Other safety alerts
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| Canada: Summary Safety Review - Methadone-containing products used to treat opioid dependence - Health Canada |
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Health Canada announces that it reviewed the potential risk of lack of effect, which may present as drug withdrawal, with methadone-containing products used to treat opioid dependence. The review was triggered by recent reports received from Canadian patients and healthcare professionals suggesting that some patients experienced symptoms of opioid withdrawal after being switched from one methadone product to another.
Health Canada reviewed the scientific and medical literature, Canadian and international information including case reports in the Canada Vigilance database as well as information received from manufacturers, Canadian healthcare professionals and patients.
Health Canada's review looked at 22 Canadian reports (12 from the Canada Vigilance database and 10 provided by the manufacturers) linked with a lack of effect of methadone-containing liquid products (taken orally) used to treat opioid dependence.
These reports suggested that these methadone-containing products did not work as well to ease withdrawal symptoms and patients who had generally been on stable methadone treatment for a long time, as they reported experiencing withdrawal symptoms after being switched from one methadone product to another. Assessing whether the lack of effect was specifically related to one methadone-containing product and why the withdrawal symptoms happened was challenging due to lack of information. However, a link between methadone-containing products used for opioid dependence and lack of effect could not be ruled out in these cases.
The Department also contacted over 40 Canadian healthcare professionals, professional associations and patient treatment centers in order to gather feedback regarding this safety issue from healthcare professionals and patients. In total, 7 responses were received (5 from healthcare professionals and 2 from patients). The 5 responses received from healthcare professionals reported changes in how patients responded to the treatment for opioid drug dependence after being switched from one methadone-containing product to another. The problem was fixed by increasing the dose of the methadone-containing product they were taking, by switching to a new methadone-containing product, or by switching back to the original methadone-containing product. One of the 2 patient responses also described that the new methadone-containing products were not working as well as the old one.
Health Canada also assessed 5 published studies found in the Canadian scientific literature discussing the issue of lack of effect when patients treated for opioid dependence in British Columbia (Canada) were switched from one methadone-containing product to another. These studies generally found that some patients did worse following a product change. However, the studies did not identify specific causes for the observed lack of effect.
Canadian and international literature, as well as feedback from Canadian healthcare professionals, suggest that psychosocial factors may play a role and some patients do not tolerate methadone-containing product changes.
While the cause has not been linked to any specific problem with the methadone-containing product used following a switch, withdrawal symptoms can be serious and patients should consult with their healthcare professional if they have concerns about switching products or if they experience withdrawal symptoms.
Health Canada's review found there may be a link between methadone and the risk of lack of effect, which may present as drug withdrawal, when switching between methadone-containing products, although the reason for this is unclear. Patients experiencing withdrawal symptoms need to be seen often by their health care professional and may need an adjustment in the dose of methadone. Health Canada will be working with manufacturers to update the Canadian product information to warn of this potential safety issue.
Please refer to the following website in Health Canada for details:
http://hpr-rps.hres.ca/../summary-safety-review-detail.php?lang=en&linkID=SSR00243
In Hong Kong, there is one registered pharmaceutical product containing methadone which is indicated for opioid dependence and currently available in the Hong Kong market, namely, Methadone Linctus 80mg/20ml (New Formula) (HK-65009), and is a prescription-only medicine. So far, the Department of Health (DH) has received 4 cases of adverse drug reaction related to methadone, but these cases are not related to switching of methadone products. Related news was previously issued by Health Canada, and was posted on the Drug Office website on 1 Apr 2020. As there is only one methadone product for opioid dependence currently available in Hong Kong, the above Health Canada’s announcement of potential differences in product effect does not have any impact on Hong Kong.
Ends/Saturday, Jul 18, 2020
Issued at HKT 11:30
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