1.	(a)	if concentration is too high it will have harmful side effects /
determination of the lethal dose (to 50 % of the population) / OWTTE;
if concentration is too low it has little or no beneficial effect /
determination of the effective dose / dose which has a noticeable
effect (on 50 % of the population) / OWTTE;
therapeutic window is the range between these doses / range over
which a drug can be safely administered / ratio of LD_50:ED_50;
for minor ailments a larger window is desirable, for serious
conditions a smaller window may be acceptable / OWTTE;
(therapeutic window) depends on the drug/age/sex/weight;
a small therapeutic window means that an overdose is a high
risk / OWTTE;	4 max
 
(b)	placebo contains none of the compound being tested as a drug;
placebo can “fool” the body into healing itself / OWTTE;
placebo is used as a control to measure the effectiveness of a
drug / OWTTE;
half/some of trial group given placebo and half/some given drug;
patients and administrators should not know who gets a placebo
and who gets a drug / double blind trial;	3 max
 
(c)	LD_50 / ED_50;
risk:benefit ratio;
side-effects;
tolerance;	1 max
[8]

2.	tolerance: more of the drug needs to be taken to achieve the initial effect / OWTTE;
in order to achieve the desired effect heroin users may reach/exceed the lethal dose /
heroin users are more likely to commit crimes to pay for gradually increasing doses
of the drug / OWTTE;	2
[2]

3.	(a)	C;	1
 
(b)	A / B / A and B;	1
 
(c)	A;	1
[3]

4.	(a)	alters incoming sensory sensations / alters mood or emotions;	1
 
(b)	(i)	the range over which a drug can be safely administered / T.I = /
ratio of the lethal dose for 50% population and the effective
dose for 50% of population;	1
 
(ii)	person needs to take ever larger quantities of a drug to gain
the original effect;	1
 
(iii)	therapeutic effect of an inert substance on the body / body is
fooled into healing itself naturally / OWTTE;	1
[4]

5.	drug is isolated from existing species / synthesized in the laboratory;
tested on animals to establish LD50;
tested on humans and half/some of the group is given a placebo;	3
[3]

6.	measure of the relative margin of safety of a drug (for a particular treatment for a
typical population) / measure for safe effective treatment;
/
ratio of the lethal dose (LD_SO) to the therapeutic or effective dose (ED_50) / the range
of dosage of a drug/its concentration in a bodily system/blood;
Definition of LD_50 and ED_50 not required for mark.
	wide therapeutic window exists for small effective dose and larger lethal dose /
toxicity occurs at much higher concentrations than for successful treatment / a
big difference between effective and lethal dose / drugs with wide therapeutic
window are safer;
narrow therapeutic window requires small doses as lethal dose is not large / OWTTE;	4
[4]

7.	(i)	an effect produced in addition to the one intended / unwanted/
undesired effect;	1
 
(ii)	range of a drugs concentration (in blood) between effective/ED_50 and toxic
levels/LD_50 / (Therapeutic Index) = LD_50 / ED_50;
Do not accept “difference of drug concentration”.	1

(iii)	Therapeutic effect of an inert substance on the body / body is fooled into
healing itself naturally / people responding positively to/psychological effect
after being given a substance that is not a drug / OWTTE;	1
[3]

8.	(i)	intravenous / into veins;
transported/pumped via blood (to various parts of body);	2
 
(ii)	intramuscular/intermuscular/into muscles and subcutaneous/into fat;
Allow [1] if all three methods are stated in (i) and (ii) but not
in correct place.	1
 
(iii)	inhalation/breathing it in;	1
[4]

à È9.	rectally/suppository;
inhalation;
injection/parenterally/intravenous/subcutaneous/intramuscular;
applying to skin/topically;	2 max
Award [2] for three, [1] for two.
[2]

IB Questionbank Chemistry