Radiopharmaceutical is topic of subject Pharmaceutical inorganic Chemistry for B. Pharmacy First year students. This slide is presented with an aim to enable the students to easily understand and grasp unfamiliar concept of this topic

1. Mr. Pravin N. Muli
Assistant professor
Radiopharmaceuticals
1

2. CONTENTS
 Radioactivity
 Radioactive rays
 Isotopes : Types of Isotopes, Applications of Radioisotopes
 Radioactive Decay
 Units of Radioactivity
 Half-life of Radioelement
 Measurement of Radioactivity
 Scintillation Detectors
 Major Uses of Radioisotopes
 Precautions to be taken while Storage and Handling of
Radioactive Material
 Radioopque Contrast Media
 Barium Sulphate
2

3.  RADIOACTIVITY
The phenomenon of spontaneous emission of certain kind of invisible
radiation by certain substance is called Radioactivity. The substances
which emit such radiation is called Radioactive substance.
It was discovered accidentally by the French Scientist Henry
Becquerel.
Radiopharmaceuticals are used in medicines. It is used to treat
cancerous tumours, to diagnose thyroid disorders and other metabolic
disorders including brain function.
RADIOACTIVE RAYS
Radioactive radiations are composed of three important rays α, β and γ
which differ very much in their nature and properties.
 α-rays
These rays or particles are positively charged. It consists of two unit
positive charge and has a mass which is nearly four times that of
hydrogen atom. These are heavy, slow moving and their penetration
power is slow. These rays ionise the gas through which they pass.
3

4. During the emission of α -particle from a radioactive element, atomic
number decreases by 2 unit and mass number decrease by 4 units.
β -rays
These rays or particles are negatively charged. They have negligible
mass. These are having smaller mass, higher speed and thus β-particles
are much more penetrating than α-particle. They have lower ionising
power than α-rays.
During the emission of B-particle from a radioactive element, atomic
number increases by 1 unit and there is no change in mass number. For
example:
 γ - rays
These rays are neutral i.e. do not carrying charge. The particle of these
rays has negligible mass. As they do not have any mass, their ionising
power is also very poor. They are not affected by magnetic field and are
having the speed of light.
+
+
4

5.  ISOTOPES
Atoms of an element which have the same atomic number but have
different mass umber are called Isotopes.
In other words, isotopes are atoms of the same element whose nuclei
contain the same number of protons but different number of neutrons.
When the radioactive isotopes undergo nuclear reactions and they produce
α, β and γ particles. The original nuclide is called the parent and the product
is termed as daughter nuclide. This phenomenon of nuclear changes is termed
as disintegration or radioactive decay.
TYPES OF ISOTOPES :
1. Natural Isotopes
2. Artificial Isotopes
Natural Isotopes:
They are found in nature for examples, hydrogen has three natural isotopes
(Protium-no neutrons, deuterium- one neutron and tritium-two neutron).
5

6. Another element containing very important isotopes is carbon, which
includes carbon 12, the referential base of atomic mass in any element;
carbon 13, the only carbon with magnetic properties, and radioactive carbon
14, very important since its average life span is 5,730 years and is widely
used in archaeology to determine the age of organic fossils.
2. Artificial :
These isotopes, manufactured in nuclear laboratories by bombarding of
subatomic particles, usually have a short lifespan, mostly due to their
unstable nature and radioactivity. Examples: iridium 192, used to verify that
pipe welding is hermetically sealed, especially as regards transport pipes for
heavy crude oil and fuels. Some isotopes from uranium are also used for
nuclear work such as electric generation.
Isotopes are also subdivided into stable isotopes and unstable or
radioactive isotopes. The concept of stability is not exact, since there are
almost stable isotopes. That is, for some time they are unstable and become
stable or turn into other stable isotopes.
6

7. APPLICATIONS OF RADIOISOTOPES:
(1) Medicine : Diagnosis and treatment of diseases, sterilization of
products frequently used in clinical and surgical environments, etc.
(2) Industry and technology : Review of materials and welding in
construction, control of productive processes, research etc
(3) Agriculture : Plague control, food conservation etc.
(4) Art : Restoration of art objects, verification of historic or artistic
objects etc.
(5) Archaeology: Geological event dating etc.
(6) Research : Universe, industry, medicine etc.
(7) Pharmacology : The study of the metabolism of drugs before they
are authorized for public use.
7

8.  RADIOACTIVE DECAY
According to the law of Radioactive Decay, the quantity of a radioelement
which disappears in unit time (rate of disintegration) is directly proportional
to the amount present. It is independent of temperature, so its energy of
activation is zero.
Various forms of equation for radioactive decay are
Rate of disintegration= -dN ⁄ dt α N
i.e. -dN ⁄ dt =λN
Where λ is a constant, and is known as decay or disintegration constant.
Integrating the above equation gives
- log N = λt + C
C is the constant of integration and log N stands for log Ne Since the number
of atoms of the radioactive substance present initially i.e. t = 0 is N0
-log N0 = λ.0 + C
C = -log N0
8

