All the patients had undergone major surgery

The patch, which has been developed in the United States, may even remove the need for intravenous needles or drips.

A study in the Journal of the American Medical Association suggests it's as good as conventional methods.

The patch, which uses a tiny electric current to deliver drugs through the skin, is due to be submitted to the US Food and Drug Administration shortly.

Major surgery

Dr Eugene Viscusi and colleagues at Thomas Jefferson University Philadelphia carried out a study to see if it was as effective as a morphine drip.

The study was funded by US company Alza Corporation, which manufactures the patch.

This is a miracle of miniaturisation Dr Eugene Viscusi

They signed up 646 adult patients who underwent major surgery between September 2000 and March 2001 at 33 hospitals in north America.

Half of the patients were given the E-TRANS fentanyl HCl patch, which is the size of a credit card and is placed on the upper arm or chest.

Patients could use the patch to self-administer the pain relief drug fentanyl hydrochloride.

The other half were linked up to a drip, which they could use to self-administer morphine.

The doctors found that patients in both groups reported similar satisfaction ratings after using them for 23 hours.

Almost 74% of those who were given the patch said it was good or excellent at relieving pain. This compared to 77% who used morphine drips.

The satisfaction ratings for both groups increased to 80% after using both methods for 48 hours.

"[The patch] is able to deliver potent pain reliever through the skin with a very, very tiny electric current at the demand of the patient," said Dr Viscusi. "This is a miracle of miniaturisation."