A general practitioner who indiscriminately prescribed sleeping pills to 78 patients - even though some showed signs of drug dependence or abuse - has been suspended for four months and fined $15,000.

Dr Joseph Heng, 66, was also penalised for not referring his patients to someone more qualified - such as a specialist or psychiatrist - for further treatment.

He was practising at Heng Clinic & Surgery in Bedok Reservoir Road at the time of the offences.

In a statement yesterday, the Singapore Medical Council (SMC) said a disciplinary tribunal had found Dr Heng guilty of professional misconduct.

Investigations into the case started in 2011, following a complaint from the Health Sciences Authority to the SMC.

In one case, Dr Heng prescribed 30 tablets of the sedative Nitrados for a patient who said that he had been sleeping only four hours a day.

When the man returned 18 days later, Dr Heng prescribed another 30 tablets.

In total, the man was given 110 tablets over a 71-day period.

Dr Heng ought to have known that the use of such drugs should be limited to four weeks at most, the medical council said in its grounds of decision.

He should also have known to refer the patient to a specialist if the drugs were prescribed beyond a cumulative period of eight weeks.

In mitigation, the counsel for Dr Heng said he had "acted out of a genuine desire to help his patients and did not seek to profit".

They also pointed to his track record of looking after needy patients, doing house calls while charging only nominal fees.

However, the SMC said that Dr Heng's inappropriate prescription of hypnotic medication - that is, sleeping pills - counts as "serious misconduct".

"The long-term consumption of hypnotics may lead to the development of drug dependence and tolerance by patients," it said. "Accordingly, we were of the view that the main sentencing consideration must be one of deterrence."

Dr Heng's suspension started yesterday and will last four months.