9. Putting the value of integration constant
-log Nt = λt - log N0
log N0 –log Nt = λt
log N0/ Nt= λt
Converting log to the base e to the base 10, we get :
2.303 log = λ
λ =
Nt = Number of atoms that nucleid present after time t.
N0 = Initial number of atoms of the nucleid at time 0.
λ = Decay constant
This equation is resembling that of the first order reaction, so that
radioactive disintegration are example of first order reactions.
log
9

10.  UNITS OF RADIOACTIVITY
a) Curie: Its symbol is Ci or C. it is equal to 3.7 x 1010 disintegration per
second (dps).
1 Curie = 3.7 x 1010 dps
b) Bacquerel (Bq): It is SI derived unit of radioactivity. It is defined as one
disintegration per second.
1 Bq = 1 disintegration per second.
106 Bq = 1 rd and
3.7x1010 Bq=1C
c) Roentgen (R): It is the unit of exposure, 1R = 2.58 x 10-4CKg-1
(C= Coulomb)
d) Gray: The Gray (Gy) is defined as absorbed dose of radiation per unit
mass of tissue
1Gy= 1 JKg-1
e) RAD: It is the unit of absorbed dose, 1 rad = 10-2 JKg-1
10

11. HALF-LIFE OF RADIOELEMENT
 Half-life period is defined as the time required for a radioactive isotope to
decay The hone half of its initial value. It is denoted by t1/2
 t1/2=0.693/λ
Where λ is disintegration constant.
 Each radioactive isotope has its own characteristic of half-life. Shorter the
half life period of an element, greater is the number of disintegrating atoms
and hence greater is its radioactivity The half-life periods or half lives of
different elements vary widely ranging from fraction of seconds to millions
of years.
 Half-lives for various radionuclides vary considerably e.g. Polonium- 122
has half life of 3x10 seconds, uranium 238 has 4.5x10 years.
AVERAGE HALF LIFE PERIOD
 The reciprocal or the radioactive constant or decay constant is called
average half life period.
 It is denoted by τ(tau). τ = 1/λ
11

12.  MEASUREMENT OF RADIOACTIVITY
 To measure the radiation of alpha, beta and gamma rays many techniques
involving detection and counting of individual particles or photons have
been available, It include lionization Chamber, Proportional counter,
Geiger-Muller counter
1. Ionization chamber : An lionization chamber consists of chamber filled
with gas and fitted with two electrodes kept at different electrical potentials
and a measuring device to indicate the low of electric current, The fill gas
can be Ar, He, air etc. These are available in various size and shapes, They
have poor resolution due to large number of charge carriers, They are
operated in current mode
2. Proportional Counter : If the electric field gradient between the anode &
Cathode is increased by increasing the applied voltage, the electrons
produced in the primary lionization further ionize the gas molecule e g. the
number of ion pair is multiplied. each primary electron liberated, a large
number of additional electrons are liberated. the current pulse through
electrical current is greatly amplified. In a certain original number of ion
pairs. Proportional counters operate in this voltage region.
12

13. They are usually operated in pulse mode and are used in the form of gas
filled or gas flow counters for α,β and fission frequent counting. The most
common file pass is "P-10"consisting of 90% Ar and 10% methane. The
energy resolution of the proportional counter is in the range of 5-10%.
3. Geiger-Muller Counter : It is one of the oldest radiation detector types
in existence, having been introduced by Geiger and Muller in 1928. It is
referred to as G-M counter or simply tube. The simplicity, low cost and of
ease of operation of these detectors have lead to their continued use to the
present time. They can detect α ,β and γ radiations.
It consists of a cylinder made up of stainless steel or glass coated with
silver on the inner side which acts as cathode. Coaxially inside the tube a
mounted fine were works as an anode. It is having the mixture of ionizing
gas which contain a small proportion quenching vapors. The function of
quenching vapor are i) to prevent the false pulse, ii) to absorb the photons
emitted by excited atoms and molecule returning to their ground state.
Chlorine, Bromine, Ethyl alcohol and Ethyl formate are commonly used
quenching agents.
13

14. Radiation when enters the tube through a thin section of outer wall
causes ionization of atoms of the gas. When a high voltage is maintained
between two electrodes, the electrons and charge ions are attracted by the
anode and cathode respectively. Each particle of radiation produces a brief
flow or pulse of current which can be recorded by a scalar.
14

