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Radiopharmaceuticals:- PPT/PDF

Class:- B. Pharm 1st Year

Semester:- I

Subject:- Pharmaceutical Inorganic Chemistry

Unit:- V

Topic:- Radiopharmaceuticals

The content of this unit are

1. Radioactivity

2. Radioisotopes

3. Radiopharmaceuticals

4. Radioactive decay

5. Units of Radioactivity

6. Half-Life of Radioelement

7. Properties of Radiation

8. Detection and Measurement of Radiation

9. Handling and Storage of Radiation

10. Applications of Radioisotopes

11. Radio-Opaque Contrast Media

    Radio Pharmaceuticals

               Presented By
     Mr. Kamble Subodh Vishnukant
             Associate Professor
    R P College of Pharmacy, Osmanabad

    1.    Radioactivity
    2.    Radioisotopes
    3.    Radiopharmaceuticals
    4.    Radioactive Decay
    5.    Units of Radioactivity
    6.    Half-Life of Radioelement
    7.    Properties of Radiation
    8.    Detection and Measurement of Radiation
    9.    Handling and Storage of Radiation
    10.   Applications of Radioisotopes
    11.   Radio-Opaque Contrast
    ï‚— The substances which emits rays or radiations are called as radioactive substances and
      the phenomenon of spontaneous & continuous emission of such radiations is called as
        e. g. Uranium,Thorium, Radium and their compounds emit radiations spontaneously.
    ï‚— These radiations can penetrate through solid material, can ionize gases, produce a glow
      on zinc sulphate paint or affect the photographic plates.
    ï‚— These radiations emits without any external help and are independent of temp.,
      pressure, conc. or catalyst.
    ï‚— Radioactive substance may exist in the form of element or its compound.

    ï‚— Every atom of an element is composed of nucleus containing protons and neutrons,
      surrounded by electrons.
    ï‚— If the atom is electrically neutral then the no. of protons in nucleus is same as that of
    ï‚— It is also known that the no. of protons in the nucleus is equal to atomic no., which
      determines its properties.
    ï‚— The atomic weight (Mass no.) is the total no. of protons and neutrons present in the
        Atomic Weight/     Where, superscript is the mass no. and
          Mass No.
                           subscript is the atomic no.
          Atomic no.
    ï‚— The elements having the same atomic no. but different atomic weight or mass no. are
      known as Isotopes.
          e. g.                     and

    ï‚— There are two major types of isotopes
      1. Stable Isotopes (Nuclide)
         Which do not decompose to other isotopic form.
      2. Unstable Isotopes (Radioisotope / Radionuclide)
         Which decomposes or decay by emitting the nuclear particles into the other isotope or
         different element.

    ï‚— The  radioisotopes which            have      medicinal       importance   are   known   as
      e. g.
      ï‚— Calcium (44Ca and    45Ca):-   used to study the bone structure and in the treatment of
        carcinoma of bone.

    Radioactive Decay
    ï‚— A radioactive substance disintegrates or decays with the emission of certain particles as

    1.   Alpha (α) particles

    2.   Beta (β) particles

    3.   Gamma (γ) radiations.

    Alpha (α) particles
    ï‚— The alpha particles are the heaviest and slowest of the radioactive emission.
    ï‚— They are helium ions He++ with two positive charge, containing two protons, two
      neutrons & has 4 amu (atomic mass unit) mass and atomic no. 2.
    ï‚— The velocity is about 1/10th that of light varies from element to element.
    ï‚— When radioactive element emits alpha particles from the nucleus of the atom, the
      resulting nucleus will have two positive charges less than the original nucleus. (++ )
    ï‚— The mass no. of the new nucleus will be less than 4 amu as compared to original.

    Alpha (α) particles
    ï‚— The penetrating power is least as compared to other emissions.
    ï‚— Because of low penetrating power of alpha particles, do not find any use in biological
      applications as they cannot penetrate tissue.
    ï‚— Alpha particles are affected by strong magnetic field.

