A technical support officer spiked the water bottle of a lecturer at Ngee Ann Polytechnic with a "love potion" in the hope that she would fall for him.

But all it did was leave her with a dry throat. The lecturer, who is Japanese, also found herself unable to think clearly or sleep at night.

Wong Fook Hiong, a married man, was caught when the woman secretly filmed him spiking her water with the concoction - a combination of a sedative meant for animals and an anti-psychotic drug that he bought online for US$200 (S$285).

The 43-year-old was yesterday given the maximum fine of $1,500 for doing an act so negligently as to endanger life on Jan 12 last year. He admitted pouring a mixture of xylazine and haloperidol, both poisons, into the lecturer's water bottle at the polytechnic on Clementi Road.

Assistant Public Prosecutor N. K. Anitha said that, some time in November 2014, the 30-year-old lecturer drank some water from her bottle and found that it tasted bitter. She immediately spat it out.

After this happened a few times, she decided to place her mobile phone in video recording mode at her desk.

On Jan 12 last year, she left at about 5.30pm, returning around 8pm. She checked her phone and noticed that Wong had walked to her desk at about 6.40pm and poured a substance from a vial into the bottle of mineral water on her desk. He then shook the bottle and put it back in its original position.

She made a police report the next day and Wong was arrested with a glass vial. On analysis, the water and the vial were found to contain the two poisons.

Xylazine is a sedative, analgesic and muscle relaxant used in veterinary medicine. The reported effects in humans include drowsiness, disorientation, lethargy, hypotension, slow heartbeat and respiratory depression.

Haloperidol, an anti-psychotic drug, is used to treat various psychoses. It can cause tremors, insomnia, agitation, excessive muscle activity and headache.

Wong stated that he believed the substance to be a "love potion".

"He claimed he had added the unknown substance in the hope that the victim would drink the contaminated water and fall in love with him," said Ms Anitha, who sought the maximum fine.

In his mitigation plea, Wong's lawyer, Mr Javern Sim, said his client has been diagnosed with "mood disorder'', which caused him to be immature and to display attention-seeking behaviour.

"He was trying his best to get the attention of the lecturer that he liked very much," he said.

Mr Sim said Wong is a simple, caring man with a good character. He was truly remorseful for his thoughtless and foolish actions, and had lost his job of 17 years as a result of them. He used to earn $4,505 a month and has been jobless since.

Wong could have been fined and jailed for up to three months.