Pseudoephedrine is a common ingredient in cold remedies and rarely produces adverse psychological affects.

Experts said its prolonged use could cause insomnia and stress but not neurological damage.

"Pseudoephedrine can't be the cause of his illness," Ramathibodi Poisons Centre director Professor Saming Kaocharoen told a news conference on Monday.

Prakitpao, 37, has been at the centre of a public drama since his family said he began acting strangely and avoiding them after meditation sessions with a group that includes a young woman described as "a close female friend". His family admitted Prakitpao, who runs a lucrative chain of tuto¬rial or "cram" schools, to a mental institution.

"Ephedrine and pseudoephedrine are very similar in structure," Saming explained.

Ephedrine has been a hot topic since tests on Prakitpao after his admission to Srithanya Hospital on February 19 showed excessive levels of the substance.

The stimulant can produce seri¬ous mental disorders and the pres¬ence of massive amounts in Prakitpao raised eyebrows. The friend Pemmika Veerachatraksit complained to police of alleged "murky" circumstances surround¬ing his hospitalisation.

The Criminal Court has ruled Prakitpao's committal was not unlawful because he was ill and required treatment.

During the court challenge Prakitpao was moved from Srithanya to the Galaya Rajanagarindra Institute, where he remains.

Saming, an expert on toxic substances, said Monday he had "suspicions" about the earlier test results and raised these with the institute.

The latest tests employed gas chromatography mass spectrometry. The two techniques are combined to form a single method of analysing mixtures of chemicals. The technique is used in the Olympic Games and other events to detect drug cheats from those who simply ingest legal medicines.

Saming explained the new tests used the same urine samples sub¬mitted for the first analysis, which had employed highpressure liquid chromatography. He commended Srithanya Hospital for checking patients for substances that could cause mental disorders.

"It's common sometimes that a second lab test is needed," he said.

Saming informed the Crime Suppression Division about the new findings. Police have been investigating how Prakitpao came to have elevated ephedrine levels.

Psychiatrists at both Srithanya Hospital and the institute have ruled out ephedrine as the cause of Prakitpao's illness and the latest findings will not affect his treatment.

The Nation