15.  SCINTILLATION DETECTORS
 Scintillation detectors rely on the atomic or molecular excitation produced.
Deexcitation then results in the emission of light, a process known as
fluorescence. This light then act as a detectable signal. It consists of a cell,
a photomultiplier tube coupled with phosphor or flour to convert
scintillations into electrical pulses, an amplifier and a scalar. Both inorganic
and organic scintillations can be used as detector.
 There are two main types of scintillator:
 1. Inorganic, such as Sodium Iodide: Single crystals of NaI, doped with an
activator such as Thallium to modify the energy levels which are used to
form detectors. They are insulators and have a wide gap between the
valence band and conduction band suitable activators are used to create
excited states which decay by emission of light in the visible range. Other
scintillation like CsI (TID, CsI (Na), Hi I (Er), BaF2
 2. Organic Scintillator: It is used for simple α and β counting with 100%
efficacy. Anthrene have high scintillation efficacy and stilbene low
scintillation efficacy. It suffer from the limitation of poor energy resolution.
15

16.  MAJOR USES OF RADIOISOTOPES
 Calcium 47 : Important aid to biomedical researchers studying the cellular
functions and bone formation in mammals.
 Cesium137: Used to treat cancerous tumors
 Chromium 51: Used in research in red blood survival studies
 Cobalt 57 : Used as a tracer to diagnose pernicious anemia
 Gallium 67 : Used in medical diagnosis
 iodine 123 : Widely used to diagnose thyroid disorders
 Iodine 131 : Used to treat thyroid disorders (Grave's disease)
 Selenium 75: Used in protein studies in life science research.
 Strontium 85: Used to study bone formation e.g. metabolism.
 Xenon 133: Used in nuclear medicine for lung ventilation
 Calcium chloride Ca 451: Study of calcium metabolism disorders, bone
cancer and other bone lesions.
 Sodium chloride Na 24: Study of Na+ exchange.
 Sodium fluoride F 18: Bone scanning and study of bone metabolism
16

17.  PRECAUTIONS TO BE TAKEN WHILE STORAGE AND HANDLING
OF RADIOACTIVE MATERIAL
A care should be taken to protect people and personal from harmful
radiation during handling and storage of radioactive material emits. The following
precautions are taken while working with radio detectors, radio assays, traces
experiments, manufacturing or handling of radioactive materials.
1. These materials should be handled with forceps or suitable instruments and
direct contact should be avoided.
2. Any substance which is taken internally (foods, drinks, smokes etc.) should
not be carried in laboratory where radioactive materials are used.
3. Sufficient protective clothing or shielding must be used while handling the
materials.
4. Radioactive materials should be kept in suitable labeled containers shield by
lead bricks and preferably in remote corner.
5. Areas where radioactive materials are used or stored should be monitored
constantly(tested regular for radioactivity).
6. The final disposed of radioactive material should be done with great care to
animals and environment.
17

18.  RADIOOPQUE CONTRAST MEDIA
 Radio opaque contrast media are the chemical compounds having the capacity
to absorb and block the passage of x-rays. So they are opaque to X-ray
examination. They are used as diagnostic aid in radiology which emits x-rays.
They can pass through soft tissues of the body but are observed at hard tissues
(bone). The ray produces a black spot on photo-graphic plate by forming
complex with silver bromide. These rays does not form a bright spot of the
similar shape as that of x-ray observing object is formed.
 X-rays are electromagnetic radiations of short wavelength and have high
penetrating power
 Radio opaque agents are typically Iodine or barium compounds and are used
tor x-ray examinations of the kidney, liver, blood vessels, heart and brain.
Although they do not have highest atomic numbers, they are the most easily
incorporated into molecules exhibiting low toxicity. They become concentrated
in the organ to be studied.
18

19. BARIUM SULPHATE
Molecular Weight: 233.4
Formula: BaSO4
Preparation In nature it is found as barite; also as heavy spar.
i) It may be prepared by adding any soluble sulphate to a soluble
barium salt. For example addition of sodium Sulphate to a solution of
barium chloride precipitates barium sulphate.
BaCl2 + Na2SO4 → BaSO4 +2NaCl
ii) Barium chloride on treatment with Sulphuric acid causes
precipitation of Barium sulphate
BaCl2 +H2SO4 → BaSO4 +2HCl
19

20.  PHYSICAL PROPERTIES
It is fine, heavy, white, odorless, tasteless, bulky powder free from
gritty particles. It is practically insoluble in water, in organic solvents
and in dilute solutions of acid and alkalies. The bulky is free from
gritty particles. It does not have any toxic effects to man and the
environment. Chemical Properties Barium sulphate on treatment with
conc. Sulphuric acid results in the formation of bisulphate salt.
BaSO4 + H2SO4 Ba (HSO4)2
Uses
i) It is used as a radiopaque contrast media for the x-ray
examination of the git tract
ii) Barium ion stimulates smooth muscles causing vomiting, severe
cramps, diarrhea and hemorrhage.
iii) It is used primarily as a whitening agent and as an insoluble
support in industrial applications.
20

21. THANK YOU
21