     Beta (β) Particles
     ï‚— Beta particles have a mass of 1/1836 of the mass of hydrogen atom and one negative (-1)
     ï‚—   As these radiations are lighter, so the velocity is little less than light.
     ï‚—   They have more penetrating power and can penetrate aluminium sheet upto 3 mm
     ï‚—   As these particles have a negative charge, they cause ionization of molecules.
     ï‚—   Beta particles affected by strong magnetic field.
     ï‚—   Beta particles can penetrate tissue so useful in biological applications.

     Beta (β) Particles
     ï‚— The emission of beta particles from an element does not alter the atomic mass, but
       alters the atomic no. and is converted to element with next highest atomic no.
       e. g.

     Gamma (γ) radiations
     ï‚— These radiations do not have any charge and thus are not affected by electric or
         magnetic field.
     ï‚—   They have properties of both a wave and particles.
        They have very short wave length resembling X – rays.
     ï‚—   They have velocity same as that of light.
     ï‚—   They have very high energy and thus have excellent penetrating power.
     ï‚—   They have poor ionising power but can produce ions or free radicals by dislodging (move
         / remove) electrons from orbital's.

     Units of Radioactivity
     ï‚— The units which are used for measurement are
     1.   Curie (C)

     2.   Roentgen (γ)

     3.   RAD (Radiation Absorbed Dose)

     4.   RBE (Radiation Biological Effectiveness)

     5.   becquerel (Bq)

     1. Curie (C)
      The basic unit of radioactivity is “Curie� symbolized as ‘C’.
     ï‚— The quantity of any radioactive substance undergoing the same no. of disintegrations in
       unit time as of 1 g of pure radium.

            One Curie = 3.7 x 1010 disintegrations/second

      The subunits are called as millicurie (mC) and microcurie (µC).
            One millicurie (mC) = 1 x 10-3 = 3.7 X 107
            One microcurie (µC) = 1 x 10-6 = 3.7 x 104

     2. Roentgen (γ)
      It is the unit of measurement of radiations mainly X – rays.
     ï‚— It measures the ionizing effect of given radiation and its damaging effect on biological
                              1 γ = 930 erg/g

     (The erg is a unit of energy and work equal to 10−7 joules. It originated in the centimeter–gram–
     second (CGS) system of units. It has the symbol erg. The erg is not an SI unit. Its name is derived
     from ergon a Greek word meaning work or task.)

     3. RAD (Radiation Absorbed Dose)
     ï‚— It is the another unit of measuring the radiation absorbed.
      RAD is defined as “The quantity of radiation which releases or absorbs 100 erg/g of a
       specified medium.�

     4. RBE (Radiation Biological Effectiveness)
     ï‚— The effects of radiation on biological system depends upon the type of radiation and
       measured by RBE.

      It can expresses the relative effects of radiations Alpha (α), Beta (β) and Gamma (γ) on
       biological system.

     5. becquerel (Bq)
     ï‚— The unit for measuring radioactive emissions is the becquerel (Bq). The Bq indicates the
       number of decays per second. The roentgen equivalent in man (rem) is an older
       standardized unit for measuring absorbed dose. The mrem, 1000th of that unit, is the
       unit used today in medicine.

     Half life of Radioelement
     ï‚— Radioactive isotopes or nuclides continue to decay for a particular period of time.
      The half – life is used to designate the time required for one half of atoms originally
       present to complete their emission of radiation.
      Half – life is defined as the time in which the amount of radionuclide decays to half its
       initial value.
     ï‚— It can be calculated by formula
       where, t = time

     ï‚— Half-life of various radioactive elements varies as 131I has 8 days, 65Zn has 150 days, 22Na
       has 2-6 days, while 238U has 4.5 x 104 years
     Properties of Radiations
     ï‚— The radiations emitted by atoms of radioactive material is in the form of energy and
       divided into two categories:
       i.       Particulate radiations                   alpha and beta particles
               Can be detected by electrical or magnetic field
               Can penetrate matter
               Can ionise gases
               Can cause certain substances to flash (Scintillation)
               Can darken Photographic plate.

       ii.      Electromagnetic radiations               gamma radiations
               Can propagate at the speed of light through a vacuum.
               Exhibits both wave properties and particle properties at the same time.

