There is much debate, yet again, around the decriminalisation of drugs in the UK. It's a debate I find confusing. I can already stroll into many pharmacies in the United Kingdom and buy a fairly hefty dose of morphine for under two pounds. And it's legal.

I'm talking about codeine linctus, which is sold as a cough suppressant. Many pharmacists no longer sell this product, but all can if they wish. If you know where to go, you can buy a 200ml bottle for around £1.80. Some "friendly" pharmacists will even sell you more than one bottle at a time, although, in my experience, they bump the price up to around £3.50 a bottle.

One 200ml bottle of the medicine contains 600mg of codeine. Codeine is converted into morphine once ingested, and this 600mg ends up as equivalent to about 90 milligrams of morphine. Taken orally, this has about the same effect as taking 20 to 30mg of morphine intravenously. If you fall over in the street and break your wrist, you might get injected with 10mg of morphine IV in the casualty department. So, just to reiterate, for less than two quid, at many pharmacies in the UK, right now, you can buy a dose of opiate analgesia that's about three times as strong as you'd get if you broke your wrist.

Opiate drugs (by which we mean morphine, codeine, dihydrocodeine – basically anything which has its roots in the opium poppy) are already legally available in this country.

Codeine linctus is probably the "gold standard" for people like me, addicted to OTC (over-the-counter) medicines. But it's far from the only way of getting your dose of drugs. Much more readily available are the combination painkillers. My personal favourite has for years been Paramol, which is mainly paracetamol, but also has a shot of dihydrocodeine in each little, white, easy-to-swallow torpedo. It's marketed as the strongest painkiller you can get without prescription ("You Can't Hit Pain Much Harder" it says on the pack), which it is, although there are plenty of other very similar ones available. Most contain codeine as the active opiate rather than dihydrocodeine, and the maximum dose is 8mg of either. Dihydrocodeine is usually quoted as being about twice as potent as its shorter-named cousin, which is presumably why Paramol is the market leader.

Although Boots now produce a pharmaceutically identical own-brand product for about a third of the price, I still prefer Paramol with its reassuringly dramatic black packaging. At times over the past decade or so, I have been necking as many as 60 Paramol a day. According to the text books, my liver should have shrivelled and died after a couple of days of such abuse (it's the paracetamol that does this to you), but mercifully, mysteriously, it has survived, though it did have an especially rough period for a few months and needed its own brief spell in rehab.

When you're getting through that many tablets, there are practicalities to overcome. Not least is the cost: at around £4.50 for a packet of 32 tablets, I was spending £200 to £300 a month on the stuff. Maybe not that impressive when weighed against a heroin or crack cocaine habit, but a significant chunk of my income. Then there is disposal of a hell of a lot of packaging – the car boot wasn't actually crammed full, but I wouldn't have wanted to open it in front of anyone. Finally, there's the rotation of chemist's shops; you can't go back to the same one every day. Changes to pharmacy opening times a few years ago were a blessing of sorts. Before, they all closed at midday on a Saturday and didn't re-open until Monday. Now a lot are open on Sundays and some are accessible 24 hours a day.

The miracle of my liver's survival is all the more startling to me as I work in "the business". As a dentist, I know a bit more about teeth and gums than livers, but they do teach you something of what paracetamol does to your insides at dental school. Doctors and nurses are quite well known to develop addictions to drugs obtained through their work, and while it is possible for dentists to have similar problems, access is more limited. But I think the main reason I chose the local pharmacy over the practice drug cupboard is the paper trail. Especially since the Shipman case, if you get caught doing anything illegal with drugs as a medic or dentist, the consequences are likely to be dire. But I could buy as much codeine or dihydrocodeine as I liked from various different pharmacies, the only consequences being those on my mental and physical health.

