A mother from Kent claims her baby son could have been caused serious harm after being given the wrong prescription by a hospital doctor.
Rachelle Keyter is relieved she sought further advice
Four-month-old Joshua was referred to accident and emergency suffering from suspected oral thrush - but he was prescribed an antimalarial medicine.
His mother, Rachelle Keyter, 19, from Walderslade, near Chatham, claimed the advised dosage "could have killed him".
Medway Primary Care Trust (PCT) said the incident was being investigated.
Joshua was prescribed Nivaquine syrup by a locum doctor at the Medway Maritime Hospital.
The PCT said he should have been given Nystan, an antifungal medicine.
A statement said: "Medway PCT sends its sincere apologies to Rachelle Keyter and Joshua.
"Although prescribing mistakes do happen, they are extremely rare.
"We have begun an internal investigation and this is still ongoing.
"The locum doctor will be attending extra training in relation to out-of-hours prescribing before he can work again."
Ms Keyter said she became concerned after reading notes that came with the Nivaquine.
"I think it said something like heart failure and things like that could have happened," she said.
She sought advice on the internet and from a pharmacy in Rochester.
Pharmacist Ferride Karson told the BBC that giving Joshua the Nivaquine in the dosage prescribed could have caused "slight damage to the kidney and partly to the liver as well".
"I'm just very glad I didn't give it to him," Ms Keyter said.
"I believe it could have killed him because he was small for his age anyway."