Original Article: http://www.mayoclinic.com/health/drug-information/DR602305
Radiopaque agents are drugs used to help diagnose certain medical problems. They contain iodine, which blocks x-rays. Depending on how the radiopaque agent is given, it localizes or builds up in certain areas of the body. The resulting high level of iodine allows the x-rays to make a "picture" of the area.
The areas of the body in which the radiopaque agent localizes will appear white on the x-ray film. This creates the needed distinction, or contrast, between one organ and other tissues. The contrast will help the doctor see any special conditions that may exist in that organ or part of the body.
The local radiopaque agents are used in the diagnosis of:
- Urinary tract diseases—Diatrizoates, Iohexol, Iothalamate
- Uterus and fallopian tube diseases—Diatrizoate and Iodipamide, Diatrizoates, Iohexol, Ioxaglate
A catheter or syringe is used to put the solution of the radiopaque agent into the bladder or ureters to help diagnose problems or diseases of the kidneys or other areas of the urinary tract. It may also be placed into the uterus and fallopian tubes to help diagnose problems or disease of those organs. After the test is done, the patient expels most of the solution by urinating (after bladder or ureter studies) or from the vagina (after uterine or fallopian tube studies).
Radiopaque agents are classified by their osmolality (a measure of concentration). There are high- and low-osmolality contrast agents. Low-osmolality agents are newer and more expensive than the high-osmolality ones. For most patients, a high-osmolality contrast agent is a good and safe choice. However, some patients are considered to be at a greater risk of having severe reactions to a radiopaque agent. Patients at risk are those who have had a severe reaction to radiopaque agents in the past. Also, patients with asthma or a history of allergies may be at a greater risk of severe reactions. For these patients, a low-osmolality contrast agent may be chosen. If you have any questions about this, check with the radiologist.
The doses of radiopaque agents will be different for different patients and depend on the type of test. The strength of the solution is determined by how much iodine it contains. Different tests will require a different strength and amount of solution depending on the age of the patient, the contrast needed, and the x-ray equipment used. Also, for tests of the kidneys and other areas of the urinary tract, the amount of solution to be used depends on the size of the bladder.
Radiopaque agents are to be used only by or under the supervision of a doctor in radiology or a radiologist.
In deciding to receive a diagnostic test, the risks of taking the test must be weighed against the good it will do. This is a decision you and your doctor will make. For these tests, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to medicines in this group or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Although there is no specific information comparing use of radiopaque agents in children with use in other age groups, these agents are not expected to cause different side effects or problems in children than they do in adults when used in the bladder or ureters. There is no specific information about the use of radiopaque agents in children for studies of the uterus or fallopian tubes.
Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults. Although there is no specific information comparing use of radiopaque agents for instillation into the bladder or ureters or into the uterus and fallopian tubes in the elderly with use in other age groups, these agents are not expected to cause different side effects or problems in older people than they do in younger adults.
Studies on effects in pregnancy when radiopaque agents are instilled into the bladder or ureters have not been done in women. Studies in animals have been done only with iothalamate, which has not been shown to cause birth defects or other problems.
Diagnostic tests of the uterus and fallopian tubes using radiopaque agents are not recommended during pregnancy or for at least 6 months after a pregnancy has ended. The test may cause other problems, such as infection in the uterus.
Also, radiopaque agents containing iodine have, on rare occasions, caused hypothyroidism (underactive thyroid) in the baby when they were injected into the amniotic sac late in the pregnancy. In addition, x-rays of the abdomen during pregnancy may have harmful effects on the fetus. Make sure your doctor knows if you are pregnant or if you suspect that you may be pregnant when you are to receive this radiopaque agent.
Although small amounts of radiopaque agents are absorbed into the body and may pass into the breast milk, these agents have not been shown to cause problems in nursing babies. However, it may be necessary for you to stop breast-feeding temporarily after receiving a radiopaque agent. Be sure you have discussed this with your doctor.
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other Medical Problems
The presence of other medical problems may affect the use of diagnostic tests in this class. Make sure you tell your doctor if you have any other medical problems, especially:
- Acute kidney problems due to a severe liver disorder (hepato-renal syndrome [HRS]) or
- Acute kidney problems before, during, or after a liver transplant or
- Severe kidney problems, acute or chronic—The use of a gadolinium-based contrast agent (GBCA) should be avoided in patients with severe kidney problems. The risk of nephrogenic systemic fibrosis (NSF), a very serious disease affecting the skin, muscle, and internal organs, may be increased .
- Asthma, hay fever, or other allergies (history of) or
- Reaction to a skin test for allergies or to penicillins—If you have a history of these conditions, there is a greater chance of having a reaction, such as an allergic reaction, to the radiopaque agent.
- Enlarged prostate—There may be blockage that makes it difficult or impossible to put the solution of the radiopaque agent into the bladder or ureters.
- Genital tract infection or
- Urinary tract infection—The risk of complications is greater in patients with these conditions.
- Pelvic inflammatory disease (severe)—The condition may be aggravated by this test.
Your doctor may have special instructions for you in preparation for your test, such as the need for a special diet or for a laxative, enema, or vaginal douche, depending on the kind of test you are having done. If you have not received such instructions or if you do not understand them, check with your doctor in advance.
For your comfort and for the best test results, you may be instructed to urinate just before the procedure.
If you are on hemodialysis and treated with a gadolinium-containing contrast agent (GBCA), your doctor may perform hemodialysis immediately after you receive the contrast agent .
Make sure your doctor knows if you are planning to have any thyroid tests in the near future. Even after several weeks the results of the thyroid test may be affected by the iodine in this agent.
Seek immediate medical attention if you experience burning or itching of the skin; reddened or darkened patches; skin swelling, hardening and/or tightening; yellow raised spots on the whites of the eyes; joint stiffness; limited range of motion in the arms and legs; pain that is deep in the hip bone or ribs; or muscle weakness. These may be symptoms of a very serious disease called nephrogenic systemic fibrosis (NSF) .
Along with its needed effects, radiopaque agents can cause serious side effects such as allergic reactions. These effects may occur almost immediately or a few minutes after the radiopaque agent is given. Although these serious side effects appear only rarely, your health care professional will be prepared to give you immediate medical attention if needed. If you have any questions about this, check with your doctor.
Check with your doctor immediately if any of the following side effects occur:Less common
- Abdominal or stomach pain and discomfort (severe)
- Burning or itching of the skin
- Joint stiffness
- Limited range of motion in the arms, hands, legs, or feet
- Muscle weakness
- Pain deep in the hip bone or ribs
- Reddened or darkened patches on the skin
- Skin swelling, hardening and/or tightening
- Yellow raised spots on the whites of the eyes
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:More common
- Abdominal or stomach pain and discomfort (mild)
- Nausea and vomiting
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.