     Detection and Measurement of Radiation
     ï‚— The method adopted for the measurement of radioactivity depends upon the extent of
       penetrability and dissipation (the act of breaking up and scattering or spreading widely) of
     ï‚— The ionizing effect is measured in ionization chamber and Geiger Muller Counters.

     ï‚— The scintillation (glow/flash) effect in scintillation counters.

     ï‚— The photographic effect in autoradiography.

     Detection and Measurement of Radiation
     ï‚— Following are the various devices used in measurement of radioactivity.
     1.   Ionization Chamber
     2.   Proportional Counters
     3.   The Geiger – Muller Counters
     4.   Scintillation Counters
     5.   Semiconductor Detectors
     6.   Photographic Plate Method

     1. Ionization Chamber
     ï‚— The detectors of this type make use of the electrical conductivity of a gas that has been
         partially ionized by radiations passing through it.
     ï‚—   Ionization chambers are of various shapes and sizes.
     ï‚—   Ionization chamber is filled with gas and is fitted with two electrodes kept at different
         electrical potentials (50 – 100 volts).
     ï‚—   It is connected to a measuring instrument to indicate flow of electric current.
     ï‚—   Radiations causes ionization of gas molecules and results in emission of electrons.
     ï‚—   This shows change in electric current, which is measured.

     2. Proportional Counter
     ï‚— It is a modified ionization method in which, at an applied potential ionization of primary
       electrons produces a very large no. of free electrons which are carried to the anode (+

     ï‚— The voltage range over which gas ionization takes place is known as proportional region
       and the counters working in this region are known as proportional counters.

     3. Geiger – Muller (GM) Counters
     ï‚— In 1908 Hans Geiger, developed an experimental technique for detecting alpha particles
         in a tube, after that in 1928 that Geiger and Walther Müller (a PhD student of Geiger)
         developed the sealed Geiger-Müller tube, which was relatively small and rugged, and
         could detect more types of ionizing radiation.
     ï‚—   It is the best known of all radiation detector.
     ï‚—   It consist of a cylinder of stainless steel or glass coated with silver on the inner side
         which acts as cathode (-).
     ï‚—   A fine metal wire is mounted coaxially inside the tube as anode.
     ï‚—   The chamber is filled with the mixture of argon.
     ï‚—   Radiation enters the tube through a thin section of outer wall called as window.

     3. Geiger – Muller (GM) Counters
     ï‚— A high voltage (800-1300V) is maintained between the electrodes.
     ï‚— Due to ionization of gas, the electrons and the positively charged ions are attracted and
       collected by anode and cathode respectively.
     ï‚— The passage of these ions through the tube constitutes the flow of current.
     ï‚— Each particles of radiation causes pulse of current which is recorded by a device known
       as scalar.
     ï‚— Which shows the total no. of pulses.



     4. Scintillation Counters
     ï‚— Alpha, Beta and Gamma radiations can be detected by scintillation counters.
     ï‚— The working principle is that, when ionizing radiations comes in contact with certain
       substances like phosphorus, a flash light is given out. This flash is collected y
       photomultiplier tube and produces electric impulse and these impulses recorded by the
       ï‚— For counting gamma radiations, sodium iodide activated with 1% of thallium is used to
         enhance the degree of fluorescence.
       ï‚— For counting beta particles, crystals of anthracene or stilbene or solution of stilbene in
         xylene, boron or cadmium compounds is used.

     5. Semiconductor Detectors
     ï‚— They are useful in measuring X-rays and Gamma rays.

     ï‚— In these detectors, the charge carriers produced by ionizing radiations travels towards
       the positive electrode (anode) with high velocities.

     6.Photographic Plate Method
     ï‚— Ionizing particle causes an activation and subsequent darkening of photographic plate.

     ï‚— The degree of darkening gives the measure of the total activity.

     ï‚— This method is used to locate the exact distribution of radioactive material in a thin

     ï‚— This method is mainly used for detecting gamma radiations in physiological studies of
       plant and animals.

