Health Canada is issuing an alert about Advil Liquid products for infants and children over a risk of inconsistent dosing.

Pfizer Consumer Healthcare issued a voluntary recall on Friday.

The concern is clumps of ibuprofen may form in the medicine’s bottles if not shaken well before each use. The result could lead to either higher or lower concentrations of the drug, making it either ineffective or leading to other health issues such as convulsions.

Health Canada says the products being recalled are Advil Pediatric Drops, Children’s Advil Cold, Children’s Advil Fever from Colds or Flu, Children’s Advil, and Advil Pediatric Drops Fever from Colds or Flu.