We all know about 'druggies' who steal to feed their addiction, but people can end up just as hooked on drugs that are feely available over the counter at the local chemist shop.

As Robbie Williams checks into rehab for his addiction to prescription drugs, Gabrielle Fagan reports on the dangers.

EVERY day, thousands of people visit chemists and GPs all over Britain to get their 'fix' of drugs to satisfy their addiction. But these are far from stereotypical junkies dependent on outlawed substances like cannabis and heroin. They're ordinary, and often highly respectable, people leading normal lives but for the grip of a little recognised dependency - on over-the-counter painkillers.

They've bought medication such as ibuprofen and paracetamol or a host of well known brandname products to treat a genuine physical ailment and unwittingly become addicted because they take it for longer than is recommended.

They then may become dependent on the feeling of 'well-being' they get from the drugs and join the increasing number of people suffering from this 'silent addiction' - experts put the numbers affected at 100,000 and rising.

Neurologist Michael Gross, who runs clinics for people dependent on over-the-counter (OTC) medication, says: ''This type of abuse is a widespread and increasing problem, which most people don't have a clue about.

''Because they get painkillers from their GPs or chemists, and see adverts constantly extolling the virtues of this medication, people wrongly assume that there's no risk attached to it.''

All too often, excessive intake of this medication has damaging health effects such as liver and stomach damage, irritable bowel syndrome or respiratory problems.

Robbie Williams has just checked into a clinic to fight his addiction to prescription drugs and eight years ago, comedian Mel Smith revealed his seven-year addiction to Nurofen Plus. He called it ''my dark secret'', and reportedly said ''they didn't make me feel high - they just helped me to relax''. His 50-tablets-a-day habit landed him in hospital with two burst stomach ulcers.

Leading substance abuse therapist Paul Russell believes the number of those suffering from OTC dependency is rising sharply.

''I see clients from all walks of life - from postmen to chief executives - some of whom may be taking up to 30 codeine tablets a day or drinking vast quantities of cough medicine. They've ended up self-medicating with OTC medication to mask and avoid dealing with a whole range of problems including stress and anxiety.

''Like alcohol abuse, their tolerance level rises and they just find they need more and more to feel normal.''

Some susceptible people can become hooked within just three weeks - 14 days continuous use of certain OTC drugs can be enough to develop a dependency.

Talking to a GP is an initial step towards help but Russell says: ''One of the problems is people with this problem find it difficult to seek help because of the social stigma surrounding addiction. They do not see themselves as the stereotype junkie but they are dependent and just as much in need of treatment and support.''

Gross advises: ''Even taking six to eight painkillers a week over a long period, without diagnosis or specialist input, can definitely put you at risk of dependency, especially if you are susceptible to it.''

If you answer yes to at least two of the following questions, you may have developed a dependency on prescription or OTC drugs.

* Have you been taking over-the-counter medicine in excess of seven days continuously without consulting your GP for advice?

* Does your medication seem to be less and less effective?

* If your original complaint has cleared up, are you continuing to take the drug because it makes you feel calm and 'normal'?

* Have you suffered, or are you currently suffering from, anxiety, depression or stress? Do you have a family history of drug and/or alcohol abuse?

Gross says: ''You might get a migraine or back pain and initially a painkiller works, but the effect starts to lessen over time. We know that the brain learns to have headaches and possibly neck and shoulder pain. Once the pain pathways are opened up, the headaches or other pains become more common and this process is exacerbated by taking the painkillers.

''Also, continual use of painkillers can make you feel depressed and unwell, but people do not recognise this is what is causing them to feel low and will blame their original ailment and step up the dosage of the painkillers. It can be a vicious circle.''

Many over-the-counter drugs contain opium derivatives. These trigger the brain to release a chemical called dopamine, which produces feelings of happiness and well-being.

Top of the list of potentially habit-forming medications are painkillers and cough medicines. Both of these often contain codeine, which is similar to a weak form of morphine and can make you feel calmer and give a 'high' effect. It is contained in products such as Co-Codamol, Solpadeine, Syndol, Panadol Ultra, Feminax and Nurofen Plus.

Gross says: ''With the codeine products you have the extra problem of the opiate addiction. People become hooked on the feeling of well-being, but of course, as with heroin, eventually you need the opiate just to feel normal.

''So when someone tries to stop taking OTC painkillers not only do they have to deal with the pain of the 'learned' headache but also with the opiate withdrawal symptoms which can include shivering, aching joints, agitation and insomnia.''

People who get severe or frequent headaches often tend to take ever-increasing quantities of painkillers. The over-use of these actually reduces their effectiveness, and not only do they not work, they can cause further headaches (known as rebound headaches).

Some people can cut down by themselves, but a GP should be consulted for advice and may refer the patient to a specialist. It may also be necessary to take a low dose of anti-depressants as part of the process of being weaned off the OTC medication.

In severe cases users may have to go to a treatment centre while they attempt to go 'cold turkey', which can cause agitation, insomnia, sweating and shaking. People can also benefit from one-to-one or group therapy.

In general, always follow the instructions on the packet and ask you pharmacist if you require help.

SOURCES OF HELP:

* Michael Gross: www.neurologyclinic.co.uk

* Paul Russell,founder of The Smart Project to help sufferers of substance abuse: www.smarttreatmentproject.com or prusselleurodetox.com

* A self-help group formed by sufferers: www.codeinefree.me.uk