Tuesday, 28 June 2011

Ten per cent of Patients taking Triazoles for Chronic Pulmonary Aspergillosis suffer from neuropathy

The National Aspergillosis Centre treats chronic fungal infections using antifungal drugs, often as a means to reduce the dose of steroids necessary to maintain good breathing. The main drugs used are the triazoles - in order of historic availability: itraconazole, voriconazole and more recently posaconazole which have many advantages over their predecessor, amphotericin B and its derivatives.

The nature of the treatment is to provide antifungal for extended periods of time as although it is active against the fungus it cannot eradicate the fungus as a general rule, it simply keeps it in check. Any drug taken for long periods of time is likely to start to cause unwanted side effects and triazoles are no different, as a quick glance at the list of side effects will testify.

The National Aspergillosis Centre uses these antifungals to treat rare conditions such as chronic pulmonary aspergillosis (CPA), allergic bronchopulmonary aspergillosis (ABPA) and severe asthma with fungal sensitisation (SAFS), none of which have been extensively studied with regard to side effects caused by the triazole drug used to treat, partly because this is a fairly recent, novel use for these antifungals.

One particularly problematic side effect noted was a collection of symptoms consistent with peripheral neuropathy; numbness and tingling of the fingers & toes, limb weakness. This is potentially a serious side effect which can necessitate the patient stopping treatment. Consequently a study has been carried out to look at how frequent peripheral neuropathy symptoms occurred in patients taking long term triazole therapy.

Results Between 2007 and 2010 those of those patients taking itraconazole, 17% developed peripheral neuropathy, of those taking voriconazole 9% developed peripheral neuropathy and for posaconazole the figure was 3%.

It is noteworthy that the newer drugs are better in this respect - they cause less neuropathy. Unfortunately they are also the more expensive drugs so most patients will have to be tried on the cheaper drugs first. This study shows us the importance of monitoring patients on triazoles for signs of neuropathy (and patients monitoring themselves), and also shows us that there is a clear progression available to patients where they can be put onto less side effect prone triazoles if needs be.

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