By Bianca Nogrady
Tricyclic antidepressants are the antidepressants most likely to be prescribed off-label, according to a Canadian study published online in the BMJ.
Researchers analysed 106,850 antidepressant prescriptions written by 174 primary care physicians for 20,920 adults between 1 January 2003 and 30 September 2015. This revealed that 29.3% of all antidepressant prescriptions were written for an off-label indication. The highest prevalence for classes of antidepressants was seen in tricyclic antidepressants, mainly due to a 93% prevalence of off-label use of amitriptyline for pain and insomnia.
Off-label use of tradozone for insomnia accounted for 82.5% of all tradozone prescriptions and 26.2% of all off-label antidepressant prescriptions.
The lowest rates of off-label prescribing – about 6% – were seen for serotonin–norepinephrine reuptake inhibitors.
The researchers noted that although 15.9% of all off-label prescriptions were indeed backed by strong scientific evidence, in 44.6% of prescriptions, neither that drug nor any other in its class had strong evidence supporting their use for that indication.
‘When evidence to support efficacy is lacking, physicians should exercise caution, prescribe conservatively, and inform patients of this information via a shared decision-making process,’ they wrote.
Commenting on the study, Professor Nicholas Keks, Professor of Psychiatry at Monash University in Melbourne, said the problem with putting all off-label prescribing into the one basket was that off-label use ranged from the trivial to the extreme.
For example, he argued that using an antipsychotic in someone with schizoaffective disorder – an indication for which there are limited approved options for treatment – was a mild form of off-label prescribing that contrasted with the more extreme practice of using ketamine off-label for the treatment of depression, which should only be undertaken in the research setting.
Professor Keks also pointed out that while in an ideal world there would be funding for all potential treatments to be investigated in clinical trials, this wasn’t the current reality.
‘Many things in medicine, while they have really good clinical experience behind them, are not necessarily supported by a double-blind randomised controlled study,’ he said, citing the treatment of night-time sedation as one example.
Off-label prescribing was also a particular issue in psychiatry because of the nature of the practice, he said.
‘In psychiatry because the diagnosis is so vexed, you couldn’t practice if you rigidly adhered to on-label,’ Professor Keks told Medicine Today.