Red hot news for back pain sufferers
1998
A new pain-relieving cream called Zacin which became available on prescription
Avid readers of newspapers and magazines have come across some recent press coverage about a new pain-relieving cream called Zacin which became available on prescription in May.
It is a much needed product which will have a major impact on people's lives, back pain sufferers included.
Capsaicin is the compound which gives chilli peppers their heat
So what is Zacin and what does it have to offer over and above the various pain relievers we already have? Its active ingredient is a substance called Capsaicin, which cooks will be aware is the compound which gives chilli peppers their heat. Capsaicin has a long history of use as a pain reliever in the folk medicine of countries such as Mexico, but interest in its use as a licensed drug has only really taken off in the last decade or so. It is now being tested as a topical reliever in a variety of painful disorders such as disorders of peripheral nerves (peripheral neuropath) occasionally found in diabetics.
Capsaicin combats pain in a unique way, but to understand this it is necessary to spend a little time considering what pain is. The human body contains many sensory nerve fibres or neurones which transmit information about touch, temperature, pain etc. to the brain.
These pain nerve fibres depend on a chemical called substance P which is released from nerve endings into the surrounding tissue in response to pain and in doing so, triggers a cascade of events resulting in the sensation of pain and local inflammation, as well as other changes at the site of the pain.
If one gets rid of substance P, by depleting the nerve endings of this compound, one can in theory get rid of the ability to detect pain. And in practice that is how Capsaicin works: when it is applied to a small area of skin regularly, it causes depletion of substance P thereby producing a long-lasting analgesic effect. By contrast, other painkillers, like for example local anaesthetics, work by blocking sensory conduction in all sensory nerves and so completely numbing the area. It's a bit like using rouge to camouflage anaemia.
Capsaicin allows the patient to feel sensations such as light touch, temperature and movement, but not painful stimuli such as that from arthritic joints.
At the moment Zacin is licensed in the UK only for the relief of pain associated with osteoarthritis. This follows a number of studies testifying to its benefits both when used alone or in conjunction with other treatments. For example, In one controlled scientific study, over 80% of patients with knee pain due to osteoarthritis reported a reduction in pain by an average of one third with regular use of Zacin. In a second study in which Zacin was added to patients existing treatments, it produced a 69% improvement in knee pain after just one week of treatment. Such studies showed that Zacin has a progressively increasing action, that is, it does not produce a 'one-off' effect: the more you use, the greater the improvement in pain that you can expect to feel.
But although only licensed for the treatment of osteoarthritis, most doctors, myself included, use capsaicin to relieve pain in a host of other related medical conditions. For example, there is other evidence showing that it has an even greater effect on pain associated with rheumatoid arthritis and I have no doubt the same applies to back pain. All these conditions share many common features: they are essentially degenerative conditions of joint cartilage; there is commonly associated inflammation; and most importantly, they are all painful.
The major problem that rheumatologists face is not just treating arthritis but dealing with the problems caused by the treatments used
What about side effects? This is an area where Zacin is particularly advantageous. The major problem that rheumatologists face is not just treating arthritis but dealing with the problems caused by the treatments used. Prescribing drugs can be like treading on egg shells: we have to constantly ask ourselves whether in prescribing a particular treatment we are doing more harm than good. For example, oral non-steroidal antiinflammatory drugs (aspirin-like agents) can cause severe problems affecting the gastrointestinal tract and in the long-term even cause damage to joint cartilage. Other treatments also have their problems.
One of the best pieces of evidence which bears witness to the safety of capsaicin is that it is part of many of our natural diest - without any adverse side effects. That aside, one of the big advantages of Zacin is that it is applied topically, which means treatment is targeted at the affected area, not throughout the body which reduces the possibility of side effects or drug interactions.
The only unwanted effect is a mild transitory stinging or burning sensation which has been reported by just half of patients. However, this burning is usually noted on initial application and quickly wears off. In the United States where Zacin has been available for more than ten years, and is recommended by the American College of Rheumatologists as early therapy of osteoarthritis, it is available over the counter and although over three million packs have been sold, no serious adverse effects have ever been recorded.
But like all drugs Zacin has to be used appropriately. Little and often is the best way. Bioglan, its manufacturer, recommend that you apply a small bead to the affected joint or painful area four times a day. Regular, frequent application is necessary because if you do not use it continually, the painkilling effect wears off. And it may take up to four weeks to have its full effect, don't be tempted to use a greater quantity of cream: it won't increase the affect or speed up the process. One 44g tube should be sufficient for one affected joint for one month.
It's also important not to use Zacin on broken or cracked skin and always wash your hands afterwards - just as you would after cutting up chillies. If not, and you rub your eyes, you will know all about it!
But the last piece of advice I give my patients, is not to fall into the trap of thinking you will get the same effect by smearing your back or joint with Vindaloo paste: the reason that Zacin is effective is that the Capsaicin is combined with a vehicle compound which ensures it passes through the skin and comes into contact with the pain neurones to have its desired effect.
It's a reassuring thought that this compound, Zacin, derived from a natural source and well evaluated, has given patients suffering pain, and their doctors, an additional weapon to comfort their discomfort. The remarkable lack of serious adverse effects makes Zacin particularly welcome.
A report by Dr Michael Irani BSc FRCP, Consultant Rheumatologist, Ashford Hospital, Middlesex