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Idiopathic Pulmonary Fibrosis Update

Summer, 2005

By Dr. Brendan M. Corcoran, MVB,
Dip Pharm, PhD, MRCVS,
University of Edinburgh, Scotland

Idiopathic Pulmonary Fibrosis (IPF) is a chronic debilitating respiratory disease which seems to be a particular problem in the West Highland White Terrier (WHWT). However, the exact clinical features of the disease in the WHWT, and in particular the best way of diagnosing the disease, have not been determined yet. Currently, a study to address some of these problems is being undertaken in collaboration among the veterinary schools of the universities of Edinburgh and Glasgow in Scotland and universities of Pennsylvania and California (Davis) in the USA. Affected dogs are being identified and recruited to these schools; further details are available at the Westie Foundation of America website (www.westiefoundation.org).

By its very nature, information from such studies takes time to come out into the public domain but in the meantime information about the disease, its recognition and recommendations regarding treatment is being disseminated to veterinarians at different scientific conferences (World Small Animal Veterinary Association Congress in September 2004, British Small Animal Veterinary Association Congress in April 2005 and American College of Veterinary Internal Medicine Forum in June 2005). This means that veterinarians are recognising this disease more frequently and are able to advise owners more accurately as to what is happening and what will happen.

Unfortunately, this is a devastating disease with an inevitable course which eventually results in respiratory failure. This, understandably, causes a lot of distress to owners, compounded by the fact that treatment is usually ineffective. Part of our studies is to see if we can find out why treatment does not appear to work.

The problem with the medical treatment of an illness is that recommendations can only be made on the basis of sound evidence. A problem with veterinary medicine, and human medicine to a lesser extent, is that there is little evidence to support the use of a variety of medications in the treatment of a whole range of diseases. This is particularly the case with IPF and it may be several years before we have the definitive evidence as to what medications are effective in treating IPF. In the meantime we use anecdotal reports (what veterinarians and owners think works) and ideas borrowed from the treatment of IPF in humans. Our selection of treatments can also be affected by what information is available on the internet. However, such a source of information can be confusing and even dangerous. But desperate times need desperate measures and it is not surprising that owners will grasp any piece of information if only there is a chance of curing their beloved pet.

So what can be recommended at present for the treatment of IPF in dogs? In effect very little seems to work in an effective and consistent manner but here are some thoughts. None of these recommendations will prevent inevitable respiratory failure but they may improve quality of life and improve survival (still to be proven). Part of the reason for treating is to make these little dogs as comfortable as possible and it is amazing how tolerant they are of their disability, and despite this, how happy they can be.

• Prednisolone: oral prednisolone (prednisone in the USA) is worth trying in IPF cases. Some will show a response but if there is no response within three weeks then continuing medication is probably of little worth. The aim is to have the dog on the lowest possible dose and to administer on alternate days.
• In human IPF, the immunosuppressive drug azathioprine is commonly used with prednisolon and may be beneficial in some patients. But it is used in human medicine mainly because human patients are very intolerant of the side-effects of prednisolone, which is not the case in dogs. There are no reports of the use of azathioprine in dogs with IPF. Cyclophosphamide is also used in human patients but the evidence for its effectiveness is a little bit thin.
• Bronchodilators: again these can be given on a trial basis but withdrawn if there is no appreciable benefit.
• Obesity: control is worth pursuing so as to improve respiratory function. In particular, if the dog is on prednisolone, there is danger of significant weight gain which can only adversely affect respiratory function.
• Exercise: controlled exercise, with restriction if necessary. Abandoning exercise completely is probably not wise as obesity may arise and exercise may improve respiratory function. But sensible levels of exercise should be allowed.
• Control of secondary lung infections: we do not know if IPF dogs are susceptible to secondary lung infections but appropriate treatment for suspect concurrent respiratory illnesses is wise.
• Anti-fibrotic drugs: there is little information on the effectiveness of these drugs in IPF in dogs and only a limited amount of information from the human field supportive of such treatments. One drug of potential interest is pirfenidone which seems to be beneficial in human patients. Other drugs such as colchicine give questionable benefit and have not been tried in dogs so far while the interferons are totally ineffective.
• Pulmonary hypertension: this is a developing area of interest. Drugs such as sidenafil (aka Viagra) and pimobendan (not licensed yet in the USA) might improve lung function by improving perfusion of the lung but have still to be evaluated.

There are studies looking at the effects of a whole range of disparate medications in human IPF and there are recommendations made by patients about a whole range of therapies they have tried themselves. But we do not know if any of these treatments would be of use in IPF dogs. Of course we will keep an eye on developments and see if newer recommendations can be made in the future but if you are going to try an unproven treatment, make sure it will cause no harm!

Further updates on the results of this research project will be made available through the WFA News and the WFA website as they become available. This project is jointly funded by the AKC Canine Health Foundation and the Westie Foundation of America, Inc.