Radio-Pharmaceuticals - Pharmaceutical Inorganic Chemistry B. Pharma 1st Semester

Radio-Pharmaceuticals

Contents

• Radioactivity

• Alpha radiation

• Beta rays

• Gamma rays

• Geiger-Muller counter method

• Scintillation counter method

• Biological Effects of Radiation

• Storage of Radio Active Material

• Handling Radio Active Materials

• Application of Radiopharmaceuticals

Learning Objectives

At the end of this lecture, student will be able to

• Explain the basic concept of radio activity

• Differentiate alpha,beta and gamma rays

• Describe the instruments used to measure radio activity

• Explain the principle involved in the working of instruments used to measure radio activity

• Choose a method for handling and storing radioactive material

• Indicate the clinical application of radiopharmaceuticals

Radioactivity

• The spontaneous emission of radiations by atomic nuclei resulting in their integration is called natural radioactivity

Types

• Alpha rays

• Beta rays

• Gamma rays

Properties of Radiations

Alpha Rays	Beta Rays	Gamma Rays
Helium atoms with a mass of four a.m.u. and with two positive charge	Highly energetic electrons	Neutral
Penetrating power is less	100 times more than alpha rays	Penetrating power is immensely high
Highest ionizing power	100 time less than alpha rays	No ionizing power

Key Words

• Z = The Atomic Number.

• It’s the Number of Protons in the nucleus of an Atom.

• Nucleus: It’s where the Protons and Neutrons are located in an Atom.

• Protons: Positively Charged Particles in the Nucleus of the atom. Mass = (approx) 1 AMU

• Neutrons: Neutrally charged particles in the nucleus of an atom Mass = (approx) 1 AMU

• Mass Number of an atom: Number of Protons + Number of Neutrons in the nucleus of an atom

Sources of Radioactivity

• Naturally Occurring Sources:

– Radon from the decay of Uranium and Thorium

– Potassium -40 – found in minerals and in plants

– Carbon 14 – Found in Plants and Animal tissue

• Manmade Sources:

– Medical use of Radioactive Isotopes

– Certain Consumer products –(eg Smoke detectors)

– Fallout from nuclear testing

– Emissions from Nuclear Power plants

Stable Isotopes

• The nucleus of each atom contains protons and neutrons.

• While the number of protons defines the element (e.g., hydrogen, carbon, etc.)

• The sum of the protons and neutrons gives the atomic mass, the number of neutrons defines the isotope of that element.

• For example, most carbon (≈ 99 %) has 6 protons and 6 neutrons and is written as ¹²C to reflect its atomic mass.

• However, about 1 % of the carbon in the Earth’s biosphere has 6 protons and 7 neutrons (¹³C) forming the heavy stable isotope of this important element.

• Stable isotopes do not decay into other elements. In contrast, radioactive isotopes (e.g., ¹⁴C) are unstable and will decay into other elements

Radioactive Decay

• Process by which an unstable atomic nucleus loses energy by emitting radiation

 Alpha particle

 Beta particle

 Gamma particle

Half Life

• The time it takes for half the R.A. nuclei to decay is called the half life

• The time taken for the radioactivity to half is the same.

• Different R.A. substances have different half-lives.

Example:

Units of Radioactivity

• Physical Units

• Roentgen (R)

• Curie (Ci)

• Biological units

• Gray (Gy)

• Rad (rad)

• Relative Biological Effectiveness (RBE)

Detection and Measurement of Radio Activity

• Geiger-Muller counter method

• Scintillation counter method

• Ionization chamber method

• Cloud chamber method

Geiger-Muller Counter Method

Argon gas is filled in the tube at reduced pressure of 0.1 atmospheres.

A potential difference of about 1000 volts is applied across the two electrodes.

 

• Argon gas is ionised wherever any alpha or beta particles enters in the tube through the mica window

• The positively charged argon ions are attracted to the cathode

• The negatively charged electrons to the anode

• Thus an electrical impulse flows between the electrodes whenever one alpha or beta particle enters the tube

• The electrical pulses are counted in an automatic counter

• The intensity of the radioactivity of any radioactive material can be found out by finding the number of pulses per minute

Scintillation Counter Method

• Scintillation means a flash of light

• Phosphor, photomultiplier tube

• In conjunction with a high voltage supply, an amplifier, a pulse height discriminator and a scalar

• Charged particles or gamma radiations from radioactive source cause phosphor to emit scintillations (flashes of light)

• Which are made to fall on light sensitive photomultiplier tube which detects and amplifies and converts it into electrical impulses

