IB Chemistry

a drug or medicine is a substance that

– alters incoming sensory sensations

– alters mood or emotions

– alters the physiological state (including consciousness, activity level, or co-ordination)

lethal dose of a drug
the dose required to kill fifty percent of the animal population
effective dose
the dose requred to bring about anoticeable effect in 50% of the population
therapeutic index
the lethal dose divided by the effective dose
drug tolerance

occurs as the body adapts to the action of the drug

the patient needs a greater quantity of the drug to achieve the original effect (the possibility of reaching the lethal dose increases as does the side effects)

four methods of drug administering

1. oral

2. inhalation

3. through the anus

4. by injection (parenteral)

three methods of injection

1. intramuscular – usually injected into an arm, leg or buttock muscle

2. subcutaneous – injected directly under the skin

3. intravenous – this has the most rapid effect as the drug enters the bloodstream directly

Antacids

– essentially simple bases, such as metal oxides, hydroxides, carbonates or hydrogencarbonates

– neutralizes the acid in the stomach

– indigestion is commonly caused by overeating, alcohol, smoking and anxiety

determining the most effective antacid

– find molar masses

– determine mole number

– using the balanced equation, determine the amount of acid neutralised by each antacid

alginates
float on the contents of the stomach to produce a neutralising layer preventing heartburn (stomach acid rises up the oesophagus)
analgesics
drug which relieves pain
aspirin

– works by preventing a particular enzyme, prostaglandin synthase, being formed at the site of the injured or pain

– this enzyme is involved in the synthesis of prostaglandins (produce fever and swelling) and the transmission of pain from the site of an injury to the brain

paracetamol

mild analgesic 

less problematic side effects compared to aspirin

 

strong analgesics

work by interacting temporarily with receptor sites in the brain with the result that pain signals within the brain and spinal cord are blocked

 

 short term effects of opiates

– induce a feeling of euphoria (sense of wellbeing)

– dulling of pain

– depress nervous system

– slow breathing and heart rate

– cough reflec inhibited

– nausea and vomiting (first time users)

– high doses lead to coma and/or death

long term effects of strong opiates

– constipation

– disrupts menstrual cycle

– poor eating habits

– risk of AIDS, hepatits etc through shared needles

– social problems, e.g. theft

depressants

drugs which depress the central nervous system by interfering with the transmission of nerve impulses in the neurons

depressants slow down the functions of the body including mental activity

short term effects of alcohol (depressant)

– relaxation, confidence and increased sociability

– dilates blood vessels leading to a feeling of warmth

– loss of balance

– slurred speech

 – concentration becomes impaired

long term effects of alcohol

– severe liver disease

– high blood pressure, coronary heart disease, strokes and dementia

– miscarriages and fetal abnormalities

synergistic effects of alcohol
ethanol can interact and considerably enhance the effect of other drugs because it depresses the CNS
detection of alcohol in breath

using acidified potassium dichromate

(turning orange to green)

amphetamines

it is a sympathomimetic drug 

(mimics the effect of stimulation on the sympathetic nervous system which deals with subconscious nerve responses)

effect of amphetamines

– short term effects include increase in heart rate and breathing, dilation of the pupils, decrease in appetite followed by fatigue

– regular use can lead to tolerance and dependence

– long term effects include weight loss, constipation and emotional instability

ecstasy

– modification to the structure of amphetamines

– mental relaxation, increased sensitivity to stimuli, hallucinations

– may relieve symptoms of Parkinson’s disease

alkaloids
nitrogen-containing compounds of plant origin containing heterocyclic rings (rings containing other atoms as well as carbon) and a tertiary amine group
nicotine

– sympathomimetic

– increases concentration and relieves tension

virus structure

– central core of DNA or RNA

– surrounded by a coat (capsid) of regularly packed protein units (capsomeres) each containing many protein units

– no nucleus and no cytoplams

difficulty treating viral infections
time taken to administer the antiviral drug, as often by the time symptoms appear the viruses are so numerous that the drug would have little effect
antivirals

– altering the cell’s genetic material so that the virus cannot use it to multiply

– preventing the new viruses formed from leaving the cell

AIDS

– virus invades certain types of white blood cells

(T helper cells)

– makes viral-DNA from the RNA template using

reverse transcriptase

cisplatin

– geometric isomer (cis)

– effective at treating some forms of cancer as it forms a complex ion that alters the cancer cell’s DNA so that the cell cannot be replicated correctly

polarity
effects the potency of the drug as it alters the solubility of the drug and hence whether or not it can pass through the lipid-based blood-brain barrier and reach the brain
beta-lactam ring

;The high reactivity of the amide group within the;

four-membered ring structure is a result of strain.;

The ring opens so that the penicillin becomes;

covalently bonded to the enzyme that synthesizes;

bacterial cell walls, thus blocking its action

parallel synthesis of drugs

involves the syntehsis of highly reactive intermediates and products are generatred separately

this method gives rise to a more focussed library

chiral auxiliary

;A chiral auxiliary is used to convert a non-chiral;

molecule into just the desired enantiomer, thus;

avoiding the need to separate enantiomers from a;

racemic mixture. It works by attaching itself to the;

non-chiral molecule to create the stereochemical;

conditions necessary to force the reaction to follow;

a certain path. Once the new molecule has been;

formed, the auxiliary can be taken off (recycled) to;

leave the desired enantiomer

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