The hospital believes it could treat 20 patients with the new drug

Rheumatoid arthritis causes inflammation in joints, making them become tender, stiff, swollen and, in severe cases, leading to joint damage.

About one in 100 people develop the condition, although it affects three times as many woman as men.

The drug, Humira, which is being used at the Royal Devon and Exeter Hospital (RDE), focuses on the causes of the inflammation in the body and is believed to improve patients' quality of life.

We think we can justify spending �10,000 a year on most patients Dr Richard Haigh

Doctors at the RDE say the top 5% of the worst affected patients could benefit from the new drug.

It suppresses a chemical in the body which affects inflammation and offers the patient the possibility of reduced stiffness and less pain.

But the chemical the drugs affects can help prevent other illnesses such cancer and tuberculosis.

Suppressing that chemical, as Humira does, lays the body open to infection.

However, doctors in Exeter say it has already greatly reduced the worst symptoms of rheumatoid arthritis.

Treatment costs about �10,000 per patient a year.

The RDE believes it could treat around 20 patients who suffer worst from the disease.

Dr Richard Haigh said: "Overall, we've calculated the costs of rheumatoid arthritis as being �800m and �1bn per year and many working days are lost through the condition.