Which, I suppose, brings us to why I started doing it in the first place. I have been asked more than once questions like "Why do you take the tablets?" and "How do they make you feel?" In answer to the first, you may as well ask why I breathe in and out every few seconds. It had just become the way I functioned, and certainly the way I coped with the stresses of life and work. I wanted to scream back at the questioner, "Why aren't you taking something?" (if, indeed, they were not). I found it difficult to believe that someone could manage their daily living activities, and take their work as seriously as I did, without some kind of pharmaceutical prop.

As for how the tablets made me feel, "insulated" is the word I most often use. It was as if I was encased in a layer of bubble-wrap when dosed up with codeine, or Paramol.

I think I first started to use the drugs for legitimate reasons – backache, as I recall. I cannot now remember if they cured my back, but they made me feel warm and confident. And so, as they say, it begins. Over the next 10 or so years, the habit came to dominate my life, but in such a subtle and insidious way that I came to see it as part and parcel of my life, rather than as any kind of intruder.

Addiction to OTC drugs is a very private affair. While celebrities end up in the papers and in the courts after partying all night, and non-celebrities gather together to celebrate their destructive habit, people like me skulk around in chemists' shops, hoping that we are not recognised from a few days before, (and in my case, hoping that none of the local pharmacists get a bad tooth), before downing some tablets in complete privacy. Or sometimes not. One day my girlfriend caught me out. It turned out she'd seen me taking tablets before, and it was obvious that the amounts I was taking were far more than it is usual to take for aches and pains. I promised to get myself sorted out, and she, I'm very glad to say, promised a while later to marry me. Unfortunately the "getting myself sorted out" bit took a while longer than I had promised.

Holidays, although somewhat problematic when you have the condition I have, do serve to highlight the twisted attitude to opiates we have in this country. For years now, I have had to smuggle Paramol into my holiday destinations and try to ration myself, usually dashing off the plane at Heathrow or Manchester as soon as I land back home in the hope that the airport branch of Boots is still open. In the Caribbean, for example, availability depends on local history and culture. Bonaire or Tobago – no codeine. In Barbados, stuff similar to Paramol, but called Remedeine, is freely available. In the mainland United States you cannot get anything with a trace of opiate without a doctor's prescription, and can almost get locked up even for asking.

The same Puritan attitudes apply in countries with an Islamic tradition, such as Egypt, where your request for codeine-based products, even in an English-speaking pharmacy, is met with the response "that is classed like drugs here". Of course, if I was a "real" addict, I would spend my time in Los Angeles, or Sharm-el-Sheikh, or Mauritius, or Turkey, trying to score some street heroin. Thankfully, while being hooked on headache tablets is a royal pain in the arse, it is not quite as much of a pain as some other addictions.

No one knows for sure how many people in the UK are addicted to OTC painkillers, although at a British Medial Association conference in 2005, the figure of 30,000 was given. I would be surprised if it were really that low. Many who do have the habit would not even think of describing themselves as addicts. But mainly, figures are impossible to come by because of the completely unregulated way in which opiate-based analgesics are sold. It's an issue that raises its polite, British head now and again – often as a result of personal stories like this one. A few years ago, I heard a spokesman for the pharmaceutical industry say that the amount of opiate in the various products whose manufacturers he represented was so tiny, that he could not believe anyone could become "addicted" to them. Well, smug boy, if they're that tiny, why include them? Let me answer that for you. The opiates are included because they make people feel nice, and they earn the pharma trade millions of pounds every year.

If I sound a tad bitter, it's because I'm entitled to be so. After years of planning my days around trips to local chemists' shops, I am finally free. It has been a rather enforced freedom, following on from a confrontation at work. Once again, the supposed secrecy of my habit was not quite what I thought. Not only had I been seen taking tablets, I had also been seen going into local pharmacies. A lot. Neither a crime in themselves, but the result was that I was "offered" the chance to take a period of sickness absence, and get well. Which is what I'm doing.

