Deworming drug, levamisole, is being evaluated by the European Medicines Agency’s (EMA) Pharmacovigilance Risk Assessment Committee (PRAC) following concerns about its links with leukoencephalopathy. The review was initiated by the National Agency for Medicines and Medical Devices of Romania (NAMMDR). 

Leukoencephalopathy is a potentially life-threatening condition that damages the brain’s white matter. Symptoms may include confusion, weakness or impaired muscle function, and impaired or lost speech or vision.

Levamisole, marketed as Decaris and Levamisol Arena, is authorized in four EU countries — Hungary, Lithuania, Latvia, and Romania — for treating parasitic worm infections in adults and children. It works by stimulating nicotinic acetylcholine receptors on the surface of worm nerve cells, causing muscle paralysis and their expulsion via the infected person’s gut. 

The review comes after new data gathered as a part of the EU’s continuous monitoring of authorized medicines, including serious cases of leukoencephalopathy following levamisole use — one resulting in death — alongside additional data from the medical literature. 

Levamisole was discovered in 1966 and originally used in veterinary medicine as an anthelmintic before being marketed for use in humans. It was withdrawn from use in countries and regions such as the US, Canada, Europe, and Vietnam around the year 2000 due to side effects like leukoencephalopathy. Its use, however, continued in others. 

A 2022 analysis of 30 cases of levamisole-induced leukoencephalopathy in Russia reported successful treatment with intravenous corticosteroids and/or plasma exchange with ongoing neurological symptoms in some patients. 

“Growing evidence suggests that a single administration of levamisole even in low doses might potentially lead to severe neurological deficit or death. Therefore, changes in medication management policies are required in order to prevent the uncontrolled use of levamisole,” the researchers wrote. 

PRAC now intends to review all available evidence on the risk of leukoencephalopathy stemming from medicines containing levamisole. The committee will also conduct a cost-benefit analysis of the drug to see whether its health risks outweigh potential benefits. These analyses will inform recommendations as to whether the drug’s marketing authorization should be maintained, changed, suspended, or withdrawn in the EU. 

Once PRAC has reached a decision, its recommendations will be sent to the Co-ordination Group for Mutual Recognition and Decentralised Procedures — Human (CMDh) for further deliberation. The resultant decision, if adopted by consensus, will then be implemented in all states where the drug has been authorized. The CMDh’s position will also be sent to the European Commission for a final legally-binding decision applicable across the EU. 

An EMA spokesperson told Medscape Medical News that it is not possible to anticipate when PRAC’s recommendations will be released as their timeline depends on the assessment. He added, however, that the EMA will publish more information about the ongoing review on its website in coming weeks. 

Annie Lennon is a medical journalist. Her writing appears on Medscape, WebMD, and Medical News Today, among other outlets.