The Health Sciences Authority (HSA) yesterday warned the public against taking modafinil, a potent prescription medicine used to increase one's alertness, which is not registered locally.

This comes after a woman in her 30s developed Stevens-Johnson syndrome (SJS), a life-threatening skin condition with blistering and severe peeling of the skin after taking the product Modalert 200.

HSA said in a statement that the woman took modafinil on alternate days for more than three weeks to increase her alertness as she worked long hours. She first developed a rash, which subsequently spread to her whole body.

This was followed by severe peeling of her skin, pain in her throat, multiple mouth ulcers and conjunctivitis. She was hospitalised.

Modafinil is available in some countries as a prescription drug that reduces excessive sleepiness associated with conditions such as narcolepsy, HSA said.

These patients experience excessive daytime sleepiness and they have a tendency to fall asleep suddenly in inappropriate situations.

There have been reports of students and adults taking the drug as "cognitive enhancers" to improve focus and memory, HSA added.

It warned that self-medication with modafinil for these purposes is not appropriate and could be harmful due to its stimulant effects on the brain. Other severe side effects include heart problems, hypertension and psychiatric conditions, such as anxiety.

Skin reactions such as SJS and a more severe form of the condition, toxic epidermal necrolysis, have been reported with the use of modafinil. These can cause health complications or even death.

Last June, The Straits Times reported that more students were using "smart drugs" like modafinil to help them get better grades. The report said the drugs could be purchased from a local website and online platforms like Carousell. However, a check yesterday found that these online avenues have since been taken down.

Those found guilty of supplying or selling unregistered health products may face a fine of up to $50,000 or jail term of up to two years or both. Anyone with information on the sale and supply of modafinil from unauthorised sources may contact HSA on 6866-3485 during office hours or e-mail hsa_is@hsa.gov.sg

• Additional reporting by Gracia Lee