D.1 PHARMACEUTICAL PRODUCTS AND DRUG ACTION BIOAVAILABILITY: the fraction of the administered dosage of a drug that enters the bloodstream, accessing the site of action
MEDICINES and DRUGS are chemical substances that do one or more of the • POLAR DRUGS: soluble in aqueous body, but poorly absorbed due to inability to cross cell membranes
following: • NON-POLAR DRUGS: these drugs are poorly absorbed because they are insoluble in aqueous body fluids
• alter incoming sensory sensations • for HIGH ABSORPTION: largely hydrophobic but have solubility in aqueous solutions
• alter a person’s mood or emotions
• alter the physiological state of the body • SOLUBILITY: ability of functional group to ionise and form hydrogen bonds (ex, carbonyl, hydroxyl, group)
• including consciousness and coordination • functional groups which enhance the lipid solubility are non-polar, cannot ionise or hydrogen bonds (ex, phenyl group, hydrocarbon chain)
• ASPRIN: carboxylate, phenyl group, ester group
MEDICINES (PHARMACEUTICAL DRUGS) are substances used for the
• phenyl group = non solubilise
treatment or prevention of disease
• solubility of asprin can be increase by reacting it with aqueous NaOH = ionic salt
MEDICINAL properties depend on their functional groups in their molecules
• drugs with acidic or basic groups can be modified to form an ionic salt
medicines contain beneficial drugs
beneficial effect of medicines = THERAPEUTIC EFFECT
examples: asprin, penicillin, ibuprofen
THERAPEUTIC WINDOW
• the relative margin of safety of a drug
• wide therapeutic window = safer drug, wide margin between doses that are effective and doses that are toxic
METHODS OF DRUG ADMINISTRATION DRUGS
• narrow therapeutic window = only a small increase in the effective dose may product toxic effect
ORALLY
• ingested by mouth
THERAPEUTIC INDEX
• drugs with many polar groups are generally water soluble
• the ratio between the dosage of a drug that causes a toxic(or lethal) effect and the dosage that causes a
RECTALLY
therapeutic effect
• in enemas
• ED50 (median effective dose) = dose that produces the therapeutic effect in 50% of the population
PARENTERALLY
I
• TD50 /LD50 (median toxic/lethal dose) = dose that is toxic/lethal to 50% of the population
• injected under the skin
SUBCUTANEOUS INJECTION
• under the skin
chemical compounds are unstable in DRUG DEVELOPMENT STEPS
the highly acidic gastric juice 1. drug is synthesise int he laboratory
INTRAMUSCULAR INJECTION
• into the muscle tissue 2. drug is tested on animals to determine the LD50
INTRAVENOUS INJECTION 3. drug is tested on humans - half of the group are given the real drug, the other half
• blood stream are given a placebo
INHALATION PLACEBO
• breathed in through the nose or mouth • administering an inert substance
• volatile or highly dispersed drugs • patients and administrators do not know who has received the drug and who has
TRANSDERMALLY received the placebo
• applied to the skin in form patches, ointments PLACEBO EFFECT
• non-polar of compounds • when the body is fooled into healing itself naturally
• FACTORS THAT MUST BE DETERMINED DURING CLINICAL DRUG TRAILS
• risk : benefit ratio
• unwanted side effects
• drug tolerance (how much a person needs before it is effective)
, D.2 ASPRIN AND PENICILLIN DISCOVERY OF PENICILLIN
SOLUBILITY OF ASPIRIN
• group of antibiotics used to treat a range of bacterial infections
• to make aspirin soluble, it needs to react with aqueous NaOH
• are derived from Penicillium fungi and can be taken orally or via injection
forming an ionic salt
SYNTHESIS OF ASPIRIN • was discovered in 1928 by Sir Alexander Fleming, whilst working with bacteria cultures
• the producet is SOLUBLE ASPIRIN (increase solubility)
• ASPIRIN (acetylsalicylic acid): produced by reacting salicylic acid with • he noticed that a fungus (Penicillium notatum) had contaminated some of his cultures and left a
ethanoic anhydride clear region where no bacteria colonies were growing
• the reaction produces aspirin and ethanoic acid
• salicylic acid is converted to aspirin through esterification (condensation PENICILLIN MODE OF ACTION
reaction) • Penicillins (are beta-lactase antibiotics) are characterised by the presence of a beta-lactam ring
• when water is added to SOLUBLE ASPIRIN = dissociates to • the beta-lactam ring is the
form sodium ions and acetylsalicylate ions part of the molecule
• ionic salts of aspirin are more soluble in water as they form responsible for penicillin’s
stronger ion=dipole interactions with water anti-bacterial properties
• concentrated H2SO4 is added to the reaction mixture which is warmed
gently
• the product is cooled to form crystals which are then suction filtered and
washed with cold water
• however, converting aspirin to ionic salt does not increase its
bioavailability as the acetylsalicylate ion is converted back to un- • the bond angles in the ring are reduced to 90 degrees celsius which puts a strain on the bonds
• aspirin has a low solubility in cold water so this process removes the • due to the strain in the beta-lactam ring, it breaks relatively easily
ionised form in the stomach’s acidic environment
soluble acids but not the aspirin
• only way to increase bioavailability is to administer intravenously
• aspirin is purified in RECRYSTALLISATION - impure crystals are • beta-lactation antibiotics interfere with cell wall formation in bacteria by inhibiting the enzymes
dissolved in a small volume of hot ethanol responsible for creating cross-links in the cell wall
• water is then added and the solution is cooled slowly and then chilled USES OF ASPIRIN • when the beta-lactation ring comes into contact with bacteria, the ring opens and binds
• the acetylsalicylic acid will recrystallise, unreacted salicylic acid will remain • mild analgesic (painkiller) - block sensation of pain at the source irreversibly to the anime responsible for catalysing cross-linking in the cell wall of the bacteria
isolated in solution • block the action of enzymes that produce prostaglandins • water enters the cell, increasing the osmotic pressure inside the cell, causing it to burst
• prostaglandins (involved in transition of pain impulses to brain) are
PURE ASPRIN prevented from being synthesised = reducing or eliminating pain
• melting point between 128-140 degrees Celsius ANTIBIOTIC RESISTANCE
• infrared spectrum of aspirin (has no C=O in esters or phenol compared to • modifying the side-chain results in penicillins that are more resistant to the penicillinase enzymes
• anticoagulant - prevent blood clotting (and so heart attacks and
salicylic acid peak) • the penicillinase enzyme could deactivate the original form of penicillin, penicillin G
strokes)
• anti-inflammatory properties, asprin is taken for arthritis and
rheumatism
SIDE EFFECT
• causes bleeding of lining of stomach
• this is increased by drinking alcohol = SYNERGISTIC EFFECT (if
• the different side-chains reduce the occurrence of penicillin resistant bacteria
two drugs increase each other’s effectiveness when taken together)
• modified penicillins are able to withstand the action of penicillinase enzyme
• the side chain can also be modified to give increased resistance to breakdown by stomach acid,
which means that the antibiotic can be taken orally