• This impulse recorded directly by means of scalar

Scintillators

• Inorganic scintillators

• Alkali halide (NaI, CsIetc)

• Organic scintillators

• Anthracene

Biological Effects of Radiation

Delayed Effects of Radiation

• The hair greys quickly

• Premature ageing

• Cancer of skin, lung cancer, leukaemia

• Sterility

• Chromosomal damage

• Mutations

Storage of Radio Active Material

• Stored in an area not frequently visited by people

• Thick glass provides sufficient shielding

• Protect from gamma radiations, lead shielding has to be used

• The storage area must be regularly checked for the radioactivity

• Radioactive materials have to be stored in suitable labelled containers, shielded by lead bricks and preferably in a remote corner

Handling Radio Active Materials

• Carried in trays having absorbent tissue paper

• Rubber gloves have to be used

• Pipettes operated by mouth should never be employed

• One should not touch radioactive emitter with hand

• It should be handled by means of forceps or suitable instruments

• Smoking, eating and drinking activities should not be done

• Sufficient protective clothing or shielding

• Areas should be monitored (tested for radioactivity regularly)

Pharmaceutical application of radioisotopes

• Radioisotopes in therapeutics

• Radio isotopes in Diagnosis

• Research

• Sterilization

Radiopharmaceuticals

• These are pharmaceutical preparations having a radioactive isotope

• Used internally

• These are prepared by Scientists at the Bhabha atomic research Centre (BARC)

• Supplied to approved hospitals and approved laboratories

• E.g.. Sodium radio iodide injection

• sodium iodide-I131capsules

• I P does not include any radioactive pharmaceutical preparation

Application of Radiopharmaceuticals

Treatment of disease

• They are radio labeled molecules designed to deliver therapeutic dose so ionizing radiation to specific diseased sites

As an aid in the diagnosis of disease

• The radio pharmaceutical accumulated in an organ of inter estimate gamma radiation which are used for imaging of the organs with the help of a next Ernal imaging device called gamma camera

Clinical Application

• Calcium (Ca-44 and Ca-45)-used to study bone structure and in the treatment of carcinoma of bone

• Cyanocobalamine (Co-57)-in the diagnosis of pernicious anaemia

• Gold (Au-198) solution –neoplasticsuppressant, used for the estimation of reticuloendothelial activity

• Hydrogen (H-2 an H-3) –determine total body water

• Iron (Fe-59) –investigation of iron metabolism and to measure red cell life span

• Sodium (Na-22 and Na-24) –used in the estimation of extra cellular fluid

• Iodine (I-131) –used in the study of functioning of thyroid gland

Opaque Contrast Media

• Radio opaque substances are chemical compounds

• Contains elements of high atomic number

• Will stop the passage of X-rays hence appear opaque on X-ray examination

• Such compounds and their preparations are known as X-ray contrast media

• Diagnostic aids in radiology

Barium sulphate suspension

• Barium meal or shadow meal

• Dry mixture of barium sulphate having suitable colouring flavouring, preservatives and suspending or dispersing agents

• Composition:

Barium sulphate1000g

Saccharin sodium0.25g

Vanillin0.10g

• Preparation: It is prepared by mixing saccharin and vanillin with barium sulphate and is given to the patient immediately

• Use: Diagnostic aid

Summary

• The spontaneous emission of radiations by atomic nuclei resulting in their integration is called natural radioactivity

• Alpha rays, beta rays and gamma radiations are the radiations

• Alpha radiations are nuclei of helium atoms with a mass of four a.m.u. and with two positive charges

• Their penetrating power is less and has got highest ionising power

• In G M counter Argon gas is ionised wherever any alpha or beta particles enters in the tube through the mica window

• Cationsand anions are attracted to the respective electrodes

• Electrical pulses are counted in an automatic counter

• Scintillation counter consists of phosphor, photomultiplier tube, high voltage supply, an amplifier, a pulse height discriminator and a scalar

• Charged particles or gamma radiations from radioactive source cause phosphor to emit scintillations

• Radioactive materials are stored in an area not frequently visited by people

• Lead shielding has to be used to protect from gamma radiations

• One should not touch radioactive emitter with hand

• Sufficient protective clothing or shielding are required

• Radio pharmaceuticals are pharmaceutical preparations having a radioactive isotope

• E.g.. Sodium radio iodide injection, sodium iodide-I131capsules etc

• Radio pharmaceuticals are used in the treatment of diseases, as an aid in the in the diagnosis of disease