• The Medicines and Healthcare products Regulatory Agency (MHRA) in the UK is proposing new safety measures for pseudoephedrine medications because of rare reports of posterior reversible encephalopathy syndrome (PRES) and reversible cerebral vasoconstriction syndrome (RCVS). • These conditions can cause inflammation and/or reduced blood supply to the brain, which are very rare side effects. • Pseudoephedrine is licensed for short-term relief of nasal congestion due to colds, flu, and allergies.