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
The medical use of diamorphine is allowed only in some countries. Give arguments in favour and
against its legal controlled use.
favour - If controlled helps with pain
non-favour - addictive, intravenous which could cause aids.
Suggest why the action of drugs in lowering the production of stomach acid is considered to be indirect in the case of H2 receptor antagonists, but direct in the case of gastric proton pump inhibitors.
The H2 starts the sequence of events so you are not directly blocking, whereas proton pump inhibitors are directly responsible for pumping H+ into the stomach.
Magnesium hydroxide and aluminium hydroxide can act as antacids. Write an equation for the reaction of hydrochloric acid with each of these antacids.
Mg(OH)2 + 2HCl –> MgCl2 +2H2O
Al(OH3) + 3HCl —> AlCl3 + 3H2O
Explain why potassium hydroxide is not used as an antacid
H is a strong base, ingesting it would be harmful.
Why are viral infections not able to be treated with antibiotics?
Viruses only have a protein coat + DNA / RNA. No targetable structures. Viruses lack a cell wall
With referents to the structure of the influenza virus, explain why it is possible to suffer from flu
several during a lifetime.
Influenza has hemagglutinin and neuraminidase on the surface. These allow it to enter and exit host cells. Different variations of these 2 surface proteins exist, so even if vaccinated against one type you could be affected later on in life.
Explain why the antivirals Tamiflu and Relenza must be taken within a very short time after the appearance of the symptoms of flu.
Because they block the action cells of neuraminidase which releases virus from host cell. To prevent flu from escaping cells must be blocked asap.
Link these up non-polar, polar, solubility in water and lipid solubility
Non-polar = low-solubility in water but enhanced lipid solubility
polar = solubility in water but low-lipid solubility
is a phenol group a non-polar or polar molecule?
non-polar
how many chiral carbons are there in taxol?
11 chiral carbons
Describe the original source of Taxol and the environmental impact of obtaining the drug
from this source.
Original way of obtaining Taxol was from the bark in the yew trees, we had to strip the tree of their barks and because of this we ended up killing a lot of trees and ruins the eco-system
Taxol has been described as a ‘very chiral molecule. Explain the meaning of this statement and why processes to synthesise Taxol® chemically are complex and must be carefully
controlled.
It has 11 chiral carbons meaning it has a lot of enantiomers but only 1 is therapeutic and it is tricky to isolate this one. Risk are that the other enantiomers are harmful.
Describe how chiral auxiliaries can be used to synthesise only the desired enantiomeric form
drug from a non-chiral starting compound.
A chiral auxiliary binds to the reactant blocking one of the possible reactions via steric hindrance. This means only the desired reactant is produced.
list 3 side effects of radiotherapy
hair loss, fatigue and nausea.
What tracer does a PET scan use?
Fluorine-18 F18
Tc-99 emits ________ (used for x-rays)
Gamma radiation
I-131 is both a __ and a __ emitter. monitor liver or kidney function).
Beta and gamma
____ is an ___ emitter used for Targeted Alpha Therapy.
Pb-212, an alpha
what is Bioavailability
The fraction of the administered dosage that reaches the target part of the human body
what is antibacterial
compounds that are able to kill or inhibit the growth of bacteria
what is blood-brain barrier
It is hydrophobic
What is a narcotic
Is a drug that is addictive and can cause change in behaviour, used for recreational purposes.
what are the 3 types of alcohol testing devices?
- breathalyser - detects alcohol by redox reaction that produces a colour change
- Alco-sensor - detects alcohol by a redox reaction
- Intoximeter - detects alcohol by infrared (IR) spectroscopy
Outline what happens in a Breathalyser
Breath is blown through a tube containing crystals of Potassium dichromate (VI). The ethanol in the breath is oxidised to form ethanoic acid. The dichromate ion is reduced to form the Cr3+ ion.
Oxidation: CH3CH3OH –> Ch3COOH + 2H+ + 2e-
Reduction : Cr2O7 +14H + 6e- –> 2Cr3+ +7H2O (Orange to green)
Outlines what happens in a alcosensor
An alcosensor contains a fuel cell with 2 platinum elecreodes and a porous acid-electrolyte material between them. The alcohol undergoes oxidation at the anode to produce ethanoic acid, protons and electrons.
anode: CH3CH3OH +H2O –> CH3COOH +4H+ + 4e
Cathode : O2 + 4H + 4e- + 2H2O
The higher the conc of alcohol in the breathe sample the higher the electric current produced by the fuel.
High-level waste (HLW) is waste that gives off ___ amounts of ____ radiation for a ____ time.
Low-level waste (LLW) is waste that gives off ____ amounts of ____ radiation for a ____ time.
High-level waste (HLW) is waste that gives off LARGE amounts of IONIZING radiation for a LONG time.
Low-level waste (LLW) is waste that gives off SMALL amounts of IONIZING radiation for a SHORT time.
What do we do with LLW
Stored in shield containers until isotopes have decayed and then disposed of as non-radioactive waste.
What do we do with HLW
Stored in shield containers in underground repositories
when does antibiotic resistance occur?
occurs when micro-organisms become resistant to antibacterials.
What do many undesirable solvents have in common?
They are VOCs (Volatile organic compounds)
what are solvents
They are used as a reaction media, product recovery and purification. They need to be carefully disposed of to protect the environment
What does HIV do, give me 2 characteristics
HIV destroys the T-cells
They can mutate quickly
Taxol was originally obtained from the bark of the Pacific yew tree.
Outline how Green Chemistry has improved the process of obtaining Taxol.
stripping the bark kills Pacific yew tree
the sustainable process uses more efficient catalysts
does phenyl have an H attached to it?
No
does phenol have an H attached to it?
Yes
Explain why using only the desired
enantiomeric form of a drug is important
CA can be removed and recycled. It is important to use the therapeutic enatomier only or unwanted side effects can occur.
