The UK's Medicines and Healthcare products Regulatory Agency (MHRA) has instructed all UK trials investigating hydroxychloroquine in Covid-19 to suspect recruitment.
This follows on from the University of Oxford RECOVERY trial halting recruitment into its hydroxychloroquine arm because results found it provided no clinical benefit to hospitalised Covid-19 patients.
MHRA CEO Dr June Raine said: "We have told those conducting clinical trials using hydroxychloroquine to treat or prevent COVID-19 to suspend recruitment into their trials.
"Neither hydroxychloroquine nor chloroquine are licensed to treat COVID-19 related symptoms or to prevent infection.
"It is important to note that patients taking hydroxychloroquine and chloroquine to treat other health conditions can continue to do so, as advised by their healthcare professional, as the balance of benefits and risks remains favourable in the licensed uses."