NPC Archive Item: Drug Safety Update from MHRA/CHM

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25 January 2010

The MHRA and CHM have published the January edition of Drug Safety Update (DSU). Highlights include:

  • A ‘Hot Topic’ article on methylphenidate, covering new patient information that is available, a reminder of product information updates that encourage its safer use, and conclusions from a CHM review of its cytogenic effect.
  • Advice on an increased risk of Steven-Johnson syndrome with phenytoin associated with the presence of the HLA-B*1502 genetic variant in patients of Thai or Han Chinese ethnic origin.

In addition, for health professionals involved in imaging, the latest advice is given on the safer use of gadolinium-containing contrast agents in the light of the serious and life-threatening risk of nephrogenic fibrosis is some patients.

Drug Safety Update is an essential read for everyone whose professional practice involves medicines. It is published every month in electronic format only.

New patient information for methylphenidate and reminder on other safety issues
Methylphenidate is a stimulant treatment for children aged 6 years or older and adolescents with attention-deficit hyperactivity disorder (ADHD). The design and content of the Patient Information Leaflets (PILs) have been updated with the latest guidance on safe and effective use for patients and carers. This includes a tear-off section written in an engaging style specifically for children and adolescents. These updated PILs for the 18mg, 36mg, 54mg and 27mg strengths of the Concerta XL brand of methylphenidate, and the 10mg strength of the Ritalin brand are available to download from the MHRA website.

In addition, the MHRA has issued a reminder for health professionals about the recently updated recommendations for use of methylphenidate. Treatment should be supervised by a specialist in childhood or adolescent behavioural disorders. Rigorous pre-treatment screening and regular monitoring of treatment, including physical and psychiatric health, is advised. Treatment should be re-evaluated at least yearly.

CHM review on the cytogenic effect of methylphenidate
The MHRA has recently reviewed data on the cytogenic effect of methylphenidate. The review concluded that, overall, there is no strong evidence from a range of data sources that methylphenidate causes chromosomal damage, and that the evidence provides no clear basis for suspecting an increased risk of cancer with this treatment. The benefits of methylphenidate continue to outweigh the risks when used to treat children aged 6 years or older and adolescents with ADHD. However, the MHRA continue to review closely the drug’s longer-term safety.

NICE guidance on ADHD was issued in September 2008 (summarised in a previous MeReC Stop Press blog).

Risk of Stevens-Johnson syndrome with phenytoin in certain patients
Phenytoin is a commonly used antiepileptic drug and is one of the most common causes of antiepileptic-related skin adverse reactions, including life-threatening Stevens-Johnson syndrome (SJS). Presence of the HLA-B*1502 allele may be associated with an increased risk of developing SJS in individuals of Thai and Han Chinese ethnic origin when treated with phenytoin. If these patients are known to be HLA-B*1502-positive, phenytoin should be avoided when alternative therapy can be given. Use of phenytoin should only be considered if the benefits are thought to outweigh the risks.

The prevalence of HLA-B*1502 is estimated to occur in about 8% to 9% of the Thai and Han Chinese population.However, available data are too limited to recommend screening of patients of Thai or Chinese ethnic origin for presence of the HLA-B*1502 allele before starting phenytoin treatment. The frequency of HLA-B*1502 in the Caucasian and Japanese population is extremely low, and so it is not possible to make any conclusions on the risk association. Neither is it possible to give adequate information about the risk association in patients of other ethnic origins at present. A previous MeReC Stop Press blog has discussed the risk of carbamazepine-induced SJS associated with presence of HLA-B*1502 in patients of Han Chinese, Hong Kong Chinese or Thai origin, which was highlighted in the April 2008 edition of Drug Safety Update.

Gadolinium-containing contrast agents: new advice to minimise the risk of nephrogenic systemic fibrosis
Gadolinium-containing contrast agents are associated with a varying degree of risk of nephrogenic systemic fibrosis (NSF), a serious and life-threatening connective tissue condition. Specific advice has been given to minimise the risk in certain vulnerable groups and these are given in Drug Safety Update.

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