     Handling and Storage of Radioactive Materials
     ï‚— Great care must be taken during handling and storage, to protect the personnel who
       handle it, from harmful radiations which emits from radioactive materials.
     ï‚— Certain precautions to be taken while working with materials, detectors and in
       experiments are as follows:
     1. Radioactive material should never be touched with hand, but should be handled by
         means of forceps or suitable instruments.

     2.   Smoking, eating or drinking should be avoided in the laboratory, where radioactive
          materials are present.

     3.   Protective clothing must be used while handling the materials.

     Handling and Storage of Radioactive Materials
     4.   Radioactive materials should be kept in suitable, labeled containers, shielded
          (protected) by lead bricks and preferably in remote area.

     5.   Area where radioactive materials are stored, should be monitored regularly.

     6.   There should be proper disposal method used for radioactive material.

     Applications of Radioisotopes
     ï‚— Radioisotopes are used in medicines in two different ways.
     1.   Radiation Source in Therapy
     2.   Radiation Source in Diagnosis

     1.Radiation Source in Therapy
      The therapeutic use of radioisotopes depends mainly on their ability to ionize atoms.
      Radiations produces destructive effect on existing cells and prevent the formation of new cells
       and tissues.
      For this reason, the radioisotope therapy is used only in those disease conditions, in which
       extensive cellular malfunction exhibits.
       e. g. Cancer

     Applications of Radioisotopes
     ï‚— Some important radioisotopes used in medicines are :
     1.   Calcium (44Ca and 45Ca): To study bone structure and in the treatment of
          carcinoma of bone (bone cancer).
     2.   Carbon (14C): Used in metabolism of carbohydrates, fats, drug excretion and
          decomposition of pharmaceutical products.
     3.   Cobalt (60Co): Used in therapy where X-rays are used, also used for the sterilization
          of surgical materials and dressings.
     4.   Cyanocobalmine (57Co): Used in diagnosis of pernicious anemia.
     5.   Gold (198Au) Solution: Used as neoplastic (tumor) suppressant.
     6.   Hydrogen (2H and 3H): Deuterium and Tritium are useful to determine the total
          body water.

     Applications of Radioisotopes
     7.    Iron (59Fe): Used in research studies about utilization and absorption of iron salts. It
           is also used to measure red blood cells life span.
     8.    Nitrogen (13N and 15N): Useful in investigation of amino acids and protein
           metabolism. It is also used in studies of nitrogen fixation by plants.
     9.    Oxygen (7O and 18O): Used in studies of organic reactions and photosynthesis etc.
     10.   Sodium (22Na and 24Na): It is employed in estimation of extracellular fluid, blood
           circulation rate, studies in cell permeability, excretion and distribution of water etc.
     11.   Sodium Chromate (51Cr) Solution: Used to study red cell volume and its survival

     Applications of Radioisotopes
     12. Sodium Iodide (131I) Capsule & Solution: Used for the diagnosis of disorders of
         thyroid function (hypothyroidism, hyperthyroidism and goiter), thyroid scan and for
         the treatment of hyperthyroidism.
         It is also used in treatment of myxedema (skin inflammation)
     13. Sodium Phosphate (32P) Solution: Used in treatment of Polycythemia (A disease
         condition in which bone marrow produces abnormally large amount of RBC’s ).
         It is also used in the treatment of “Chronic Granulocytic Leukemia� (Blood Cancer).