Ironically I have, in part, the pharmaceutical giants to thank for this breakthrough, because I now take a daily tablet called naltrexone, which has the strange effect of blocking the effect of all opiates on my body. The main downside is that if I am unlucky enough to fall and break my wrist, morphine will be completely ineffective. The main upside is, well, everything else. And by that I mean everything – tastes, smells, sights and sounds, sex, sunshine, searing hot showers. Everything is more intense when my ex-best-friend Paramol is away. I've always had a habit of shedding a tear at seemingly inappropriate moments, such as a particularly poignant judgement on The X Factor. Now I simply blub like a child, which is a source of unending amusement to my lovely and long-suffering wife. It's been a scary ride though, involving sleepless nights, much diarrhoea and some vomiting.

But I still miss my friend terribly sometimes. For years, codeine has been there to hold my hand when times are rough, and fight my enemies for me. It's as if someone has taken away a lovely, fluffy, blister-pack security blanket (look at chat-rooms on the topic, and you'll find that it is not only me who refers to their tablets in these terms). It has left a huge gap in my life, one that will be hard to fill with something more healthy.

Without doubt, the weirdest side-effect of quitting painkillers is that I'm in less pain. I used to get the occasional deep sports massage on my back, and it was agonising. I had huge areas of tense, knotted muscle which when massaged would make me yell out in pain. Within three weeks of stopping the Paramol, they had gone, helped on their way by two visits to a hopefully non-habit-forming Chinese therapist. He said that painkillers were bad as they merely masked the pain and made my muscles even more tense and diseased. There is a recognised condition called "analgesic headache" which is caused by taking too many painkillers. But with drug companies making so much money from analgesics, and with those same drug companies providing almost all of the funding for medical research these days, don't expect proper research into whether painkillers actually make pain worse any time soon.

As hinted at earlier, I really don't know how I feel about where we should go with OTC opiates. Undoubtedly, they are not needed to treat pain; the United States demonstrates that. Up until now, the only time over many years I have ever been at least temporarily free from codeine is when holidaying in the US. We could easily do the same here – have absolutely nothing but plain paracetamol and ibuprofen available without prescription. But I also know how personally disastrous it would have been for me a few months ago had someone cut off my supply. The sad fact is that thousands of people in this country need opiates to be available without prescription. Not necessarily to treat their pain, but to allow them to function. To suddenly cut off that source would not only be cruel, it would end in tragedy for many.

Take the argument further in the other direction and we could probably improve the health of dozens, perhaps hundreds of people by making pure codeine more freely available, without the liver-mulching paracetamol. It sounds attractive, only I know that I would simply have taken more and more codeine until it had little noticeable effect (tolerance of opiates is one of the reasons they are so dangerous.)

Rather than changing the regulations, what we really need, and need desperately, are more treatment services. Services for the treatment of OTC addiction are virtually non-existent, perhaps not too surprisingly as there is little if any crime associated with the problem, so even less political pressure. Addiction services in general are over-stretched already, and likely to have little time for someone whose habit does not involve needles or probation officers. As a health professional I had a hard enough time finding help, and it's still a struggle. My rapid detox came courtesy of a consultant psychiatrist, but ongoing treatment still has to be finalised. There are a few fairly random services aimed specifically at dental and medical professionals with addiction problems, but my experience with these has not been good. A few years ago I rang one helpline on an evening when I was feeling particularly in need of help. Unfortunately, the person answering sounded so drunk I could not fully understand their advice.

For others, especially those who have drifted into addictive patterns by complete accident, who simply wake up one morning and realise they can't go to work without a few of the headache pills for the headache they no longer have, finding help can prove impossible. The only service dedicated to OTC addiction of which I am aware is completely voluntary, and funded (only just) by donations.

I am not by nature a preachy person. And even less inclined to preach knowing as I do the risks of relapse with this condition. But a little preaching may be in order, if only to say that if you do take more painkillers than you know you need to, you can get help. Finding someone to take you seriously is the first step. If you're lucky enough to do that, then take it from me, the rest can be done.

Some of the details have been changed to protect the author's identity.

High-profile and hooked

By Jamie Merrill

Nicole Richie

Richie was arrested in 2006 for driving under the influence of the painkiller Vicodin. She claimed the medication was for menstrual cramps and after her arrest said: "I kept making bad decisions or mistake after mistake after mistake."

