UP TO 80 students in a Bangkok school were rushed to hospital on Wednesday after suffering nausea, irregular heartbeat and severe headache, all symptoms thought to be a result of a drug overdose.

The culprit? Over-the-counter cough pills which the students are suspected to be taking in large amounts for its euphoric side-effects, said a report in Bangkok Post.

Taksin Hospital director Kittiya Srilertfa said initial tests showed the children had taken dextromethorphan.

Dextromethorphan is an active cough-suppressant ingredient found in several commercial cough remedies such as in the yellow tablets the students took.

Twelve who were sent to Taksin Hospital were in serious condition and had their stomachs pumped.

Most of the students were in a stable condition and were discharged, said the report.

Deputy Bangkok Governor, Dr Malinee Sukvejchavarakit, said initial investigations showed that some children had been taking the drug for up to three days as a defence against school bullies, said a report in The Nation.

Some students had consumed up to 10 tablets until nausea and shock overcame them.

Dr Malinee said she had alerted schools to watch out for this drug and has urged district directors and police to prevent a repeat occurrence of this drug binge.

A fifth-grader, going only by the name Somsak, said he and his friends had bought 20 tablets at 1 baht (4cents) from the owner of a computer-gaming shop, who said these pills would make them impervious to pain.

Thailand's Food and Drug Administration (FDA) deputy chief Weerawan Taengkaew said dextromethorphan was a dangerous drug, and adults could take only eight 15mg tablets per day and a child no more than four tablets.

Upon overdosing, a person could suffer nausea, breathing difficulties, lose consciousness and even die.

To be sold only by pharmacies

Since drugs can be sold only by pharmacies, it was illegal for it to be distributed by a computer-gaming shop, she said, adding that parents and teachers should keep an eye on children and stop them from buying or taking unknown drugs.

The mass student overdose has raised concerns about public education on drug use and the effectiveness of controls on drug sales by pharmacies.

Dr Malinee said the Bangkok Medical Association would file a report with the Education Ministry so precautionary steps could be taken.

Police swiftly acted and detained the games shop owner opposite the school for questioning.

Suwamit Montriwibulchai, 24, who admitted to selling the drugs to some students, was charged with selling medicine without permission.

He claims he sold the tablets only to high school students but not to primary school pupils.

Suwamit told the Bangkok Post that he used the pills to treat himself and, after a while, he felt "rejuvenated".

He said: "I told my friends about this and I guess the word spread to the kids who came to the shop. I sold the drugs for about two weeks and the customers kept growing."

Police and FDA authorities also raided Sunny Pharmacy where Suwamit said he bought the pills and found a large amount of dextromethorphan.

The owner faces charges of selling drugs without the supervision of a registered pharmacist.

This article was first published in The New Paper.