On 28 March 2019, the Health Sciences Authority (HSA) recalled 3 brands of the high blood pressure medication losartan over cancer risk. All losartan products in Singapore have been tested and three out of the 10 brands of losartan being sold here contain higher than acceptable amounts of nitrosamine impurity, specifically N-nitroso-N-methyl-4-aminobutyric acid (NMBA), which can potentially cause cancer.
Losartan and nitrosamine impurity
NMBA is a nitrosamine impurity that has been observed to cause cancer in animal studies and has been identified as a potential cancer-causing risk in humans. Nitrosamine compounds can be found in very small quantities in some food products like pickled vegetables, salted fish and processed meat and also in tobacco products. The potential risk of cancer is with long-term exposure to unacceptable levels of the impurities.
The presence of NMBA impurity in losartan was unexpected. It was not previously recognised that there could be a chemical reaction during the manufacturing process that could produce this compound. Any presence of such impurities in drug products is not acceptable; hence there was a need to recall the 3 brands of losartan as a safety precaution.
Losartan is still an effective medication
The problem is not with the medication; NMBA is a contaminant that was included or formed in the manufacturing process of the 3 brands of losartan that caused the problem. A 2016 study that involved analyzing data involving about 150,000 patients found that there was no evidence of cancer risk associated with the use of losartan and its family of medication.
Losartan can be found on the World Health Organisation’s List of Essential Medicines, which lists the most effective and safe medicines that are needed and should be made available in a healthcare system. A 2010 research paper which reviewed the previous 15 years of losartan use, reports that losartan is beneficial for controlling blood pressure, reducing stroke risk and protecting kidney function in certain groups of diabetic patients.
HSA is working with the companies and international regulatory authorities to identify the root causes of the contamination and the required measures to address the issue. Patients should not lose faith in the medication itself. Other brands of losartan are still available that have been tested and does not contain NMBA. You can refer to the full list of affected and unaffected brands on HSA’s website here or consult your healthcare provider if you are unsure if you are taking an affected brand.
Losartan belongs to the family of medication called the angiotensin II receptor blockers (ARBs)
Losartan was the first in the family of ARBs to be approved for medical use in the United States in 1995. Since then, other ARBs have been developed. Other ARBs available in Singapore include candesartan, irbesartan, telmisartan and valsartan. As a family, ARBs mainly work by preventing the production of chemicals in the body that constrict blood vessels. This helps to expand blood vessels and reduce resistance to blood flow hence resulting in a lower blood pressure. ARBs are most commonly being used to treat high blood pressure. They can also be prescribed for other reasons, always check with your doctor.
As losartan is used to treat high blood pressure, it is very important not to stop taking this medication on your own until you consult a doctor. High blood pressure is often referred to as a silent killer as most patients with untreated high blood pressure usually have no obvious symptoms to alert them that something is wrong. Over time, detrimental damage to the heart and kidneys can occur. Untreated high blood pressure can lead to an increased risk of heart attacks and strokes.
If you are currently taking the affected brand of losartan, HSA advises that “there is no immediate health risk associated with taking the affected losartan”, in fact, “sudden stopping of losartan can pose a greater and more immediate risk to patient’s health.” Always consult your doctor or pharmacist who can review and provide you with a replacement brand of losartan or an alternative medication that is best for you.
Blood pressure medications such as losartan are just one aspect of the treatment of high blood pressure. Taking your medications everyday is necessary but it is not a substitute for a good lifestyle. Lifestyle and dietary changes play an equally important role in reducing blood pressure.You can contact the HSA hotline at 6866 3538 or email email@example.com if you have further enquiries on the recall of losartan. More details and updates on the recall are posted on the HSA website via this link.
About the Author: This article is written by Vanessa Ong. Vanessa is a registered pharmacist with the Singapore Pharmacy Council. She spent several years in the inpatient setting in a local hospital. She enjoyed her time spent in the wards working with a dedicated healthcare team passionate about better patient outcomes. She strongly believes that evidence-based health information can be made simple so that the public can find joy in taking ownership of their health and live life to the fullest.
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