BANGKOK - With less than 10 per cent of its population of more than 70 million fully vaccinated and a healthcare system under increasing pressure, Thailand has turned to a traditional herb known for its bitter taste and purported immunity-boosting capabilities to treat mild Covid-19 cases.

The herb, Andrographis paniculata, commonly known as fah talai jone or green chiretta, has been used for centuries to treat flu, sore throat and inflammation.

It is now being used as a tool in the government's arsenal of treatment options for Covid-19 patients with mild symptoms or who are asymptomatic.

Although the herb is not listed as an effective Covid-19 treatment by the World Health Organisation (WHO), Thai authorities say its use can relieve pressure on the overstretched healthcare system as daily caseloads hit 20,000 and hospitals run out of intensive care beds.

Taxi driver Nuttakit Wongwanich, 35, takes fah talai jone pills for four to five days whenever he feels the onset of fever, cough and flu.

"Before Covid-19, I didn't know much about this herb. But now I take it whenever I feel ill. It has worked," says Mr Nuttakit, who is fully vaccinated, but keeps the pills on hand after hearing about them from a pharmacist friend.

Similarly, Ms Luksina Loke, 55, who works in the import sector, has multiple packets of the pills in her bag.

"We have to take care of ourselves," says Ms Luksina. She has not yet been vaccinated as she does not want the Sinovac and AstraZeneca jabs, which are the primary vaccines offered by the government.

The popularity of the age-old herb, which is also native to other countries such as India and Sri Lanka, soared last year after Thai authorities started looking into the use of the plant extract to treat the early stages of Covid-19.

A Department of Thai Traditional and Alternative Medicine study, which involved more than 300 Covid-19 patients, yielded promising results, the authorities said in April.

"We are confident that fah talai jone can cure Covid-19 patients who have mild symptoms or are asymptomatic," says Dr Kwanchai Wisitthanon, the deputy director-general of the department.

However, the department says that while the herb can stop the symptoms of Covid-19 from worsening, it cannot provide any protection against the coronavirus.

In another trial where the herbal remedy was used on 11,800 prison inmates with mild symptoms, the corrections department says that 99 per cent of them recovered.

Health authorities say adults with mild symptoms should take 60mg of fah talai jone three times a day before meals. A single course of the medication usually lasts five days.

With demand soaring, some hospitals which use the herb together with modern medicine have been running low on stock.

"(We are) currently accelerating the production of fah talai jone pills to meet the surging demand," says Chaophraya Abhaibhubejhr Hospital, one of the country's leading herbal medicine producers.

The hospital also warns people against consuming the herb in large amounts as it can damage the kidney and liver.

Dr Kwanchai advises against consuming the herb for more than five to seven days as it can cause numbness in the hands and feet, lower blood pressure and impact the kidneys, reported the Bangkok Post.

Pregnant women and breastfeeding mothers, as well as those who have kidney and liver problems, should avoid the herb too.

Some medical experts have said there is a lack of scientific evidence to show that the herb is an effective remedy for Covid-19.

Responding to The Straits Times' queries, the WHO says: "At present, fah talai jone is not listed by WHO as a known effective treatment for Covid-19."

The WHO adds that it welcomes the recognition of any new therapeutic agent to treat the coronavirus, but for it to recommend the herb for Covid-19 treatment " would require a high standard of evidence based on robust research".

Evidence supporting the use of the herb also took a hit earlier this month when researchers who conducted a study affirming the use of fah talai jone to treat Covid-19 withdrew their paper from online pre-print journal medRxiv due to an error. The team will resubmit the research paper once the error is corrected.

The Department of Thai Traditional and Alternative Medicine defends the study, saying it was confident of the accuracy of the finding that the herb can prevent Covid-19 lung infections from worsening.

Users of the herb tell ST they are aware of the risks and that the herb does not prevent infection.

Mr Taxin S., 62, who works in a water filtration company, says: "My wife and daughter told me not to take it for more than five days straight. After that, it can cause dangerous side effects like muscle weakness."

With increased demand across the country, Thai authorities plan to grow and harvest fah talai jone in free spaces in prisons.

Justice Minister Somsak Thepsuthin says the first batch will be ready next month and will yield eight million fah talai jone pills.

Thai conglomerate Charoen Pokphand Group says it will be growing the herb on 16ha of company land in central Saraburi province. It will also build a factory to turn the herb into capsules and give them to the public for free, reported the Nikkei newspaper.

Meanwhile, some scammers have tried to cash in on the herb's popularity. The Bangkok Post reported that a man was arrested in Nakhon Pathom province with more than 400 bottles of fake fah talai jone pills.

He had allegedly made the fake pills by filling empty capsules with the powder of another herb that also has a bitter taste.