Jack Osbourne

Osbourne was treated for addiction to the opioid OxyContin in 2003 while his sister Kelly was treated for a similar dependency a year later. Father Ozzy said at the time: "It's a family illness. It's in the genes."

Jamie Lee Curtis

Star of True Lies and A Fish Called Wanda, Curtis fought a five-year battle with painkillers that threatened to destroy her career and marriage. She beat her addiction in 1998.

Rush Limbaugh

US political commentator Limbaugh's addiction was exposed in 2003 by the National Enquirer and he admitted all on his radio show: "I need to tell you... that part of what you have heard and read is correct: I am addicted to prescription pain medication."

Courtney Love

Courtney Love has never confirmed an addiction to painkillers but the former lead singer of Hole and former wife of the late Nirvana front man Kurt Cobain was charged in 2003 for possession of painkillers OxyContin and the semi-synthetic opioid hydrocodone.

Michael Jackson

Jackson's addiction to painkillers caused the cancellation of his worldwide tour in 1993. He claimed the stress of persistent charges of child-molestation fuelled his addiction: "I was humiliated, embarrassed, hurt and suffering great pain in my heart," he said in a 1993 statement.

Anna Nicole Smith

The inquest into the death of glamour model Anna Nicole Smith in 2007 ruled out an overdose, but she had a history of painkiller addiction which, she claimed, began when her 89-year-old millionaire husband, J Howard Marshall II fell ill and died.

Elvis

The King's death in 1977 raised questions after it emerged he'd been receiving a concoction of prescription medicines from his doctor. Investigations found Presley took more than 19,000 doses of medication in the last two-and-a-half years of his life.

Eminem

The rapper liked to mix his painkillers with ecstasy and rum, according to one "friend". But Eminem has cleaned up. "Hailie's [his daughter] birth was a wake-up call. She made me get in gear," he said in 2003.

Cindy McCain

McCain, wife of Republican presidential nominee Senator John McCain, claimed that emotional stress caused her addiction to painkillers Percocet and Vicodin in the late 1980s; she even stole medicines from a charitable foundation she had created: "I was an addict. That's why," she told CNN when asked about the theft.

Addiction to opiate-based painkillers: the facts

By Edward Fortes

Medicines containing opiates can include cough/cold treatments, painkillers, analgesic tablets and capsules, and some diarrhoea medication, according to the Over-Count Drugs Information and Advice Agency.

A type of opiate, codeine has the same roots as heroin and cocaine; in fact, in 1898 a German company patented heroin and began to sell it as a cure for the common cough.

Codeine acts as a depressant on the central nervous system, and effects can include euphoria and relaxation but also mental detachment.

During a recent interview with the BBC, a neurologist was quoted as saying that it "took as few as six or eight [painkiller] tablets a week", consumed over an extended period, to develop dependency.

Some of the risk in over-the-counter (OTC) preparations is also linked to paracetamol content. While the drug is convenient due to its rapid absorption properties, even in limited doses it can damage the liver. Overdoses can be fatal. Paracetamol was introduced in the UK in 1956 as a prescription-only drug; it was then added to opioid analgesics such as codeine and dihydrocodeine after 1963.

White-collar employees working long hours and prone to tension headaches are those most likely to become addicted to painkillers, according to Dr Alan Wear, medical director of the rehab centre Priory Hospital Marchwood in Southampton. What starts as "a couple of paracetamol before work" can soon escalate into "frightening quantities" of tablets on a daily basis, he says.

Others vulnerable to addiction include those taking treatments for pre-menstrual pain, back pain, or insomnia.

Dr Robert Lefever, director of Promis rehabilitation clinics, notes that painkillers can become "just as addictive" as illegal drugs. The difficulty, however, lies in recognising an addiction to a drug that does not initially appear 'serious'.

www.codeinefree.me.uk ; www.over-count.org.uk ; www.promis.co.uk