Paper 3 Flashcards
What is the definition of a drug?
A substance that has some type of physiological effect when introduced into the body
What do most drugs act with
?
Some kind of receptor molecule in the body
How do drugs work?
Receptors generally large protein molecule
With an active site, which has a specific shape
Only allows a limited number of molecules to fit depending on their shape
Drug Development (Explain the stages)?
Identifying the need
Identifying the possible structure of a new drug
Modification + Testing the drug activity of a range of molecules –>
1.) In Vitro
2.) Then in Vivo
Synthesis of the possible drug or extraction of the drug from a natural source
Animal Studies dose equation?
LD50/ED50
Human Studie dose equation?
TD50/ED50
How do we decide which drug to administer?
- Is it solid, liquid or gas
- How quickly/effectively it can reach a certain part of the body
- How stable is it in bodily environments
Definition of bioavailability?
The fraction of the administered dosage that reaches the target part of the human body
Factors affecting Bioavailability?
Method of administration
The polarity of the drug
What affects the polarity of a drug?
- Dependent on the functional group
Tolerance?
Human body constantly adapts to the chemicals it meets
Repeated use –> Drug Tolerance
- Need larger amounts for the original effects
Why would increasing the dose be a bad thing in regard to Tolerance?
Increasing the dose
- ST –> temporarily overcomes tolerance
- LT –> Greater tolerance
Definition of Side effects?
adverse effects which the drug was not prescribe for
Addiction?
When the patient becomes compulsive about taking the drug regardless of the consequences
- Increased problems of Tol and SE
What is aspirin?
an Ester
Equation of Aspirin
Displayed Formula
Salicylic Acid + Ethanoic acid –> Aspirin
This does not produce a vast yield of Aspirin so Ethanoic Anhydride might be needed.
What is the catalyst in the reaction that results in the formation of Aspirin?
Conc. sulfuric acid
How to prep Aspirin?
- Add Salicylic Acid into a conical flask
- Add excess ethanoic anhydride and mix reagents carefully
-Leave the flask until the reaction is completed
- Add cold deionized H2O –> convert excess ethanoic anhydride into ethanoic acid.
- Filter the mixture by vacuum filtration
- Recrystalise the mixture
How to recrystallize the mixture of aspirin initially made?
Re-dissolve aspirin with hot ethanol
Filter using vacuum filtration
Cool in ice bath
Filter mixture again
does Aspirin have an OH group?
yeah
How soluble is Aspirin in water?
Aspirin is not that soluble in water due to the large non-polar phenyl group
How can aspirin’s aqueous solubility be improved?
Neutralisation with a base to give it ionic sodium salt
Mechanism of Penicillin?
Structure: Beta Lactam ring
Four membered ring is strained
Makes carboxamide group reactive
Ring opens up and reacts with the enzyme that is responsible for the formation of vital cross-links in the new bacterial cell walls
Cell wall is weakened and permeable
Leads to the bacteria taking too much water and dying
How does Aspirin work?
Mild Analgesic
functions by intercepting the pain stimulus at the source, often by interfering with the production of substances that cause pain
How else can aspirin be used?
Can be used as an anticoagulant
–>
Helps to prevent blood clots
Why do people who take aspirin are not advised to drink alcohol?
synergistic effect –> caused by the presence of both drugs that is greater than the sum of their individual effects
can lead to bleeding in the stomach
Names of all functional groups
SEE
What are two reasons for tolerance of drugs?
- More you use –> Greater Metabolism –> More drug excreted and less remains in the body
- Body adapts by desensitizing target molecules which drugs bind to so it is not able to produce the same effect
What is the mutation that is resistant to penicilin
penicilinase
What do strong analgesics do?
- Temporarily bind to opiod receptors in brain whch block transmission of pain signals
Advantages of taking Opiates?
- Relief of severe pain
- Used in cancer patients
Disadvatages of taking opiates?
- Naseau and vomiting
- Constipation
- Respitory Depression
- Physical and pshycological dependence
how do mild analgesics relieve pain?
