What is Nuclear Pharmacy?

Prior to discussing the field of nuclear pharmacy, it is important to understand some background regarding radioactivity and how it is used in patients.  Most people hear the word radiation, and immediately have an image of danger or injury.  However, most people do not realize that there is radiation in everyone’s lives in many different forms.  Electromagnetic radiation is emitted from the sun, from signals sent from radio and TV stations, from radar used to track airplanes, and even visible light.  In this particular field, we are interested in a type of radiation termed radionuclides.  A radionuclide is an atom that has an unstable nucleus.  Recalling chemistry, the nucleus of an atom consists of protons and neutrons.  If a nucleus, for whatever reason, has an excess of either one of these constituents, it will try to “get rid of” the excess component and return to a stable state.  By doing so, the atom is said to give off this energy in the form of radiation.  There are quite a few naturally occurring radionuclides.  Any nuclide with an atomic number greater than 83 is radioactive.  An atom’s atomic number is simply the total number of protons found in the nucleus.  There are also many naturally occurring radionuclides with lower atomic numbers.

While some radionuclides occur naturally in the environment, there is another class of “man-made” or artificial radionuclides.  Artificial radionuclides are generally produced in a cyclotron or some other particle accelerator, in which we bombard a stable nucleus with specific particles (neutrons, protons, electrons or some combination of these).  By doing so, we make the nucleus of our starting material unstable, and this nucleus will then try to become stable by emitting radioactivity.

An unstable nucleus can give off its energy in a variety of ways.  The type of emission that is given off will determine whether or not the radionuclide will be useful for imaging or treating a patient.  The radiologic specialty of nuclear medicine uses small quantities of radioactive materials with a known type of emission.  By “tagging” the radioactive source to some compound that is known to localize in a specific area of the body, the compound will carry the radioactive material to the desired site.  By using a specific detection device called a gamma camera, it is possible to detect the emissions given off by the radioactive material and create images of the relative distribution of the radioactive source in the body.

As nuclear medicine procedures became more widely used, the need for someone to prepare the labeled products for administration to the patients became more evident.  While many large hospitals were able to use pharmacists with training in the handling of radioactive material, smaller hospitals were unable to utilize nuclear medicine procedures because they did not have the staff to prepare the necessary doses in a cost effective manner.  As a result, in the early 1970’s, the concept of centralized nuclear pharmacies was born.  When developed, the centralized nuclear pharmacy served as the “drugstore” for the nuclear medicine department.  When a particular radioactive material was needed, a trained nuclear pharmacist was available to prepare the product and dispense it to the end user.  When you look at a nuclear pharmacy, its operation is not much different than that of a traditional pharmacy – a “prescription” for a particular product is presented, and the nuclear pharmacist must prepare and dispense that “prescription”.  Where a traditional pharmacist will dispense doses in milligram weight units, a nuclear pharmacist will dispense in millicurie activity units.  Where a traditional pharmacist dispenses tablets and capsules, a nuclear pharmacist dispenses the radioactive material in liquid or capsule form.  Where a traditional pharmacist will generally dispense the prescription to the patient, the nuclear pharmacist will dispense to a hospital or clinic nuclear medicine department where the dose will be administered to the patient.  In general however, the 2 branches of pharmacy are strikingly similar.

There are some inherent differences in nuclear pharmacy practice, which ultimately warranted its designation as a specialty pharmacy practice.  There are certain areas of practice unique to nuclear pharmacy, as well as a separate class of drugs that are used.  The most striking would be the fact that radioactive material is being used to create the final products.  While the quantity used is small, there are still certain precautions that must be taken into account when handling on a day to day basis.  The nuclear pharmacist is extensively trained in radiation safety and other aspects specific to the compounding and preparation of radioactive materials.

In most nuclear pharmacies, the nuclear pharmacist is responsible for obtaining the desired radioactive material, either from a manufacturer, or from an in house generator system.    The most commonly used isotope in nuclear medicine is Technetium-99m that is readily and continuously available from a generator system.  The generator forms the radionuclide that is retained on an internal column until the generator is “milked”.  When “milking” the generator, sodium chloride is passed over the column, which removes the radioactive material.  The eluate is then collected in a shielded evacuated vial.  After performing quality assurance tests on the eluate, it can be used in the preparation of the final radiopharmaceutical products.

With over 100 different nuclear medicine procedures performed today, there are many different products that can be used.  Most radiopharmaceuticals are available as “kit” formulations.  All materials necessary for preparation are available in the nonradioactive kit with the exception of the radioactive isotope.  When the radioactive isotope is added to the kit, the chemical reactions required for binding the isotope occur within the vial.  In most cases, when the tagging reaction is complete, the final product will be ready for quality control verification and unit dose dispensing.

Since nuclear pharmacy practice involves the on-site compounding of most of the products being dispensed, each product that is compounded in the nuclear pharmacy must be tested prior to dispensing any individual doses.  Simple instant thin layer chromatography tests quickly and accurately provide information on the radiochemical composition of the kit that was prepared.  When the radiochemical purity of the compounded product is verified, it can be dispensed for use in patients.

In addition to preparing and dispensing the radioactive products, nuclear pharmacists are available to provide drug information to other health professionals, to aid the nuclear medicine staff in the selection of products, and to assist in the interpretation of unusual studies.  Nuclear pharmacists receive extensive training on the various radiopharmaceuticals that are used, as well as training on the safe handling of radioactive materials and the procedures that will minimize radiation exposure to themselves and to others.  There are very few schools of pharmacy that have any courses in nuclear pharmacy – Purdue University is unique in that it has several undergraduate courses available to students enrolled in the school of pharmacy, as well as a continuing education certificate program which allows licensed pharmacists who have had no exposure to nuclear pharmacy the opportunity to receive the necessary training to become a nuclear pharmacist.

Nuclear pharmacists serve as vital links in the provision of nuclear medicine services.  By working closely with the nuclear medicine staff, nuclear pharmacists can contribute a tremendous amount to the provision of care for the patients who are undergoing nuclear medicine procedures.  While similar to traditional pharmacy, nuclear pharmacy is also in many ways unique, and can be a challenging and rewarding career choice for pharmacists.