Drugs with decongestant pseudoephedrine can be taken but with caution: Experts

SINGAPORE – There is no need to discard medications containing decongestant pseudoephedrine unless an individual has serious medical conditions like uncontrolled hypertension or kidney failure that increase the risk of serious side effects, said medical experts.

However, they stressed the importance of adhering strictly to the prescribed dosage and seeking immediate medical attention if unusual symptoms such as nausea and visual disturbances emerge.

Some readers of The Straits Times have expressed concern after reading a report about pharmaceutical giant

GSK’s decision to stop producing Zyrtec-D,

its popular antihistamine and decongestant, which contains pseudoephedrine, a drug that has been linked to rare but severe side effects.

Pseudoephedrine is found in about 30 medications registered in Singapore. Others that contain pseudoephedrine include Clarityn-D, Telfast-D and Sudafed.

The drug has been linked to posterior reversible encephalopathy syndrome (PRES) and reversible cerebral vasoconstriction syndrome (RCVS).

Although the risk of the drug inducing problems is small – and in most cases reversible – the two conditions can be serious.

PRES can cause visual problems, seizures and headaches, and affects thinking. It is treatable with early diagnosis.

RCVS has symptoms resembling those of stroke, as it is caused by blood vessels that suddenly spasm and constrict. Almost one in three people with RCVS may suffer some long-lasting disability, such as muscle weakness.

Dr John Cheng, chief medical officer of Healthway Medical Group, Singapore’s largest general practice clinic chain, said it is important to note that these severe reactions “are exceedingly rare”.

He explained that they are “associated with multiple contributing factors, such as pre-existing conditions, excessive dosing, or concurrent use with other medications that affect the central nervous system or blood pressure”.

“The potential risks emphasise the need for caution, especially in patients with risk factors like hypertension, migraines or a history of stroke.”

Dr Cheng added that it is important for patients to strictly adhere to the dosing instructions. They should also speak to their doctors or pharmacists before starting on the medicine.

If they suffer from any unusual symptoms, such as severe headaches, visual disturbances, or confusion, while taking these medications, they should seek immediate medical attention, he said.

In a safety alert issued in April 2024, Singapore’s Health Sciences Authority said it will work with drug companies to strengthen the warnings on PRES and RCVS and their related symptoms in the package inserts or patient information leaflets of products with pseudoephedrine that are registered for use here.

The medical regulator added that healthcare professionals “may also consider counselling their patients on symptoms that require immediate medical attention to facilitate the prompt detection of PRES and RCVS symptoms and the necessary medical intervention”.

“These include sudden onset of severe headache, nausea, vomiting, visual disturbances, seizures and altered mental status,” it said.

On its website, Britain’s National Health System (NHS) advises people with heart problems not to take pseudoephedrine.

It says: “Pseudoephedrine works by narrowing the blood vessels in your nose, but it also narrows the blood vessels in other parts of your body. This can increase your blood pressure and your heart rate.”

NHS advises that people who may need to be cautious about using the drug include those with glaucoma, enlarged prostate, and liver or kidney problems.

It also says the drug should not be taken for more than seven days, as the risk of side effects increases with longer-term use.