A new HIV drug with few side effects has been made available to patients.

It is hoped the medicine, launched today, will be able to help people who have become resistant to other HIV treatments.

Maraviroc, made by Pfizer, has been proved to have very few side effects compared to other drugs and can be taken when other drugs stop working.

Anyone in Brighton and Hove who has been taking anti retro viral drugs for some time has about a 50 per cent chance of being able to take Maraviroc.

Dr Martin Fisher, consultant at the Elton John Centre in Brighton, the Royal Sussex County Hospital's HIV and Aids unit, said patients who feel their treatment is not working should ask their doctor or specialist nurse about the possibility of change.

He said there were a few new drugs on the market which could bring benefits.

He said: "There are a number of other drugs coming through at the moment for people who have had some treatment before and will have resistant virus.

"This offers them new options for long term treatment for people who have experienced tolerability and toxicity with other treatment.

"We are hitting quite an optimistic era at the moment. We have three or four new drugs so for somebody whose treatment currently isn't working very well or whose treatment is causing them side effects, it is a good time."

Maroviroc works in a different way from other treatments by blocking the HIV from entering the human immune cells, working outside the cell rather than when the virus is inside it.

It is taken orally twice a day and needs to be taken with two other drugs. It was discovered and developed by Pfizer scientists in Sandwich, Kent.

Anyone interested in taking it can have a test with a sample sent off to San Francisco for analysis.

There are about 1,500 people receiving treatment for HIV in Brighton and Hove and there are believed to be another 500 people who do not realise their status.

New drugs tend to be more expensive until they are used more widely. An individual with HIV costs the NHS an estimated £500,000 to £1million during his or her lifetime.

Brighton is renowned for its HIV treatment and some patients choose to move to Sussex because of its reputation.

But the virus is still thought to be spreading at an increased rate each year, particularly among the city's gay population. This is thought to be happening because of complacency about infection as people erroneously believe HIV can be cured or easily treated.