A family doctor has called on people to keep a close eye on the use of coronavirus medication by elderly relatives, to ensure there is no mixing up of drugs and that treatment courses are completed.

Lam Wing-wo estimated that up to a fifth of his elderly patients had refused to take prescribed oral drugs to treat their Covid infections over concerns about allergies and side-effects.

But he noted that severe side-effects from the medication are rare.

"In my experience, even some very old people don't experience many side-effects, only mild diarrhoea or feeling a little unwell at most," he said on an RTHK programme on Monday.

The doctor stressed that oral Covid medication works best when taken early on in an infection.

Lam also said that some elderly patients decided to stop their Covid treatment after symptoms subsided, describing this as inadvisable.

"I've reminded them the virus could fluctuate and if you don't fully suppress it, it may rebound. So I think we may need family members' help on this," he said.

He added that people also need to be aware that some drugs, such as blood thinners, may work against Covid medication.

Lam also advised families to tell elderly relatives to do rapid Covid tests as soon as they feel unwell and assist in reporting any infections, so that Covid drugs can be prescribed as soon as possible.

"If I can prescribe drugs within half a day after an infection is identified, my experience shows that this can greatly ease the suffering of elderly patients," he said.