Medicinal cannabis may be available within two years

Pharmaceutical companies invest millions to develop new painkillers as Medical Research Council tests enter their final phase

The world's oldest euphoric drug is poised to make a return to the medicine cabinet. Cannabis, reputedly taken by Queen Victoria to quell her period pains but banished from Britain's schedule of medicinal drugs in 1971, is on the point of winning scientific backing for its role in easing the symptoms of chronic disease.

This week the Medical Research Council is due to announce that it has recruited the last of 660 patients to a £1.2m trial of cannabis-based medicines in the treatment of multiple sclerosis, the largest in the world. Most of the patients recruited over the past two years have already completed the 15-week trial, in 30 centres round the UK.

Although final results will not be available until next summer, researchers are optimistic. Dr John Zajicek, consultant neurologist at Derriford Hospital, Plymouth, who is leading the research, said: "I'm fairly confident we are going to find an effect in reducing spasticity, or muscle spasms, and it is also going to have an effect on bladder control.

"Anecdotally some patients have had tremendous benefit from it. One or two who couldn't walk or go to the loo found they were able to when they were on the drug. There have been some whose lives have changed dramatically."

Next month, a venture capital firm, GW Pharmaceuticals, is due to report preliminary results from its own Phase III trials of cannabis-based medicines in patients with multiple sclerosis, spinal cord injury and other conditions. Phase III trials are the largest and most rigorous, and must show positive results before a drug can be licensed.

Last week the company published results from an earlier, smaller Phase II trial which showed that 28 out of 34 patients suffering severe pain benefited from the medicines and had elected to continue on the trial. Geoffrey Guy, GW's executive chairman, said: "One can be confident the Phase III trials are going to yield results reflective of Phase II."

If such hopes are fulfilled, cannabis-based medicines could be on the market in two to three years. The National Institute for Clinical Excellence, the government watchdog on new medicines, has been alerted by its horizon scanning unit in Birmingham, whose job is to spot drugs in development before they hit the NHS.

The medicinal benefits of cannabis have been known for at least 2,000 years. Its analgesic properties were described by the British herbalist Nicholas Culpepper in 1653. Two drugs based on the active constituent tetrahydrocannabinol (THC) have been used in the UK for over 30 years to treat nausea in cancer patients undergoing chemotherapy, although their use has declined as better anti-emetics have been developed.

Medicines derived from the cannabis plant are being tested by drug companies around the world as treatments for pain, stiffness, tremor, weak bladder, loss of appetite and high blood pressure. It is being tested in people with behavioural disturbance caused by Alzheimer's and in sufferers from Parkinson's disease.

Research is also going on into its role in stimulating appetite in cancer and Aids patients ­ cannabis has long been known to give users the "munchies".

But one hurdle remains to be overcome. Scientists have not so far succeeded in isolating cannabis's medicinal properties from its euphoria-inducing ones. Although patients in both trials have not got high, that is believed to be because they were taking low doses.

"Most of the active ingredients of cannabis can give a high. What the Government wants is a drug that can be used without being abused," Dr Zajicek said.

In the 1970s, researchers discovered morphine-like opioid receptors in the spinal cord that led to the development of epidural painkillers, which did not have the psychoactive effects of morphine. They are now widely used in childbirth, after surgery, and increasingly for intractable pain such as that caused by cancer.

Similar receptors for cannabinoids have been identified in the spinal cord, and the hope is that cannabis-based drugs can be developed to target them which would have a painkilling effect without a psychoactive one.

With scientists confident that they can harness some of the 60 active constituents of cannabis to alleviate a range of symptoms, millions of pounds are being invested by drug companies in developing unique combinations of the constituents or finding a unique means of delivering them to the body, which would be patentable. As cannabis is a natural plant, neither it nor the oil produced from it can be patented.

In the MRC trial, patients were given either THC ­ cannabis oil derived from the whole plant ­ or a placebo in a capsule to be swallowed. The THC was manufactured in California and the cannabis oil was derived from plants grown in Switzerland and processed in Germany.

One drawback of using an oral drug is that there is great variation between patients in the dose needed to produce an effect. Patients in the MRC trial were started on a target dose based on their weight, which was adjusted over the first five weeks, depending on side effects.

GW Pharmaceuticals have developed an under-the-tongue spray which they claim is absorbed more quickly, making dose adjustment simpler. Their patients received THC or cannabidiol, either alone or in combination, manufactured from cannabis plants grown in a secret location under tight security in southern England.

The Multiple Sclerosis Society has taken a close interest in the research, but has declined to fund patients who wished to continue on the drug after the end of the MRC trial ­ to the anger of some of its members.

A spokesman said: "There is a tremendous amount of anecdotal evidence that cannabis in various forms can be helpful in alleviating some of the most unpleasant symptoms of MS.

"But we also know that there have been people with MS who have had very bad experiences. So the main concern is whether the substance is safe in the long term, because people with MS have a condition that is going to last the rest of their life."

'It was brilliant just to be able to stand'

The pills Hazel Walker swallowed as part of the Medical Research Council's (MRC) cannabis trial helped her get out of her wheelchair and walk. She took them for 15 weeks last year and the effect was dramatic.

"I could walk a couple of lengths of the hallway and do simple things that other people take for granted. It was brilliant, really brilliant," she said.

She still doesn't know what was in the pills because the trial was "double blind" to prevent both the patients and their doctors knowing who was taking the active ingredient and who was taking the placebo.

But the improvement in her condition was so striking that after a fortnight's break at the end of the trial she elected to go back on the pills for another year and continued to reap the benefits.

"The first week after I came off the pills I really went downhill. I tried to do things I had got used to and I found I couldn't. When I went back on them I noticed a change again – more mobility and fewer spasms. It is very hard to stand at the sink and wash the dishes if you have got spasms in your legs."

Her love life improved, too. "It was brilliant to be able to stand up. It is difficult to get passionate stuck in a wheelchair."

Aged 47, she has had multiple sclerosis for seven years. She is confined to a wheelchair and when her husband, a fisherman, is away, she needs two carers to get her up and dressed in the morning and put her to bed at night at their home in Plymouth.

The only drugs that have helped during those seven years have been steroids, but they have damaging effects if taken long-term. Medicines based on cannabis are her only hope but now they, too, have been taken away.

Funding was only available to provide one year's supply of pills. For Hazel, they ran out this summer. The MRC's researchers applied to the Multiple Sclerosis Society for financial help to continue supplying the drugs, but the society declined.

Hazel said: "I was left in limbo. I was annoyed, to be honest. The MS Society says it won't fund the drug, yet it gives benefits to people with MS. It's frustrating."

She experimented with herbal cannabis for a while: "I tried it for a fortnight. I sat watching telly and started laughing. I don't know whether it helped because I was giggling all the time."

"I didn't fancy going out if I was going to be in the street giggling. People already think if you are in a wheelchair you are practically braindead and if they saw me giggling they would probably think I had lost it altogether. You need your wits about you. My hope now is that the trial is successful, the drug is licensed and I can start taking it again."