Doctors have warned patients to be careful about buying unregulated remedies over the internet after the death of a patient.

The 55-year-old had been diagnosed with facial and sinus cancer, but had refused to undergo any sort of surgery, radiotherapy or chemotherapy, turning instead to an alternative medicine called hydrazine sulphate.

After using the therapy for four months, he developed a rash, and went to the doctors two weeks later.

Tests showed severe damage to the liver and kidneys, and the patient developed a blood disorder which stopped it from clotting.

Despite treatment, he died from internal bleeding.

Doctors say that because the treatment was not available on prescription, no mechanism for reporting possible adverse effects exists.

Dr Mark Hainer, from Moncrief Army Community Hospital in Fort Jackson, South Carolina, said: "Although the internet can be a valuable resource for patients, this case graphically illustrates the potential danger of therapies purchased online.

"It illustrates the importance of reporting adverse events resulting from the use of medications, medical devices or special nutritional products."

'No evidence'

The report of the incident was carried in the journal Annals of Internal Medicine, and an accompanying editorial criticised the easy availability of hydrazine sulphate.

Dr Mark Black and Dr Hamid Hussain, from Temple University Hospital in Philadelphia, said: "There seems to be little evidence to support its ability to shrink tumours or cure cancer.

"There seems to be little justification for the drug's easy availability and unsupervised use."

Advocates of the drug, who say it can improve quality of life and possibly increase survival times, claim the medical establishment has been unjustly dismissive of the drug.

Some trials of its efficacy have been carried out, and while they did not show any advantage to hydrazine sulphate, campaigners said these were flawed.