Radiopharmaceuticals are drugs that carry a limited degree of radioactivity, and are usually used in nuclear medicine as an alternative to standard radiation for the treatment of certain cancers as well as a diagnostic tool to allow better internal imaging of certain organs and arteries. They are usually able to focus on just one particular part of the body, which can make treatment a lot more effective — not to mention a lot more targeted — than regular radiation, which tends to focus on the entire body. Drugs in this class are generally very specialized, and require a lot of related equipment and expertise to use. Most of the time people only take them under the close guidance of a physician or care provider, and usually have to be monitored throughout the time the drug is in the body. There are some risks and safety concerns but, when used properly, these sorts of pharmaceuticals generally get good results for patients in most situations.
How They Work
This class of drugs is usually somewhat complex from a manufacturing standpoint since it requires not only a live radioactive element but also a targeted delivery mechanism. In most cases they are built around a radioactive isotope that can be injected safely into the body, which is then paired with a carrier molecule to deliver that isotope in response to certain nerve or other signals in the body.
Once radiopharmaceuticals enter the body and travel to an organ, they begin to interact with the processes of that organ. The radioactivity is picked up by cameras or computers and used to map the process. For example, an ultrasound can show an image of an organ and reveal if a tumor or other abnormality is present. Nuclear medicine can show how the process of glucose metabolism is functioning in the organ.
One popular nuclear ingredient is an isotope called technetium (Tc), the lightest radioactive element known, which is used in a variety of nuclear tests. Thallium-201 is used for cardiac stress tests. Other common nuclear components used include indium-111, gallium-67, iodine-123, iodine-131 and venom-133. These sorts of medications usually have to be made in specialized labs, but the radioactive portions that actually appear in individual doses are relatively small. Some degree of care and special handling is usually needed during transportation or shipping, but in most cases they aren’t considered a hazard.
As a Diagnostic Tool
The majority of nuclear medicine involves diagnostic testing. When radiopharmaceuticals are injected into the body, they emit radiation that can be traced with special cameras or computers. The amount of radiation a patient is subjected to is about the same as a normal X-ray, but the information gathered is significantly different. Non-nuclear diagnostic methods, such as X-rays and ultrasounds, show the size and shape of a bone, organ or tumor. Nuclear medicine allows a medical professional to see how an organ is functioning.
The drugs can target almost every organ of the body, and are common in brain scans, bone scans, cardiac stress tests and thyroid studies. Prior to the test, the radiopharmaceutical is administered to the patient orally, intravenously, or by inhalation. The radioactive material is short-lived, and either converts to a non-radioactive substance, or passes quickly through the body.
In Cancer Treatments
These sorts of drugs are also often used for certain cancer treatments, particularly when the disease is detected in its very early stages. In part this is because the radiation in these drugs does not harm cells growing at a normal rate, but it can destroy fast growing cells. When they are injected into tumors or growths they can kill the harmful cells without disturbing the surroundings, for instance, and a compound known as radioactive iodine (I-131) has traditionally been very effective in the treatment of thyroid cancer since it can destroy thyroid growths without damaging anything else in the body. This is a stark contrast to standard radiation treatment, which typically impacts all healthy cells.
In some cases the drugs can also be used to relieve the pain associated with chronic conditions like cancer, often by responding to internal nerve signals. A drug called Quadramet® is given intravenously to relieve pain caused by bone cancer, for instance.
One of the biggest benefits of radioactive drugs is how they show diagnosticians and health care providers exactly what is going on inside a patient’s body in a very targeted, limited way. Two of the most commonly used pieces of nuclear imaging equipment in this endeavor are the positron emission tomography (PET) scans and single photon emission computerized tomography (SPECT) scans. The PET scan uses cameras and computers to construct three-dimensional images of the area being examined, while the SPECT scan creates cross-sectional images of an area. The PET scan typically emits gamma rays, while the SPET emits photons which convert to gamma rays. In either case, patients are usually hooked up to a machine and closely monitored throughout the course of their treatment.
Risks and Concerns
Drugs in this class tend to have more severe side effects and adverse reactions than do most regular pharmaceuticals, but a lot of this goes hand in hand with the nature of what the medication is trying to do. Skin sensitivity, low red blood cell counts, and general fatigue are some of the most common reactions, though more serious things like allergies have been reported, particularly when delivered intravenously. Swelling at the injection site and nausea are common, too. In most cases pregnant women are discouraged from undergoing this sort of treatment to avoid risks to their unborn children.