Medicine safety update
Medicines Safety Update
- Aust Prescr 2013;36:168-71
- 1 October 2013
Medicines Safety Update is the medicines safety bulletin of the Therapeutic Goods Administration (TGA)
Atomoxetine is indicated for the treatment of Attention Deficit Hyperactivity Disorder (ADHD), as defined by DSM-IV criteria, in children aged 6 years and over, adolescents and adults.
The risks of suicidal ideation and behaviour with atomoxetine are well known and are reinforced in the Product Information in the precautions section, as well as in a boxed warning.
A greater risk of suicidal ideation was observed in children and adolescents receiving treatment during clinical trials compared with placebo. A pooled analysis of 12 short-term (6–18 weeks) trials (11 in ADHD and one in enuresis) showed the average risk of suicidal ideation in patients treated with atomoxetine was 0.4% (5/1357) compared with 0% (0/851) in patients treated with placebo. One suicide attempt was reported in patients being treated with atomoxetine.
To July 2013, the TGA received 74 reports of psychiatric disorders associated with atomoxetine.
In 65 of these cases, atomoxetine was the sole suspected medicine. Over half of the reported cases (42) were reports of suicidal ideation. Of the 38 reports of suicidal ideation in which the age of the patient was given, 28 reports were in children and adolescents aged 18 years and under. The TGA also received two reports of attempted suicide in children and adolescents and one report of completed suicide in a child being treated with atomoxetine.
When considering prescribing atomoxetine in children and adolescents, health professionals should carefully weigh the risks of suicidality against the benefits of atomoxetine therapy.
Patients who are prescribed atomoxetine should be carefully monitored for suicidality, especially in the first few months of treatment and whenever there is a change in dose.
Parents and caregivers should be warned of the risks and alerted to the need to monitor for signs of unusual changes in behaviour or precursors of suicidality, such as anxiety, agitation, panic attacks, insomnia, irritability, hostility, aggressiveness, impulsivity, akathisia, hypomania or mania. Parents and caregivers should also be advised of the importance of seeking immediate medical attention if such signs are identified.
Health professionals are encouraged to report all adverse events associated with atomoxetine to the TGA.
The TGA, working in collaboration with state health authorities, has completed an investigation into this association. Interim results of the investigation were published on the TGA website in February 2011 and in Medicines Safety Update in April 2011 .1
The final study included data from six jurisdictions (NSW, Victoria, Western Australia, South Australia, Queensland and the Northern Territory) for a three-year period from July 2007 to June 2010.2 Validated cases of intussusception in children aged 1–12 months were identified from hospital admissions data and, in some states, through the Paediatric Active Enhanced Disease Surveillance System. Vaccination status for each case was obtained from the Australian Childhood Immunisation Register (ACIR). There were 306 cases of intussusception suitable for analysis, of which 260 were recorded to have received rotavirus vaccination.
The association between rotavirus vaccination and the risk of intussusception was examined using a self-controlled cases series (SCCS) method and was confirmed with a matched case-control analysis using matched controls from the ACIR.
Using the SCCS method, there was clear evidence of an elevated risk of intussusception following the first dose of both rotavirus vaccines. There was also some elevated risk of intussusception 1–7 days following the second dose of both vaccines (see Table). There was no evidence of increased risk of intussusception following a third dose of RotaTeq.
Prior to the introduction of rotavirus vaccination, there were an estimated 10 000 hospitalisations annually in children under five years due to rotavirus gastroenteritis. Since the introduction of Rotarix and RotaTeq onto the National Immunisation Program, emergency department visits for acute gastroenteritis in young children have declined and hospitalisations for rotavirus gastroenteritis in the under-five year age group have been reduced by over 70%. 3, 4
Based on the established benefits of rotavirus vaccination and the rare occurrence of intussusception, both the World Health Organization and the Australian Technical Advisory Group on Immunisation have recommended the continued use of rotavirus vaccine for infants.
Health professionals are advised that information about the risk of intussusception following rotavirus vaccination has been added to the postmarketing adverse events sections of the Product Information of Rotarix and RotaTeq.
Health professionals should advise parents and caregivers of the risks and signs of intussusception, and the importance of seeking early medical attention if they suspect their child has intussusception.
Because there is no pathognomonic injury type associated with DILI, the diagnosis is often one of exclusion. However, it should be included in the list of differential diagnoses in any patient with new-onset liver disease and in any patient with deterioration of existing liver disease after the recent addition of a new drug.5
Important differential diagnoses include viral hepatitis, alcoholic liver disease, autoimmune disorders, liver congestion from cardiac failure, liver injury from shock or septicaemia, and biliary tree disorders. Rarer infiltrative liver diseases, such as haemochromatosis and Wilson's disease, may also require exclusion.
