medicinal chemistry Flashcards
the four types of administration routes are…
1. oral
2. ???
3. rectal
4. topical
parental
capsules, suspensions, solutions and tablets are all ______ administrated
orally
what are two rectal dosage forms?
suppositories, creams
what are three types of injections
- intravenous
- subcutaneous
- muscular
why are there different administrative routes? (2 short)
- increase bioavailability of drug
- prevents degradation by acidic pH in the stomach environment
- incr patient compliance
what is bioavailability?
fraction of of administered dosage that enters the blood stream
which type of administration has 100% bioavailability?
parental
what is pharmocokinetics? (short recap)
what the body does to the drug after it enters the body
the four processes of pharmokinetics are…
- absorption
- distribution
- metabolism
- elimination
(All Dogs Make Eggs)
what is one way absorption is negatively affected?
poor solubility in water -> poor uptake
distribution is affected by the _______ity and _____ity of drugs
hydrophilicity, lipophilicity
what affects the hydrophilicity and lipophilicity of drugs?
the functional groups present on compounds
what type of drug administration is usually affected by metabolism?
oral
drugs that become metabolites undergo ______________
first pass metabolism
how does metabolism affect bioavailability? (3)
- drugs experience ‘first-pass metabolism’ by the liver
- cannot exert therapeutic affects
- this significantly affects F
what is the therapeutic window? (short def.)
the range of acceptable dosage strengths where the drug will exert its therapeutic effect without causing toxic effects
what is the formula for therapeutic index for animals
LD50/ED50
what is the formula for therapeutic index for humans
TD50/ED50
is a high therapeutic index good? why?
- yes
- greater safety margin btw effective and toxic/lethal dose
- when taken in higher doses than required for it to exert therapeutic effect, the drug will still be safe
how does aspirin work as a mild analgesic?
it binds to COX 2 enzyme and prevents it from releasing prostaglandin
aspirin prevents pain detection at the source by
preventing nerve messages from being sent to the brain
aspirin reduces swelling by
- preventing dilation of blood vessels
- decr swelling
- reduces inflammatory response
what does prostaglandin do? (2)
- send nerve messages to brain -> pain detection at source
- causes inflammatory response -> dilation of blood vessels -> swelling -> incr pain
what reagents and conditions are required for the synthesis of aspirin?
- reagents: salicylic acid, ethanoic anhydride
- cond: catalyst H2SO4, warm e mixture
what are the products of aspirin synthesis
aspirin + ethanoic acid
write out the reaction of aspirin synthesis
-
how is aspirin purified from aspirin synthesis?
- dissolved and heated in ethanol
- recrystallisation in ethanol -> due to low solubility
- filtration
what does a lower than expected melting point of aspirin tell us?
there are impurities
what is the m.p. of salicylic acid?
159ºC
what is the m.p. of aspirin
138-140ºC
what method can be used to differentiate between aspirin and salicylic acid?
- IR spectroscopy
- aspirin: presence of C=O peak
- salicylic acid: presence of O-H peak
what does synergistic mean?
when taken together, the drugs have a greater combined effect than individual effects
what are 2 other purposes for aspirin?
- anticoagulant
- synergistic effects w alcohol
why is aspirin made into a salt?
- improve solubility of aspirin in water
- incr F
write the reaction of how aspirin is made into a salt
-
what is penicillin
an antibiotic
why is penicillin so reactive?
it has a beta-lactam ring which has ring strain
how does the beta-lactam ring in penicillin kill bacteria? (2)
- binds irreversibly to enzyme transpeptidase in bacteria
- disrupts formation of bacterial cell wall
- when water enters bacteria, bacteria lyses
why is penicillin modified? (2)
- to improve stability of drug in low pH environment
- improve oral F
- overcome antibiotic resistant bacteria
- has enzyme penicillinase which prematurely opens up beta-lactam ring
- prevents bacteria fr recognising drug
why is there increased antibiotic resistance?
- overprescription of antibiotics
- when patients do not complete the full course of antib
- use of antibodies in animal feed -> enters food chain -> humans end up eating it
how do opiates function as strong analgesics?
- bind reversibly to opiate receptors in CNS
- prevents transmission of nerve impulses
how is morphine derived?
from opium
which opiate is methylated morphine?
codeine
diamorphine is the ________ form of morphine
esterified
why is diamorphine the most potent?
- it is least polar
- it can cross the lipophilic blood brain barrier most easily
codeine and diamorphine are _____, precursors to the active form morphine
pro-drugs
what are pro-drugs
- inactive form of drug
- metabolised in the body into active form
what reagent can be used to react convert morphine into diamorphine
ethanoic anhydride
what are 2 advantages of opiate usage?
- provides stronger + faster pain relief
- suppresses cough reflex
what are 3 disadvantages of opiate usage?
- addiction
- tolerance -> overdose
- constipation
what is tolerance?
it is when a higher dosage is required to exert the same effect
why is tolerance dangerous?
higher dosages may reach lethal dosage –> overdose
what condition is caused by excessive production of HCl?
dyspepsia
what are three things you can take to counter dyspepsia
- ranitidine
- omeprazole/esomeprazole
- antacids
how does ranitidine counter dyspepsia?
- competitive inhibitor of H2-receptor
- prevents histamine from binding
- prevents parietal cells from releasing HCl
ranitidine inhibits ____ while omeprazole/esomeprazole inhibits ____
H2-receptor, proton pump
how does omeprazole/esomeprazole counter dyspepsia?
- inhibits proton pumps
- directly prevents parietal cells from releasing H+