At the height of her addiction, 41-year-old lecturer Susan was taking up to 25 tablets of Stilnox, a sleeping drug, a day.
She had problems sleeping as she was troubled by relationship woes and a doctor prescribed the drug.
Susan (not her real name) said: "At first, the Stilnox knocked me out but gradually, I also experienced a feeling of euphoria when I took it. So I started taking it when I was feeling anxious or down."
If she did not take the pills, she felt "anxious, suffered terrible headaches, could not eat, could not get out of bed and could not function".
Addiction to sleeping pills is a common problem, and like gambling addiction and alcoholism, is treated at the Institute of Mental Health's National Addictions Management Service (Nams), said associate consultant Melvyn Zhang.
In the past three years, 196 patients sought help at Nams because they were hooked on sleeping pills.
Dr Munidasa Winslow of Promises HealthCare said the addicts he sees include lawyers, healthcare professionals and teachers.
Most started with one pill at night to reduce their anxiety or to sleep but found themselves needing more and more as they built up tolerance to the drug, he said.
Dr Thomas Lee of the Resilienz Clinic has one patient who takes about 50 Dormicum pills in a day. The businessman, who is in his 40s, began using the pills some 20 years ago because of his business and marriage woes. When he tried to quit, he suffered a seizure and had to be hospitalised.
Doctors warn that benzodiazepines, the class of drugs many sleeping pills fall under, are "highly addictive" and they advise addicts to seek help from a psychiatrist.
Other addicts take sleeping pills, which are easier to obtain on the black market, as an alternative to illegal drugs such as heroin or Ice, said Mr Anson Yoo, the director of the HCSA Highpoint Halfway House.
Like Susan, who went from clinic to clinic to get her pills, many addicts doctor-hop. They may also get them on the black market or from clinics in Johor Baru, Malaysia.
Susan said her sleeping pill habit cost her at least a few thousand dollars a month and "controlled her life". Susan, who is now seeing a psychiatrist for her addiction, said: "There is no quick fix for insomnia."
•The Nams helpline is 6732-6837