Determining the cause of liver injury is often complex, as initial symptoms may be non-specific, the date of commencement of drugs may not be clearly recalled, and the picture may be confounded by underlying disease processes.
There is a wide spectrum of presentations of DILI, ranging from mild asymptomatic elevation of liver function tests to serious DILI with acute fulminant hepatic failure.
Liver injury associated with medicines occurs via two mechanisms. The pathogenesis involves either direct biochemical effects or the stimulation of an immune response by the toxic drug or metabolite.5
Most significant hepatotoxins cause a hepatocellular pattern of injury, but cholestasis and mixed-pictures can also be drug-induced.6 However, individual drugs that cause liver injury tend to cause patterns of injury and latency periods characteristic of that drug. Exceptions include amoxycillin/clavulanic acid, which can produce more than one pattern of injury.7
Examples of drugs known to cause elevated liver enzymes are in the Table. These drugs are also included in a list of substances most implicated in DILI-Acute Liver Failure (ALF).8 Caution should be exercised and more regular liver monitoring undertaken when combining two or more drugs known to cause ALF in vulnerable patients, such as the elderly, those on polypharmacy, those with potential liver ischaemia, or those with existing liver disease.
Latency periods can be short (hours to days), intermediate (1–8 weeks) or long (1–12 months or more). In rare cases, the reaction can occur after the drug is ceased.
Alanine transferase (ALT) and alkaline phosphatase are considered the most useful of the liver function tests to determine the type of hepatic injury but, despite a high sensitivity, they carry a low specificity for predicting serious hepatotoxicity. ALT values that are within the reference range at baseline and rise two- to threefold should lead to enhanced vigilance in terms of more frequent monitoring. ALT values 4–5 times higher than the reference range should lead to prompt discontinuation of the drug.7
Bilirubin levels twofold greater than baseline, when accompanied by a rise of ALT of more than threefold, indicate a more severe liver injury has already occurred and must prompt investigation. If a drug is suspected to be the causative agent, it should be promptly discontinued.
Because the diagnosis and prediction of a serious DILI is difficult, recent research has focused on the role of biomarkers, such as micro-RNAs.
Treatment of DILI is largely supportive. Most events resolve with the withdrawal of the causative agent. While the time to recovery can take a few days to a week, more commonly there is improvement on cessation of the drug with slower resolution over several weeks to months. In very rare cases, liver injury is permanent and a liver transplant is required.
It is advised that a drug suspected of causing liver injury should not be re-introduced, as the subsequent reaction may be more severe than the initial one, especially if the reaction was hypersensitivity related. In cases where a number of possible medicines could have been involved, careful consideration should be given to recommencement of the medicines, together with careful monitoring.
Health professionals are encouraged to report all cases of liver injury associated with prescription, over-the-counter and complementary medicines to the TGA.
What to report? You don't need to be certain, just suspicious!
|The TGA encourages the reporting of all suspected adverse reactions to medicines, including vaccines, over-the-counter medicines, herbal, traditional or alternative remedies. We particularly request reports of:||Reports may be submitted:|
Medicines Safety Update is aimed at health professionals. It is intended to provide practical information to health professionals on medicine safety, including emerging safety issues. The information in Medicines Safety Update is necessarily general and is not intended to be a substitute for a health professional's judgment in each case, taking into account the individual circumstances of their patients. Reasonable care has been taken to ensure that the information is accurate and complete at the time of publication. The Australian Government gives no warranty that the information in this document is accurate or complete, and shall not be liable for any loss whatsoever due to negligence or otherwise arising from the use of or reliance on this document.
© Commonwealth of Australia 2016.
This work is copyright. You may reproduce the whole or part of this work in unaltered form for your own personal use or, if you are part of an organisation, for internal use within your organisation, but only if you or your organisation do not use the reproduction for any commercial purpose and retain this copyright notice and all disclaimer notices as part of that reproduction. Apart from rights to use as permitted by the Copyright Act 1968 or allowed by this copyright notice, all other rights are reserved and you are not allowed to reproduce the whole or any part of this work in any way (electronic or otherwise) without first being given specific written permission from the Commonwealth to do so. Requests and inquiries concerning reproduction and rights are to be sent to the TGA Copyright Officer, Therapeutic Goods Administration, PO Box 100, Woden ACT 2606 or [email protected].