MEDICINAL CHEM Flashcards
What is the therapeutic index
The therapeutic index is the ratio between the dosage of a drug that causes a toxic (or lethal) effect and the dosage that causes a therapeutic effect
What is the therapeutic window
measure of the relative margin of safety of a drug
give an explanation of wide and narrow therapeutic windows.
drugs with wide therapeutic windows are safer; narrow therapeutic window requires small doses as the lethal dose is not large
State an equation for the reaction of stomach acid with this antacid NaHCO3.
NaHCO3+HCl –> NaCl + H2O + CO2
list the 3 different ways drugs can be injected into the body
intravenous, inter-muscular and subcutaneous
list the 3 different ways drugs can be injected into the body, predict, giving a reason for which of the 3 methods will result in having the most rapid effect.
intravenous, inter-muscular and subcutaneous
Intravenous would have the most rapid due to the bioavailability of 100%.
state what is meant by tolerance towards a drug
Overtime a person may need an increased amount of drug to reach the desired therapeutic effect.
state what is meant by tolerance towards a drug and explain why it is potentially dangerous
Overtime a person may need an increased amount of drug to reach the desired therapeutic effect. This narrows the therapeutic window which puts them in a higher risk of adverse side effects and lethal overdose.
explain why the therapeutic index is defined differently in animal studies and in humans
Ethical considerations. In animals = lethal dose/effective dose for 50% of population. In humans = toxic dose /effective dose for 50% of population. It is not ethical to give humans a lethal dose, but it is okay to do this to animals.
Outline the factors that must be considered when determining the dosage of a drug
age, body weight, route of administration, effective dosage, toxic dosage, tolerance.
Why can it be challenging to determine the dosage of a drug that has a low therapeutic index?
A low therapeutic index means a low therapeutic window which is tricky to ensure an effective dosage is given and does not become lethal.
Describe 3 factors that influence the bioavailability of a drug
polarity, functional group, and way of administering.
how do you check the purity of aspirin?
IR spectroscopy - identify functional groups that are specific to salicylic acid vs aspirin
Melting point analysis - aspirin has a lower melting point
Describe how a chemical modification of aspirin can increase its bioavailability
Aspirin is a salt, so reacting it with a base such as NaOH would produce the Na salt of aspirin + water. The salt is more soluble which means it’ll dissolve in body fluids better increasing its bioavailability.
What is a mild analgesic
Mild analgesic is for the relief of mild pain and it is not addictive and doesn’t cause loss of consciousness
what is a anticoagulant
Prevents blood from clotting that causes heart attacks
Why is it dangerous to consume alcoholic drinks while taking aspirin
Synergistic effect. Acute, severe side effects can get stomach upset, bleeding and ulceration.
what is the molecular formula of penicillin?
C7N2SH9O
Where on the penicillin can the side chain be modified and why is this done?
To allow it to move through the stomach without it breaking down
To help with anti-biotic resistance, resistance to “Penicillinase”
What part of penicillin is responsible for its antibiotic properties and explain on the basis on its mode of action
beta-lactam ring binds permanently to the enzyme in the bacteria which is responsible for cell wall construction. Without a cell wall, the bacteria takes in water and busts and dies.
give 3 reasons why human activities have caused an increase in resistance to penicillin
Not completing the anti-biotic course, taking antibiotics for problems that do not need them, antibiotics in farming passed through meat/dairy products to humans.
State 2 functional groups common to codeine, morphine and heroin
alkenyl and phenyl group
State a main effect and major side-effect of morphine
main effect - pain relief as morphine blocks opioid receptors in the brain
Side effect - constipation, suppressed cough reflex
By reference to its chemical structure, explain why diamorphine is more potent in its action as a
strong analgesic than morphine.
It has 2 ethanoate groups while morphine has 2 hydroxyl groups. Hydroxyl is polar so it struggles to cross the blood-brain barrier, Ethanoate groups are non-polar so it crosses the blood brain barrier easier making it more potent