     Sodium Iodide                                                                       I131
     ï‚— Sodium Iodide I-131 is a solution which is suitable either for oral or intravenous
         administration, having radioactive I-131 which is processed in the form of sodium iodide
         from the products of uranium fission or the neutron bombardment of tellurium until it
         becomes essentially carrier free and is having only minute amounts of naturally
         occurring iodine-127.
     ï‚—   The solutions are clear and colourless, but over a period of time both the solution and
         glass may darken due to the effects of radiation.
     ï‚—   The pH of both solutions is between 7.5 to 9.0.
     ï‚—   For injection suitable preservative such as benzyl alcohol is added.
     ï‚—   A reducing agent sodium thiosulphate is added to the solution to prevent the oxidation
         of sodium iodide in aq. Solutions.
     Sodium Iodide                                                                           I131
     ï‚— Packaging and Storage:
       ï‚— The solution has to be prepared in single dose or multiple dose containers that have been
         previously treated to prevent absorption.
       ï‚— To avoid absorption of radionuclides on the walls of the containers including laboratory
         vessels, it has been recommended that containers used to handle sodium iodide I-131
         solutions should be first of all rinsed with a solution having approximately 0.8% of sodium
         bisulfate and 0.25% sodium iodide and then with water until the last rinsing has been neutral
         to litmus.
       ï‚— The expiration date has been not later than one month after the date of standardization.

     Sodium Iodide                                                                                        I131
     ï‚— Uses:
       ï‚— It is used as diagnostic aid for studying the functioning of the thyroid gland, and in scanning
         the thyroid for determining size, position and possible tumor location.
       ï‚— The isotope is administered orally or by intravenous injection. Then, the activity is measured
         over the thyroid at various time intervals up to including 24 hours after the dose was given.
       ï‚— The normal patient will be taking up from 1% to 45% of the administered dose in 24 hours.
         ï‚— If the uptake has been found to be less than 10% the patient has been hypothyroid, and uptake of over 50%
           has been an indication of hyperthyroidism.
       ï‚— It is also used in the treatment of hyperthyroidism.
       ï‚— Cancer of thyroid will generally be treated with doses ranging from 100 to 200 mc.

     ï‚— Radio-opaque substances are those compounds, that have the property of casting a
       shadow on X-ray films.

     ï‚— These substance have the ability to stop the passage of X-rays and hence appear opaque
       (nor reflecting light & allowing little light to pass through) on X-ray examination, so called as
       X-ray contrast media.

     ï‚— In diagnostic study using X-rays, the soft tissues are permeable to the passage of X-rays
       and hence causing darkening on X-ray film.
       The bony structure casts a shadow on the film, as the bones contains high atomic no. like
       calcium and phosphorus.

     ï‚— Inorganic compounds like barium sulphate, iodinated compounds and some bismuth
       compounds are useful as radio-opaque contrast media for diagnostic use.
     ï‚— These compounds are useful for examination of GIT, Kidney (Urography), Liver
       (Cholesystography), Gall bladder, bile duct, blood vessels of heart (Angiography &
       Cardiography) and bronchial tract (bronchography) etc.
     1. Barium Sulphate (Barium Sulphate Suspension)

     2.   Bismuth Compounds (Bismuthyl nitrate & Bismuthyl carbonate)

     Barium Sulphate
     BaSO4                                                                                  Mol. Wt. 233.4
     ï‚— It contains 97.5 to 100.5% w/w BaSO4
     ï‚— Properties:
       ï‚—   It is a fine, white, odourless and tasteless powder.
       ï‚—   The powder is free from grittiness.
       ï‚—   It is insoluble in water, organic solvents and dilute acids & bases.
       ï‚—   It is soluble in conc. Sulphuric Acid.
     ï‚— Action and Uses:
       ï‚— It is used as a contrast medium for X-ray examination of GIT (Alimentary tract).
       ï‚— It is administered by enema for examination of colon (large intestines).
     ï‚— Dose: 200-400 g oral.
     ï‚— Assay: Barium Sulphate is assayed by Gravimetrically (measuring wt.)

     Barium Sulphate for Suspension
     ï‚— Synonym: Barium Meal or Shadow Meal
     ï‚— It is a dry mixture of barium sulphate containing suitable color, flavor, preservative and
       suspending agent.
     ï‚— It contains not less than 90% w/v BaSO4.
     ï‚— Action and Uses:
       It is used as barium meal.
     ï‚— Assay:
       It is assayed by Gravimetrically.

     Bismuth Compounds
     ï‚— Bismuthyl nitrate and bismuthyl carbonate in 30-60 g as suspension in water used for
       examination of GIT.
     ï‚— Nowadays, these compounds are not in use.

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