Option D Flashcards
What do medicines and drugs do?
Alter incoming sensory sensations
Alter a person’s mood or emotions
Alter the physiological state of the body including COORDINATION and CONSCIOUSNESS
Define a drug and describe the difference between a pharmaceutical drug and recreational drugs
A substance that causes a physiological change in the body. A pharmaceutical drug is taken for medical reasons whereas recreational drugs are taken for leisure purposes e.g: cannabis, ecstasy, alcohol
What is a therapeutic effect
The beneficial effect of a medicine
Describe the oral way of taking medication
Medicines are taken by mouth e.g: tablets, capsules, pills
Describe inhalation
Vapour breathed in by smoking, e.g: asthma medication, neubilisers
Skin patches
Absorbed through the skin into the blood e.g: hormone patches
Suppositories
Rectum, e.g: laxatives for constipation
Eye or eye drops
treatment for eye or ear infections
Injection (parenteral)
Injected into the muscle, blood or under the skin
Describe intramuscular injection
Drug is injected directly into the muscle
Intravenous?
Drug injected into bloodstream - 100% bioavailability as directly in bloodstream
Subcutaneous?
Drug is injected directly under the skin
Describe the layers of the skin
Every Doctor Sells Medicine
Epidermis
Dermis
Subcutaneous tissue
Muscle
Which drug administration method has the fastest effect?
Intravenous
What is bioavailability?
The fraction of the administered dosage of a drug that enters the bloodstream, thereby accessing the site of action
What factors affecting bioavailability:
Method of admin
Polarity (solubility) of the drug
Types of functional groups present in the drug
Describe the bioavailability of an oral drug
They are often broken down during administration during digestion before reaching the bloodstream. An oral dose of a drug must be 4 times higher than dosage that is given intravenously
How does the polarity of a drug affect its solubility?
Very hydrophillic drugs are soluble in aqueous body but are poorly absorbed due to their inability to cross cell membranes which are composed of lipids.
Very hydrophobic drugs are not soluble in body fluids
For a drug to be readily absorbed, it must be mostly HYDROPHOBIC but also have some solubility in aqueous solutions.
What are the 2 major properties that contribute towards water solubility of a functional group?
Ability to ionize
Ability to form hydrogen bonds
E.g: COOH, NH2
Examples of non-polar functional groups
Phenyl group
Hydrocarbon chain (alkyl group)
Describe aspirin solubility
Largely non-polar molecule and so has low solubility in WATER due to presence of phenyl group
How to increase aspirin solubility
React it with aqueous NaoH, forming an ionic salt
How can drugs be chemically modified to increase their bioavailability?
Drugs containing an ACIDIC or BASIC functional group can be chemically modified to form an ionic salt
What is the therapeutic window
Measure of the relative margin of the safety of a drug. The wider the therapeutic window, the safer the drug.
A wide therapeutic window means that there is a wide margin between doses that are effective and doses that are toxic
A narrow therapeutic window means only a small increase in the effective doses may produce toxic effects
What is the therapeutic index
Ratio between lethal dose and effective dose
Formula for Therapeutic index in humans
TI = median toxic dose/ median effective dose
Main stages of drug development
Drug is synthesized in the laboratory
tested on animals
tested on humans - half given real drug, other half given placebo
Placebo effect
When the body is fooled into healing itself naturally
What are the factors that must be determined during drug testing
Risk: benefit ration - balance between risks and benefits
Unwanted side effects
Drug tolerance - when patient needs to take larger doses to gain original effect
BRIEF:
How is aspirin produced? (acetylsalicylic acid) and state the 2 catalysts that can be used
Ethanoic acid is excess and sali is LIMITING
Reacting salicylic acid with ethanoic anhydride to produce ASPIRIN and ETHANOIC ACID
Catalyst: CONCENTRATED sulfuric acid or H3Po4
Salicylic acid turns into aspirin via ESTERIFICATION - a condensation reaction
Mr of Aspirin
C9 H8 O4
Detailed steps of aspirin production
- Concentrated sulfuric acid is added to the reaction mixture of salicyclic acid and ethanoic anhydride which is warmed gently. This is the catalyst.
- The product is cooled to form crystals which are then suction filtered and washed with cold water
- Aspirin has very low solubility in cold water so this removes the soluble acids but not the aspirin
- Aspirin purified in a process called re-crystallisation
- This involves dissolving the impure crystals in a small volume of hot ethanol
Water is then added and the solution is then cooled, then chilled
acetylsalicylic acid then crystallises and the unreacted acetylsalicylic acid remains dissolved in solution
How can the purity of aspirin be determined
Infrared spectrum - 2 peaks: OH group and C=O in ester and carboxylic
Melting point - pure aspirin has a melting point between 128 and 140 degrees. Impurities lower the melting point and cause it to melt over a much wider temperature range
Describe the difference between the IR spectrum of acetylsalicylic acid and salicylic acid
Prescence of a peak corresponds to PHENOL in salicyclic which is absent in aspirin
Abscence of a C=O group corresponding to esters in salicyclic acid. Instead there is only one bond which corresponds to C=O group in carboxylic acids
Describe the 3 functional groups in aspirin
Phenol group
Carboxyl group
Ester
Although it has a polar carboxylic group, sol is limited due to non-polar phenol group.
Sodium acetylsalicylate
When water added to ^, dissociates to form Na+ ions and acetylsalicylate ions
Ionic salts are more soluble in water as they form stronger ion-dipole interactions with water