Summary Safety Review - Iodinated Contrast Medium - Assessing the Potential Risk of Decreased Thyroid Hormone Production (Hypothyroidism)
April 24, 2017
Iodinated Contrast Medium (ICM)
Potential Safety Issue
Decreased thyroid hormone production (hypothyroidism)
- Iodinated contrast medium (ICM) products are medical imaging dyes authorized for sale in Canada for viewing the insides of different body parts.
- Health Canada reviewed the potential risk of transient or permanent hypothyroidism with the use of ICM because one of the manufacturers proposed to include this risk in the safety information for their product.
- Health Canada's review concluded that there is a rare potential risk of hypothyroidism with the use of ICM in certain patients, mostly infants. Health Canada is working with the manufacturers to update the safety information for all ICM products to inform about this potential risk.
- A Health Product Risk Communication will be published to further inform healthcare professionals about this safety information and recommendations to monitor thyroid function following ICM use in infants.
Health Canada reviewed the potential risk of hypothyroidism with the use of ICM because one of the manufacturers proposed to include this risk in the safety information for their product after updates were made to all product labels in the United States. There are concerns about hypothyroidism, especially in infants, as they may be more likely to experience this side effect and it can affect their development.
Use in Canada
- ICM products are medical imaging dyes authorized for sale in Canada for viewing the insides of various body parts.
- The review included the following products available in Canada: Gastrografin, Ultravist, Sinografin, Isovue, Cholografin, Meglumine, Telebrix, Optiray, Conray, Visipaque and Omnipaque.
- The first ICM marketed in Canada was Gastrografin, introduced in 1978.
Safety Review Findings
- At the time of review, Health Canada had not received any Canadian reports of ICM and hypothyroidism.
- This safety review looked at 23 international side effect reports of hypothyroidism with the use of ICM. Of these, 10 were considered to be related to the use of ICM. Of these 10 reports, in 3 reports the patients recovered, in 2 reports the patients did not recover and in the remaining 5 reports there was no information provided on whether or not the patient had recovered. The remaining 13 reports did not contain enough information to determine if the ICM product played a role in the onset of hypothyroidism. While the reports represented patients from all age groups, 6 of the 10 reports related to ICM use involved infants (less than 1 year of age).
- The review also looked into the published scientific literature and found a link between ICM use and the potential risk of hypothyroidismFootnote 1,Footnote 2,Footnote 3. Most of the reports involved infants but adults also experienced this side effect. The scientific literature explains how ICM exposure might lead to hypothyroidism in sensitive populations (e.g. infants, the elderly and those with underlying thyroid disease). The iodine in the ICM may affect the production of thyroid hormone, which also contains iodine.
- Studies have reported that untreated hypothyroidism following ICM injection in infants may result in life-long negative effects including severe delays in growth and development (including mental development)Footnote 4,Footnote 5,Footnote 6.
Conclusions and Actions
- Health Canada's review concluded that there is a rare potential risk of hypothyroidism with the use of ICM in certain patients, mostly infants.
- Health Canada is working with the manufacturers to update the safety information for all ICM products to inform about this risk. In addition, a Health Product Risk Communication will be published to inform healthcare professionals about this safety information and recommendations to monitor thyroid function following ICM use in infants.
- Health Canada will continue to monitor safety information involving ICM products, as it does for all health products on the Canadian market, to identify and assess potential harms. Health Canada will take appropriate and timely action if and when any new health risks are identified.
The analysis that contributed to this safety review included scientific and medical literature, Canadian and international adverse reaction reports and what is known about the use of these products both in Canada and internationally.
For additional information, contact the Marketed Health Products Directorate.
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