic drug?
It is most commonly derived from morphine, but it can also be found in small quantities in opium.
How does codeine differ from morphine?
It replaces one of the hydroxyl groups with a methyl ether group. This makes it less polar and easier to cross the blood-brain barrier.
What is the name of the process used to turn morphine into codeine? And what effects does this have on its effectiveness?
Methylation (it gains a methyl ether) and it makes it less polar so it can pass more easily through the blood-brain barrier, but it makes it less able to bind to the opioid receptor site in the brain
What is the name of the process used to turn morphine into diamorphine? And what effect does this process have on the effectiveness of the drug?
esterification (both hydroxyl groups are replaced by ester groups) this makes it much less polar, so it can pass through the blood brain barrier most effectively of the three opiates
What also increases as the narcotic and analgesic effects of opiates increase?
the side effects and its potential to cause addiction and tolerance
What must happen to diamorphine inside the brain before it can bind to the opium receptors?
Its ester links are broken by enzymes called esterases and it turns back into morphine so that it can bind to the opium receptor sites