Intercepts the pain stimulus at the source
Interferes with the production of substances that cause pain.
what is the definition of a synergistic effect?
an effect caused by the presence of both drugs that is greater than the sum of ther individual effects
Why should you not take alcohol with aspirin?
Synergistic effect
Can lead to bleeding in the stomach
Explain the importance of beta-lactam ring in penicilins?
- Interferes with enzyme responsible for bacterial cell wall
- Beta lactam ring is strained
- Has smaller bond angles
Why is the over prescription of penicillin a bad thing?
- Bacteria can become resistant to the antibiotic due to a greater number of bacteria being exposed
- A greater probability of resistance developing
Explain how a strong analgesic relieves pain?
- Crosses the brain blood barrier
- Binds to opiod receptor sites in the brain
- Supresses the transmission of pain receptors in the brain
What are two effects of an excess of stomach acid?
Acid Reflux - A burning sensation when acid flows up into the oesophagus
Peptic Ulcers - a painful open sore in the lining of the stomach or small intestine
What are antacids?
Things that can simply neutralise excess acids in the stomach
What are some examples of antacids?
Calcium Hydroxide
Magnesium Hydroxide
Aluminium Hydroxide
Sodium Carbonate
Sodium Bicarbonate
Which drugs inhibit the production of Acid?
- H2 agonists
- Proton Pump Inhibitors
How do H2 agonists inhbit the production of Acid?
- (rantadine) Zantac block the action of histamine
- Rantidine molecule prevents the secretion of this acid by reversibly binding to the H2 histamine receptors in the cell
- Part of Rantadine molecule has a similar shape to histamine and so fits into the receptor side
- Inhibits the secretion of acid by the cells in the lining of the stomach
How do Proton Pump Inhibitors inhibit the production of acid?
Prilosec and Nexium
- Blocks the enzyme responsible for pumping the Hydrogen ions out of the cells and into the stomach
Can you describe how omeprazole works to reduce the secretion of acid?
- Omeprazole is less polar
- More easily crosses the lipid base cell membrane into the cellls
- Becomes charged to creates and active form
- Active form binds to proton pump
Why are Proton Pump inhibitors more effective than H2 Agonists in prohibiting thr secretion of acid in the stomach?
- Much more effective than H2 agonists because their action is irreversible, so they permanently deactivate the proton pump
What is the point of the buffer solution?
When you add medicine into your body might be acidic or baisc so the pH of the medicine might affect your body.
The buffer solution keeps your pH constant in the body when a drug is administered
A buffer solution is added to the drug formulation
What is the definition of a buffer solution?
A buffer solutiuon is one that resists change in pH when small amounts of acid or alkali are added
Why do you not suddenly stop taking Prilosec or Nexium (PPI)?
You run the risk of a rebound effect (acid reflux)
- You have to decrease the dose gradually
equation of pH?
pH = pKa + log([A-])
[HA}
Are viruses always parasitic?
Yes
Why are viruses more difficult to target than bacteria with drugs?
-Viruses lack a cell structure and only reproduce inside living cells
- Many viruses can mutate rather easily –> leading to changes in the composition of their protein coat –> leading to the resistance to drugs
How do Antiviral drugs work?
- They alter the cell’s genetic material so that the virus cannot use it to multiply
- Preventing the viruses from multiplying by blocking enzyme activity involved with either replication of DNA within the host cell, or the release of the new viruses
What are examples of anti-viral drugs?
Tamiflu and Zanamavir
How do Zanamivir and Tamiflu work?
They inhbit the enzyme neuraminidase
Neuraminidase is produced by the virus as part of the mechanism that allows the new viruses to leave the host cell after replication
Where are synthetic drugs always made?
Labs
What is the definition of Metabolism?
The speed and the ability to absorb and use the medicine
State one factor that can affect the ability of the body to absorb a drug?
- Age
- Weight
- Method of Administration
- Polarity
- Solubility
Therapeutic Effect
A desirable and beneficial effect; it alleviates symptoms or treats a particular disease