Iobenguane 131 (Intravenous)

Overview

Iobenguane 131 is a radioactive agent which is primarily used in the detection of cancerous tumors resident in the adrenal glands. Because it is readily absorbed by the adrenal glands, it can highlight the presence of any tumors there, which will show up on diagnostic x-rays or computer screens. A treatment plan can then be formulated, once the characteristics and precise positioning of the cancerous tumor have been identified.

Condition Treated

  • Cancer of the adrenal glands

Type Of Medicine

  • Radiopharmaceutical

Side Effects

There are some very beneficial effects provided by Iobenguane 131, but there is a potential for some unwanted side effects to be imparted to any given patient, as well. Some patients experience a sore throat and or fever, and, in the aftermath of being injected with the drug, there can be unusual bruising or bleeding for a time, as well as abnormal weakness or fatigue.

Since this is a drug that is delivered intravenously, there is the potential for many different kinds of irritation to appear on the skin surface surrounding the injection site. There can be reddening of the skin, small reddish or purple colored spots, dryness of the skin and general itchiness at the location.

For most patients, however, these symptoms clear up fairly soon after they appear - usually within a couple days, and there is no further effect on the patient. In some uncommon cases, patients experience nausea or vomiting, or a slight increase in blood pressure that lasts for no more than a day.

In fact, almost any kind of side effect attributed to the intravenous delivery of Iobenguane 131 will be of the type that appears briefly and then subsides all on its own, without any need for medical attention. If you should experience these side effects or any others in the aftermath of an injection of this medication, you should contact your doctor and explain the nature and severity of the side effects you are experiencing.

Dosage

Because this is a radioactive agent, Iobenguane 131 must be administered to a patient with considerable care, both during preparatory steps and for several days following the actual injection. Prior to administration of this drug, it will be necessary to block the patient's thyroid gland with a potassium iodide oral solution, and this blocking iodine must be delivered to the patient on the day prior to injection of Iobenguane 131, and for at least five days following the dosage of radioactive solution.

Although precise dosages will vary from patient to patient based on a number of factors, there is standard dosage that is considered to be fairly effective in carrying out the expected function of this medicine. The dosage will be different for pediatric patients as opposed to adult patients, and will also be different for obese patients weighing more than 65 kg.

  • The recommended dosage for adults is .5 mCi.
  • For obese adult patients, the amount will likely be modified to some level between .3 mCi/m2 on up to a maximum of 1.0 mCi.
  • The recommended dosage for pediatric patients is .3 mCi/m2, with a ceiling dosage of .5 mCi. It is necessary to deliver at least .135 mCi of solution in order for the drug to adequately carry out its intended function.

During the delivery of Iobenguane 131, the injection should be a slow intravenous infusion that lasts somewhere between 15 and 30 seconds, and possibly longer than that if medical professionals deem it necessary. During this period, a patient's vital signs must be closely monitored because of the possibility of rebound hypertension, and this monitoring should continue for a time after the injection, as well.

It's very important that all appropriate precautions are taken to ensure that there is minimal exposure to radiation for both patient and medical personnel. For instance, the actual preparer of the drug will need to be wearing waterproof gloves and a shielded syringe should be used during administration.

Prior to the actual delivery of the drug, the solution should be inspected for any kind of particles that may be present or a discoloration of the solution itself. In either case, the medication should not be used and instead should be discarded according to proper disposal methods for radioactive agents.

The precise dosage level of this medication should always be measured by a well calibrated system, so that the exact amount desired is actually delivered. All personnel involved with delivery of the dosage should be highly trained and experienced in carrying out the procedure.

Interactions

As with almost all medications, there is a potential for Iobenguane 131 to interact with other specific drugs, and when that happens, there's a possibility that any side effects may increase in severity or quantity, or that the effectiveness of either of the two drugs may be diminished in some way. In the case of Iobenguane 131, there is a potential for other drugs to interact with it and cause false negative results, which, of course, would be extremely undesirable.

It is, therefore, necessary for any patient who is about to be injected with this radioactive agent to prepare a list of all medications being taken at the time, so that a doctor can review the list and make a determination on whether any of those listed drugs have the potential for interaction with Iobenguane 131. When preparing this list, be sure to include all over the counter drugs, other prescription drugs, vitamins and herbal supplements, because there is the potential for any of these to have an impact on Iobenguane 131. Some of the other medications that fall into the category of potential interactions with Iobenguane 131 include the following:

  • Antihypertensives, such as reserpine or labetalol
  • Antidepressants, such as amitriptyline and any of its derivatives
  • Imipramine and any of its derivatives
  • Serotonin inhibitors
  • Sympathomimetic amines, such as phenylephrine, phenylpropanolamine and pseudoephedrine
  • Ephedrine
  • Cocaine

Warnings

There are a number of precautions or warnings that patients should be aware of prior to being injected with Iobenguane 131 and there are some that medical personnel should check for in patients who are candidates for being injected with this medication. Here are some of the most common precautions observed by medical personnel, with regard to patient eligibility:

  • Hypersensitive reactions 'some patients have had hypersensitive reactions because of the iodine content used, so patients must be questioned about any past sensitivity to iodine or any products that contain iodine. Where there is suspicion of potential hypersensitivity, patients can be tested for anaphylactic reactions and for hypersensitive reactions.
  • It may be necessary to increase dosage for renal patients, due to the delayed evacuation of the drug because of abnormal kidney function. This may also be a factor in deciding that Iobenguane 131 is not the best alternative for diagnostic imaging of cancerous tumors.
  • If there is a failure to block the thyroid gland prior to administration of Iobenguane 131 and for several days afterward, there could be an increased risk of thyroid neoplasia. This will also be possible if the thyroid blockage procedure is not properly carried out.
  • There is a risk of elevated blood pressure for some patients in the period following administration of Iobenguane 131, so monitoring of readings is strongly recommended, even though the risk is generally a temporary condition.
  • There is a potential for harm to an unborn fetus carried by a pregnant mother who has been administered Iobenguane 131, so pregnant women should have a thorough discussion with their doctor about advisability of using this drug.
  • While it is not known if Iobenguane 131 is passed on to a nursing infant through breast milk, it is known that iodine is passed on to the nursing infant. For this reason alone, it is not advisable for mothers to breast feed during the period after injection with this medication.

Storage

This drug should be stored constantly at a temperature between 68 and 77 degrees Fahrenheit, although brief departures from this range are permissible as long as they are neither drastic or prolonged. All precautions must be observed for storing radioactive agents and all handling activities should be given the full consideration that radioactive materials require. The actual storage location should be in a lead-shielded environment so that no harmful radioactivity can be radiated out.

Summary

Iobenguane 131 is a radioactive agent that is primarily used in the detection of cancerous tumors in the adrenal glands. It is effective in this regard, because the adrenal glands typically absorb the drug readily, and that allows for highlighting tumors on any kind of display or imaging which is taken of the glands.

Since it is a radiopharmaceutical, all appropriate precautions must be taken with administration to a patient, as well as with storage and handling. It will also be necessary to dispose of expired or unused Iobenguane 131 according to strict procedures used for the disposal of radioactive materials.